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T100R pinking bad - advice?
#141286 05/14/08 12:27 am
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OK folks,

Need some advice here.

My 500 is pinking really, really bad. This happens as it gets warm,say, about 25 minutes of riding. It gets progressively worse as it get s hotter. Bad enough that it becomes near impossible to take off from a dead stop without it pinking all over the place. Thing is, it runs great when the motor is cold. I can whack the throttle open in the first part of the ride and she pulls great. But once she's warmed up, the pinking starts.

Some specifics...

- 1971 500cc T100R
- Timing is dead-on (strobed)
- Boyer
- Valve adjustment dead-on
- Compression 130 in each cylinder
- Brand new Amals adjusted as best as I can tell (1.25 turns out from full-in; needle in the first position)
- Unleaded 91 from Shell

Thoughts? Ideas? Sage-like advice?


McQueen
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Re: T100R pinking bad - advice?
#141287 05/14/08 2:27 am
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What size main jets? Here in Jersey I had to up the size to 200 mains with #2 1/2 slide. Book calls for 160's, caused the motor to seize after a short run.

Re: T100R pinking bad - advice?
#141288 05/14/08 3:21 am
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We use Chevron 94 and go out of our way to find it.


The roadside repairs make for the best post ride stories.
Re: T100R pinking bad - advice?
#141289 05/14/08 4:19 am
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Quote
Originally posted by rockersj:
This happens as it gets warm,say, about 25 minutes of riding. It gets progressively worse as it get s hotter.

- Unleaded 91 from Shell

I'd guess airleaks around carbs or manifolds when hot leaning mixture out, but then you'd probably be spitting back thru the carb too.....

I seem to have read some threads here about staying away from Shell gas.....do a search and see what you find.......I've used BP 93 exclusively now for a couple of years and have had good luck with it...

I also run Boyer and run it slightly retarded....~36 degrees BTDC...

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: T100R pinking bad - advice?
#141290 05/14/08 6:17 am
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SJ,

Can you post a picture of your plugs (both) taken with the engine all the way up to temperature at the side of the road where you pull them after cutting your engine (no idling)? We need to see stuff as we're just guessing otherwise.

You said timing spot on, but I'll bet you have never verified TDC is where you think it is? You could be carefully timing it a couple of degrees advanced - that'd do it.

Blapper redwine

Re: T100R pinking bad - advice?
#141291 05/14/08 10:11 am
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Ok, some nice ideas.. but... you are in Califax, and we got sh** for gas. 91 is the best pump gas available, and somee of that is suspect... So you must make the engine run on what we got, unless you go to race gas, which is not practical for street riding...

So, we need to look at the issues. First it is NOT a main jet issue if you have a problem taking off from a stop.

It could be an air leak issue, easy to check, so I would suggest you do that first. But, how does it idle when hot..? If it idles good, then not likely an air leak, but still worth checking (do the easy stuff first).

Also just for grins, make sure you have a good gas tank vent.. and good fuel flow, even though your symptoms do not match, this is easy to check.

And yes you may need to retard the ignition timing. You can retard the timing until the power goes away. That said, the advance curve comes in to play at low revs and especially when taking off from a start. Boyers usually have a good timing curve.....

OK so if timing does not help you, and no air leaks, then it is time to richen up the carb settings. This can be frustrating... because the symptoms you describe could be slide cutaway leaness. But then you say it runs good cold, so slide cutaway would affect that a bunch too.. Hmm... raise the needles... all the way and see what that does. IF it helps then there is your answer. Hopefully that is enough adjustment to make it happy. If not, then anything from pilot jet size to slide cutaway to needle jet may need changing to fix this. The last tuning step is the main jet, on the street you rarely use the main jet, so do that last.

Keep in mind Cali "fuel" is oxygenated which is designed to lean out carb type engines. Modern engines with an O2 sensor will adjust for it...

Good Luck, tell us what you end up with...

Cheers..!

Ron

Re: T100R pinking bad - advice?
#141292 05/14/08 10:23 am
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how do know your timing is spoton...has it been strobed at full advance (5000rpm) with the timing marks KNOWN to be correct..change yo r fuel to highest octane you can get...correct plugs gapped correctly...carbs setup right, and float level right...just because it/they are new means nothing...heas of carbon on the piston crown(longshot but maybe)


1970 tr6r dryframe
Re: T100R pinking bad - advice?
#141293 05/14/08 10:50 am
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Interesting comments re the effect of modern gas. Not to hijack the thread but I have, perhaps, a related question.

Rode my T100 15 miles to the garage to get it inspected and the thing ran like a cat on fire! 15 mins for an inspection during which time the bike was never out of my possesion. Get on bike to ride home, and on the first straight away open the throttle in 3rd gear, at about 45mph, and the motor bogs, same thing in 4th but worse. 1st and 2nd gear roll on seems fine.

Had bike out last week and it ran perfectly for 1/2 hour of continuous up hill and down dale riding at anything from idle to 70+ mph.

I generally fill up at the local Mobil station on whatever the highest octane gas they have available, typically 94. Last refill about 10 to 14 days ago.

Any ideas? confused


1971 Triumph T100C
1974 Honda XL350
1982 Suzuki GS750T
2000 Honda VFR800FI
Re: T100R pinking bad - advice?
#141294 05/14/08 11:43 am
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You should be able to test if the carb mixture is too lean by closing the choke and seeing if it runs better.



1965 Triumph T100SR
Re: T100R pinking bad - advice?
#141295 05/14/08 12:02 pm
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As mentioned, timing on a Boyer must be over 5000 rpm to get an accurate full advance. You may need to retard the timing to run 91 octane.

Is this on one tank of gas? I filled up my supercharged Miata with high test and it pinged like crazy everytime I got on the throttle. The station had 87 in the 93 pump. I had to disable the blower to drive the tank empty.

Tom Graham

Re: T100R pinking bad - advice?
#141296 05/14/08 1:30 pm
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Bodgers have been known to reface an exhaust valve to a sharp [hot] edge.


1969 TR6R
7.62 x 51 is not a maths puzzle.
Re: T100R pinking bad - advice?
#141297 05/14/08 1:52 pm
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Matt's T,

Sorry, forgot to mention that yanking the choke around didn't make the slightest bit of difference, either with the motor under load or cruising.


I'll clean out the carb this weekend and put some new gas in. If that doesn't help it'll be strobe and rotor time. :rolleyes:


1971 Triumph T100C
1974 Honda XL350
1982 Suzuki GS750T
2000 Honda VFR800FI
Re: T100R pinking bad - advice?
#141298 05/14/08 4:23 pm
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Toughening a motor against detonation starts with the selection of the bits, preparation and assembly. As Tiger mentioned there are some causes like sharp edges around the piston's valve pocket, a standard diameter copper head gasket used on a significant overbore, or a imporperly designed or refaced valve margin. There are dozens of these little mistakes that can add up to detonation. All this continues through final tuning and selction of fuel. Often the cause is a series of what seem to be unrelated mistakes, that when all present, cause the problem.

In the old days we didn't have to be concerned with all of these details as we could just throw some higher octane fuel at the problem. Now we have to understand the causes of detonation and take steps to insure it doesn't happen.

Several good suggestions have been given, but as there are many reasons motors detonate, some obvious others not, can you share some history?

Re: T100R pinking bad - advice?
#141299 05/14/08 4:24 pm
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Oh, and if you haven't verified the timing mark on your rotor you are wasting your time!
John

Re: T100R pinking bad - advice?
#141300 05/14/08 4:56 pm
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John,

At TDC, I checked that RH valves are at same height in their travel, and the pointer inside the inspection cover is right on the timing mark on the rotor. Is that what you mean?


McQueen
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Re: T100R pinking bad - advice?
#141301 05/14/08 5:34 pm
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I'm with John on this one. In California where I'm from we had the crap gas way before anyone else and we dealt with these problems sucessfully already. I took the advice of some excellent car mechanics and began to look at the combustion chamber first before I did anything. This led me to polishing the tops of pistons to eliminate the razor sharp edges of the valve cutaways, paying special attention to the head gasket edges protruding into the chamber, making sure that sparkplug threads do not protrude into the chamber and so on unitl you have no sharp edges in there to act like a glow plug. All the bikes I have built since then run stock jetting and advance without that annoying and destructive pinging you are experiencing.
Bill


Bikes
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1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Black Tiger"
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Re: T100R pinking bad - advice?
#141302 05/14/08 6:03 pm
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rockersj- Your engine isn't just full of carbon is it? This caused my bike to keep running after the ignition was switched off so was probably pinking down the road but at that time I hadn't been giving it much stick so I didn't notice much. The carb was way to rich but before I put it right I had to get all the carbon out and there was masses of it. I would probably have damaged it if I had simply reset the carb and made it run hotter without the clean out.

What grade plugs have you got?

Have you got a tdc plug hole behind the cylinders on that machine?

Probably is over advanced timing, however. If your battery is bad the Boyer may be going barmy too! Have you got the points to put back in and try?

Dave

Dave

Re: T100R pinking bad - advice?
#141303 05/14/08 6:11 pm
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Dave,

Using the Champions recommended for it.

I have the TDC hole. Used it to find TDC and verify the timing mark on the rotor.

The local Brit shop strobe timed it for me.

I'm going to try a new battery since the one I have came with the bike and is questionable. Plus, I just replaced the wiring harness and the stator (problem started prior to these replacements). New battery won't be a "wasted" purchase.


McQueen
+ Ton Up Club NorCal +
Re: T100R pinking bad - advice?
#141304 05/14/08 6:14 pm
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Rock: The timing mark SHOULD NOT be aligned with the pointer at TDC!!!!! If your pointer aligns with the line on the alternator rotor at TDC and you use the pointer/line to time the bike with a strobe the bike is seriously out of time! Check to be sure the pointer aligns with the line when the piston is 39 degrees BTDC!

The pointer should be aligned with the line when the piston is 39 degrees before top dead center ( BTDC).
There is a tool to put into the hole Dave Jones is referring to above.

The tool can engage the flywheel at two positions. 1. At TDC and 2. At 39 degrees BTDC. Be sure you use the slot in the flywheel that aligns the piston at 39 degrees BTDC.

Re: T100R pinking bad - advice?
#141305 05/14/08 7:05 pm
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Toughening a motor against detonation starts with the selection of the bits, preparation and assembly. As Tiger mentioned there are some causes like sharp edges around the piston's valve pocket, a standard diameter copper head gasket used on a significant overbore, or a imporperly designed or refaced valve margin. There are dozens of these little mistakes that can add up to detonation. All this continues through final tuning and selction of fuel. Often the cause is a series of what seem to be unrelated mistakes, that when all present, cause the problem.

In the old days we didn't have to be concerned with all of these details as we could just throw some higher octane fuel at the problem. Now we have to understand the causes of detonation and take steps to insure it doesn't happen.

Several good suggestions have been given, but as there are many reasons motors detonate, some obvious others not, can you share some history?

Re: T100R pinking bad - advice?
#141306 05/14/08 10:05 pm
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thanks everyone. That's a lot to digest.


McQueen
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Re: T100R pinking bad - advice?
#141307 05/14/08 11:25 pm
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Look, just do the jets first. Its cheap and easy. Start one size up from what you have. Believe me I know. My motor would run good then nip up during a ride also run on after ingnition shut off. There I was redoing the bores TWICE. Also PJ-1 octane boost works well but you will still have a bit of pinging if you lug the motor. My motor runs like a raped ape now.

Re: T100R pinking bad - advice?
#141308 05/15/08 7:22 am
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Rockersj- You should have mentioned that your trouble started after some electrical work! Boyers are very sensitive to electrical faults, apparently.

Good luck and keep us posted.

Dave

Re: T100R pinking bad - advice?
#141309 05/15/08 10:43 am
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Quote
Originally posted by John Healy:
The pointer should be aligned with the line when the piston is 39 degrees before top dead center (BTDC). There is a tool to put into the hole Dave Jones is referring to above.

The tool can engage the flywheel at two positions: 1. At TDC and 2. At 39 degrees BTDC. Be sure you use the slot in the flywheel that aligns the piston at 39 degrees BTDC.
Rockstar -
This is not necessarily true, despite John's good intentions. I went back over the thread and couldn't find a model year listed. All you've told us is that you have a 500cc Triumph. That really doesn't tell us squat. Triumph made 500cc engines from sometime in the 1920's until 1973 or so.

We are all ASSUMING you have a unit twin, but the dual crank hole for the timing tool wasn't used until about 1968. Before that, there was only 1 hole and that was TDC.

Sorry to say, but even in a "Brit bike shop", unless the guy was about 50 years old you may have not gotten much for your efforts. The issue being that most young mechanics learn on Jap bikes that are 100 times easier to time. You can't simply put a strobe on an old Brit bike and then pat yourself on the back. Back in the 1960's you had to KNOW timing to set timing.

There's some good info here. However it's usually simple things that get you first. I'd start with the basic stuff: timing and carb air leaks. If your bike has a dual carbs, then when was the last time you replaced the balance tube? Those need replacing about every 2 years.

:bigt:


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: T100R pinking bad - advice?
#141310 05/15/08 10:46 am
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PS.

Oh yes, the only way your bike can be "pinking" is if it's been hanging around with the "poof boys" or "girly men".

The correct term is "pinging", aka "spark knock", technically known as "pre-ignition".


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
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