Armstrong Cmt310 Pre Ignition

[islandbultaco]

My Armstrong CMT310 with the Hiro 323cc engine starts pinging about 30 minutes into a ride. I am running premium fuel with an octane booster and an NGK BP6ES plug. The ignition is a Kokusan CDI, can the timing be adjusted with this ignition? All I can find in the hand book is to center the screws in the slots on the stator backing plate. Anyone have any ideas to try? I have a spare CDI unit and have swapped out the original but stil have the same problem.

Rick

[dan williams]

I had the CanAm badged version. I went through replacing all kinds of things to get that bike running properly including a steel cylinder sleeve and the only spare cylinder in the US. It would idle fine but when I'd go to the higher revs it would heat up and ping and just never seemed to run right.

Then one day while checking the timing with a timing light for the Nth time I noticed something odd. When I revved the engine the spark would retard. HUH???

The ignition had two wires coming out, a charge wire and a trigger wire so I tried the only option. I swapped them and retimed the bike at idle. It ran perfect after that. At which point I promptly sold it and got the 350cc Jumbo powered version. Now that was a scary bike.

Soooo check your ignition advance with a timing light. Yours may be hooked up the same.

Good luck.

Edited June 27, 2010 by Dan Williams

[islandbultaco]

Hi Dan, I looked over the ignition and there are 3 wires coming from the pickup to the CDI module. 1 is a ground and the other 2 come from the pickup itself. Are these the 2 wires you switched over?

[dan williams]

Yes but check it with a timing light first. As always with such off the wall advice do at your own risk. It worked for me but by that point I was desperate.

[stork955]

Gday, if it only does it after a period of warming up and riding I would say your ignition timing isnt the problem. I would still check it with a light anyway. Many 2 stroke CDI's retard a bit before advancing so that is probably normal. Check the plug is the correct one for the bike. After that I would be having a close look at the piston crown and combustion chamber. Decoke for a start. Pinging is often caused by excessive compression - it happens to 4 strokes all the time. Also look for any small "dags" of metal in the area that may be able to heat up to the point of causing pre-ignition. These you can smooth away with a file etc. After all of that if it is still no good find a reputable 2-stroke tuner in your area to have a look at the squish band. This is most likely the source of the problem but most expensive to sort and not a job for someone who doesnt know what they are doing. I wouldnt even have a go at reshaping that. Good luck.

Cheers,

Stork

[islandbultaco]

Thanks for the reply Stork. The plug I am running is one step cooler than the plug I have seen recommended (I am running the NGK BP6 rather than the BP5). Would cooler plugs help this situation? What about aviation fuel?

[stork955]

Gday Rick, colder plugs etc may help, but you are most likely masking the true symptoms. If there is a bit of metal getting hot in the combustion chamber or a massive buildup of carbon a colder plug wont make a zot of difference. Id be doing the checks mentioned previously, it probably wont be doing the engine any good.

Cheers,

Stork

[islandbultaco]

Thanks for the suggestions guys. I'll go though everything.

[dan williams]

Heh heh the timing error wasn't a little bit. When I revved the engine it just folded right over. It pulled OK off idle though and that was what threw me. Once I got the light on it the timing was clearly going the wrong way. My bike also ran sort of OK but there was no power and it would start pinging after a while even on VP race fuel. When the engine was cold it didn't ping or knock. I've always wondered if my bike was that unique "built on a Monday" machine. I'm really interested to find out if there were others. Maybe why the bikes didn't really catch on. Sprinkle a few of these out there and the bike gets a bad reputation that the factory never figures out.

[john]

Heh heh the timing error wasn't a little bit. When I revved the engine it just folded right over. It pulled OK off idle though and that was what threw me. Once I got the light on it the timing was clearly going the wrong way. My bike also ran sort of OK but there was no power and it would start pinging after a while even on VP race fuel. When the engine was cold it didn't ping or knock. I've always wondered if my bike was that unique "built on a Monday" machine. I'm really interested to find out if there were others. Maybe why the bikes didn't really catch on. Sprinkle a few of these out there and the bike gets a bad reputation that the factory never figures out.

[john]

Heh heh the timing error wasn't a little bit. When I revved the engine it just folded right over. It pulled OK off idle though and that was what threw me. Once I got the light on it the timing was clearly going the wrong way. My bike also ran sort of OK but there was no power and it would start pinging after a while even on VP race fuel. When the engine was cold it didn't ping or knock. I've always wondered if my bike was that unique "built on a Monday" machine. I'm really interested to find out if there were others. Maybe why the bikes didn't really catch on. Sprinkle a few of these out there and the bike gets a bad reputation that the factory never figures out.

Hi

You've probably got this sorted out by now, but check the sealing of the inlet manifold to the cylinder. I've had the same problem on 2 bikes. The design is terrible - there is an 'o' ring but it's fitted to a very rough casting and the three bits of metal that hold the manifold in place don't hold the manifold square into the cylinder. check the fit of the 'o' ring and use some non-acidic silicone sealer between the manifold and cylinder. This fixed both of mine.

Cheers

John