Now it won't idle..... By olblindman (Read 447 times)

[olblindman]

OK. 139qmb with 72cc big bore, stock CVK carb with .88 main. Starts right up, revs up to 9700 WOT with no load, and 8600 WOT with my big butt on it. "Tuned" exhaust, unrestricted CDI, performance coil, free flow air filter, supposedly performance cam, Dr Pulley sliders (Don't remember what weight) and performance variator, 2.88 final drive gears, and new clutch with 1.5k torque spring, and 2k clutch springs. Top speed on a flat at 8600 is reading 35 mph (give or take---flats are hard to find, and short lived around here, and speedo errors are common on these cheapo jobs). Climbs hills very nicely now.

After a run, she will not idle. She just gets slower and slower, until she stalls out. I can give her the goose, and she'll keep running, but it should idle, no?
 Should I jump up a size on my pilot jet, and should I be seeing more top end with what I have? I have a .92 main sitting in my garage, and if I am changing the pilot, I can change the main, but I do not know if that is too much gas for a 72cc bore,etc.

Thanks in advance for any help!

[albanianagi]

Are the valves set to 0.003 or .005, you might need to get a feeler gauge on that head.Only reason i say this is that it kinda sounds like the problem i had, and that fixed it right up better then before

[olblindman]

The big bore kit was done about 75 miles ago...the scooter only has about 300 on it. The valves were set right then. I cannot imagine them being way out so soon, although not impossible. They were set to .003. I remember this as my feeler gauge still has the .003 sticking out!

[Alleyoop]

I would first RECHECK the valves and make sure they are at least .003 inchs gapped.

Then if it still not holding idle then the problem is to much fuel on the low end. The Main jet at this point is NOT the problem it is the PILOT JET and or the FUEL RATIO MIXTURE screw adjustment.

Does turning the IDLE SPEED SCREW clockwise a little to bump up the IDLE HELP?
Also at IDLE the REAR WHEEL SHOULD NOT BE SPINNING if it is that will load it up at idle and can also cause it to die.
Normally if coming down to idle from a rev or run the idle KEEPS ON DROPPING the problem is to much
fuel and it is flooding the plug.

The RPMS are really to high and the problem there is the weights in the Variator are to LIGHT you need to put in at LEAST 2 GRAM heavier weights to get the RPMS down into the 7000 range. 8000+ rpm range is the RED ZONE on these GY6 motors. Also the speed should be near 40 mph but that may be due to the weights being to light and putting in 2 gram heavier weights may give you a few more mph.
Alleyoop

[olblindman]

Yea, I will recheck the valve adjustment first. I tried turning up the idle adjustment, but it got to the point where it was all in ( over a few days).It might have gotten to the point where the clutch was engaging, thereby bogging her down. I am also going to re-adjust the fuel/ratio after the valve adjustment. I may be mistaken on the RPMs...I was going by what the max rpm on the tach read at shut-down.....that may have occurred on a down-hill.
The sliders are easy enough to replace, but I do not know what weight I have in there now......May have to be a bit of trial and error there.
Once again, thanks for the advice! I will iron out all these bugs sooner or later. I won't be able to play with it much til the end of the week, due to work, and life......

[olblindman]

The valves were right on, as I thought they would be. The air/fuel screw adjustment was out way too far, and I did change the pilot jet up a size. I think it is more in the ball-park now, as the air/fuel screw is out about 2-1/2 turns, and it is idling very nicely, and the idle speed adjustment screw has plenty of room for further tinkering. I have yet to take it for a drive, as I haven't had time to put all the body panels on(one can only do so much before going to work!) I have a set of 8 gram sliders on the way, but as I do not remember what I have in there now, I do not know what sort of difference it will make. At least now I will have a starting point!

Thanks again!

[cyborg]

great!!!!! good job

[olblindman]

Finally took it out for a run. Pushing 35+ mph at about 7600 rpms. I have the idle set at around 2400. The 8 gram weights and the larger pilot jet, along with PROPER adjustment to the air/fuel made a good improvement. If I could find a run enough flat run, I think she would top out near 45, but not likely to find one here!
I also added an oil catch can, as most of the time I am running at full throttle.

I got this thing for about 800 brand new in '08....and probably have come close to spending that much to make it run nicely! It has lots of torque now (a necessity with all the hills here), and it isn't so snail-like in speed. We are now required to register these in NC, and they aren't supposed to exceed 30 on a flat......

Thanks again for the help, folks!