Super Jet Cant figure this out for the life of me?

[millnoff]

So I have a 760 62t/62t in my sj, fp blaster mod pipe, milled head- 175psi, rec cylinder porting, ported case, carbon tech reeds, stock 38's with prok fa's and a primer kit. compression is within 1psi each cylinder, hot and cold. rebuilt carbs to try and help chase down this issue so all parts are new also. 99% of the time it starts without primer or throttle. idle is consistant and smooth and I can easily change it with the idle screw. seems to have great response and overall runs good until I hold it at a constant rpm for more than about 15 sec? it physically runs ok but when I go wot I get what feels like to me a slight lean hesitation? I get a sporadic slight bog off idle also? I tried 3 diff springs on my n&s, going up and down on my mains and lows and it changed it some but my original jetting seemed the best (135m, 75p, 2.0ns, ls 1, hs 1.25). this is where it gets weird? as I jetted up the pto cylinders plug got way dark, the mag plug didn't seem to change much if at all? tried staggering the screws, and eventually the jets but I still couldn't get the plug to what I would call safe? any ideas whats going on? could I have some bad reeds? crank seel leaking? any ideas? let me know what you think. -Jesse

 

[JT_Freeride]

I had a similar problem. May not be your issue but worth checking. Pull your manifold off and check your reeds I had a single reed pedal break and would cause a lean hesitation off idle but the motor still ran great. It's worth taking a look

 

[millnoff]

that's what im thinking or atleast hoping is the problem and not crank seals_ thanks!

I had a similar problem. May not be your issue but worth checking. Pull your manifold off and check your reeds I had a single reed pedal break and would cause a lean hesitation off idle but the motor still ran great. It's worth taking a look

 

[millnoff]

BTW im by no means a pro tuner so It could be a rich bog but from looking at the plugs im going with lean>

here is a few pics of the plugs:

 

[jamesgunter68]

Plugs look like its lean to me
they should be a darker brown

 

[Joker]

Plugs look like its lean to me
they should be a darker brown

Ya richen it up a quarter turn and see how it goes. Also if you feel a bog right off the throttle and you know that your carbs are tuned perfectly you can try and dry your pipe out.

 

[Harbor]

Check valve on fuel is good? Also a Sj set up like your I sold 1.75 turns out on both low and high

 

[millnoff]

that's the thing, I tried going from 75-77.5 pilots and the pto plug looked way to rich, the bog was still there from 1/4 throttle to wot, so I went back to 75's. then tried going from 115g springs to 95, not much change but noticed more surging in the midrange? then down to 80g springs and the bog was about the same but it ran worse at low throttle. 115g spring felt the best and the motor seemed to run the cleanest at idle to midrange. went from 1 turn out to 1/2 turn on low screws and the bog was BAD, so tried 1.5 turns, bog was about same as at 1 turn but again the pto plug was almost black and it was all girgly at low throttle so i went back to 1 turn. I then tried 137.5 mains (135 were what I had) with all the above combos, same issues. its a random thing, one time it does it the next it doesn't? the really weird thing is that I tried staggering the jets, 77.5p jet and going out an extra 1/2 turn on the low speed screw and the mag plug didn't really change color at all? im running a 3mm restrictor in the stinger sprayer, head pipe is - bottom screw is open 1/2 turn, top about an 1/8 turn. I tried closing the top screw all the way and seemed to actually hurt lowend hit but mid and top was better. I think im going to try my old stock reeds and see what happens? thanks for the help so far!

 

[millnoff]

Check valve on fuel is good? Also a Sj set up like your I sold 1.75 turns out on both low and high

yep, brand new lines, filters, and check valve in the last month. there what I tried after the carb rebuilds didn't seem to help. I thought anything above 1.5 turns ment you need to go up on the jets?

 

[millnoff]

well I pulled the intake mani, tossed the 75 pilots back in, and 95g spring, new gaskets and swapped the reed cages to the opposite cylinders and it runs mint? so maybe had a slight air leak or something? plugs still look lean but the ski runs fine now? thanks for the help guys.