E: Engine comet with concentric mk1

[erik]

i have read about the jets and the needle Position for a comet with a amal concentric mk1.if i use a 230 it is much to rich and with a160 Jet it is to rich in a 30mm carb.the carb is nearly new with a new slide.the needle is in the lowest Position and a105 needle Jet is fitted.and i tested the Motor with colortune and i can see a yellow flame which is for to rich mixture.what could be wrong?

 

[Bill Thomas]

Hello Eric, I would think it's just the slide too rich ?, But we need to know what state of tune your engine is, Or if it's standard, Unless your readings are at 5,000 rev's. Cheers Bill.

 

[erik]

the engine is standart and the bike runs okey but not perfect.the mixture is to rich with full throttle opening ,too.there is no influence of the slide.

 

[Bill Thomas]

Maybe the silencer is too blocked. Cheers Bill.

 

[erik]

this defenetly not.when you drive with full throttle the bike becomes quicker when you Close a Little bit.

 

[Bill Thomas]

If you are not running an air filter, I give up !!, I would think you need about 190 ish main jet, Cheers Bill.

 

[erik]

there is a bellmouth mounted and a 160 mainjet.i would go to 150 or 140 mainjet.the float and the floatbowl is new,so i think the Level of gas should be okey?

 

[Bill Thomas]

there is a bellmouth mounted and a 160 mainjet.i would go to 150 or 140 mainjet.the float and the floatbowl is new,so i think the Level of gas should be okey?

That sounds too small to me , But you are the Man, There have been some jets that are Fake, So the numbers may be wrong ?. Good Luck, Bill.

 

[greg brillus]

If the bike gains power as you back off the throttle from fully open, this suggests to me that at full throttle the mixture is too weak. If the bike is running rich from part to 3/4 throttle then it sounds like the slide is too rich.......Do you know what number cutaway the slide is......??? A number 3 is probably too rich. Cheers............Greg.

 

[Howard]

i have read about the jets and the needle Position for a comet with a amal concentric mk1.if i use a 230 it is much to rich and with a160 Jet it is to rich in a 30mm carb.the carb is nearly new with a new slide.the needle is in the lowest Position and a105 needle Jet is fitted.and i tested the Motor with colortune and i can see a yellow flame which is for to rich mixture.what could be wrong?

Eric, I'm running a standard Comet with a 30 mm MkI Concentric. I've got a bellmouth on the carb and an open silencer. 230 main jet will be slightly too big (I think I'm on 210) 160 will be WAY too small. The needle jet will be better at 106. I think I'm running a size 3 slide, but it may be 3 1/2 (I've had two or three Comets with concentrics apart lately, so I'm not sure). I like MkIs they wear out a bit quickly, but they're easy to work on and they work well. You may have trouble in the float bowl, check the float height, and make sure you've got the Viton tipped float needle.

I use as a starting point New jet = Standard jet X new choke area / original choke area Which for a 30 mm carb is a 220 jet - nothing very scientific, but it's a start.

Have a look at this website http://jba.bc.ca/Bushmans Carb Tuning.html

Good Luck,

Howard