30% mileage drop

[PvtIdaho]

I just got my 5.5 Adv S back from it’s initial service. Before the service I was getting right around 40 mpg. After the service I’m getting just under 29 mpg.

Any thoughts on what the most likely cause would be?

Here are the stats by fill up:

Miles Gal. Mpg
165.2 4.65 35.52
166.1 4.49 36.96
186.4 4.51 41.32
176.1 4.37 40.30
Post service
124.9 4.34 28.78

All fill ups were after the Low Fuel light came on. The light seems to be pretty consistent by the small difference in fuel added numbers (all fill ups done on the center stand). WS=21.

I’m riding the bike on the same circuits in the same manner. Getting gas at the same stations. The only variable is the initial service.

I did a search on the forums (fuel lights/mileage/mpg) and the closest thing I could come up with was kinked vent hoses causing an early low fuel light. If I understand that issue correctly, it causes an early low fuel light because one tank will not feed correctly. Kinked vent hoses don’t actually cause mileage to drop (correct?). My last fill up showed the tanks to be about even at just over 2 gal. a side.

I’d like some ideas before I take it back to the dealer.

Thanks,
Mark

[Flanny]

Originally Posted by PvtIdaho

I just got my 5.5 Adv S back from it’s initial service. Before the service I was getting right around 40 mpg. After the service I’m getting just under 29 mpg.

Any thoughts on what the most likely cause would be?

Here are the stats by fill up:

Miles Gal. Mpg
165.2 4.65 35.52
166.1 4.49 36.96
186.4 4.51 41.32
176.1 4.37 40.30
Post service
124.9 4.34 28.78

All fill ups were after the Low Fuel light came on. The light seems to be pretty consistent by the small difference in fuel added numbers (all fill ups done on the center stand). WS=21.

I’m riding the bike on the same circuits in the same manner. Getting gas at the same stations. The only variable is the initial service.

I did a search on the forums (fuel lights/mileage/mpg) and the closest thing I could come up with was kinked vent hoses causing an early low fuel light. If I understand that issue correctly, it causes an early low fuel light because one tank will not feed correctly. Kinked vent hoses don’t actually cause mileage to drop (correct?). My last fill up showed the tanks to be about even at just over 2 gal. a side.

I’d like some ideas before I take it back to the dealer.

Thanks,
Mark

Sounds like they adjusted the valves too tight.

[jsrider]

Originally Posted by Flanny

Sounds like they adjusted the valves too tight.

Either that or they backed the air mixture screws way out on you.

[markjenn]

You may have a problem, but you're banking an awful lot on one lousy fillup to compute post-service mileage. And if this fillup spanned the service, then perhaps they lost (or ripped off) a little fuel during the service.

I'd wait and get an average over three or four fillups before concluding you have a problem.

- Mark

[Flanny]

Originally Posted by markjenn

You may have a problem, but you're banking an awful lot on one lousy fillup to compute post-service mileage. And if this fillup spanned the service, then perhaps they lost (or ripped off) a little fuel during the service.

I'd wait and get an average over three or four fillups before concluding you have a problem.

- Mark

Yeah...that's a really good point.

[hogmolly]

Maybe some fuel was spilled during service. The tanks are removed.

[JediBri]

Make sure all three fuel valves are opened completly.

Brian

[PvtIdaho]

Originally Posted by markjenn

You may have a problem, but you're banking an awful lot on one lousy fillup to compute post-service mileage. And if this fillup spanned the service, then perhaps they lost (or ripped off) a little fuel during the service.

I'd wait and get an average over three or four fillups before concluding you have a problem.

- Mark

I am in the process of running it down to the low fuel light for a second time as a check.

The second to last (40.3 mpg) tank spans the service and may not be completely accurate for the reasons mentioned above. I filled it up about .5 miles from the dealer after I picked it up. The 28.78 average for the last tank should be a true average.

If the change in mileage had been back down to the low 30s I wouldn't be as concerned. This seems like a rather large difference to pass off as just an anomaly, but I agree, one tank is not the final word.

The mech who did the work said that, on the valves, the front cyl. was good and the rear only needed some minor adjustment. I don't know if they were tight or loose.

"Make sure all three fuel valves are opened completly."

I pulled over and checked that first (after reading previous threads here)

I will see what the second tank shows and then run by the dealer tomorrow.

I'll update the thread with any info.

Thanks for the replies!

[PvtIdaho]

Originally Posted by Flanny

Sounds like they adjusted the valves too tight.

I read one of your posts where you mentioned that your valves were tight at the 10k km service and that your mileage suffered.

Do you rember about how much it was down?

Cheers

[Flanny]

Originally Posted by PvtIdaho

I read one of your posts where you mentioned that your valves were tight at the 10k km service and that your mileage suffered.

Do you rember about how much it was down?

Cheers

Nope - I don't remember exactly, but it was noticeably lower.

[Desmofan]

This happened to my bud right after the 9000 service-it turned out the dealer accidentally moved the needle clips down to the 4th position: very rich, crappy mileage! If you had them poke around in there, I'd be suspicious

[msusslin]

A rich setting does not alter the mpg as significant as described. However, it seems that your mechanic made the mistake of laying the gas tanks on its side during the service and spilled the gas all over the place. I had the same problem and was concerned that the service messed my gas consumption up, till I found out from the mechanic as to what happened.

[PvtIdaho]

I just filled it up again. Got the Low Fuel light at 140 mi. Filled it at 142.3. Put 4.21 gallons in it, with 2.16 gal in the right tank. MPG works out to 33.81.

This tank was 100% street with a conscience effort to go easy on the throttle (short shifting, never got above 6k rpm...). All the other tanks were, on average, 70/30 street/dirt.

My invoice for the first service shows 3 shims for the valve adjustment: "D=10/2.8", "D=10/2.9", and "D=10/2.5". Don't know if that means anything to any of you, or not. (mech said he only adjusted the rear cyl.)

I have also noticed what I would call a metallic clatter sound that seems to be coming from somewhere above my right heel (below the seat, above my heel, right side). I only hear it at low speed (most noticeably accelerating away from a stop). I first noticed it after I picked it up from the first service. I'm not jumping to any conclusions, just including all avaliable info.

I'll ride it "normally" for the next tank.

I'll take it over to the dealer later today and talk with them ( "Honey, I've gotta take the bike out...") and see if they have any ideas.

I'll update when I have more info.

Thanks again for the replies.

PS I seem to have gooned up the font color on this post somehow

[jsrider]

Originally Posted by PvtIdaho

I just filled it up again. Got the Low Fuel light at 140 mi. Filled it at 142.3. Put 4.21 gallons in it, with 2.16 gal in the right tank. MPG works out to 33.81.

This tank was 100% street with a conscience effort to go easy on the throttle

At some point I naively followed a recommendation to turn the air mixture screws out an additional half-turn. My mileage dropped from 35 to 31 mpg. Flanny suggested I set the mixture screws back to stock (2 1/4 turns out). Mileage went up to 36. The mixture screws control idle and low throttle so they would come into play here.

[PvtIdaho]

Originally Posted by jsrider

At some point I naively followed a recommendation to turn the air mixture screws out an additional half-turn. My mileage dropped from 35 to 31 mpg. Flanny suggested I set the mixture screws back to stock (2 1/4 turns out). Mileage went up to 36. The mixture screws control idle and low throttle so they would come into play here.

Looks like you and Desmofan were on the right track .

Just got back from the dealer. The mech. is on vacation this week so I couldn’t talk to him. However, the owner (also a 950 rider) said that the mech. probably “did to yours what I do to mine.� Which involved adjusting the carbs – moving the needles and airflow screws. He told me that the stock settings “are too lean.� He also thought that my carbs might need resynching .

I’ll take the bike back in next week and will go from there.

I’ll just stay a little closer to gas stations until then

From the Gem State.

PS How do I quote more than one message in a reply?