Pinging, detonation, pre ignition - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 30 (permalink) Old 04-23-2019, 08:43 AM Thread Starter
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Pinging, detonation, pre ignition

There'a a lot of misunderstanding on vintage bikes forums about the effects of lower octane fuel and the potential problems it causes...I believe once you understand abnormal combustion ,you can deal with effectively one way or another.
This short video by Kevin Cameron is easily understood...Cameron is considered to be a leading motorcycle engineer and theorist..His many articles are worth reading



This is an article by Allen Kline who was the head General Motors emissions engineer.It's also fairly easy to follow and often quoted as an excellent expalnation

http://www.contactmagazine.com/Issue...ineBasics.html
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post #2 of 30 (permalink) Old 04-23-2019, 09:05 AM Thread Starter
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This is an example of detonation (pinging) damage on my dual Triumph engine land speed race bike.. Unknown to me the supposed fresh race gas was not fresh, the engine went into detonation at high rpm, the piston heated and seized quickly...This is an expensive forged piston, a stock cast piston may have failed causing catastrophic engine damage.



This is a 650 Triumph engine a friend wanted me to fix... A classic case of pre ignition punching a hole in the piston...it was caused by lugging the engine on year old gas....There is no pinging to alert the rider, it just happens in a second as mentioned by Kevin Cameron...


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post #3 of 30 (permalink) Old 04-23-2019, 09:10 AM
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Out of curiosity, I wish I knew why I donít detect any ping under any circumstances. I know I ride fairly flat roads in my area compared to many parts of the country, but still, most people have a problem with it, donít they ? Or am I over estimating the amount of people that have an issue. Itís not like my bike is in a super state of tune, itís not. Gearing is higher than normal, that should make it worse. Stock points and advance mechanism ( new springs ) Modified air box with Uni filters, straight through short megaphones, Barnett clutch. I use 10% corn premium fuel of any brand available when Iím not near a station that sells corn free stuff. I use SeaFoam with every tank. Iíve had cars that pinged on these same roads. Iím not complaining, but I do wonder why I never have a problem with it.
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post #4 of 30 (permalink) Old 04-23-2019, 10:20 AM Thread Starter
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Cam timing is very important in regards to detonation....Stock T140 750 cam timing is more cause of detonation than in earlier 650 engines..
A sound Triumph can and will tolerate a brief period of light ping from time to time..I know this from experience over the years...Pre igniton will kill a Triumph in two seconds...

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post #5 of 30 (permalink) Old 04-23-2019, 11:53 PM
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tony, how old was the gas on your double?

was it out of a sealed can?

i be kevin
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post #6 of 30 (permalink) Old 04-24-2019, 12:00 AM
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Someday Iíll correct the cam timing. Though Iíve only owned the bike a few years the PO didnít appear to be mechanically inclined and heíd owned the bike for many years. Iíd be surprised if anything had been done to it at all.
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post #7 of 30 (permalink) Old 04-24-2019, 06:21 AM Thread Starter
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Quote:
Originally Posted by speedrattle View Post
tony, how old was the gas on your double?

was it out of a sealed can?
It was in the original tightly capped can, about 3/4 full, but about 6 months old..I made a mistake ..Why one piston out of four had a problem despite all having the same clearance . timing and jetting is anyone's guess..My single engine bike was run on fuel opened a month before with no problems..
Jim the dyno guy I use has equipment to to test the RVP of gas and has found new sealed cans of race fuel do not met specifications sometimes...As you know there's more to a fuel's resistance to detonation than just octane rating..
Are you going to try and dyno the race bike this year?

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post #8 of 30 (permalink) Old 04-24-2019, 02:15 PM
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shoot, i'm having so much trouble getting wheels on the machine i don't know whether i'll have time to dyno it or not. i'm having to use outrigger plates for the front wheel bearings in order to fit a larger axle into the fork legs. still don't know whether i like that, but they're being machined right now.

i've got a couple of two-year old unopened cans of C12, but i'm just going to dribble that into the street bikes and use completely fresh stuff this summer.

would still like to get it on a dyno, though.

i be kevin
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post #9 of 30 (permalink) Old 04-24-2019, 04:15 PM Thread Starter
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K, On the various front end and wheel swaps, I make bushings to fit the axle to the fork or cut down the axle ends in the lathe..But your situation might be a bugger....
You would like the dyno shop owner. He's a friend of Kevin Cameron and is a hands on guy, you ride the machine on the dyno while he directs the action...
VP says their gas is good for three years in factory sealed cans.....
When you stop by my T140 will be available for flogging....You can experience a 9.2 compression Triumph running on 89-90 octane gas without sounding like a can full of marbles..

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post #10 of 30 (permalink) Old 04-27-2019, 01:26 PM
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my problem is that there are no bearings that fit the wheel with a 0.675 ID to match the conical sliders.

the 90 GSX 750 front wheels had little axles.

i be kevin
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