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wwoberg wwoberg
10/17/2017 5:11 PM

To make a long story short:

I posted back in July showing my sons RMZ250 engine after a piston failure. What I didn't write is that it happen on a big step up, in mid air (of course), and he ended up with a broken pelvis and collarbone. I was kinda tore up over the whole thing (since I do the work on the bikes) and didnt have the attitude to tear it down. So a buddy of mine, whos is an expert moto mechanic and fomer local pro, offered to do it. I pulled the motor, he rebuilt it with a wrench rabbit kit and OEM valves and springs and also had the seats cut. A couple weeks ago he got done (no hurry, since my son is still not cleared to ride) and I put it all back together. He also found have a circlip in the oil strainer so it could have been a circlip that worked it way out and destroyed everything. I know how you need to install the circlip with the opening either up or down. So it could have been my fault. anyway....

I started it and rode it around the yard. It ran like a dog. would not rev worth a crap. Almost felt like the rear brake was on constantly. I then hopped on my bike, (13 RMZ250, identical bike with same gas from the crash and uncleaned air filter from that day of riding) and it ran fine. So I called my buddy, took it over there, he rode it and we all agreed it ran like a dog. Our guess it was 1 tooth off on timing.

He checked timing and it was good. Took off the head and there is a sticky goo on top of the piston. This is essentially a brand new engine that has 2 trips around the yard on it. It almost looks like air filter oil burnt up. Air filter is fine, nothing in the intake, just looks like poor combustion which is making the bike run like crap.

Has anyone else had this problem? Any guesses of what it could be? It has new plug, air filter is fine, gas is fine. When I take off the injector/throttle body I take it off as one piece and replace as one piece. I have no idea what inside there. The bike ran excellent up until castostrophic failure. Any help appreciated.

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Paw Paw Paw Paw
10/17/2017 8:40 PM

Old fuel will cause this. It will clog the injector.
Also, was the cam chain replaced when the rebuild was done? If not they can stretch enough to cause cam timing issues and make the bike run poorly.

Paw Paw

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wwoberg wwoberg
10/17/2017 8:48 PM
Paw Paw wrote:

Old fuel will cause this. ...more

Cam chain was replaced. How do you clean an injector? If it was old fuel, I'd be happy. But an identical bike with identical fuel ran exactly Like it should.

Thanks for the advice

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walent215 walent215
10/18/2017 4:15 AM

We had a crf250 that wasnt right after being " blown" up. Ended up that the cam sprocket slipped on the cam ever so slightly. Wouldnt be surprised if your dealing with the same problem.

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Paw Paw Paw Paw
10/18/2017 6:55 AM

Look at youtube for injector cleaning.

Paw Paw

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RCF RCF
10/18/2017 8:23 AM

If the bike was seized you have to look at the cam sprockets on Suzuki they will spin, you think you have the bike in time but you're actually out , there's holes in the cam sprockets that should line up the cam lobes.

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wwoberg wwoberg
10/19/2017 1:51 PM

Here are some pics of the piston.Photo

Photo

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Paw Paw Paw Paw
10/19/2017 6:43 PM

That shows signs of bad and leaking valve seals.

Paw Paw

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wwoberg wwoberg
10/19/2017 8:15 PM
Paw Paw wrote:

That shows signs of bad ...more

New OEM seals. Do you think the timing (as mentioned from others) with the sprocket slipping could be the issue?

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RCF RCF
10/20/2017 9:11 AM

Here's a picture of a Suzuki cam, see the hole in the cam gear How It lines up with the lobes now check yours
Photo

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wwoberg wwoberg
10/20/2017 8:13 PM
RCF wrote:

Here's a picture of a ...more

Thanks. Checked them tonight. They are dead on. I was really hoping that was the problem.

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Paw Paw Paw Paw
10/21/2017 4:25 AM

I know you said the valve seals are new, but they may not be sealing. Also the fuel injector needs to be cleaned.

Paw Paw

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wwoberg wwoberg
10/21/2017 5:35 AM
Paw Paw wrote:

I know you said the valve ...more

Ok. The valves and seals are new OEM. The shop cut the seats and put the head together. Never had a problem with them before. I checked the seats by filling the intake/exhaust with gas. Nothing leaked. Before I replace seals, can I fill buckets with gas and see if it goes into intake or exhaust, or does the valve have to be moving to actually test that? Also, I've got an extra set of seals that came with wrench rabbit kit, can I use those or should I get OEM?

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Paw Paw Paw Paw
10/21/2017 10:04 AM

Worn valve guides will allow the seals to leak. Seals can fail causing the leak.
Did you ever clean the injector? If dirty it can allow larger than usable droplet size of fuel to enter the combustion chamber and not burn. When that happens you have poor performance and it can create the deposits.
I would clean the injector or replace it before I did any thing else.

Paw Paw

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wwoberg wwoberg
10/21/2017 12:44 PM

Haven't cleaned it yet. Been out of town and went a saw everything last night. It will be one of the first things we do. Before we put cylinder/head back together just want to be sure we do every thing we need to, so I can save on another set of gaskets.

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Whymee Whymee
10/23/2017 2:03 PM

For shits & giggles, swap out the injectors between bikes. Might save you from chasing your tail.

A big thanks goes out to Donnie at Morgantown Powersports and RJ at Beaver Creek Cycles

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wwoberg wwoberg
10/23/2017 6:06 PM
Whymee wrote:

For shits & giggles, ...more

Yea. I'm racing this weekend (son still not cleared to ride) and then we are gonna start swapping parts. Just dont want to swap heads out.

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wwoberg wwoberg
11/13/2017 10:30 AM

Thought I would update this thread for lessons learned purposes. My buddy did all the work, so I can't give every spec of detail. He ended up swapping just about every significant part from the good bike to the bad bike without any success. The bad bike still ran bad. He even swapped out cams. He ended up splitting the cases and found that the oil reed valve was backwards. I guess, since I bought a wrench rabbit kit the gasket is somewhat more universal. If I would of got OEM gasket the cut out prevents it from going in backwards. At least that is what I was told.

Anyway, finally got 2 good bikes running again and me and my son can go riding. whew

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