550 Tuning

[RX86JS]

I have a 85 550 with 44 SBN on it. It has a half pipe, worx waterbox, and a milled head. I was told to set the Low at 1&3/4 and the High at 2 turns out. I was wondering if this is correct.

[SuperJETT]

It depends on the jetting inside the carb. 100L/125H used to work for me, but every engine is different---mine was mildly ported, pipe, head, carb, Jetcraft silencer, etc.

[sunny_az]

I'd try 2 turns out on the low and 1 3/4 on the high.

With new plugs, take a plug wrench for a 10 minute ride in the mid-range, give it a couple full throttle sprints then stop(preferably w/out a no-wake zone), pull the plugs and diagnose.

[sflsurfrider]

i would do a popoff test then take the carb apart to make sure its 100% and see what jaets are currently in it before even thinking about installing it.

[djyox]

I'm running on my 550 1 1/4 low, 1 high I'll have to look at what jets I'm running though..

[onesojourner]

mine is set up like this...
jetsoprt pipe and copper head gaskets are my only mods. they say for a stock ski total jetting should be around 225-230

sbn44 mikuni part number BN44-40-8067. it came with a low jet at 120 and high at 140. the needle was a 2.5 with a 80g spring. i tried to put in a 2.3 needle valve and it made my ski hard to start. the way it is now it starts right up no primer. when i got it i didnt touch anything and it ran rich. i have been working my way down. the last set up i had before it was to cold to ride was low low 115 high 130. with that set up i was still very rich. i was getting the best power with both screws turned all the way in. i now have low 105 and high 120.

[sunny_az]

I'm running on my 550 1 1/4 low, 1 high I'll have to look at what jets I'm running though..


That's a decent setting to be at, Nick. If you have jets next size up you could experiment with them. Or, if it ain't broke don't fix it. ;-)

We're just starting out rich(hopefully) and leaning it out to find the sweetspot. If it's lean that far out, bigger jets. If it cranks down to less than 1 turn out on either and is still too rich, smaller jets.

[SuperJETT]

they say for a stock ski total jetting should be around 225-230

Stock 44 SBN *carb* likes 220-230 total jetting, 38's like ~210, and 46's 240-250 but it also depends on other things like porting.

[RX86JS]

I rebuilt the carb over the winter and have it running as of now. I was wondering how do you tell if its too lean? Will it be like its starving for fuel?

[RX86JS]

Also, with the plugs should I be looking for black and slightly moist?

[sunny_az]

Brown and moist is the goal.

Black and wet = too rich

white and dry = too lean

Better too rich than too lean.

[djyox]

My plugs are reading too rich, but I have been over doing it with oil because I would rather have it smokin then locking up on me.

Matt, that avatar is pimpin!