carb jetting

[Red Viking]

I just put a full FMF fatty pipe and FMF slip on, I also put a new top end on it same size as OEM, I am also taking the original air box off and running air filter straight off the carb. Question I have is what should I change the main jet to, was thinking 290 or 300 any suggestions?

 

[tbrooks]

Cheap ebay cylinder? Did you champfer the ports first? Premix or injection? temps? elevation?

 

[XxWRAITHxX]

You may have to jet a little bigger than that. The air filter off the carb is most likely going to allow a lot more air than the stock airbox. More air = more fuel. Im not jetting expert so you might wait to see what other people post. If it was me i would start 320 _ 330 and plugchop down

 

[tbrooks]

The 300 is probably large enough, unless your riding at 100+ outdoor temps, but if your at 10000ft above sea level you could need a 230. No matter what as said^^^ you have to plug chop to confirm

 

[Red Viking]

The 300 is probably large enough, unless your riding at 100+ outdoor temps, but if your at 10000ft above sea level you could need a 230. No matter what as said^^^ you have to plug chop to confirm

What is plug chop? Never messed with a carb before?

 

[XxWRAITHxX]

A plug chop is done to determine how lean or rich your main jet is by reading the spark plug. Warm the bike up on the plug you currently have in. Then when warm put a new plug in. Get the bike up to full speed and hold it wide open for a quarter mile or so, hit the kill switch and hold the clutch in and let it roll to a stop. You want to go wide open throttle because the main jet only works at 3/4 to full throttle. Take the plug out and look for a mocha brown color around the electrode and on top of the ground strap. There should also be a thin brown ring around the insulator towards the bottom its kinda hard to see. Black is rich grey or white is lean. This is how i do it some people may do it a little differently. There are other posts on here that have pictures or you could look it up on you tube.

 

[Red Viking]

A plug chop is done to determine how lean or rich your main jet is by reading the spark plug. Warm the bike up on the plug you currently have in. Then when warm put a new plug in. Get the bike up to full speed and hold it wide open for a quarter mile or so, hit the kill switch and hold the clutch in and let it roll to a stop. You want to go wide open throttle because the main jet only works at 3/4 to full throttle. Take the plug out and look for a mocha brown color around the electrode and on top of the ground strap. There should also be a thin brown ring around the insulator towards the bottom its kinda hard to see. Black is rich grey or white is lean. This is how i do it some people may do it a little differently. There are other posts on here that have pictures or you could look it up on you tube.

Awesome thanks for the information. I only bought different size main jets, hope I don't need others.

 

[XxWRAITHxX]

No problem man, with your mods your pilot jet should be good based upon other threads ive read on here.

 

[Red Viking]

No problem man, with your mods your pilot jet should be good based upon other threads ive read on here.

That's good wife is going to kill me if I spend any more money. Lol

 

[Blaaster]

Before you make the plug chop run it is important that the float level is correct, the idle is set correctly and there are no air leaks in the system, otherwise the smoke ring may lie about the AFR.


WHEN ALL OF THE ABOVE ARE CORRECT PROCEED WITH THE FOLLOWING.


Warm up motor to operating temp.

Fit new B8ES plug, ride WOT through the gears and hold WOT in 5th or 6th gear for 10 seconds, or as long as you can safely.

Switch off the motor and pull in the clutch, apply brakes to come to a stop quickly.

Take the plug out and replace the old one for the ride home.

Carefully cut the threaded end off the plug to expose the insulator.

There should be a smoke ring of a cardboard or biscuit colour around the insulator.

If it is non existant or a very light colour, you are lean and require a larger main jet.

If it is a lot darker you are rich and may go down a size in main.

I prefer to run a little on the darker side, I may loose a little power but it is worth it for the peace of mind that I won't need a rebuild so soon.

You have to get up a reasonable speed so that you can get the motor to pull strongly.

Then hold it Wide Open Throttle (WOT) for 10 secs or as long as you can.

The idea is not to get speed but to make it pull strong at full throttle to get onto the main jet circuit.

I find I can safely do it on a short run by applying the brakes some.

If you have not enough room you can use 4th or 5th gear with good results.

 

[Blaaster]

Putting the air filter directly on the carby throat will need a larger main jet, 3 sizes larger usually does the trick.

If you are using the stock carby the jetting should be easy , but larger carbs have been known to been a headache to jet with the filter directly on the carby!

A #330 would be a good start to plug chop at.

 

[Red Viking]

Putting the air filter directly on the carby throat will need a larger main jet, 3 sizes larger usually does the trick.

If you are using the stock carby the jetting should be easy , but larger carbs have been known to been a headache to jet with the filter directly on the carby!

A #330 would be a good start to plug chop at.

Is there a trick to getting the needle back in the carb? It seems to stop and it does not seem that it is all the way seated like it should be, and the last thing I want to do is force it in.

 

[XxWRAITHxX]

There is an alignment pin inside the carb and a groove on the slide. Sometimes the needle wont line up to go into the emulsion tube just reach your finger in there and line the needle up with the hole then push it the rest of the way down and tighten the cap.

 

[XxWRAITHxX]

When i say push it i dont mean force it once everything is lined up it will go all the way down easily

 

[Red Viking]

There is an alignment pin inside the carb and a groove on the slide. Sometimes the needle wont line up to go into the emulsion tube just reach your finger in there and line the needle up with the hole then push it the rest of the way down and tighten the cap.

When i say push it i dont mean force it once everything is lined up it will go all the way down easily

Check thanks fire the help.

 

[Red Viking]

Before you make the plug chop run it is important that the float level is correct, the idle is set correctly and there are no air leaks in the system, otherwise the smoke ring may lie about the AFR.


WHEN ALL OF THE ABOVE ARE CORRECT PROCEED WITH THE FOLLOWING.


Warm up motor to operating temp.

Fit new B8ES plug, ride WOT through the gears and hold WOT in 5th or 6th gear for 10 seconds, or as long as you can safely.

Switch off the motor and pull in the clutch, apply brakes to come to a stop quickly.

Take the plug out and replace the old one for the ride home.

Carefully cut the threaded end off the plug to expose the insulator.

There should be a smoke ring of a cardboard or biscuit colour around the insulator.

If it is non existant or a very light colour, you are lean and require a larger main jet.

If it is a lot darker you are rich and may go down a size in main.

I prefer to run a little on the darker side, I may loose a little power but it is worth it for the peace of mind that I won't need a rebuild so soon.

You have to get up a reasonable speed so that you can get the motor to pull strongly.

Then hold it Wide Open Throttle (WOT) for 10 secs or as long as you can.

The idea is not to get speed but to make it pull strong at full throttle to get onto the main jet circuit.

I find I can safely do it on a short run by applying the brakes some.

If you have not enough room you can use 4th or 5th gear with good results.

New problem when I use the throttle it goes in and dies not go back like it's stuck? Had a hard time getting it together don't understand what the problem can be.