TOPIC:

Have been working on my old bike for a while and have it coming along very well. It is running good but only getting a little over 20mpg. It has PODs (yes I know), but otherwise it's stock. After reading on here I put in 40/140 jets, and 3 washers on the needles. I have read to got up 4 sizes that would be 135. I read go up 15% that would be 140. Am i close? Where might the MPG killer be? Pilot? Mains? Needles? I know I'll have to play with them to get them to run good after a change but right now it wont pass a gas station.
Ken

wow..20mpg...wish i could help you but im not familer with tuning Cv carbs. but my 79kz1198cc with z4 cams and 29mm gives me an average of 30-35mpg.
what does the spark plug look like?

I always went with a 4% increase for either filters or exhaust as a starting point.
Along with one washer to raise the needle. If your using BS34s, I think there is a
different needle you need to use.


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ffltstn wrote: Have been working on my old bike for a while and have it coming along very well. It is running good but only getting a little over 20mpg. It has PODs (yes I know), but otherwise it's stock. After reading on here I put in 40/140 jets, and 3 washers on the needles. I have read to got up 4 sizes that would be 135. I read go up 15% that would be 140. Am i close? Where might the MPG killer be? Pilot? Mains? Needles? I know I'll have to play with them to get them to run good after a change but right now it wont pass a gas station.
Ken

If you spring for a proper jet kit you can go back to the 37.5 pilot and down on the mains. Use the mains and needles that come with the kit. The way you're doing it is ancient and totally inefficient. The key is in the needle taper when you put pods on the carburetors. The stock needle doesn't have enough taper no matter how many washer you put under it to every be correct...it's a band aid and guys that do it lean that from guys that were too cheap to buy a proper jet kit...PERIOD

They would get 50mpg when new. Part of the price to be paid for mods such as pods ect is worse running and mpg.

Just completed my KZ(?) 1100 top-end build with 84 GPZ cams and ZN 1100 "Bath tub" head over a low mi. cylinder block with new (modified) oem standard pistons and rings...with new pins for good measure.
It has the factory air-box still, and the original unmolested BS34 carbs with 42.5 pilot and 132.5 main jets.

Here is what the spark plugs look like today, after the first 600 miles.

Back to 40 pilots per LarryC suggestion that plugs look "quite sooty". Will start with the pilot screws adjusted to 1.5 (vs. 2.5) turns out, and see what happens...

Looks like you got them dialed in pretty good. was the factor pilot jets 40 or 37.5?

37.5 pilot (factory)

What Larry said, your way big on the main jets then added to your problem by putting shims under the needle. . My ELR Clone has a GPZ1100 engine bored to 1170 with High compression pistons, performance cams, porting pod filters, 4 into Kerker with a HUGE baffle and Mikuni RS36 carbs. I get 34mpg at 80mph.

ffltstn wrote: Have been working on my old bike for a while and have it coming along very well. It is running good but only getting a little over 20mpg. It has PODs (yes I know), but otherwise it's stock. After reading on here I put in 40/140 jets, and 3 washers on the needles. I have read to got up 4 sizes that would be 135. I read go up 15% that would be 140. Am i close? Where might the MPG killer be?

When it's off tune, you have to open the throttle a lot more just to get enough power to run.

Sounds like you are too rich as well. I think you should probably get 35 mpg (city only) and probably 50 ballpark for highway but that's a guess.

I've always gotten 42 MPG average, when it was a 903 and 1015. CV carbs are supposed to be stingier.
Steve

What jet kit are you using? I bought a dyno jet kit, I have pods and 4 to 1 exhaust and was trying to figure out what size main jets to go with.
Thanks,
Jeff