300/440/550 My 650sx mystery and question

[Sidsol]

Ok,, i picked up 650sx and it seemed pretty rough. I already cleaned it up and it appeared to be completely stock except it has a PJS rideplate on it and some stickers for performance parts. This is my only clue to that something may have done to it.

Two things about it for sure the oil injector hose was not connected to the intake and the guy I got it from put oil in the can and it made a nice mess . Lucky for me he said he was running pre-mix. The guy I got it from got it from some other dude with the intent to learn to ride it but was a moron and sold it to me in a week after he got it.

The second thing is that on a compression test I got 170 on both cylinders and I am not sure how. The engine has a stock head on it (i compared with internet pictures) and it rides very well in the water .
I guess the question is can a stock 1990 650sx have a compression of 170psi or has something been done even with a stock head? I am looking to purchase a new head but do not want to leave premium pump gas.

I want to start modding this ski and looking into a dual Carb, head and exhuast ASAP but wanted to see if 170psi was legit or should I start being curious about foul play. I didn't pay to much and this is my first ski so please respond back in a simple form =).

 

[six5hooSX]

my ski is a 90 650sx i milled the stock head i got 178psi i run premium 93

 

[Justanotherusername]

I have a dead stock head on mine and get 169 psi in each cylinder. And it's an '89.

 

[Sidsol]

i guess i can hold off on a head....I Just got a dual Carb system and looking for exhaust. I already have a ride plate but notice my impeller is a little dinged .. so after complete exhaust that is the next thing.

Anyone have suggestion in how I should build this beater let me know please

 

[Shifty]

If you really like riding I wouldn't spend too much on the 650sx. Save a little then sell for a better platform.

Two common and cheap mods for the 650sx are to upgrade the carb (if it is pre-1989???) from the 28mm to the larger 38mm I think? If you have the smaller 28mm carb you will have an external fuel pump mounted on the side of the hull. Also do some searching for the 650sx exhaust mod, I never tried it but its free if you have the means and can make for some additional power I hear.

 

[tbaer]

save your money. i bought a 650sx for my first ski. I still have it. I ride it for a month and then I ride a buddies 750sx and wanted to dump the 650 right then, but soon after that I rode a superjet and that sold me! I went out and bought a superjet and ripped it apart and made it mine. now the 650 just sits there. So just ride the 650 for a while and then upgrade because I know you will want to.

 

[Sidsol]

Ill probably just stop at the exhaust and paint it up to look alttle pretty. I am going to try to stick with the 650 for at least 10 months and if I am still skiing regularly the wife said I can buy a new 2010 Superjet when next year.

 

[tbaer]

Ill probably just stop at the exhaust and paint it up to look alttle pretty. I am going to try to stick with the 650 for at least 10 months and if I am still skiing regularly the wife said I can buy a new 2010 Superjet when next year.

for the price of a 2010 sj you can buy a tricked out used sj that runs stronger, handles better...

 

[Sidsol]

Well i have to do my time on the 650 for 10 months .. ill revist buying new or used SJ when the time comes . I appreciate everyones opinion... The exhaust is the las mod I am doing and maybe a refresh on paint and sticker removal. I belive the wife will be taking the 650 when I upgrade so its a win win.

Again thanks to everyone for stopping me from going over board. The next question is if I like freestyle or race ....10 months should help me figure this out.

 

[Pro-pulsion]

*Edit, didn't realize the date lol*