550SX compression 180/90 psi

[catfish4767]

I just bought a 95 550sx off Craigslist and ran a compression test on it. The results were 180 psi in one hole, 90 in the other. Im guessing Ill need to replace the top end. So here's a dumb question, is the stock bore on a 95 SX reed motor 75.5? I see a lot of rebuild kits but at .5 over/1mm over etc. I dont know how to bore or hone a cylinder so the easiest swap option would be the best. This is just a back up ski if a friend wants to ride with me or I want a change of pace. Also since the domes on my head are toast, should I just get a new head? Thanks for the help

 

[TheBuzzard]

stock is 75mm and it sounds like a ring is stuck to the piston. if you are careful, you may be able to unstick the ring and sand things a bit. i've done that on more than one motor and some never had another problem.

 

[catfish4767]

Something's jacked. Here's a picture. The dark piston/cylinder has 180. The chewed up pitted looking one has the 90.

 

[TheBuzzard]

that could even be the crank coming apart. better rip it to pieces and find out. i've seen the connecting rod thrust washer vaporize and make it look similar to that.

 

[Quinc]

Damn thats nasty! Send them off to CPT @Nuklear6 and have them bored and ported. He will set you up with new domes rings etc too

 

[catfish4767]

Should I even mess with it or just part it out and cut my losses? I paid $525 for it and like I said its just going to be an extra ski

 

[Quinc]

Thats cheap. Put another 300-500$ into and have a great reliable ski.

 

[catfish4767]

Yeah that's what I was thinking too. It's a 95 with the reed motor and I've always seen those go for close to $1,000. It's got AM everything. Ha just sucks since I am building up my SJ too

 

[TheBuzzard]

95 was the last year. i sell clean fairly stock reed boats for $1200 when i have them.

 

[catfish4767]

My only trouble is when I search for top end rebuild kits I never see 75mm piston kits for a 95 SX. I was told the only difference between the JS550s and the SXs was the SX has two piston rings. Unless I'm blind (legally without contacts I am) I can't find a top end kit with dual rings that's 75mm. It's always .5 over or a higher bore. Any suggestions?

 

[Big Kahuna]

Send your cylinders to a trusted builder. He can spec the correct parts.

 

[kwakhead]

hey, id reccomend sending your cylinders to group K. they will bore out the cylinders and fit new bigger pistons into them and port them for you, I COULD DO IT FOR YOU TOO, but group k has been doing it way longer than i have. For a top end rebuild kit it will be like $155? off of ebay, if you buy it, dont screw around, those cylinders look pretty bad, just buy 1mm oversize, and then send the rebuild kit and your set of cylinders out to group k, should be around $200 for group k to do everything am i correct guys? and while your at it get em ported, youll have a really fun ski, dont part it out and waste a perfectly good ski is my opinion on the matter, the 1995 550sx is one of the prize skis IMO. theyre really fun, good on power and fuel economy, and are reliable and lightweight. if i were you, rebuild that thing, or sell it to me!! lol

 

[kwakhead]

if i were you, heres what id do.
1- buy a 1mm oversize (76mm) top end rebuild kit
2- remove your cylinders and inspect your crank (MAKE SURE THERE ARE --ZERO-- METAL SCRAPS IN THERE OR YOURE PROBIBLY REBUILDING THE BOTTOM END TOO)
3-send everything to group k. go to group-k.com for details

 

[catfish4767]

Yeah my brother and friend down the street convinced me to keep it and rebuild it.