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#717280 - 11/30/17 8:55 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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As far as I know, pre-unit 120's were 8.5/1, so Oliver Barnes told me when selling a pair to me!
They had large ribs under the crown, which I haven't seen on any of the ones I've used since. I think that we are in a "one size fits all" place unless we stumble upon something special.
So 9/1 is what is generally offered for 650s these days. I can't say I noticed any difference, with my fairly std engine.
However, yours is not std, and the question of actual compression ratio is interesting, considering we're chasing ghosts.
I don't know if any piston supplier really checks the CR of their piston in a real situation (I have my doubts) but instead just gives a rough higher or lower number based on comparison with a std piston.
Significant variations in true compression can derive from such variables as cylinder base gasket, head gasket, head skimming, valve sunkeness.
The way to measure combustion chamber volume is to lay the bike over such that the plug hole is vertical, at TDC valves closed, slowly fill the chamber from an accurate burette till the oil is at the bottom of the plug hole. That is the only important measurement, everything else can be calculated. It is not the volume of the head hemisphere upside down that you need to know.

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#717896 - 12/06/17 9:30 am Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Geneva, Switzerland
Hi Folks, got a sunny day and managed to get a ride in (those of the more eagle-eyed persuasion might notice the snow in the back of some photos).

Those of the less eagle-eyed persuasion will also have no trouble noting that I disobeyed the cardinal rule: “only change one thing at a time”. With one or two days of riding left and motivated by an urge to prevent my engine detonating itself to death, I fixed everything I could and then did a test, figuring I don’t really care what it was as long as its fixed...

So to briefly summarise the situation up to this test:
- Changed carbs to new premier ones (old ones had sticking slides and were running very rich)
- Carb had same jetting as before (190 mains, 106 jets and standard pilots, #3 slides)
- Engine idles beautifully with new carbs
- With new carbs engine running hot and lean - plugs (especially right one) showed traces of detonation
- Engine dies if snapped open from idle
- Double checked tappets – all spot on.
- Triple checked timing – found timing was 2 degrees retarded (running 36 degrees at max advance)
- Checked for intake manifold leaks – possibly found warped bowls – fixed this.
- Checked fuel level –7 mm. I adjusted the floats to be level with the top of the bowl which gives about 7mm fuel height from top of bowl. (Seemingly the highest possible level achievable with stayups).

So after all that I decided to make sure the baseline was OK and try to set everything as rich as possible to get it to run rich at which point I could dial things back to normal mixture from a safe starting point. (Spoiler - I was only partially successful).

I did the following:
- Adjusted carbs with vacuum gauges (found my throttle stops were out by about ¼ of a turn based on the “point where the screw just touches the slide”). Not a big deal either way though. slides move all the way up into the body.
- Retarded timing to 35 degrees for the hell of it, just in case
- Installed 230 main jets for the hell of it, just to make sure I’m starting from a rich place at all carb operating points
- Kept needles at highest position (bottom clip slot) for richest running
- Taped carb flange with masking tape to avoid any chance of air leak there
- Taped up carb lid and cable inlets with masking tape to avoid any chance of air leak
- Drained and refilled tank with 100 Octane shell V power
- Adjusted idle air screw down to about 1 turn out for right carbs and 1.25 out for left carb (point where RPM stopped increasing)
- New B8ES plugs gapped at .025”
- My IR thermometer packed up on the last test new one not yet arrived so was guessing relative temps through the sizzle test
- Put some copper anti-seize grease on the plug threads, you can sometimes see it on the plugs if it touched the surroundings when I removed them- ignore that.

Warmed her up and then went for a short ride:
- The problem of bike dying if throttle snapped open was still there. Turned the air/idle screw in a bit on both but it seemed to make no difference.

- 1st ride was pottering around at openings up to a half throttle getting to the test stretch of road. Plugs are new and very little carbon but OK for about 5 km ride I guess. Right still looks leaner than left.
[Linked Image]

- 2nd run at around ½ to ¾ throttle. Right plug looks ok but lean-ish while left looks ok but rich- ish.
[Linked Image]

- 3rd run at WOT: Both plugs look significantly leaner than the previous run with the ceramic becoming very white again. As before right looks leaner than left
[Linked Image]

- Final run was getting back home – pottering around again at lower throttle opening – Plugs now very rich, porcelain on the left plug is completely black while the porcelain on the right plug is being covered by carbon but the white from the WOT run is still visible so it is "blacking up" more slowly. This is expected from the rich idle air screw settings.
[Linked Image]

Things I noticed on the run,
-heads were on hot side (sizzling) while the right seemed hotter than left (more sizzle ;-)) as one would expect from the plugs
-Bike definitely had less power- probably due to timing being more retarded, was easier to maintain WOT this time around during tests. Previously speeds got a bit hairy.
- for both carbs there is not really a point where the engine slows when turning out the idle screw (too lean) past 1.5 turns. It does however slow when tuned inwards (too rich) less than about 3/4 turns.

It seems as though the problem is still there, although attenuated; seemingly still very present at WOT. I was very surprised by this with the 230 Main jets installed. I was expecting evidence of 8 stroking but instead, I still have lean running at the top. While at the same time bike dying on acceleration off idle...

I'm leaning towards swapping the carbs and air filters (left for right) next year to see if the problem follows the carbs or stays with the pistons. I wonder if I should get a couple of 240 or 250 main jets just for the hell of it although I might just drill out a pair of old jets to ensure that I can actually get it to run rich at WOT, or I coul djust run without mains to make sure the needle circuit is not limiting. I'm going to double check the carb throat, make sure its, in fact, 30mm (is there a specific way to check this?). I'm considering using the old carbs with known good needle jets as a reference but the throttle sticking issue I had on them (reason for the change) is putting me off from testing it, but seeing as I'm making little progress I might give it a try. I never did do plug chops at different throttle openings on that set-up. Just rode it as I got it and checked plugs occasionally after use. were always black/sooty, I know this does not say much though...

Any ideas or comments greatly appreciated


3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
#717906 - 12/06/17 12:21 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Brett,

I think the idea is get a picture angle more like the top pair of photos. You want to see the porcelain that is more inside the plug. The plug is drawing heat from the head. Yes the aluminium balls will show on the tip, but deeper inside can read the heat. Shadows are a problem.

It would seem the new carbs made a difference.

Are those the extended plugs?

There seems to be a difference between putzing in the top photo and putzing in the bottom.

Last edited by btour; 12/06/17 12:25 pm.

Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#717947 - 12/06/17 7:07 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Maui Hawaii
Keep at it Brett. Your get 'er done attitude and clever approach will win in the end.

However, looking at the results I see, it appears to be an almost impossible collection of evidence. Off hand I'd say that your carburetor was way too rich on the low end and way too lean on the mains.

But, I find it hard to accept that it actually could be considering the settings you have.

I would be looking at float levels again. I really looks like the carbs are set up too lean, but flooding at low speeds.

Also, be aware that if your particular motor doesn't like 35 degrees advance it will run hot and may even give false rich readings on the plugs. Less advance means less time to burn fuel and some won't be burned and will end up on your plug as soot.

If it was my bike, I would be doing all this work running pump gas which is a known factor. The unknown factor is the fuel. What is it? How does it perform in other similar bikes?

Cheers,
Bill


Last edited by HawaiianTiger; 12/06/17 7:14 pm.

Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
#717957 - 12/06/17 8:56 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Geneva, Switzerland
Hi Bill,

You are right, it really seems strange.
Interesting point on the fuel, reminded need me me that our European octane is about 5 higher than the north american octane so my 100 would be your 95-ish (I believe).
I'd used shell vpower in Canada as it was ethanol free, but I think it's formulation there was 91 (us) octane.
Over here the only I brands I know are shell and BP.
Any European members want to chime in?

I have a 250 main jet lying around. I'll try it in the right carb to see if makes any difference at WOT. If not I'll just take the main jets out all together. Tomorrow is last day before the real snow. Hopefully I can get a short run in.

The dying when snapping open off idle might have been due to richness all along rather than leanness... I wondered why choke made no difference. Or maybe it was caused by lean mixture previously and now by rich... Starting to see the attraction of fuel injection!

Btour, not sure what you mean by extended plug?
I think the early chop was on brand new plugs hence little carbon. Later had more running time.

Last edited by BrettF; 12/06/17 9:02 pm.

3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
#717961 - 12/06/17 9:25 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
Joined: Mar 2005
Posts: 10,001
John Healy Online content
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Quote
Interesting point on the fuel, reminded need me me that our European octane is about 5 higher than the north american octane so my 100 would be your 95-ish (I believe).


The US number is referred to as the anti-knock index (AKI). It is the Research octane number plus the Motor octane number/ divided by two. You see on the US pumps R+M/2.

The number referred to in the owners manual and what is on UK pumps, and what used to be on the US pumps: the Research number.

With the AKI the Research number is always higher than the Motor number. A fuel rated as 91 AKI will typically have a Research octane number of about 96 while the Motor number of around 87 - 88.

So as far as the Research number is concerned a 96 # in the UK, would typically be equivalent with a US AKI # of 91!!!!!!!!!

Research octane number is determined in a variable compression single cylinder engine running ay 600 rpm. The air intake is set at 125°F.

Motor octane number is determined in the same engine running at 900 rpm. The air intake is set at 300°F.

When it comes to detonation, the Motor octane (the lower number) is the more severe test and is the number you want higher higher - Yes, it is counter intuitive.

Almost as important when it comes to detonation is the volatility of the fuel. As the incoming fuel vaporizes it cools the air. Also a well vaporized air/fuel mixture burns better leaving little, if any, "end gas" responsible for detonation.

A lot of fuels with the same AKI listed on the pump do not vaporize as well as others. Sometimes you will find a lower grade AKI will ping less than one with a higher AKI. There is more to all this than the AKI octane numbers on the pump. Trying different brands, and grades, to see which works better in your bike is definitely in order!

Last edited by John Healy; 12/06/17 9:34 pm.

#717962 - 12/06/17 9:43 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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John Healy  Online Content



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Boston, Massachusetts
Quote
Interesting point on the fuel, reminded need me me that our European octane is about 5 higher than the north american octane so my 100 would be your 95-ish (I believe).


No, see above!

Quote
The dying when snapping open off idle might have been due to richness all along rather than leanness.


Dying, as in no sound from combustion, is a classic lean symptom. Its like you turn off the key!

Quote
I think the early chop was on brand new plugs hence little carbon. Later had more running time.


Reading plugs takes years to perfect. You must use a new plug for each "plug chop". You must be prepared to remove the threaded portion of teh plug in a lathe or such to expose the porcelain. Then you have to compare what you see with what you have experienced in the past. Smokey Yunik, who made plug reading a science, had every plug he had ever ran in his race cars. They included extensive notes as to the tuning and the results of the race.


#717963 - 12/06/17 9:48 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
Joined: Jun 2007
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HawaiianTiger Online content
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Maui Hawaii
20 years ago I lived in SoCal where we had the distinction of being the lab rats for the petroleum industry. There was a lot of fuss when they first introduced ethanol to the fuel. Octane ratings went down. Marginally tuned motors suffered immediately and others had problems ei. when climbing some notable grades in the area, like the
Grapevine.

Where before we could get away with running regular leaded gas, only the higher priced fuels would work.

Before long, all my vehicles needed the best fuel available at the pumps.

Adapt or die....

So, along with some folks I worked with, we developed methods to get the most out of the fuels available without resorting to mixing sport gas or avgas to them. We didn't go so far as to adopt twin plug heads. That wasn't an appropriate solution for our vehicles.

I dropped the compression ratio on the bike I rode the most and suffered with the loss of power. Bummer.

Then I started to harden the combustion chambers in order to help with pinging and possibly detonation.

It works well enough to allow these bikes to run with the original timing figures. Well most of them, anyway. There's always one in the crowd that misbehaves...

Fast forward a decade or so. The same stuff happened here. I was living on Kauai at the time and when they started adding ethanol to the fuel there was absolutely no warning as to what to expect. A number of fishing boats got stranded and the coast guard had to rescue them. The local marine mechanics made bank changing fishing boat motors and fuel tanks to ethanol tolerant ones.

My Norton fiberglass tank melted in my garage, totally gumming up my carbs and inlet tracks. It took me several months to sort out all of that.

Don't expect the petroleum industry to warn you about what they're up to. That was a hard lesson.

[Linked Image]74Commando01 by [url=https://www.flickr.com/photos/152305986@N08/][/url], on Flickr


Cheers,
Bill

Last edited by HawaiianTiger; 12/06/17 9:50 pm.

Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
#717980 - 12/07/17 12:10 am Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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koan58 Online content
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Isle of Wight, UK
"My Norton fiberglass tank melted in my garage, totally gumming up my carbs and inlet tracks. It took me several months to sort out all of that."
Following a rebuild ~2004 using a new fibre tank the bike never made sense, with plug fouling, strange behaviour, sticking throttles, pinhole tank leaks etc.
I wasn't aware of what was going on petrol wise, pre-occupied with personal stuff at the time.
When I started digging into it, I was horrified at the gunge that I found from the carbs inwards, on the valves, combustion chamber, ports etc. It wasn't the stuff you easily scrape off, the hardest decoke, more of a de-tar.
I tried one of the main treatments in the tank, which worked well in sealing the leaks, but the damage was already done and the outer gel coat on the tank kept bubbling.
Did I curse the environmentalists! Especially as this is mainly to support south american countries to produce alcohol rather than cocaine or even food for their own folk.

#717982 - 12/07/17 12:24 am Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Dave, it is actually a political sop, subsidy to our corn growing states. Environmentalists are against this. They call it "burning our food". Just saying, so you blame the right people. Why can't I just let it go? Dunno.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#717985 - 12/07/17 12:34 am Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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btour Offline
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Massachusetts, U.S.A.
Brett,

NGK makes a plug that has an extended nose. It extends a bit more into the combustion chamber. The idea was that would create better combustion. Lest I think that was the idea. ( You see my bike was smoking. The cause of that, I found out here later from reading John Healy's posts) was a too small washer under the inner head bolts. A well known design flaw on some years. ) But before that, Al jr. took my brand new champions, and threw them in the trash and put in the extended NGK's. That was shortly before it blew a piston apart. Just saying. He is another know it all Triumph mechanic.(sarcasm) One who fixes out of shape carbs with emory paper and swears he is right. He probably also skims heads. I have seen him do the former. And let his kid over tighten carbs with the wrong spacer and strip primary oil plugs. Oh the pain of it all. Aghast.

I am looking at the E, in your NGK's and wondering, if that was the plug. I still have one around somewhere I think, in my bag of junk from the explosion. You got to see the piston. I know where that is. Broken rod too.

Not that I think the extended plug did it. But who knows right? I just use the Champions. Breakfast of Wheaties. Or is that backwards?

Last edited by btour; 12/07/17 12:39 am.

Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#718006 - 12/07/17 8:29 am Re: Bonnie Carb Jetting help needed [Re: John Healy]  
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Geneva, Switzerland
Mr Healy, i'd like to clarify a point - I think we might be saying the same thing but I'm not sure :

I said, regarding our swiss fuel relative to your US fuel (Id realised that folks in the US might think I was using US spec 100 octane)

Quote
Interesting point on the fuel, reminded me that our European octane is about 5 higher than the north american octane so my 100 would be your 95-ish (I believe).


while you disagreed stating said:

Originally Posted by John Healy
[quote]So as far as the Research number is concerned a 96 # in the UK, would typically be equivalent with a US AKI # of 91!!!!!!!!!


Should I have said " our European octane number is about 5 higher than the north american octane number, for the same fuel" to make it unambigious or am I missing something?

Regarding low throttle rich /lean point.

Originally Posted by John Healy
[quote]Dying, as in no sound from combustion, is a classic lean symptom. Its like you turn off the key!


Yes, that is exactly how it happens, turn throttle slightly more slowly and revs up fine, snap open fast and it dies as you describe. The only way I can make the carbs still richer is going to a larger pilot + cutout. I might go to a 3 groove pilot just to see what happens (pilots are expensive but cheaper then slides) after I've run it without mains to make sure there is no other limiting factor.

Mr Tiger, float level would really seem a likely candidate. If I don't get any joy elsewhere Ill take up AMAL on their kind offer over the winter to check out the fact that I can't seem to get the level into the "specified range" with the supplied kit.

What is doing my head in is the consistent difference between the carbs after all this fiddling.

If anyone has experience/recommendations on European fuels that will be very interesting.

this is the fuel I use. I hope that Chrome translates it automatically from German for you all like it did for me.

http://www.shell.ch/de_ch/autofahre...wer-nitro-plus/shell-vpower-hundred.html



Last edited by BrettF; 12/07/17 8:32 am.

3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
#718027 - 12/07/17 2:13 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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btour Offline
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Sorry if this is already posted. My Mac gets an internet clog sometimes.

Brett,

Those look like extended reach plugs.....

From the sound of the carbs response to adjusting the idle, you might be doing what is called, "idling on the slide". Which means the throttle stops are set too high, and then you try adjusting the idle air mix.

Question, does it idle immediately after starting without warming the bike up for a bit, without holding the throttle on? It shouldn't. Usually you have to drive a mile or two before it will. I lost my link to John Healy explaining how to tune the carb. I have to review it myself.

But you can start here.

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=358792&Searchpage=1&Main=40048&Words=%2Bhard+%2Bstarting+%2Bspark+%2Bplug&Search=true#Post358792

Sorry if I am wrong but I think you mentioned using a vacuum gauge. It needs experience. Something about dampening the signal. John mentions it there.

He Also mentions that not all slides, even it they are stamped the same, are indeed the same size, cutaway. And indeed the pilot jet size needs to be checked despite the number that is stamped on it, and checked after it is installed since tightening it too much can alter the size. Whew, hope all this was not already covered. We would assume that all that is correct with new carbs, and that it is the correct, 4 stroke not 2 stroke needle. One never knows.

Try losing those extended plugs. I may be wrong and it is P for projected, but I think the E stands for extended which means the electrode goes further into the chamber. That also messes with the heat range. And I think you mentioned that your bike is modified. I wouldn't trust an extended plug not to hit the top of the piston. Especially so since your engine is modified. You could try some modeling clay, or you could try some Champions just for ha ha's find homebase, and tune the idle following John's advice. There is a more complete description in another thread. Perhaps someone can post it. The carbs are two carbs in one. Slow speed running will be effected by the idle air mix/tune. You are at altitude. Check the slides for the correct cutaway at altitude, and for being equally cut. I think you did try different cutaways. Right? They can be made to be equal, and fine tuned with with some emory.

I apologize for not rereading the whole thing in one go. I am being lazy.

Last edited by btour; 12/07/17 2:18 pm.

Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#718028 - 12/07/17 2:21 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Geneva, Switzerland
HI folks,

Bike packed away for the winter- fuel tank drained and carbs drained,

However, managed to get these plug chops today on the last run (New N3C plugs that I had just received)

[Linked Image]

A beer to anyone who can guess the settings that got them looking like that.....

Brett
PS Btour - the E stand for 19mm thread length - the same as the N3C - not extended. Idle is good, takes few minutes to warm up and run without throttle and idles nicely at 900 RPM.

Last edited by BrettF; 12/07/17 2:25 pm.

3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
#718029 - 12/07/17 2:34 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
Joined: Mar 2005
Posts: 10,001
John Healy Online content
John Healy  Online Content



Joined: Mar 2005
Posts: 10,001
Boston, Massachusetts
Quote
Should I have said " our European octane number is about 5 higher than the north american octane number, for the same fuel" to make it unambigious or am I missing something?


In the US we use two octane numbers. The old Research octane number (RON) that is used in most of the rest of the world, and a more severe test to create another number referred to as the Motor octane number (MON). The number on our pumps is an average of the two numbers. Research + Motor divided by 2. You see that R+M/2 (also known as the Anti knock index (AKI) displayed on the pump.

Our 93 AKI, as shown on the pump, would have a RON # of at least 96, or higher. So a 93 AKI would be equivalent to, or have a higher RON, than your 96 RON fuel. Because the parameters of the MON test are much more aggressive, it better reflects the fuels ability to prevent detonation. The problem is the MON # is never posted on the pump, only the AKI average of MON and RON.

Let's look at some possibilities: MON 88 - RON 98 (88+98/2 = 93); MON 87 - RON 99 (87+99/2 = 93); MON 86 - RON 100 (86+100/2 = 93). With the AKI as the Motor Octane Number goes down the Research octane number goes up for a given AKI. The only thing you can find out about the spread between the RON and MON numbers is they tend to be about ten numbers apart. It would be more helpful for our engines if we knew what the MON number really is.

With all the talk about alcohol in the fuel, ethanol has a RON of 109 and a MON of 90 giving it a AKI of 99.5. It helps supplement the loss of lead.

Also because altitude effects the density of air, as you climb to 5,000 feet, and above, few, if any gas, stations will offer 93 AKI fuel.


#718030 - 12/07/17 2:38 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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kommando Online content
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You fitted larger mains and dropped the needle a notch or 2.

#718036 - 12/07/17 3:30 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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But did it balk when you snapped the throttle open?

What are you doing those runs at that time of the morning in the cold? Are you a polar beer?


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#718038 - 12/07/17 3:37 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Not fair. You did two things 1) changed the heat range of the plug 2)? advanced the timing.

I forget the equivalence for NGKs I had 7's in my bike. 8's are hotter? So the champions would be a cooler plug? Asking because I forget.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#718040 - 12/07/17 4:40 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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htown Online content
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NGK 8's are cooler than 7's. NGK plugs the higher the number the cooler the plug. Champions the higher the number the hotter the plug. If you study the plug charts, NGK and Champion appear to be a half step off in being equivalent. In other words an NGK 7 would be half way between a Champion 3 and 4. On most bikes this doesn't seem to matter, but it might be useful for fine tuning.


1978 Bonneville T140E
1974 Trident
1970 BSA Thunderbolt
1971 Norton Commando
1972 Norton Commando
2-1974 Norton Commandos
2004 XL 1200R Sportster

Everything will be alright in the end. If its not alright, its not the end.
#718048 - 12/07/17 5:36 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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argyll. scotland, uk
In the UK we have similar fuel options, my A65 gets the number 98 stuff usually, but runs OK on the cheap stuff, gets less mpgs on the lower numbers. otherwise I cant tell much difference. CR about 9:1. Ignition is retarded a degree or so from stock .
I think you need richer slides, futzing with the pilot s wont stop it gasping if the slide is too lean. Your last WOT chop looks OK to me.
bike doesnt need to be moving to get the slides right, if it spits back and gasps when the throttle is opened from idle then the slides are too lean.
What is your intake and exhaust system, stock with filters? , bellmouths? megas? A less restrictive set up , no filters and mega might need a big jump in mains from std.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
#718075 - 12/07/17 8:12 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Maui Hawaii
I'd say you dropped the needle all the way to lean. The earlier plugs were super rich at low speeds, but appears that the idle settings were just about typical for this bike.

Other than re-setting the floats which might have been way too high, I can't explain why the plugs would soot up like that. Unless you returned the ignition to the factory perhaps?

All this armchair quarterbacking is pretty frustrating, so I'm dying to know what the solution was.

Cheers,
Bill


Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
#718078 - 12/07/17 8:40 pm Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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I can't see any significant difference, I've never attached much to carbon around the rim, both insulators are very pale and the ground electrodes are almost entirely burnt clean. I'd hazard no major changes, just different plugs?

#718114 - 12/08/17 6:24 am Re: Bonnie Carb Jetting help needed [Re: BrettF]  
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Many of you had touched on bits of what happened. Beers all around! pint beerchug pint. That's the problem with virtual bike clubs.;-)

I have not solved the problem unfortunately, but I'm getting to understand it better.

Firstly I removed the inline fuel filters. "Ah-ha", you say, "I knew those cause more problems than they are worth". Unfortunately, it was not that easy, because they were so clean they really had certainly not done any useful work over the last years. However, took a run afterwards, and plugs looked identical to before, too white.

Tried to put some new emgo air filters in (I know, this would make the bike leaner if the filters were blocked before, but I figured whiles I'm rejetting i should try to make everything as pristine as possible) However they fitted so badly that I went back to the old ones after blowing them out, but they seemed perfectly clean still. (The emgo's were slightly too small in diameter and slightly too thin. The front and back plates had freeplay in and out when these filters were installed. Another few bucks wasted.) anyone else found this with emgo filters?

So I put the timing back to where it had been before, just above 36 degrees. Put the idle air screw back at 1.5 turns, went for a ride, and same as before, white plugs but now without the very sooty plugs from very rich idle.

So I finally dumped the petrol in the bowls on the side of the road and pulled the main Jets (don't tell the local flora folks), continued my ride, and as expected at 3/4 throttle Bike started 8 stroking. So now at least I know that the bike can get to this overly rich point at WOT. The plugs looked disgusting after that.

I had a selection of new large single jets for the T110, so i put a 260 in the left and 270 on the right. Went for a short ride, the right plug started cleaning up a little bit while the left one was still very sooty.
I put the 230 plug back on the left which was the next smallest one I had, put in new Champion plugs N3C, and went for a ride.

And that's how the pictures above were taken. I think a 240 and a 280 setup might be perfect. However, I would feel quite uncomfortable riding a bike with such a big difference in main Jets.

Unfortunately, I did not have time to swap the carburettors around left to right, which would have decisively pointed to a carburettor problem or an engine problem.

So, I don't have a real solution yet...

Anyone ever seen a bike need such different mains?

At this point, I'm tempted to get a TR6 head!

Cheers for the help all.




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Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
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