500 LTD very low mpgs :(

[Juancho]

2003 500 ltd 23,000 miles

I took her to a crappy mechanic for a bunch of stuff, and the bike returned with new symptoms. Took her back to him TWICE and still had the symptoms, so I definitely have to work my way through this one by myself.

"work done" Complete carb cleanup, carb sync, 17 tooth front sprocket ( up 1 tooth from stock), adjusted chain slack.

The bike returned with a terrible miss which turned out to be pilot screw adjustment. I ended up drilling the carbs myself to access the screws ( bike is my MAIN mode of transportation to school, so I can't just wait around) and tuned the bike to get rid of the miss. The problem is I used to get 45-48 mpg city driving with stock sprocket, dirty carbs, etc.

On the last two tankfuls I've NURSED the bike all the time, keeping it at 55 mph on fast streets, smooth shifting, no racing, etc. And all I managed to get was 40mpg on first tankful and 41 on second.

Can the pilot screw adjustment be off and screwing over my mpg's?
Tire pressure = 40 psi front and back ( front=Pirelli Night Dragon, back=Shinko something)
Mods = K&N air filter, Harley Dyna mufflers with the center thing punched out ( you can see right through the muffler). These mods have been there for over a year, this began 2 months ago.

Thanks in advanced! Other than the mpgs, she rides great, idles great, etc. I use sea foam every other tankful too.

[Juancho]

Cliff notes. .
1. mechanic screwed around with my bike
2. cleaned my carbs, and I developed a strong hesitation at low fuel input ( typical symptom of pilot air screw adjustment )
3. adjusted pilot air screw to eliminate symptom BUT, ( I will count turns later today because I suspect that the adjustment eliminated the symptom at around 3 turns out, which is a LOT)
4. mpg's took a cliff dive ever since the bike was returned from the mechanic.
Bike detailes = 500 ltd 17 tooth front sprocket, Dyna mufflers, K&N air filter stock jets. 23K miles.
Looking for ideas as to where to begin my scavenger hunt as to what is causing such bad mpgs.

[bikerbill]

Originally Posted by Juancho

Cliff notes. .
1. mechanic screwed around with my bike
2. cleaned my carbs, and I developed a strong hesitation at low fuel input ( typical symptom of pilot air screw adjustment )
3. adjusted pilot air screw to eliminate symptom BUT, ( I will count turns later today because I suspect that the adjustment eliminated the symptom at around 3 turns out, which is a LOT)
4. mpg's took a cliff dive ever since the bike was returned from the mechanic.
Bike detailes = 500 ltd 17 tooth front sprocket, Dyna mufflers, K&N air filter stock jets. 23K miles.
Looking for ideas as to where to begin my scavenger hunt as to what is causing such bad mpgs.

Juancho,

Here are a few suggestions to look at:

1) Check the carburetor float level using the 'wet' method. It should be even with the bowl flange +1.5/-0.5mm

2) Verify the jetting. The mains should be 102 and the pilots 35

3) Inspect the needle jet/jet needle for wear. Any significant wear will cause it to run richer. Has someone 'shimmed' the jet needle? If so remove the shim(s). If there is an e-clip on the jet needle it is an aftermarket part and by design they tend to run richer. Get an OEM jet needle with N2WE stamped on it.

4) Are the slides working properly? Are the springs in good condition? Does the jet needle holder secure the jet needle?

5) The pilot screw doesn't do a whole lot beyond 10% throttle so I wouldn't fret too much about it. 3 rounds is pretty close to what mine are. I think one is 2 1/2 and the other is 3 1/2 turns.

6) Check carburetor synchronization. (i.e. balance the carbs) Look up 'DIY manometer' for how to make one yourself.

Hidalgo has been averaging 39-40 mpg lately. But that's fighting the west Texas wind, 70 mph and a huge windshield. Whenever I slow down, like I did last year riding the 'Dragon' and Cherohala Skyway, it jumped up to about 55 mpg.

Hope this gives you hope.

[Easy Rider]

Originally Posted by Juancho

The bike returned with a terrible miss which turned out to be pilot screw adjustment.
Can the pilot screw adjustment be off and screwing over my mpg's?

I use sea foam every other tankful too.

Pilot screw: If it was still SEALED, then that was NOT the problem. Mis-adjusting it just made the problem go away......or appear to.

Normally with the mods you listed, you need a bigger main jet in the carbs to keep it from running lean. If your mechanic did that for you, it might explain ALL the symptoms. Mis-adjusting the mid-range needle can cause things like that too.

And finally, your sprocket change might actually have cost you some mileage......because now you can stay in each lower gear longer.

How much SeaFoam are you using ? Too much can screw things up too.

If the bike is running basically good, you might just have to eat the lower fuel mileage. Messing with the air intake and pipes makes things like this almost impossible to fix......in some cases.

[Juancho]

Originally Posted by Easy Rider

Pilot screw: If it was still SEALED, then that was NOT the problem. Mis-adjusting it just made the problem go away......or appear to.

Normally with the mods you listed, you need a bigger main jet in the carbs to keep it from running lean. If your mechanic did that for you, it might explain ALL the symptoms. Mis-adjusting the mid-range needle can cause things like that too.

And finally, your sprocket change might actually have cost you some mileage......because now you can stay in each lower gear longer.

How much SeaFoam are you using ? Too much can screw things up too.

If the bike is running basically good, you might just have to eat the lower fuel mileage. Messing with the air intake and pipes makes things like this almost impossible to fix......in some cases.

Well the problem arose from when he " cleaned" the carbs, so I thought " clean carbs, more flow, leaner condition versus dirty carbs, restricted flow, etc."
He didn't change any jets, all stock jetting. In fact, mileage was better BEFORE he screwed around with the bike, and the mods had already been there for a year. That's why I can't seem to blame the mods for a symptom that turned up so much time after they were installed!
I use an 1oz/gallon usually, which is what I've read on some posts. I've also received mixed answers as to wether I would need to rejet or not with those mods, since it's only the mufflers and not the entire piping, and since it's the same original air box with the K&n filter.

I think I need to do plug chops. . and see what the heck is going on in there. GGRRRRRRRRRRRRRR


btw every thread I've read about the extra tooth on front sprocket raves about better mpgs, never read a post that even implied having the same mpgs, much less having decreased mpgs/. :/ oh well...

[crazy88]

you said +1 on the front sprocket? that's a factor in the fuel milage. your crusing rpm is probably alot higher. remember that +1 in the front is close to -3 or -4 in the back.

i used to ride sportbike for a large part of my life... i'm pretty familiar with sprocket changes and how that effects things.

hope this helps

[crazy88]

check your air filter too... but if you really are running rich, you'll be able to smell it and you'd feel some stutter and your plugs would be alot darker too which brings me too... have you checked your plugs? that will tell you if you running rich or not

[crazy88]

oh, and change out that dang shinko asap... get a nice pirelli to match your front or whatever your favorite brand of tire is. them shinkos are pretty slippery... cheap, but not grippy at the same time.

[sfair]

Bikerbill gave you some excellent tips and you should take a look at every one of them, in particular #1.

[Blaine]

Originally Posted by crazy88

you said +1 on the front sprocket? that's a factor in the fuel milage. your crusing rpm is probably alot higher. remember that +1 in the front is close to -3 or -4 in the back.

i used to ride sportbike for a large part of my life... i'm pretty familiar with sprocket changes and how that effects things.

hope this helps

Going up one tooth on the front lowers RPM,which should increase fuel mileage.
???