Having a hard time jetting my 08 SJ

D

DemianM

i am really having a hard time finding a good all around jetting solution on my 08 SJ. Only mods are a LTD B pipe and tau ceti FAs.

I started with the FP suggested change to 135 mains, it ran well but wasnt really that great on WOT. It also had a stutter when punching it after a long wot run (like coming to a bouy, when you punched it again it would go dead). I was told this is lean on the low speed circuit, although I tried opening the screws which only made the ski run rougher at low speed but the stutter was present.

I posted this on the forum and many suggested I change to 75 low speed jets, 95 gram springs (mine were 115 stocks) and go back to the stock 130 Hi speed jets.....well, no matter what, the ski runs quite rough on plane (1/4 throttle) and after a wot run, it shut down....I am afraid of a seizure, tomorrow I will check compression...

Meanwhile, what do suggest? Go back to 70-135? Go back to the 115 spring? I want the ski to be good allround (not only bottom end or top end). My 97 was quite spot-on with the FP settings.

Thanks a lot!
 
SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
Use 75 low jets, 135 high jets, with the stock needle valve and 115 gram spring.
Yes, you will have a 1/4 throttle steady 4 stroke burble. This will always be there using a 'B' pipe exhaust system.
Aftermarket 44/46 Mikuni system will be way better than the emission mandated stock 38 carbs no matter what jets you use in them as the internal circuitry is too lean and over jetting is necessary to get rid of the shutting off when hitting throttle after high rpm running.
 
D

DemianM

Thanks chucky!
Do you know the possible cause for a shutdown at wot (other than a seizure)? This has happened twice,first time at about 3/4 throttle and yesterday at WOT. I measured compression but it checks same at both lugs.....yesterday it happened again, I was running 75/130 with 95 gram spring and the Hi speed screw at 1.5 turns doubt, do you think it could be so lean as to seize with these settings? Strange thing is ski runs fine after this.
 
D

DemianM

Update: Changed to 75/135 with 115g spring, runs great! Except for the bog after a wot run which is more pronunced if I close the lo speed screws. I am runing them 3/4 open and the ski runs great but the bog is present. If I go richer the bog is less noticeable but the ski is not smooth.

Has anyone tried adding one more check valve at the carbs? Also, is there any procedure for syncing both carbs other than visually??
 
D

DemianM

Is there any bad reason for running them that far in? Should I change to 72.5 jets and open them? If I open them (say 1/2 turn more) the ski loads up a bit on plane and lo throttle.

There is a suggestion in the mikuni manual to get rid of the bog after WOT, which is adding an additional clear check valve in the jets cover, does it work?
 
Last edited:
You must log in or register to reply here.
Top Bottom