125 jetting

[skipperclyde]

I have putten together a 125 from parts.  It is a fresh rebuild.  The carb is a 27mm Bing.  I just can't seem to get it set up right.  The book says it should use a 40 pilot, 140 main and 2.70 needle and needle at the 4th position of 4.  I have good pitcocks and the float needle seals well.  All jets and needle are new.

I have reduced the pilot to a 30. Reduced the main to 135. Bike runs well, still loads up but not as bad.

All suggestions are welcome.

 

[Richard]

Try 140 main, 35 pilot, 2.70 needle jet, and jet needle 2nd position from the top. Run the engine at 1/8 to 1/2 throttle for a couple of laps (3 minutes or so) and check the spark plug for a golden brown color. Move needle up  if plug is white, or move needle down if plug is black. Next check plug color after runing engine at 1/2 to full throttle to confirm main jet.

 

[john durrill]

Skipper,
stock theones we got came with a 140 main, 276 needle jet , and a 40 pilot jet. We had good results with a 135 main , 273 needle jet and a 35 pilot jet , useing a 32 to 1 mix of golden spectro and high test gas.
we are at sea level. dont know what mix oil to gas you are running or the height above sea level you are at. i would start off with the needle rich and drop it slowly looking at the plug as you go.
hope this is a help.
John D.

 

[skipperclyde]

I'm running 32:1 fuel to oil.  3:1 93 octane to 110 octane.  Elevation 600 ft.  

My consern with running a 2.73 needle is that I'm already at the lowest needle position with a 2.70 needle.  But I'll give the 2.73 a try.

I don't have a 35 pilot.  If anyone out there has one to lend me. I would be much appreciated.

Thanks



Edited by - skipperclyde on 10/05/2001  08:08:22 AM

[Richard]

Skipper,

When you wrote that the jet needle was in the 4th position do are you counting from the top or bottom?  My manual shows the 4th position as the richest position. What does the plug look like when you only run at low rpm?  What does the plug look like when you run at high rpm?

 

[skipperclyde]

The needle is set at its leanest setting, all the way down.  At full  RPM Plug looks alittle dark.  Bike runs great at full RPM.

I'll report on mid range plug color aftrer I get home and test it.



Edited by - skipperclyde on 10/05/2001  1:20:33 PM

[skipperclyde]

quote:
The needle is set at its leanest setting, all the way down.  At full  RPM Plug looks alittle dark.  Bike runs great at full RPM.

I'll report on mid range plug color aftrer I get home and test it.

 

Edited by - skipperclyde on 10/05/2001  3:49:52 PM

[skipperclyde]

I ran the bike at low to mid range RPM.  Sputtered some.  Plug is rather dark.

 

[john durrill]

Skipper,
if you can get me on yahoo or icq. ill see if i can help in real time. if not send me an e-mail and set up a time when we are both at the computer k? Ill leave icq and yahoo up and running tonight.


 

[SS440]

Did You check the timing? I had a problem down low and it appeared to be jetting but was timing. When I set the timing to spec's stock jetting was real close. Good Luck

 

[Doug Wilford]

It is possible that you need to have your ignition checked.   If it is a moto-plat.

 

[john durrill]

Doug I seem to remember that one could check
the timing with a timing light. it would have to involve a degree wheel and a dial indicator The first time. Make sure the markes on the case and the markes on the fly wheel line up at tdc. Then mark the Fly wheel at 2.8 mm 2.9 mm 3.0 mm 3.1 mm and 3.2 mm. You could then use the timimg light to see where the ignition is actually fireing.
 It would be some trouble the first time , but take no time at all to check after that.
 Could you shed some light on this?
 John D.

 

[SS440]

To check the timing you need a dial indicator
and a small pin or a small drill bit. Bring the piston up to the correct spot BTDC(sorry I don't remember the specs and I'm at the office) and see if the flywheel hole and stator hole line up (thats what the drill bit is for) if not move the stator. I suspect
your timing might be retarded. Good Luck

 

[Doug Wilford]

Sorry guys, I wasn't refering to timing.  I was refering to quality, quantity of spark at low RPMs'  Magnetisum in the flywheel and further testing done with special equipment at Penton Imports, PVL, Dane Leimbach is still doing the testing.




Edited by - Doug Wilford on 10/08/2001  7:53:07 PM