Damn yamaha 250 wont stay running

[Captain PegLeg]

I put hour meters on all my bikes right when i get them. My 09 yz 250 has 29.4 hours on it and i have went through two top ends, 2 cylinders, and now my crank just went out for a 2nd time!! My premix is 32:1, i keep up on all my maintenance.... I have had hondas all my riding career and seems like i may go back. Any advice on what is making this thing eat these parts?!?

 

[RobertoGatos]

Air leak somewhere? crank seals? Sucking in coolant, causing loss in lubrication? You should post this on Thumpertalk, or a moto website, you will get more help.

 

[RobertoGatos]

Might be sucking in dirt too, airboot, or air filter seal not seated properly. I would not get rid of that bike for a 2s honda, the yami's are better in my opinion.

 

[jvann13]

How does it run? I would guess a lean condition but with all that stuff it should not be running all that good. Something is not right to have all that happen with only 29 hours.

Did the top ends seize?

 

[Andrew1289]

Clean your air filters after ever ride, sometimes bring a clean extra one with you pop it in half the day. (you probably do this)

When you wash your bike, water will get into your airbox and the dirt from your filter will flow down into the carb and then into your engine. You can buy something that covers your air box up when washing or just throw a plastic bag over the just cleaned filter when washing.

How does your spark plug look? Picture? Im guessing you got that carb set lean and thats whats wearing it out so fast. Could be an air leak.

 

[Andrew1289]

Have you been checking coolant levels? How does the head gasket look when it gets disassembled? Maybe the cylinder and head surfaces need to get lapped a bit.

 

[Captain PegLeg]

all coolant levels have been fine. We have replaced every gasket/seal while we rebuilt it. I have had the same mechanic for 6 years and he has been in the bussiness for over 20. I know what im doing as far as the maintence goes. Air filter is after every ride ect. My guess is the carb is to lean....

Note: The first top end and cylinder where not the bikes fault, as i was running 93 octane and it detonated. But the two cranks are the issue....

 

[Billybo455]

hmm, 93 octane and you lost a top end? unless the bike is heavily modded there is no reason to run anything more then 93. reeds and a pipe isn't highly modified either. sounds like it's lean to me also. does it run the best right before it gives out?

once i gave up 2 strokes and moved to a 4 stroke it was the best thing i ever did. you might want to give it a shot

 

[Andrew1289]

2 stroke for ever. Check your timing as well!

 

[yamanube]

Sounds like the problem is behind the bars.

 

[Schmidty721]

As mentioned before pictures will help us out. How much heat are the cranks showing?

What are you using for oil? Does your premium fuel contain Ethanol?

I'm sure you know the tricks of spaying carb clean or something similar around the intake track to test for air leaks and you're letting it warm up before ripping it right?

How long did the top ends make it? Did it just seize or did the piston come apart throwing particles everywhere?

Make sure the inside of your pipe is clean. The reverberations in the two stroke exhaust timing can suck crap back into the engine.

 

[fmx_Bud]

that's insane, I've had my 06 yz 250 since new and I'm still on the original top end, hell still factory spark plug! I bet I've got 100 hours on that sucker. I just ordered a new top end just because I figured it was over due. Sounds to me like u got a sockie friday bike. I would never go back to a honda 2 stroke over a yz. I'm sorry to hear about ur luck with the bike.

 

[jvann13]

2 stroke for ever. Check your timing as well!

I would agree with this. I know some of the 250 guys talking about the timing being off from the factory on some bike around your year.

A yz250 should last 29 hours with no maintenance (not that you should do it).

 

[Billybo455]

not to hijack, but have you guys rode a new 450? CR>YZ get some pics up!!!

 

[Captain PegLeg]

Pulled the plug and it looks like it was a little rich actually.... I will have my mechanic check the timing.

As far as fuel... 110 octane sunoco race fuel and yamalube premix. Im not putting junk in there.

Im not new at dirtbikes either, thats why i am stumped on this. I bought it to race the lites class and big bike class on one machine. I have been racing since 02 and been everywhere from Loretta lynns am nationals, to branson, mini os, florida winter ams, you name it. Im not a squid. haha! I have had many hondas, starting with a 01 125, then every year 250f and every year 450 after 05... and LOVE four strokes, but the ease of this seemed to good to be true. this is my last shot at rebuilding this sucker, then its back to a four stroke for me!!!!

 

[Captain PegLeg]

Here is a pic of it right before it blew... Still managed to pull a pretty sweet 240 bucks out of the first two motos!

 

[Captain PegLeg]

I used to ride for white brothers before they shut down... and just for sh!ts and giggles i will post some pics of my white bros team bike!

 

[Billybo455]

that is a nice looking crf!!! stock pipe on the yz?

 

[Andrew1289]

You said your going through cranks and top ends, correct? What is really happening? Loosing compression but the motor still turns over? Is the motor seizing up?

THAT many problems, I might just sell it and get a different one. haha You got gremlins.

 

[Captain PegLeg]

Nope... pro circuit works pipe. Along with a pro circuit silencer, v force reeds, ported cylinder, cases matched.... small stuff!