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How to tell cause of engine failure?

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Ok, where to begin? I bought a used 04 CRF250R in feb.. 05. We rode the bike for a few months and didn't check valves, although I new that there had been a problem. After it got hard to start I checked them. Yes they had zero out on the exh side. Shimmed them and rode till it was hard to crank again. They were zero'd again.

I decided to do some research and and upon reading this board decided to go with a stainless steel setup. I only wanted to do this one time. The ultimate fix. I also swore to myself that I would be way better at upkeep. I blamed myself on the factory stuff failing.

I had one of the stainless kits installed and new seats install on the exh. side (bronze seats). Intake seats where fine. About $900 later and armed with a new hour meter we were ready to ride....FOR A LONG TIME... Well I had already checked the valves three times in the 7.5 hours on the bike.

That was short lived folks. The bike just quit during a race. Both exhaust valve destroyed (one broke off) holed piston, ruined cylinder, head and both intake valves.

How can i tell what caused this? I did the work of taking apart the engine and putting it back together of which I feel real confident in my work. Did a valve break and cause this? I didn't assemble the head and valves.

I'm a poor hard working guy and I can't afford this shit. But my son did nothing to deserve this so I will try to soldier on and repair it. He want's to sell ana buy a 2 stroke (I'm close)

How can I tell if the bottom end is ok. It seems to be.

Thanks,

Gerald

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Find a new mechanic/tuner/shop maybe. All 4 seats should have been done if you spent the big bucks...

Hard to tell the cause without seeing the parts.

RHC just posted that some valves being offered are strong but brittle and they break. He is working on finding a happy medium between life and performance and price.

You mention bronze exhaust seats but no intake seats...could you have ment bronze exhaust guides ?? just curious about the guides.

The Exhaust guides go bad and the valve will rock, it then eggs the seat and can break very quickly.

Goodluck.

IMO get some new OEM parts and slap it together. As far as the bottom end ???? pull the motor and try to clean all the chunks out. Best way is to split the left side case off. I would do that if I was going to keep it.

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Find a new mechanic/tuner/shop maybe. All 4 seats should have been done if you spent the big bucks...

They said only the two exhausts needed replacing. I originally took the head to have the seats cut/touched up. They said the exh. seats were to beat up and the intakes cleaned up fine.

You mention bronze exhaust seats but no intake seats...could you have ment bronze exhaust guides ?? just curious about the guides.

No, bronze seats but they did put in new guides while in there. I was wary of the people that did the head work...Not at first but after I gave them my head and all my new valve it took like a damn month to get the stuff back. Never a return phone call or nothing. I'm kinda leaning toward something they did wasn't right but not sure.

Goodluck.

IMO get some new OEM parts and slap it together.

I have it sitting here now. New head, valves, springs, cylinder. I'm just not sure about the bottom end (bent rod/crank)

As far as the bottom end ???? pull the motor and try to clean all the chunks out. Best way is to split the left side case off. I would do that if I was going to keep it.

I've never split one of these cases but have done a CR85 a few times. Are they comparable as far as work involved?

thanks,

Gerald

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It's actually easier than an 85.

The cases practically fall apart once you take the bolts out. The only special tool you need is a flywheel puller.

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It's actually easier than an 85.

The cases practically fall apart once you take the bolts out. The only special tool you need is a flywheel puller.

You do have to remove the balancer shaft from the right side (clutch basket has to come off) and the rt side gears are timed (watch the marks).

Sounds scarey but it is harder to get the motor out of the frame then split the cases. :banghead:

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You do have to remove the balancer shaft from the right side (clutch basket has to come off) and the rt side gears are timed (watch the marks).

Sounds scarey but it is harder to get the motor out of the frame then split the cases. :banghead:

I actually have the balance shaft out already as I was replacing the seal. I didn't have to remove the clutch basket though. I just took the side cover off and removed that nut that held the gear on the balance shaft.

Do I have to take the kickstarter assembly, clutch components, etc like I did on the 85? When your splitting it do all the gears and shit want to fall out like on the 85?

Thanks,

Gerald

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Yes, you have to remove the kickstarter and the basket.

The cases split in half and you can keep the trans intact all assembled in one half of the case.

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