180 out?

[RiverJim]

i have a 110cc that has all new electronics, new carb and getting great fire to the plug. The problem is when it does decide to try to fire it's like it's trying to fire on the exhaust stroke? It blows through the carb. Any help here is greatly appreciated.

[Mudflap]

Have you checked the valve lash? BTW these engines use a wasted spark ignition system that fires several degrees before TDC on the compression stroke as well as the exhaust stroke.

[RiverJim]

I don't know what a valve lash is lol

[pistolclass]

Originally Posted by RiverJim

I don't know what a valve lash is lol

Neither do the manufacturers.

[Adjuster]

Is it actually backfiring? Fuel igniting back up out of the carb? Or you just see some compression/air coming up out of the carb?



/

[Adjuster]

Originally Posted by pistolclass

Neither do the manufacturers.

Now this was funny.



/

[Megadan]

Originally Posted by RiverJim

I don't know what a valve lash is lol

In simple terms, valve lash is a small gap between the rocker arm and the tip of the valve it pushes against to open it. This gap exists to allow the expansion of the parts when they heat up without compromising the seal of the valves in the combustion chamber. Usually set in thousandths of an inch, with most Honda clone engines having a specified lash of .003" plus or minus .001".

Almost all of these clone engines are sent from the factory with no lash, and sometimes the adjusters even putting a bit of tension on the valves. This causes the valves to not seal and will result in backfires like you are getting, afterfire - think exhaust backfire, which causes the exhaust to get super hot and can damage exhaust seats and exhaust valves. and generally hard starting and poor running.

If you are unsure about how to set the lash, I advise trying to search for specific lash information for your bike/engine or maybe somebody here can provide the info if it is different from the numbers I gave above. Otherwise, lash on most rocker arms is generally set the same way.

As far as being 180 degrees out, did you remove any of the mechanical parts of the ignition system, such as the stator or flywheel?