Our 300ex has always been alittle hard to start, but now it won't even try to start. Its getting gas, and has good spark. It acts like the valves are to tight and might be holding open. Question is, how do I go about adjusting them? Is there anything else I'm overlooking? The crazy thing ran Saturday morning, but when I went to start it Saturday night it wouldn't even try. (Not even when pull starting) SOMEBODY PLEASE HELP!!!!!!

 

Have you checked the compression? If the valves are out of adjustment enough to cause a no start, itll show up on a compression check. Have you tried holding the throttle at 1/4 open while cranking?
Try starting with a new plug.
Have you tried having someone pull you with a tow strap, and bump start?

 

I have not tried a compression check yet. (almost scared to) I have tried 1/4 throttle, full throttle, no throttle, either, and pulling it. All with no luck whatsoever. We have a Yahama Badger that would act up like this about once a year and the valves would tighten up enough to cause this. I didn't know if the 300 would be the same or not and if so, what to set the valves at.

 

I dont have the specs for that motor, bt im sure someone else will come up with them. Usually the valves get looser, rather than tighter. Motors need three things to run....fuel to the cylinder, spark, at the right time,and enough compression. If you have the first two, its got to be compression.
Are you sure the gas gets to the combustion camber?Just because theres gas in the tank, doesnt mean it gets to the cylinder.Have you tried a new plug?

 

When you say pull start did you mean you were towing the bike?

 

Not yet. I've been in the hay field in my spare time when 'm not here at work. The 300 has to wait till I get time or feel like messin with it. I need to do a compression check and change the plug. But I got a very bad feeling on the compression. It seems to have all of the signs of a valve being held open. This is the first Honda that I've own. And I bought it used with out any manual of any kind. Is there not a way to adjust the valves without pulling all the plastic off? Our plastic is in really sad shape, ( it will fall apart if I have to cut all the wire ties holding it together) and I was hoping to replace it soon, but if it is more than just a valve, I cannot afford to fix the motor and replace the plastic.

 

When I said pull start, We tried to start it when pulling it with my SP500ho. 3 days ago it acted up and I pushed it over a hill and got it started. The next day it started on its own, but that night it would just crank over and never try.
I might add that when trying to roll start it, I have to put it in at least 3rd and plop my 220+ butt down on the rear of the seat to keep it from just sliding. (kinda seemed like it had fairly good compression then)

 

DID U PUT A NEW SPARKPLUG IN??????

the carb could also be clogged up