07-14-2012, 01:51 PM #1
650sx with mods... need carb tuning advice
Just got out my wife's 650sx standup this weekend. We bought it early last season from the original owner who absolutely babied this ski. He put a lot of money into aftermarket stuff for it. It runs good once warmed... but I always have to peg the throttle (WOT) when starting... like it's sorta flooded. I dealt with it last season and it's the same this year. So I want to try and get it right.
Here is the aftermarket stuff it came with:
Mikuni SBN44 carb
PJS exhaust (blue curved pipe, stainless rest of it)
K&N flame arrestor/air cleaner (oval)
NGK BR8ES plugs
Westcoast ride plate
Skattrak impellor (unknown pitch)
So I took apart the carb to clean and confirmed 125main and 100pilot jets. I did not remove the spring/needle valve because everything looks spotless... but I'm guessing they are the factory new carb settings like the jets were (factory settings are needle 2.3, spring 65g). I cleaned everything again, and blew out the fuel passages. This carb looks new. It has a primer on it, no choke.
The mixture screws are set at (High = 7/8 turns out) and (Low = 1-1/8 turns out)
Compression is 158 Front, 153 Rear
Plugs are black and wet
The ski runs great with great throttle response once it is warmed up. But it does not restart when warm well. I always have to hold the throttle WOT while cranking (no primer used) and it'll finally catch and go. I've heard you should be able to just hit the starter button on a warm engine and it start right up and idle. Mine won't. Feels like it's flooding... thus having to pin the throttle.
When it's cold... you still have to pin the throttle to get it to start... even with primer (which I probably don't need to use). But it will blubber for a while... even when holding the throttle WOT... it just stumbles and won't go for a while. Then eventually it'll get past the blubbering and finally rev up high and take off. Pretty annoying.
I've read a bunch of your SBN44 jetting threads and it sounds like I have small jets for all my mods. Yet it seems to be indicating too rich??
I'd appreciate any jetting or mixture setting suggestions.
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