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Compression test got an average of 112 psi. With oil I got 140 psi. Someone said compression should be at least 119psi on the js300 so I guess I'm a little low. Is it ok to just get new rings and use old piston if its ok. If that is the problem, since I don't have a dramatic drop in compression...

bumping my old thread as I still never got the ski to start. I did get the flywheel off and it seemed ok. I put in a new key and made sure the stator was dead on. Again same thing.

Sent PM about JS300 quote

Is the kerker pipe have more low end than the Mariner for the 300? Is there much of a difference between the two?

Cool well thanks for the info (and cool kerker install document). Guess I have to just search, but still finding the info and parts is a pain :(

Sounds baller. I know the 650sx motor is very similar (like the pistons are the same), are the reeds the same, any other interchangeable upgrade parts?

It is so hard to find information on js300 skis (since almost everyone hates them). I have an 86 js300 that im trying to get started right now. After that I will probably (hopefully) ride it around this whole summer then get into modding it. What mods do you have on your 300? are the pipes for...

So I took off the flywheel cover and it looks like the flywheel bolt in the center is all :-):-):-):-)ed up. Never seen one before since as I said I'm new, but it is all oval shaped and doesn't seem to be any surface to put a ratchet on there.

I took off the waterbox before and blew in it and air passed through it fine. I could feel the backfires coming through the exhaust exit.

haha no thx. I like hearing

So I just switched the lines on the tank because I only had about a gallon of gas in there the main pick up line was to short to get gas. So I put the main fuel line on the reserves stick and it primed fine. Now I tried to start it and there is fuel, but all I am getting is a back fire ever so...

Ok so I took off the return line at the carb, plugged my tank up and blew into it. Nothing happened. So I figured I would try a compressor and all that did was make the tank expand a little bit. Now that I think about it I bet I need more gas in the tank. I only put one gallon so the pressure...

Is there a fuel pump? (haven't got my book in the mail yet) Because when I turn on fuel I don't hear anything. And the sediment tank never got full (not sure if it should). Unless I get good answers from you guys I probably will just wait for my book to get here so I can read it.

Ok, someone replied to my thread. They said the reason my exhaust popped of was probably because too much gas was poured in the carb. Then when it backfired it ignited the gas in the exhaust. Seems logical.

I'm pretty new but what I read about plugging the oil system is very simple. I just bought my first ski (a js300) the other day. The js300 and 650sx are similar in terms of fuel injection if I'm not mistaken. You can buy a block off plate but I did it the ghetto way and still looks fine. I...

Ahh, I see. Yeah I need to learn more about carbs. Everything I know about cars is fuel injection, so this is all new to me and interesting as well. Thank you

Yeah, i just tried to start my js300 for the first time the other day and it backfired and blew the exhaust off the waterbox just like yours. I never got a reply in my thread though. Maybe someone will answer that question in here.

Took off the exhaust and doesn't look like it is plugged up but I'm cleaning it off anyway. Thought it could have been the waterbox but that seems to be passing air. Could have just been a back fire or something. I'll have to finish cleaning off this stuff put it back and try it again. Any...

First of all I'm new here. Saying hello for the first time. I'm also new to skis, and plan to learn about them. I'm more of a car guy but I have always wanted a ski so figured what the hell. So I bought a 1986 JS 300 (yes I know most don't approve) that wasnt running. It has spark and...