Hi everone

I've got a 1982 honda ATC200. The engine is a great runner and has alays had maintenence done on it, but other then changing the pull rope has never been apart or pulled. It has just recently started backfiring when ever I let off the throttle. It has blown the exhaust in to two pieces so its definately upset with me.

The only thing I could think of is the timing chain being streched? I read the book on how to adjust it or whatever by loosening the bolt on top of the crankcase - didn't do any good. I also cleaned the air filter and changed the spark plug..thought I'd start with the easy stuff.

Does this sound liek the timing chain going to you? especially since it has never been changed? Also have i done any damage to any other part of the bike by leaving it this long (other then the exhaust, and I did stop riding it after it started backfiring and after the exhaust broke)?

If so how hard is it too change the timing chain? I have a little bit of expirience with small engines such as lawnmowers and briggs and stratton, is this way out of that league? Also should i replace the guides, chain and sprockets? or will just the chain do?

Thanks alot

 

Unless you bogged it down and it shut down hard and suddenly it probably is not the timing, but backfiring can be caused by the timing being off. Usually a mixture that is too lean will cause backfiring and burn out the exhaust valve in a hurry. Are you having other problems with it? Stalling, hesitation, rough idle etc...? Before tearing into the engine check the logical things some of which you already did, right heat range on plug, air filter, set the carb up (or rebuild it, pretty cheap to do), check the exhaust for blockage, air leaks around intake etc.

Yeah if you change the timing chain you should change all the sprockets at the same time, but then it depends on how much you plan on riding it too. If you only buzz around once in a blue moon on it, then a new chain alone should last you years. It's not that hard of a job to do, but it is time consuming. If you were comfortable playing with the small engines then you should have no problems doing this job. Good luck!

 

Thanks alot, one thing I forgot to add was that the brakes are shot so before it started backfiring i had been gearing down a lot to slw down, would this have something to do with it do you think?

As for the carb I think its perfect, it starts 3rd pull religiously or better and the only time it ever stalls is when the air filter is clogged (obviously) I cleaned it and it will run until u stop it, but I will check the intake hose I never thought of that, thanks again

 

Gearing down should not hurt it, increases the wear a bit maybe but not to an extent where the damage would be overnight. You may want to check the compression on the engine too, just to be safe, especially if your gonna be tearing in there anyways, piston and rings are not that expensive. A quick way to check the intake for leaks is to spray carb cleaner on it while the engine is idling. If the idle speeds up then you got a leak somewhere. Just make sure to keep the spray from the air filter! [img]i/expressions/face-icon-small-happy.gif[/img]

 

Alright I'll do that, thanks a lot for your help[img]i/expressions/face-icon-small-smile.gif[/img]

 

I would advise you to change the timing chain. It can get so loose that it will eventually skip a tooth and the piston will hit and bend your valves. The hardest thing in doing that is removing the flywheel.

 

Actually shifting down like that with the throttle closed as a means of braking is just like running your engine lean, because you still have all that air coming into the combustion chamber at high rpm but only enough gas to run idle rpm. Doing this a couple times would not be the end of the world, but If done enough on a already tired motor it could possibly finish it off. The newer machines of today have a diaphram in the carb that closes with the throttle to cut the air flow to get rid of the lean condition when engine braking.