300/440/550 JS300 Newbie Tuning/Diagnosis.

jetski9010

jetski9010

Team RTYD
Location
Lancaster PA
that carb for the 550 is the same BN style you have its just a larger 44mm one so no you do not want that carb. The ones you are looking for are the Mikuni SBN carbs. These come with jets that you can change out to help you tune and will make the ski run a lot better.
 
jetski9010

jetski9010

Team RTYD
Location
Lancaster PA
I dont know of any that have the 34 SBN besides the WR500/WJ500 but there are a lot of 38 SBN carbs out there. I am not sure if they have the same bolt patteren or not as the 34 SBN do. Someone can chime in here and anwser that question.
 
J

johnnyb

Location
New Zealand
No update on actually pulling anything apart or finding a replacement carb, but I ran it for a few minutes at work, took a bit of coaxing to get 'er going, and had black oooze out the exhaust when she finally did fire up.
So I'm going to ignore the potential water issue for now and keep going on carb/dodgy oiler system.
 
J

johnnyb

Location
New Zealand
Ok there is definately no access cover or similar on the front of the motor, only one on the back which I'm pretty sure is ment to have oil in it.
I am attempting to point to it here.
UNI_0173.jpg


Indicating 200mls of oil right?
UNI_0174.jpg
 
J

johnnyb

Location
New Zealand
Oh, and when I called into work to check these plugs I ran it for a few minutes and observed, Oil tank is still pressurising, had a closer look, bottom hose from the oil tank goes to crankcase near the front, and the upper hose goes to a T coming out of the fuel tank.
My guess is that there is/was some kind of mechanical oiler in the crankcase that metered the flow a little?
Should I just be blocking off oil tank completely.
Oil tank has a substantial amount of fuel in it also.

You just can't trust other peoples work/word can you....
 
Jetpilot106

Jetpilot106

Kickin it old skool
Location
Kansas City,Missouri
Don't put any oil in that thing you pointed at. I got my 300 sitting and the previous owner put oil in it. I think thats why he gave up on the project cause he thought it was blown up cause oil was coming out of the exhaust.
 
L

Laserman

World's Fastest TYPHOON
Location
Orlando, FL
The "no oil in the crankcase plug" Thing is about the 440 or 550 engines!

I suggest referrring to the manual for this.

The 300 engine is NOT THE SAME as the other JS engines!

Not too many members here run the 300 engine -

we have easy access to 440\550\650\750 engines to bolt into these things!
 
J

johnnyb

Location
New Zealand
Alright so I'm having a quick tinker in my lunch break at work, there is oil in the crankcase section marked 'OIL', and the cap doubles as a dipstick, I'm leaving oil in there unless someone can 100% confirm there isn't ment to be.

Just blocked the engine oil feed to the crank case, now appears to be idling fine, not pressurising the oil tank, will reset the adjustment on the carb and report back, might not be today though as it is FRIDAY THANK GOD.

Also, I've looked into getting a manual for it, not having a lot of luck, could get brand new for ~$100NZD, I will get it if I have to though.

Cheers for your help.
Johnny B
 
J

johnnyb

Location
New Zealand
That could be sweet, even perhaps if its just hosted on the net somewhere.

But yeah, I ended up taking it out over the bar last night into the surf, ran the best it ever has, seemed to idle nice and not bog down.

Jesus Christ those waves are bigger than they look.

And then got chased by our local friendly dolphin coming back over the bar.
 
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