New engine seized in less than an hour...

[JxxxOxxxE]

I'll try to make this short....

..basically bought a basket case 250r with some good parts here and there....Had a CT 330 cylinder with it with a messed up sleeve...Had it re-sleeved locally, sent back to CT to have port matched for a stroker. New +4 crank, new bearings, new 76mm piston and had bored locally....

PWK 39 mm carb with 52 pilot and 190 main, ESR trx MX pipe...compression checked before initial start up was ~160 (seemed low to me), started on 110 gas with 32:1 mix

Started it up for the first time yesterday, drove it around 3 or 4 times, never going over 1/2 throttle, short 5 minute runs. Started it up today rode it another 2 or 3 times for short runs today...

Then decided to take it out and go 3/4 throttle or so....After about 10 minutes of riding, it locked up under about 3/4 throttle...Get it back home pull the plug, its unlocked now, comp test shows 150....decided to tear it down anyway...Here's what I've got...



http://img213.imageshack.us/img213/4941/img2335j.jpg

http://img402.imageshack.us/img402/5644/img2336n.jpg

http://img832.imageshack.us/img832/9049/img2337xw.jpg

http://img804.imageshack.us/img804/6025/img2340b.jpg

http://img810.imageshack.us/img810/15/img2344c.jpg

http://img208.imageshack.us/img208/8836/img2345e.jpg



So....doesn't look like it went lean to me, the plug doesn't look lean to me....

Was this bored to tight? That's really my only thought right now....

The ride it locked up on, 10 minutes, was the longest ride since it was put back together...


Any ideas or comments are appreciated...

[Meat]

Whats your 'ring end gap' ? That should tell you if you're bore it too tight.

Cold seize is my best guess for now.

[Burns310r]

Looks like a 4 corner cold seize.

[JxxxOxxxE]

A cold seize after 10 minutes of riding though, and for the first 9 minutes, didn't see anything over half throttle...???


Ring end clearance is at .015 and .020.

the wall clearance measures to about .004, which seems okay to me, although through searching I see people having possibly the same problem with some ESR stuff and running up to .006...



I'll post a pic of the plug here in a bit....

[dabeechman]

New sleeve...?

These cylinders are terribly notorious for leaking after being resleeved.

[JxxxOxxxE]

Originally posted by dabeechman
New sleeve...?

These cylinders are terribly notorious for leaking after being resleeved.


Yes, it was a new sleeve....the water level looked the same as before though....

[jhtrx250r]

From what I see it was most likly a nice tight fit and you must have had it up to speed in colder weather. when the cylinder cools quickly and the piston is still warm it will seize.
I have done it my self twice over the years. big bore cylinders cool way better than stock they also cool down a lot quicker as well.
I run my CPI a little loose.

[Gresham250R]

What did your spark plug look like? I toasted a brand new engine in less than 100 yards after the initial break in but it was because it ran lean due to a faulty flywheel seal...bad from the factory! And my piston looked like that!

[JxxxOxxxE]

plug...

http://img338.imageshack.us/img338/5761/plugchop.jpg

[pope59]

i had the same problem found out my cylinder was out of round at the bottom