XLT 800 Rebuild Questions

[themist456]

Hello Everyone,

I am making an attempt to rebuild my first 2 stroke PWC engine. The engine is a 800 out of a XLT 800 and I have run into some issues that my inexperience is making me question.
First, I tore into this engine because PTO side had 50psi compression (pictured). Other had 120 PSI (that is perfect on these engines correct?).

After digging in, I discovered that both power valves were practically missing, not just not low compression side looked like the photo below. Pretty much just the stem is left. However, the cylinders, to my inexperienced eye, look perfect. There is no scratches or gouges at all. There was a tiny bit of metal in the exhaust port but the motor still spins easily by hand so
I do not think any got into the crank. However, there is damage to PTO piston and head.

My question is if I am okay to replace pistons with WSM original size (full top end kit), get a used head, and buy two new power valves?

[jeffg426690]

Welcome to GH!
You're doing good so far, and yes, 120psi is on point for compression.
You can simply do a top end kit but in my opinion that's taking a gamble. Just because the motor spins by hamd doesn't mean there aren't tiny fragments in the crank bearings that can cause problems. If you just do the top end you simply don't know whether the crank is really clean or not and are going with a hopeful assumption.
Personally, I'd pull the motor and split the cases to clean the crank and also replace the crank seals. Reassemble and do a leak test prior to going back into the ski. All of the above is more work and a lil' more $ but not hard to do and you know you've got a good solid starting point moving forward.

At a min, to fully assess your cylinders you need to pull them and get a really good look. While you have it apart, if the ski is new to you it's also time to go through the fuel circuit and also do a carb rebuild (not hard and you can do it yourself, everything you need to know is documented on here). Mikuni kits on the carbs, aftermarket kits have probs. Replace your oil lines as well.
Good luck with whatever route you choose, if you keep updates and pics posted you'll get plenty of feedback along the way.

[butterbean_29512]

I have seen my fair share of 800's that broke a PV, and the blade slips through the exhaust, not doing any damage. Looks like that's what you've got here. That head is good, reuse it. I agree with others, you should split the cases, check and clean the crank, and replace crank seals.