Jetting problems..... Weird....

[Boxer29]

I have a blaster.... With ported head, fmf fatty, stock silencer, reed spacer, kn filter, no airbox.....

With the stock jet it ran ok... The whole plug was a mocha brown.... Didn't do a plug chop as this is how I got it.... He put in a different needle...

Switched to a 280 jet and it has no power.... In any gear, just like hesitating and all that.... Guessing it was to much fuel.... I guess I'll have to wait for my jet kit and slap in a 250 or 260 maybe?

Everyone on here was saying 290/300.... 280 was to much fuel weird....

 

[Boxer29]

Found a 240,250,260 jet and tried the 260 still to much fuel.... Put in 250 ran great.... All threw lowend and mid.... But when in 5th and 6th pinned..... It randomly pops and loses power.....

 

[Surfrjag]

What's your elevation? If your up in the higher elevations you will have a smaller jet that most of us around sea level. Also go over a few things. Start with your fuel vent line and be sure its not clogged. How does your spark look? Did u put a new plug in? Good fuel? Did you adjust your air screw at all? I have seen bikes not run well till I adjusted the airscrew then be lean up top. You can start around 1-1/ 2 turns out

 

[Boxer29]

I'm at sea level.... 20min from jersey shore..... 93 gas with a 32.1 mix.... Spark is great... Fuel line is brand new not clogged.... Just cleaned the carb...yup new plug with every jet change I did today....

And nope didn't mess with the idle screw.... I'll try that.... Right now I'm at a 250 jet it screams through 1-4 but in 5th and 6th it pops so not enough fuel.... But a 260 jet it bogs like a mother... Hesitates through 1-3

 

[Larry's Shee]

Check that the tank cap vent is clear and the hose also.

 

[Boxer29]

What would that do? But I'll check....

 

[Surfrjag]

As you start drawing fuel out it creates a vacume in the tank. If the vent line is clogged it won't let enough fuel out.

 

[Boxer29]

Like vent line on the gas cap right? I don't have one on there. It's just a open nipple....

 

[Blaaster]

Could that problem be with that stock silencer messing with the FMF pipe. Pipes seem to prefer silencers that are designed for them!

 

[Boxer29]

Ya I plan on buying the silencer.... Hopefully Monday or Tuesday..... Could that really make a difference between a 250 jet and a 280 jet?

 

[94fiveohvert]

try pulling the baffle off the silencer?

 

[Larry's Shee]

Pull the cap and blow the nipple see if air goes thru it. I:I What size pilot you running? Did you set float level? Try pulling carb, remove float bowl and turn fuel on draining it into clean cotainer for 30-45 seconds , see if it starts to slow down or is slow from the start.

 

[Boxer29]

Stock pilot..... I blew air threw the cap that was working.... I'll try the pulling the carb tomorrow and letting fuel run threw it....

 

[Larry's Shee]

Also pull petcock from tank and clean that.

 

[Blaaster]

You seem to be lean WOT high gear. But OK in lower gears. Try a 260 or 270 to richen up the WOT, but drop the needle one notch to compensate and lean it back for 3/4 throttle.
This may seem not to conform to the norm, but you may be surprised it may work, those little stock carbys can be very difficult to jet. Took me quite a while to get mine as I want it.

 

[Boxer29]

That is my problem.... Low gears are ripping....in part throttle and wot but in 5th and 6th in WOT it seems lean.... Got a pop... When I had a 260 in it... Low gears wouldn't even rev good... Maybe I'll try dropping the needle with it.

 

[con8quest6]

My stock 06 blaster did this same damn thing.....I had a leak in my intake. Problem solved.

 

[Boxer29]

Leak in your intake? Hmm..... Mine is all covered in black tape to try and keep that fro
Happening but maybe somehow its leaking

 

[Awk08]

you must do a leakdown test, and be sure the floats are set to 20-21.5 mm before you even try to jet that carb, and i would suspect that needle, put a stock needle in there, middle position, then try the 290-270 jets
but.........techblaster in philly says he's jetted numerous bikes with an fmf at a 250 main, maybe theres sumthin in the air around the philly/nj area ??? hahahaaa

check them floats for cracks too, submerge in fuel and look for bubbles < as suggested by larry in another thread

 

[Larry's Shee]

Leak in your intake? Hmm..... Mine is all covered in black tape to try and keep that fro
Happening but maybe somehow its leaking

I've seen a horsefly, I've even seen a needle wink it's eye, but I've never seen a piece of tape stop an intake leak I:I
Maybe try fixing that first or you'll be asking why you blew up