Poor Gas Mileage-Advice

[erichjohn]

hello,

i have a 97 max, and the mileage is about 18 mpg. i had the carbs all cleaned out and it ran better but no improvement in mpg. any ideas of why its so bad? i haven't owned a bike in nearly 18 years before this so my knowledge is way down. also, my car was stolen so i cant really dive in and try to fix this myself due to my bike being my only form of transpo for the next few months. finally, i put rec 90 ethanol free gas from Valero in my bike and it ran horribly! i could have put pancake syrup in the tank and can't imagine it running worse. any idea what that was about? thanks for any responses, mechanical stuff on bikes is a weak point for me at the time being ... :ummm:

 

[davesax36]

How long has your mileage been like this?
Who "cleaned the carbs"?
Is your exhaust smelly and black?
Mods to intake? Exhaust?
If you are the original owner, have you ever taken your carbs apart before?
Do you know what jets you have where?
These questions will help the real brain trust on here help you out much more easily.
My limited experience says you are running really rich and need to check float levels. There's a thread in the how-to section about that.

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[erichjohn]

it's been like this since i bought the bike last august. i had a highly recommended service shop give the carbs a servicing and it ran much better but still poor mileage. mods never done as far as i know. exhaust is pretty clean, except for when statring. runs fine except i have to ride the clutch out of a dead stop, and it seems to miss when running in high gear a little. jets and stuff no idea; and i don't wanna start messing with the carbs because if i can't get in running i'm screwed because my car is gone. i'm thinking of having the carbs all rebiult, totally. thanks for respose. off to night job so if you respond i'll get to in tonight ...

 

[85vmax]

I've had that problem couple times before, forgot what I did to fix it:ummm:
I get about 90 before the light comes, on spirited riding comes on at 85ish.
120 is pretty safe for me before I'm pushing.....and I have pushed a couple times.

Have you synced your carbs?
A/F screws set.......gas smell at idle?
What about plugs.....bad plugs will cut your milage in half.

What happens when starting....smoke?
Riding the clutch out sounds like you still have junk in the carbs.
Have you tried any Seafoam?

I'm in Davie if you want me to take a quick look at it.

 

[The Beekeeper]

I would give the plugs a good look, I would guess they would be pretty fouled at that kind of MPG, make sure the motor oil isn't saturated with fuel too.................................Tom.

 

[sdt354]

I would give the plugs a good look, I would guess they would be pretty fouled at that kind of MPG, make sure the motor oil isn't saturated with fuel too.................................Tom.

Bet they're sooted up well. Big prob there, unless the air cleaner is 90% blocked or the choke/fuel enrichment is on all the time.I like to look at cheap and simple first. I haven't read all the post yet though. You prolly alredy got great advice knowing this forum. I don't think I could make my bike get 18mpg. Long distance riding at 75mph I get 40mpg.
Steve-o

 

[ninjaneer]

+1 have a look at the plugs. what is idle RPMs? R the carb synched? Also how are you determining your gas mileage?

Bet you're rich in one or more of the circuits.

am on phone so it is hard for me to find the thread, but somewhere in the Carb section is a thread that has four tests which help tune main and pilot mixes. Try them out to see what state you're carbs are in.
The thread is called something like "same old jetting questions" {edit}found it: http://www.vmaxforum.net/showthread.php?t=1024{/edit}

also google "CV carb tune v max" and look for the v max outlaw site. There you find steps for tuning the carbs. perhaps trying them out will shed some insight into why the bike is underperforming {edit} here ya go: http://vmaxoutlaw.com/tech/cv_carb_tuning.htm{/edit}


If any of the latter guides/steps tell you that you're rich or lean, I'll bank that the PO rejetted the carbs, that is if you're not the OO. Are you the original owner? If not, what region of the country was the bike before it landed in your garage?

If what you say is true and the carbs haven't been modded, i'm willing to bet the A/F mix is too F. readjust (one cab at a time) by first slowly seating the adjustment screw which will cause the bike to stumble and then open a quarter turn until motor recovers. {edit} the latter is how most of the carb gurus here tune their max's idle circuit. i had trouble getting the bike to stumble and ended up doing this guy's variation on the same theme: http://bikeadvice.in/tuning-carburetor-optimal-performance-fuel-efficiency/ {/edit}


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[RaWarrior]

Close all 4 a/f screws, then back each one 2.5 turns out, which I believe is the factory setting. Make adjustments from there in 1/4 turn increments until the idle speed is the fastest(then adjust the idle stop screw to set it back at 1000).

Look at the side of the carbs and work the choke lever. Notice the little forks pull the plungers up? Ensure the plungers go fully down when the choke lever is pulled up/off. If one or more is sticking open that'll definitely tank your mileage.

These bikes shouldget mid to high 30's for mileage, or top 40 if you drive conservatively.

A new set of plugs isn't a bad idea either. Stock plugs are fine, no need for spendy iridiums or other nonsense. NGK DPR8EA-9. Any auto store should have them.