650/X-2 First time owner; 650sx Engine questions

[BWalt302]

So I picked up an 89 Kawi 650sx for 150 bucks. Pulled the motor apart, nothing looked broke, cylinders were a little scarred but no pits or anything you can feel.

The ski has an aftermarket head and it looked like the pistons had been hitting the head. I turned it over and did a compression check before I dissembled. Front was 60psi, back was 150psi. I Didn't hear any knocking or anything.

Should I buy a new motor or just rebuild? Any things to look for in the bottom end? The bearings looked alright, and they had no up and down play, just dont know if it is worth taking the gamble on rebuilding the top end if the bottom is trash. Any advice is greatly appreciated.

Thanks!

 

[Kohldanielzimmer]

Post pictures of the head. It is likely you had a bearing breakdown or severe detonation rather than the pistons hitting the head. I would look for a used motor on pwctoday

 

[VXSXH20]

you can tear it down and look at the crank rods and bearings, its only how far you want to go. If you are in more of a hurry or just dont have the time or skill set to teat it all the way down then pay for possible machine work..then you may want to find another engine. typically if the top end is torn up and walls are scored. then some material may have made its way into the crank bearings and or effected that rod and bearing on the bad cylinder. i say keep it for a rainy day teardown maybe you wil find a use for it. meanwhile 650 kawis are plentiful , you'll find one, I tossed one out a year ago, it was rebuilt at one point but had been sitting in a hull full of water. I tried to give it away, no one wanted to pay shipping on it at the time. Good Luck

 

[Vumad]

If one is at 150 and the other at 60, the piston didn't touch. Something flew around in there and got mashed into the head by the piston. It's not the piston itself.

Do not reuse that crank unless you can confirm where the metal came from. You can assume its from somewhere other than the crank but if you can't confirm it, I wouldn't risk it. It's unlikely that the bearings let go I the crank and there is still no play, but anything is prissible. If you can't find a broken piston skirt, damaged reed, missing retaining clip, chunk of ring or so forth, then don't take chances.

 

[BWalt302]

I just bought a 30hr 650 motor w/ 155/159 Ready to go!

However, the reason I say the piston hit the head is because it had a circle faint circle imprint on the top of the piston that matched the aftermarket head perfectly? I didn't see any major damage that indicated something going through the motor. Like I said the pistons were actually good shape other than those marks on top.

 

[BWalt302]

Attached are the photos, I am thinking about throwing it back together w/ new gaskets and seeing how it goes.

 

[VXSXH20]

That needs a hone a really good hone and new rings and pistons at a minimum, it could be saved good luck

 

[Kohldanielzimmer]

Looks like it was full of water and has rusted to hell...if so that crank is dusted

 

[BWalt302]

Ok, well since I bought a motor, do you all think that head still good to use?

 

[VXSXH20]

honestly, why risk using it, aftermarket heads are cheap and alot of guys have stuff laying around. I unloaded all my vintage kawi stuff.. dont re use it.

-there are guys that could cut it down and clean it up and give you more compression, if you want to go that route. much like an aftermarket head.

 

[Jpass]

I have a stock 650 head that I just removed from my '88. If you want it let me know.

 

[BWalt302]

The new motor I bought has a stock head, I'll just keep it stock, should be plenty quick enough.

 

[iangdesign]

The new motor I bought has a stock head, I'll just keep it stock, should be plenty quick enough.

Said no 650 owner ever...haha!

If you are interested in rebuilding the bad motor...I have a good set of cases and crank I need to get rid of. Or anyone else for that matter.

 

[Jpass]

Said no 650 owner ever...haha!

So true. I rode my stock 650 (backup ski) for 1 season. This winter I put on the following:

high compression head
46mm carb
Larger intake to match carb
two stage reeds
full frankenexhaust (no markings on it, but we think its a mariner).
flame arrestor

Now the ski finally has some snap.

 

[BWalt302]

What are the chances of that high compression head I have having something wrong with it? I dont want to put it on my new motor when it gets here and have it hit something... (if it is shaved down to much would the pistons hit?)

I think its a mariner, anyone wanna buy it? Make an offer!