Best way to tell if a 2-stroke is ready for a rebuild?

[350Kris]

I bought my 85 250R about 4 years ago. One of the things that impressed me when I bought it was that the motor looked it's never been opened! I've ridden it minimally the last 4 years and it runs strong. What is the best way to tell if this R is ready for a new top-end? I have a NOS crate motor sitting on the shelf ready to go in...

I've always heard that 2-stroke run their best right before they blow!

[mohadib]

well, when the POS stops moving.

[350Kris]

A well thought out answer. Thank you.

[mohadib]

lol :D sorry. I would use a compression test to tell

[350Kris]

Haha...that's what I was thinking. Compression test. Where can I get a decent compression tester?

[mohadib]

not sure, i use a cheap POS I got from Checker Auto Parts store. I figure its good +/- 30 psi :D

[Twilight]

Do a compression test, pull the head and check the rings, the gap and the squish clearance, if not within spec, its time for a re-ring or a top end rebuild. Depending on how old that crate engine has been sitting, if it had oil then it may be okay but could have gone past the seals, and if not then the bottom end seals are probably dried and need replacing. Thats one thing people dont realize about 2 strokes is that when you store an engine you cannot store them dry.

If compression is low, then do a top end, check your reeds and intake also.

[350Kris]

What should I be looking for in the reeds and intake?

[bonkers_200s]

They always run best right before they blow up. Getting a little more scared lately?

[Bunnyhop]

The tips of the reeds should seal tightly against the reed cage. If they are chipped or frayed they need to be replaced.

[lndy650]

that saying comes from a lean running two stroke because they have more power lean but are more likely to sieze. obiously if you have a wore out top end its not gonna run at its best lol... a compression test is the easiest way. a more in depth check would be to take off the top end and measure the ring clearance, piston to cylinder wall clearance little end side shake, big end clearance ect ect...

[lndy650]

after years of messing with two strokes you can tell by the sound and the feel of it. if you slowly turn the engine over at tdc you will hear a small thunk the louder the sound the more wore your piston/rings are...theres many tricks you can learn to tell.

[350Kris]

Wow....great advice Indy650. Those are the types of tips you can only get on a board like this...

[Macs]

Depending on how old that crate engine has been sitting, if it had oil then it may be okay but could have gone past the seals, and if not then the bottom end seals are probably dried and need replacing. Thats one thing people dont realize about 2 strokes is that when you store an engine you cannot store them dry.

.

Most NOS crate engines come with a coat of lithium grease on everything. So it has very long shelf life. Where the problem comes is with engines that have been cranked, just for a few minutes and this layer of grease is gone. they then sit up.

[Twilight]

I have always checked crate engines, got a new FL350 engine that was still in honda's bag, both seals were dried leaked. Have heard similar stories, so for me its better safe than sorry.

[Macs]

I have always checked crate engines, got a new FL350 engine that was still in honda's bag, both seals were dried leaked. Have heard similar stories, so for me its better safe than sorry.

hmmm, i learn something new everyday. I have bought a couple GT750 crate engines and they were always coated well. When you first cranked them up they would smoke like a chimney until the grease burned out. Even came with an instructions stating everything was coated in grease. I just thought all manufactures did this. Maybe be just a suzuki thing........