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#43803 - 07/28/05 10:35 am Re: "Detonation", by Kevin Cameron  
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Quote:
Originally posted by Mark Z:
apparently only at low throttle openings, because I can eliminate the detonation by opening the throttle wider. jetting change.
Mine does that too.


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#43804 - 07/28/05 10:54 am Re: "Detonation", by Kevin Cameron  
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Mark,
My A65 pinged horribly with the old 4ca points and advance. It was a major improvement since I went to a Boyer. You can see the less radical advance curve with a light. Also, I forgot to mention the most obvious. Higher octane gas really helps. Mine will ping (a little) on hot days under hard acceleration, at low rpms, on 93 octane pump gas. If I mix 3 parts 93 octane with 1 part 110 leaded, there is no pinging whatsoever. So I keep a can of the 110 from the local race track around. When I am out on longer rides and have to use straight pump gas, I don't push the bike as hard at lower RPM's. Just living with the reality of things.
Mr Mike

#43805 - 07/28/05 12:50 pm Re: "Detonation", by Kevin Cameron  
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Gordon Jennings tells a story about his early days learning to read spark plugs. He was at a major motorcycle event with a Velocette and was having problems. Gordon might have learned in school that the porcelian part of the plug should be between 700 and 1000 dgress, but like most of the people in those days he grabbed his plug and made his way to see Bobby Strohlman.

Bobby was Champion's field representative and was the guy with the wiffle at every major motorcycle and car event in the US. Wiffle as best as I can understand is term was used in the North East of the states to describe a military style hair cut with some hair left on the top which stood straight up, but I digress.

After looking at the offending plug Bobby was heard saying, "Gordon, you're magneto's points have oil on them." Gordon returned the Velocette and removed the magneto's points cover and sure enough the points were covered with oil. A bit of cleaning and Gordon's Velocette was soon back on full pipe.

I mention this because there was little information availbable to the young gearhead in the 50's and 60's when I first got oil under my finger nails. All we had to go by was that God, awful Champoin spark plug poster which displayed all sorts of things that one could only hope he would never see, or if he did that it was in some one elses motor.

It wasn't until Smokey Unik started to talk about reading spark plugs did I start to see any of the "secrets" start to come out. Smokey was the first person I knew who cut away the bottom of the plug so he could look at the porcelian (I am sure others did it before him, but he was the first guy I knew of that passed this on to the public). As Ron indicated above this opens a whole new world on how to read spark plugs.

The answer to why your motor pings at low to mid-throttle openings is in the reading material included as links in this post. Consider yourself lucky to have such a vast source of information a click away. Sure you have to sort through the miss-information, but all us old timers had was that lousy Champion poster and some rumors. Few of us could walk up to Bobby Strohlman and have him check the plugs on our Indian Chief.
john
edited for readability :rolleyes:


#43806 - 07/28/05 10:29 pm Re: "Detonation", by Kevin Cameron  
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Yes that dragracer link makes very interesting and informative reading (thanks Dave).

BTW, I have used those fine wire gold palladium plugs (NGK8EV's) for about 4 or so years now in my stock BSA Rocket Three. They have never showed any tendency to foul that is supposed to be a problem with the BSA/Triumph triples. So I really like them. However, don't think that they are available any more. Think that they have been replaced by Iridium fine wire plugs (BR8EIX). Methinks these might work well with Boyer Digital systems that call for resistance in the ignition system.

Getting back to the subject of detonation, I've decided to go with 9.5:1 compression ratio pistons on my re-build in order to lessen the risk of another piston failure. However, will still try to follow the advice of the gurus on all of the other factors that could lead to detonation.

beerchug

#43807 - 07/29/05 2:00 pm Re: "Detonation", by Kevin Cameron  
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and they laughed at me when I used early squish band pistons with the late Daytona head...

Fill 'er up with pump gas and let 'er roll!

Really this has been an amazingly informative thread for me, as a newby to the finer points of engine tuning. Thanks to all you gurus for sharing the info!

Kyle beerchug


Kyle#44x

1969 T100R Daytona
1979 Powroll Honda XR250 "Dallas Baker" flattracker
1975 XL350 project bike
#43808 - 07/29/05 2:54 pm Re: "Detonation", by Kevin Cameron  

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If you're going to hand-fit squish bands on pistons for max efficiency, remember that the thrust axis clearance (front-rear) is always bigger than the lateral axis clearance (left-right), since the piston rocks quite a bit @ TDC as a function of rod ratio, bore size, skirt clearance etc. but is almost stable in lateral location (i.e., not disturbed by reversing @ TDC). What you're left with is no longer a toroid with a continuous cross-section as the squish band, because its section thickness is higher (at least .005", perhaps as much as .010") front and rear. IMHO a small bore motor like T150 could go as tight as .020" @ the pin axis.

#43809 - 08/08/05 4:18 pm Re: "Detonation", by Kevin Cameron  
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O.K., have read the thread more closely (tho' not the links). Can't comment on the racing applications as I don't race, but am wondering about the typical street applications here.

Unless I missed something, there is a "curve" of lean that has to be rounded before the temps start to drop.

Using modern Japanese motorcycles as an example, they're essentially set at "factory lean" settings. They're also laden with EPA stuff from both the carb & exhaust sides of the engine & many are also water-cooled. There's probably some modern metallurgical changes as well. Will assume that since "too lean" is dangerous, the factory must have rounded that "curve" in designing their engines.

If one makes changes to either the carb or exhaust side of these modern bikes, they almost invariably have to enrichen their jetting. Am I correct in thinking that the alteration to carb or exhaust has brought the state of tune "back" to the dangerous side of the "curve" ?

More importantly, I'm concerned about trying to apply modern technology to 30 + year old Brit bikes that have no water cooling & no EPA gear installed on them.

Would this be considered accurate ? :
Too Rich or Too Lean = Bad in either direction for a variety of reasons

Slightly Rich = Cooler running (Safe ?)
Slightly Lean = Hotter running (Less safe ?)

For normal street applications in running these old Brits, wouldn't it be better to strive for "Slightly rich rather than lean of any degree" ?


"Factory Stock Is A Suggestion Only"
#43810 - 08/10/05 2:37 am Re: "Detonation", by Kevin Cameron  
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FWIW, that makes a lot of sense to me. Street use sometimes requires travelling at low speeds after a hot run, something race bikes don't have to do. I've always felt that the factory jetting for Amals was intentionally on the rich side at idle for this reason. Yes, a little rich = cooler; a lot rich = build up of carbon in the combustion chamber, which retains heat... oops!

We haven't talked about fuel much. My Chilton book for BSA (circa 1973) recommends a minimum of 95 octane (which would be by the old rating system and would also be leaded), and I don't remember ANYone's Brit bike pinking back in the Seventies. In the Eighties, running 1/2 AV gas with pump gas COMPLETELY eliminated the pinking in my '67 Lightning.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
#43811 - 08/10/05 5:31 am Re: "Detonation", by Kevin Cameron  
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Much appreciated, Mark...

Was just trying to think this thru, to clarify the difference between racing applications & street applications.

Racers will always look for the optimum performance they can get from their machines, pushing the envelope, trying different things to see what works best & then even better & that's great! It's as it should be for them.

But for those of us who ride these Brit bikes for street use only, am thinking that the old tried & true methods (the ol' "better rich than lean") might still be safer is all.

Thanx again...


"Factory Stock Is A Suggestion Only"
#43812 - 08/10/05 3:35 pm Re: "Detonation", by Kevin Cameron  
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Riff Raff,

Personally, I think you are on track with your theory, however, it all comes back down to reading plugs.

From what I see, a lot of folks who want to tune just slightly to the rich side are really running extremely rich. If you read related postings here and follow some of links, there is plenty of info on what a plug looks like out of a properly tuned engine. It's general appearance isn't "coacoa colored" as some shoot for. If your state of tune develops this color plug in a couple of hundred miles, your too rich...same color plug in less miles, extremely rich. Those people who are happy to get a couple of hundred miles out of a set of plugs before fouling (for the sake of piston safety and cooler operating temperatures)are creating more problems than they are preventing. You can recognize these people who prefer the "fuel soaked" bikes as they are the ones with 3 or 4 sets of plugs in there tool bag and their bike is the slow one with poor gas milage. You may not want "racing optimum" tuning but you shouldn't be too far off from the right mixture. Race bikes are tuned for optimum/efficient performance based on their engine build...yours should be tuned for your engine build (stock or otherwise). A properly tuned engine requires a little warm-up time when cranking cold and if not, may be a tale-tell sign that your still too rich on the low end.

Something else to consider is that modern fuel, which is formulated to burn cleaner, doesn't color new plugs as much or as fast as the good old leaded fuel from the past. Therefore, what appears to be slightly rich with modern fuel would probably result in a fouled, sooted plug on the old stuff.

Riding style, IMO, has to be considered when concerned with top-end health. Personally, I use 2500 rpm as my minimum when riding. Down-shifting is cheap and to me, anything below is just lugging it around. Sure, it sounds cool to lope around like the big-inch, long-stroke V-twin, but it is not a HD and subsequently, your engine will hate you for it. These engines were designed to rev and although it may contradict how you think, it is easier on the engine if it is allowed to turn the rpm's. Besides, a well tuned Triumph turning a few RPMs sounds better than potato, potato, potato, anyway.

When tuning my most recent bike and starting from the rich side, my oil tank would run around +/-160 degrees (could hold your hand on it). After tuning in to the proper plug readings, the temperature went up a few degrees (discomfort to the hand, shortly) but the performance increased 50%. These engines were designed with clearances at operating temperatures as parts grow, especially, aluminum. If it is not up to operating temps, essentially, your reducing clearances. On a semi-related note, Caterpillar did a study on their engines at elevated temperatures (2 to 3 times normal temps). They determined that the performance was increased and the component/bearing life was improved...the only pit-fall to these temps was the development of a practical, road-going, cooling system that would handle these elevated temps.

Be cautious but, don't take it to the extreme. Nobody wants to destroy what they just built but if you don't tune close to right, your settling for second rate performance, wasting gas/plugs and will have to deal with the problems associated with the too rich condition not too far down the road.

Z

#43813 - 08/10/05 11:24 pm Re: "Detonation", by Kevin Cameron  
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Interesting read, Z, & I thank you as well.

Before tearing down the top-end, had been running much too rich & the carbon build-up was a PITA to remove & no doubt had some serious temps building up in there as mentioned by Mark Z & others. Tho' it hadn't holed a piston, there was some minor blow-by past the worn rings. Replaced the rings using the same pistons.

In the other thread ("Metal Shavings") on the Triumph Board, had mentioned the re-jet. Dropped the main jet down 2 sizes & she's running leaner than ever before & feels fine. The plugs don't show carbon build-up, but they're a lightish tan (no spooky "white" markings). In reading your post, am guessing that I may be on the "leaner side of slightly rich" & definitely in a much safer place than before the re-jet. Actually was a bit concerned that I might be running too lean, but now am feeling a lot better simply knowing that the state of tune has been brought closer to "right".

As per your post, she does require a warm-up after a cold start, where previously, she'd fire & go immediately (too rich). Have been taking it easier on the engine since doing the work, but there's definitely times when I'm giving her a healthy blast during each run. Before the teardown, had ridden the dog-snot out of her & considering the too rich state she was in, am VERY lucky that there was no major breakdown.

When you refer to the Caterpillar study & the enhanced performance with elevated temps, I'm following what you're saying. It's the part about Caterpillar having to add a cooling system to handle the increased temps that keeps me thinking that increased temps on air-cooled Brit bikes also have to be taken into account & carefully watched.

All in all, even tho' I still subscribe to "better rich than lean", believe that I've finally gotten her to a "much less rich" place that I'm actually comfortable with.

Thanx again, Z, very much!


"Factory Stock Is A Suggestion Only"
#43814 - 08/11/05 12:39 am Re: "Detonation", by Kevin Cameron  
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RR,

Glad to hear your getting it sorted and feeling comfortable about it. Being at ease with your machine is based on a level of knowledge of your bike. You, now, know what you have and your in control of its destiny.

On the Caterpillar heat thing, the point I was making is that the balance of the engine absorbing a few more degrees from heat sink due to the mixture being closer to right has no ill effects and may even improve things. If your plug reading is spot on, the top-end temp is self regulating. Power is heat and vise versa. Can't have more power without more heat.

The general consensus, for some time, is to scare the hell out of everybody about lean conditions and rightly so due to so many people having bad experiences starting out on the wrong side of right. It is a frightening thought that you will melt down a year-long project in 5 minutes as you don't know where you've gone from the green into the red.

Competent plug reading is where its at. There are people that can tell you volumes about your bike (other than the obvious) by looking at the plugs (under a bright light with magnification). We need to envy those people and learn from them. And I believe that this is the key for those who are tired of less than optimum performance from their machine that has everything required to run right but doesn't. Anybody with a service manual can assemble parts, but to have them work in harmony, efficiently...that is an art that is earned through study, research and the never ending desire....and it keep you young, to boot.

Z

#43815 - 08/11/05 4:51 am Re: "Detonation", by Kevin Cameron  
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So, with the plug reads being spot on (or at least pretty close to right & not straying into the danger zones of either too rich or too lean) the top-end temps are self regulating & the machine will be put thru less stress under normal riding conditions ? Got it.

Yep, know of a person locally who melted down his top-end in very short order by running too lean. He'd been given the incorrect jetting advice from another bud & as you said, it happened before he even had a chance to realize there was a problem.

Can appreciate that plug reading is an "art" & more power to those that have spent the time to refine those reads. At this point, am content to be much closer to right as opposed to definitely too rich like before. But I also agree with you...continuing to learn keeps the Journey exciting & refreshing!

Saw a post somewhere on these boards where another member complimented you on being a "philosopher". They, also, were "spot on". bigt


"Factory Stock Is A Suggestion Only"
#642733 - 03/03/16 4:41 pm Re: "Detonation", by Kevin Cameron [Re: Anonymous]  
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hey folks

this ancient conversation is a very useful thread, but one that has been curiously difficult for me to find, what with departed or banned members, posts that the search engine cannot find but that i can see on my phone, and no references in the list of threads on the board.

i'm posting here so that the thread is more easily retrievable while i go through the links in it.

here's the original article:

http://www.factorypipe.com/t_deto.php

thank you for your patience.


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#642757 - 03/03/16 7:06 pm Re: "Detonation", by Kevin Cameron [Re: Anonymous]  
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<http://contactmagazine.com/Issue54/EngineBasics.html>Many of the machines we cherish were engineered for fuels that are no longer readily available. When the laws changed (USA) in the late '70's Sunoco 260 became a R+M/2 fuel of 97.5 and then it dropped to 96. Still adequate for '60's muscle cars and bikes requiring 100ron. 93 don't cut it, and 91? laughing . And you guy's across the pond still had 5star long after the good stuff went away over here. I'm amazed by the lengthy debate and destroyed engines. Ante up,run the proper fuel,or drop the compression ratio.I think there is a large,untapped market for quality,forged, Made in USA/EU 8:1 pistons for T120/A65 and other britbike engines.Please examine<http://victorylibrary.com/mopar/otto-c.htm> if you think dropping one full point in compression is the end of the world. Race and street are apples and oranges.


1969 BSA A65T w/A70 engine
1970 Royal Enfield Interceptor S ll
#642760 - 03/03/16 7:19 pm Re: "Detonation", by Kevin Cameron [Re: Anonymous]  
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You will also find that Cameron article in an old issue of Vintage Bike.


#642799 - 03/04/16 5:55 am Re: "Detonation", by Kevin Cameron [Re: Anonymous]  
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Never seen this thread before interesting material indeed.


Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
#642846 - 03/04/16 1:50 pm Re: "Detonation", by Kevin Cameron [Re: Peter R]  
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Going back to Ron's comments on page 1:

Bantams (BSA's 2 stroke) are known to seize on long downhills. This is usually because you close the throttle and shut off the gas.....which also shuts off the oil flow.

Some of this isn't really all that complicated.

and....the articles are great reading.


Alan
Cleared m out....left only
59 BSA Bantam (Trials)
78 Triumph Bonny (UPS)
02 Suzuki GS500
#642946 - 03/05/16 10:08 am Re: "Detonation", by Kevin Cameron [Re: Anonymous]  
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Great to revisit this old thread. I'm finding this stuff to be relevant at this point as I just got the new race bike on the track last weekend. Aermacchi's are a pretty similar design to Triumph head and pistons and I was able to apply my rather basic tuning skills. I thought I had carb jetting pretty close, bike ran strong, sounded good, but was still looking lean on the plug. Rob H suggested to try a colder plug. Color on the plug improved. Piston crown looks good, too.
Would anyone like to comment on the "line" that forms on the curved plug electrode which can be an indicator of where the motor is timed?
Mike

#642948 - 03/05/16 10:12 am Re: "Detonation", by Kevin Cameron [Re: Anonymous]  
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I used to regard that line as being a indication of timing. Until I had to adjust my timing, the mark never moved.


beerchug
#642965 - 03/05/16 12:10 pm Re: "Detonation", by Kevin Cameron [Re: Mike Baker]  
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#643016 - 03/06/16 1:28 am Re: "Detonation", by Kevin Cameron [Re: Mark Z]  
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Originally Posted By Mark Z
FWIW, that makes a lot of sense to me. Street use sometimes requires travelling at low speeds after a hot run, something race bikes don't have to do. I've always felt that the factory jetting for Amals was intentionally on the rich side at idle for this reason. Yes, a little rich = cooler; a lot rich = build up of carbon in the combustion chamber, which retains heat... oops!

We haven't talked about fuel much. My Chilton book for BSA (circa 1973) recommends a minimum of 95 octane (which would be by the old rating system and would also be leaded), and I don't remember ANYone's Brit bike pinking back in the Seventies. In the Eighties, running 1/2 AV gas with pump gas COMPLETELY eliminated the pinking in my '67 Lightning.


Wow, it's weird to read my own words from eleven years ago; so much has changed since then. Since then I converted the bitsa back into a swingarm frame, rebuilt the engine, lowered the gearing to 20-47, and switched back to stock replica (Armours)silencers. Still had occasional pinking. Then, in the fall of 2013, I ran the bike without oil in it for about 20 miles and trashed the lower end. Then I spent the next two years rebuilding the engine once again, this time with a '65 ball-bearing lower, crank, and connecting rods.

To get back on point, since this last rebuild, I've experienced no pinking whatsoever, and this is with no overt tuning changes. Here's what's different and what's the same:
Different:
- Ball-bearing lower (already mentioned) and balanced crank (never did that before). New big end shells (of course). TS bush was the original and was within spec. Polished conrods (never did that before either).
- OE cast iron oil pump from a '71.
- New camshaft and cam followers. (The old camshaft was worn down pretty good. It's now apparent that this was due to running the wrong valve springs and not the lack of oil.)
- New valves, valve guides, and new *correct* valve springs (thanks to Ed V.).
- Replaced the two six-volt coils with one 12-volt dual lead coil (Emgo HD Sportster knockoff).
- Proper break-in procedure (now that I've learned what that is).
The same:
- Same 9:1 Taiwanese pistons with new Ricor rings. Bores were within spec and just required honing.
- Same Mik VM32 carbs with the same jetting.
- Same Boyer analog ignition, with same timing (I've always set it to spec, 34 degrees BTDC, or just a hair below.)
- Same stock replica exhaust.
- Same fuel (I run only Sunoco 93).

I don't know which of these changes eliminated the pinking, perhaps the combination of them all. The bike certainly runs better than it did, smoother, faster, revs higher, which I've attributed mainly to the crank balancing, but I'm thinking the combustion would be affected more by the cylinder head work.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
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