help with plug reading, sudden problem

[gman1320]

I was wondering if race gas looked significantly different than regular pump gas. While doing wide open jet checks the plug looks really lean. I richened the main jet until it practically wont run at half throttle but it still cleans out and runs top end and plug is still white with absolutely no black or brown color. Long rod motor with shaved stock head. 35mm pwk carbs. 45 pilot CEL needle , had mains in from 158 to 180, v-force reeds , K+N pods, runs at 4000 ft elevation. Compression 150. Ran great in another bike then switched to mine. Changed only gearing, stator,flywheel, pilot jet, advanced timing 4 degrees. When I first changed the motor it wouldn't start because it was so rich. I found it would start cold without putting the choke on so I dropped the pilot from 52 to 45, now it idles and needs choke when cold. I have lurked here for awhile and I could use some help from you experts. Why does it need so much fuel at WOT and how come it became so rich when starting and idling. Plug turns black when running 1/4 to 3/4 then white at full throttle. Midrange power is now really poor. Same motor, same reeds, same carbs , same coil, ran great a week before I switched it. Am I dealing with a stator problem?

[Handyman]

I was wondering if race gas looked significantly different than regular pump gas. While doing wide open jet checks the plug looks really lean. I richened the main jet until it practically wont run at half throttle but it still cleans out and runs top end and plug is still white with absolutely no black or brown color. Long rod motor with shaved stock head. 35mm pwk carbs. 45 pilot CEL needle , had mains in from 158 to 180, v-force reeds , K+N pods, runs at 4000 ft elevation. Compression 150. Ran great in another bike then switched to mine. Changed only gearing, stator,flywheel, pilot jet, advanced timing 4 degrees. When I first changed the motor it wouldn't start because it was so rich. I found it would start cold without putting the choke on so I dropped the pilot from 52 to 45, now it idles and needs choke when cold. I have lurked here for awhile and I could use some help from you experts. Why does it need so much fuel at WOT and how come it became so rich when starting and idling. Plug turns black when running 1/4 to 3/4 then white at full throttle. Midrange power is now really poor. Same motor, same reeds, same carbs , same coil, ran great a week before I switched it. Am I dealing with a stator problem?

 

 

What kind of motor/cylinders??? Stock.....cubs....powervalve?? I guessing from the mains you are running a cub or a powervalve motor... if that is the case then I would drop to a 150main with a 45pilot clip in 3rd slot. air screw 1.5-2 turns out. At that elevation on my power valve I run what i just suggested and the jetting is almost dead on..I've gone no higher than a 160 and that was rich...It may have ran great in another motor but no 2 motors are the same and the jetting will be different...

 

If it's a stock motor/cylinders I'd go up to a 310-340 main and a 27.5 pilot....

[gman1320]

Stock cylinders, 35pwk Keihin carbs, I'm gonna say this again. Ran great one week before changed to another bike. Now its so rich that I can start it without the choke on. Changed the pilot to get past that problem but something else is going on. How about some thoughts on what happened?

[brian]

It does not need that much fuel.

You need to look up threads on "Plug Chop" in this forum.

When doing a wide open check like that the insulator will look white around

the electrode for sure. You are not looking at the right part of the insulator.

Read the info on plug chop and it will explain how to do it and what to look for

when reading the plugs, but you have to follow the directions.

You might also find some helpful info when doing an internet search.

 

I have not really noticed a difference between race gas and regular pump

gas when reading the plugs. Just make sure that you use the same premix

oil and oil/fuel ratio that you are gonna use when you are riding.

Edited November 14, 2007 by brian

[brian]

It does not need that much fuel.

You need to look up threads on "Plug Chop" in this forum.

When doing a wide open check like that the insulator will look white around

the electrode for sure. You are not looking at the right part of the insulator.

Read the info on plug chop and it will explain how to do it and what to look for

when reading the plugs, but you have to follow the directions.

You might also find some helpful info when doing an internet search.

 

I have not really noticed a difference between race gas and regular pump

gas when reading the plugs. Just make sure that you use the same premix

oil and oil/fuel ratio that you are gonna use when you are riding.

 

 

Also, you can do the plug chop for 1/2 to 3/4 throttle readings in the same manner.

You just have to be more careful to hold the throttle in the same position throughout

the test.

 

Where did you get this motor ?

Edited November 14, 2007 by brian