whats wrong with my yz125

[littlenasty]

my yz125 is really hard to start, and when we finally get it to start, it will rev up, but will not reach the power band, for about 4 months the yamaha shop has been giving me the wrong type of spark plug that we just now realized, would it be possible that it couldve damaged the piston, rings, or any thing like that?

 

[cr125freak]

Jetting mabe? I just put in a rev pipe on my cr125 and that is what is exactly what it is doing. I can run but not enough to shift or ride at all

 

[1991rm125]

you may need a top end. the piston may be damaged. tak ethe exhaust of and look at the piston with a light.the ring may be welded to the piston. or check your reeds.

 

[TimberPig]

You don't provide enough information to make any real directed recommendations on where to look for the problem. If you have trouble starting, you could have low compression, bad reeds, very lean jetting or a fouled spark plug. When it revs up like that, it is normally a sign of a lean condition,which is normally caused by lean jetting, a dirty carb, or an air leak.

If you describe what it is doing, what has been tried, and any other relevant information, it will help in getting advice on how to fix it.

 

[motodawg]

What year is the bike? What plug did they give you? Anything close to a BR9__ and ends with an ES, EG, EV or EIX (example: BR9EV) should work fine. In fact, an 8, 9 or 10 heat range, depending on jetting should work better than what you describe and should not damage the engine. You need to check for all the things Timberpig mentioned before running the engine anymore. You can also pull the exhaust and get a look at a small portion of the piston for damage. Does it smoke really bad? A leaky main seal can suck in tranny oil and keep the engine from revving, foul plugs and smoke like a freight train.

 

[yz125223]

i suggest you take the sparkplug out and do a compression check, hold ur finger over the sparkplug hole and push the kick starter, if it doesnt blow ur finger off the hole, then u could have a bad piston ring that didnt seet, which means a new top end