i just bought this moto 4 and it wont start, it turns over and gets almost to the point that its running, but never fully starts, weve got spark and fuel, any ideas?

 

Have you tried starter fluid? Are you POSITIVE it is actually sparking? If you are not sure, pull the plug out and ground it to the frame and see if it sparks when you try starting it. If it does, it can only be a compression issue or timing issue.

To test compression, put your hand over the exhaust and see if its sucking in and puffing out. If it does, youre good there.

Next check fuel. Pull the carb and clean the jets. I usually remove the jets and put a needle through them to be sure they are clear. Also, make sure the float hasnt gone bad. An easy way to do this is to put it in the bottom of a bucket of water and see if it flies to the top when you release it. If so, the float is good.

I have a technical diagram for you located here: yamaha partsmanual fiche yfm225t 1987 yfm225 quad bike

That will give you exploded views of every single piece on your bike. Let me know what happens

 

can't remember the year model, but i recently got one of these running for a buddy of mine. check to see if it has the decompression lever on the top/front of the engine. double check that to make sure you're not losing there. like already stated, the carb has to be clean. his was so plugged up, it took about 2 hrs to clean, BUT, it's been sitting outside for 6 yrs. his decompression lever was stuck slightly open, he thought he lost compression when he parked it, BUT, lo and behold, the lever was stuck. check that, check spark, check fuel, clean carb, get a hot/fully charged battery, and BAM, it oughtta start..........

 

definitely a compression issue, got the motor pulled last night, getting into that sometime this week, sorry took so long to reply. ill keep it updated.

 

Prolly needs values adjusted, inspect clearance.

 

well, got into it tonight anyway, rust on the cylinder wall and piston. any ideas? best plan of action?