fmf pipe should i jet my carb

ENERGY INC

New Member
Feb 11, 2013
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ohio
Ok so I'm going to get an fmf pipe and I saw something how I should jet my carb do I have to or is it just a good idea cause I'm in the middle of a complete rebuild and figured I would just do it now while everything is apart
Also the reason for.me rebuilding is I lost second and 5th gear and IV not taken it aprt yet but found good deal on new trans for 25$ should I just go ahead
and buy it
 
Depending on elevation you will be around a 270. Start with 280 and plug chop down. We ride at sea level. One of our bike has an fmf on it. We have a 270 with lid removed and it's a nice cardboard color in 40 degree weather.
 
Well I'm in Ohio so I'm about 500-750ft elevation wat would be a good jet kit to go with
Also wat exactly is a plug chop
 
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Forget about kits they seldom contain any jet you can use.

Buy them singly.

Also chuck away any needle contained in a kit!

Little info for you..

FMF calls for #260 main, needle clip on middle setting.

+ 1 size for pre mix at 32:1,
+ 1 or 2 if you use an aftermarket air filter
+ 2 if you take the airbox lid off
+ 1 for cold weather.

What I am saying is buy a range of jets from #270 - #310.

Plug chop to confirm any change in jetting.
 
You say exactly what engine/pipe/carb mods you have or will have and I will offer an educated guess.


Plug chop.

Warm up motor to operating temp.

Fit new B8ES plug, ride 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, roll to a stop.

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.

http://www.blasterforum.com/do-yourself-20/how-plug-chop-38674/

http://www.blasterforum.com/engine-13/plug-chop-how-vid-48226/

This is a good to go plug.

2wr2fwo.jpg



This one is a little rich, but I would run it, I like to be on the safe side.

plug152mainmediumoi2.jpg



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 curcuit.

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.
 
It's cheaper to buy plugs and a few jets instead of a new piston. I'm in wv right across the river. elevation around 700 to 800. I have full fmf and a uni filter with air box lid. Spring and summer I run a 280, winter a 300 usually. Listen to the vets on this site. They'll help you alot
 
Wish I had a dollar for every time Blaaster posted that, :eek:.

Contact these guys: Carburetor Parts Warehouse
Get the range that Blaaster suggested.
Or if you have a local dealer/shop go there. Jets are non-returnable. If you are going to be fireing it up soon, might want to get one size larger also, unless you're in S. Ohio. You will have to learn to jet to compensate for the temperatures.

$25 for that trans night not be bad price.

Any time amount of air flow is changed in or out of the engine you have to rejet
 
Last edited:
Wish I had a dollar for every time Blaaster posted that, :eek:.

Contact these guys: Carburetor Parts Warehouse
Get the range that Blaaster suggested.
Or if you have a local dealer/shop go there. Jets are non-returnable. If you are going to be fireing it up soon, might want to get one size larger also, unless you're in S. Ohio. You will have to learn to jet to compensate for the temperatures.

$25 for that trans night not be bad price.

Any time amount of air flow is changed in or out of the engine you have to rejet

dude we'd never get outta the bar with that many singles lol ha3
 
Forget about kits they seldom contain any jet you can use.

Buy them singly.

Also chuck away any needle contained in a kit!

Little info for you..

FMF calls for #260 main, needle clip on middle setting.

+ 1 size for pre mix at 32:1,
+ 1 or 2 if you use an aftermarket air filter
+ 2 if you take the airbox lid off
+ 1 for cold weather.

What I am saying is buy a range of jets from #270 - #310.

Plug chop to confirm any change in jetting.

This is similar to my experience on our three blasters. We run a 250 in a stock bike with autolube and a K&N, a 280 on a bike with 32:1 premix, FMF fatty and K&N with open lid, and a 290 on a ported bike with 32:1 premix , K&N with open lid.
 
You say exactly what engine/pipe/carb mods you have or will have and I will offer an educated guess.


Plug chop.

Warm up motor to operating temp.

Fit new B8ES plug, ride 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, roll to a stop.

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.

http://www.blasterforum.com/do-yourself-20/how-plug-chop-38674/

http://www.blasterforum.com/engine-13/plug-chop-how-vid-48226/

This is a good to go plug.

2wr2fwo.jpg



This one is a little rich, but I would run it, I like to be on the safe side.

plug152mainmediumoi2.jpg



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 curcuit.

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.




So if I get an fmf, air box lid off, k n filter, and v force reeds, what jet size should I do? Also, I’m at 1000ft elevation
 
With lid and filter mods add at least two sizesto FMF recommendations. AloA, that's for 70* F, add one size for each 20* colder. Winter jetting.
 
With lid and filter mods add at least two sizesto FMF recommendations. AloA, that's for 70* F, add one size for each 20* colder. Winter jetting.

Awesome thx. Is 1 size up, 10 digits up? For example one size up from 270 is 280? If not, plz explain how it works thx
 
I have no odea how the jet sizes work, so can you give me a start with the following, and then I can work from there : k n filter, open airbox, fmf, vforce 4, 1000ft elevation, and 30 degrees thx.