MPG Help

[VMAXXIMUM]

I cannot figure out what is going on. I'm only getting 27MPG. Steve O has been helping me try to track down the issue without much luck. I was only getting 25 MPG so we are moving in the right direction. A/F screws have been checked and adj.(by Steve O) I found the PO has shimmed the needles .04" with washers that have now been removed. My bike is running 100% better with much crisper sound and throttle response but still crappy MPG. Anyone with any idea's? I did notice a "puffing" kind of sound when it idles. Other than that the bike seems to be running great to me. It's driving me nuts that I can't figure it out and there doesn't seem to be any major symptom to help narrow the search.

:bang head:

 

[Dragmaxster]

I cannot figure out what is going on. I'm only getting 27MPG. Steve O has been helping me try to track down the issue without much luck. I was only getting 25 MPG so we are moving in the right direction. A/F screws have been checked. I found the PO has shimmed the needles .40 with washers that have now been removed. My bike is running 100% better with much crisper sound and throttle response but still crappy MPG. Anyone with any idea's? I did notice a "puffing" kind of sound when it idles. Other than that the bike seems to be running great to me. It's driving me nuts that I can't figure it out and there doesn't seem to be any major symptom to help narrow the search.

:bang head:

My mileage is 44mpg right now with 152.5 mains,170 pj1 and 90 pj2- stock pipe and cops from gsxr750 and r1 coil wires.
I highly recommend the cops if you don't have them as it helped a ton on power and mileage. K&N single filter.
When you say you removed the washers from the needles i am asuming you do not have stock needles?
That would be the major reason for losing mpg's.

 

[Biker Dash]

Is there any chance the butterflies for the V-boost are not fully closing? The puffing sound has me wondering about that.

 

[Dragmaxster]

Also your "puffing" sound like too rich at ide and that would be your a/f mixture screws turned out too far--what are they at now?
It would help if you listed the modifications.

 

[VMAXXIMUM]

I'm running stock main's, the PO put washers on the ends. Stock pipes with slip on Supertrapps. a/f screws are approx. 2 3/4 turns out. When Steve and I checked them they were all screwed up, one was 6 1/2 turns out, the rest were all over the place but none less than 4 turns out. They are all set now. I did also check the vboost butterflies but they are opening and closing fine.

 

[Traumahawk]

Are they stock needles too?

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[VMAXXIMUM]

I believe they are stock needles. There are no clip spots and they are 152.5's. This is just driving me crazy.

 

[Traumahawk]

One thing that might help is changing the main jets to 150's....instead of the 152's

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[eggohead]

I hear you with the MPG. I have 2 bikes. My 90 has muscle jet kit and 4-1 UFO- Fuel light came on at around 72 miles last night. My 95 has 4-2 Holeshot and K&N filter I got 2 weeks ago from a friend, and I still haven't messed with the carbs to find out what has been done. It gets between 72-80 before the light comes on... I am thinking both need smaller main jets to get better MPG. If weather stops raining or being 95* and 50% humidity I might work on them...lol If not I will ride and enjoy the nice hot rides...lol minus the rain..


Trama- I don't remember what size main I said I put in? Messed with electrical way too long. No issues in over a month so I guess I fixed it.

 

[Traumahawk]

I hear you with the MPG. I have 2 bikes. My 90 has muscle jet kit and 4-1 UFO- Fuel light came on at around 72 miles last night. My 95 has 4-2 Holeshot and K&N filter I got 2 weeks ago from a friend, and I still haven't messed with the carbs to find out what has been done. It gets between 72-80 before the light comes on... I am thinking both need smaller main jets to get better MPG. If weather stops raining or being 95* and 50% humidity I might work on them...lol If not I will ride and enjoy the nice hot rides...lol minus the rain..


Trama- I don't remember what size main I said I put in? Messed with electrical way too long. No issues in over a month so I guess I fixed it.

Glad that it fixed it. The easiest way to get an increase in mileage is to drop the needle 1 clip.

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[eggohead]

It is already 2nd clip from blunt end.

 

[Traumahawk]

OK. ....I will look thru past emails and see if I can find what the main jets are. Do you know that the plugs are gapped at and when was the last time that they were changed?

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[eggohead]

on the 90 I gapped plugs at .32 I think.. and they are fresh from this year.

 

[Traumahawk]

You might try increasing the gaps to .035. The bigger the spark, the better fuel is burned.

 

[sdt354]

Lots to check here. +1 on the plugs Eric. I like to eliminate compression issues as a cause. The bike does run decent. Then there is a matter of the last guy in the carbs and where the floats are set. A/ f is in the balll park. Best bet might be to put a set of known good carbs on, and go riding. I just happen to have them in a box Christian. We'll get it licked.
Steve-o

 

[Dragmaxster]

Glad that it fixed it. The easiest way to get an increase in mileage is to drop the needle 1 clip.

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+1 you can adjust the needles and with the supertrapp adjust at the pipe also.

 

[Dragmaxster]

I'm running stock main's, the PO put washers on the ends. Stock pipes with slip on Supertrapps. a/f screws are approx. 2 3/4 turns out. When Steve and I checked them they were all screwed up, one was 6 1/2 turns out, the rest were all over the place but none less than 4 turns out. They are all set now. I did also check the vboost butterflies but they are opening and closing fine.

Stock airbox with stock filter? Again the cops (total cost $25) and a single K&N raised my fuel mileage to 44mpg. I rode 88 miles then stopped and could only get 2 gallons in it.We are running the same main jets same a/f turns out, i have stock pipes with 8 5/16 holes drilled. You have the advantage of tuning the exhaust.
I ran supertrapps for 20 years and you can take one plate at a time for tuning.

 

[one2dmax]

Float levels?

 

[VMAXXIMUM]

I really appreciate the time you all have taken to help me. I will check the float levels next. The huffing sound is coming out of the right exhaust. Dragmaxster suggested it might be a rich a/f setting but when I checked the plugs after idling for 5 to 10 minutes they looked pretty lean to me.

 

[eggohead]

Can wet float level be check with connecting a clear line and putting it next to the marks on the carbs? Or do you need a special connector to do this? I am thinking why pull the bowls if you can just do a wet check?