Seized

[gowen]

Well, I finally killed it yesterday. I went out and fired it up, warmed it up. Took off and within' 1 to 2 minutes it was losing power, thinking it was a plug fouling (not normal), I headed back to my truck and before I knew it, the motor seized up. I have not taken the motor apart, but I did notice that the engine was hot (evaporating water immediately). I waited about 5 minutes and poped the radiator cap, had little pressure and the water was cool. Not even warm. Thinking the waterpump? Not sure.

It was slowly losing all top-end power, like yhou'd hit the power, and alot of noise but little pull. Anyhow, going to tear into it. Any ideas?

Update: Just for reference - I'm running C12 with MC1 @ 50:1 - Also, was able to unlock by rocking back and forth in gear. Have yet to tear into the motor.

[Arigato]

It could be a bad crank seal.  Isn't your motor bored to 520?  On mine that was that size the bridges in the intake port broke.

[doordie]

gowen,

Maybe the impeller nut ,it often brokes,it?s only 5 mm size.
Change to better steel quality  

//doordie

[gowen]

Hi Doordie, it looks pretty bad, I'll get pictures, but I did check the impeller nut, it is still on and good. The impeller looks like it is functioning fine, it rotates with the piston just fine, but it does feel like the bearing is bad, like the you can slightly pivot the impeller. But, none the less, works fine. I will get pictures in a second.

Gabe

[hughes]

With it lossing power on top and would not pull just might be top end seizure.

[gowen]

With it lossing power on top and would not pull just might be top end seizure.

Yeah, it was definately the top-end. It looks totally bad, but let me know anyhow. Pictures are also in my gallery on the last page under Seized. Thanks Guys, let me know what you think and if you need anymore information.

[hughes]

How many hours on that top end It may not be as bad as it looks. The piston is softer than the plating. After the alum. is cleaned off the cylinder walls you will know more about the shape of the cylinder. Can't see the top of the piston real good but does not look like detonation. May be a ring was sticking. Just starting engine and warming it up 2 mintues later it failed sounds like a ring sticking. Are you running stock compression

[gowen]

Hi Hughes, it is all aftermarket. Big bore, running all aftermarket flywheels. It has roughtly around 100 hours. The rings are free and in good shape. :-/

[Arigato]

4 corner seizures like that are usually caused by a lean main jet or too quick of a warm up.

[gowen]

It's hard to say, I have my main jet pretty much dialed in. I'm betting it is from warming up too quick.. Now, I'm going to assume hone, but should I replate?

[Arigato]

You'll have to see what it looks like after you get that aluminum off.  I'm betting you're gonna have to re-plate.  You should probably go through the whole motor if it has 100hrs on it.  Those 520's make a lot of power and are hard on everything.  Mine twisted and bent the crank.

[gowen]

Arigato, it is looking like the rod and bearings are ok......I think. The crank bearings sound whacked, I'm assuming just worn out. I'm due for a rebuild, which I do have a new 88mm piston kit, (520), but hoping I can avoid replating.... If not.... Dammit I'll just have to replate.

[reknelb]

Looks like a cold seizure to me.

I just read Rich's response saying 4 corners almost always means lean jetting. What were you running?

[hughes]

How long to do you allow the engine to warm up My old 87 500 gets about 5 mins or so while I get geared up and then it get about a mile and 1/2 run at low speed going easy through the gears. Next I lay the wood to her. I agree with the other guy's about warm up. Not warming up properly will allow the piston to heat to fast and grow(no piston to cylinder clearnace) before heat can be transfered into the cylinder. Both the cylinder and piston need to grow as they heat up together.

[KXcam22]

Gabe,
  Yuk!  I'm guessing sudden air leak.  Before you assemble, check your cdi too.  My rule of thumb is heat seizure shows mostly on the exhaust side and lubrication seizure shows on the intake side of the piston.  Cold seizure shows on the 4 corners, but lightly.  (somebody correct me if I'm off on this).  When it's everywhere (like yours) it is often something more drastic.  I had a similar unexplained massive sezure on an older cr500, piston looked very much like yours.  Looked everywhere for causes but it had me stumped.  On re-assembly I noticed no spark.  The CDI black box and gone and must have thrown the timing way off, taking the engine wit it.  Anyway it's worth a check. Hope this helps. I'm off to disneyland with the kids in the morning. Cam.