Yamaha PW50 Help will not start

[Supercrossfan]

Yamaha PW50 Help will not start!
I have cleaned out the carb (all jets), cleaned air filter, new oil in case, and new oil injector tank, new plug, new choke cable. Bike only starts when exhaust is off the bike after 10-20 kicks. With the exhaust on it does not start at all. I have just used a plumbing snake to clear out the carbon from the head of the pipe into the expansion chamber but it still doesn't start with the pipe on the bike.

Does the pipe need to be cleaned out more of Carbon and if so how do I do this with out a BBQ? can I use a hand held blowtorch? if this doesn't work what else should I check? Will the bike not start if the oil injector not supplying oil to the carb too? I have that next on the to do list to clean out. But it does start up when exhaust is not on.

 

[Justin82]

A few things to check in addition to what you've done:
- Check for week spark. There are a few youtube vids showing the difference in spark.
- Strip the start/run switch and clean out with contact cleaner (this was the problem I had). You can also by bridge the the connector to rule that problem out.
- You can use a blow torch on the exhaust, but I've also see it down with a heat gun connected up to the pipe.

Have a read of this build thread, contains a lot of information about the pw50 http://www.miniriders.com/jap-builds/38214-my-new-used-yamaha-pw50-thread.html?highlight=pw50

 

[xLOCOx]

PLEASE CHECK THE piston/rings you may not have a enough comp, inspect your rings/piston skirt by looking up the exhaust port,
the bike will start with oil pump disconnected, will run lean.... just put some premix in the tank, hang the oil pump hose off to one side,
have you trouble shooted above such as justin has said?
checked your carb settings?
regards loco

 

[Supercrossfan]

Thanks: I checked the spark on and it has good spark, disconnected the start/run wiring. I guess next thing is to tear into the top end.

 

[jonathanpg]

kick 10-20 times, not normal, so engine problems more than exhaust problems