What else uses fuel on my 650?

[BigD_83]

Okay,

I'm just getting a little silly here, but now that the 650 is running well (enough), I've started really keeping an eye on the fuel mileage, and it's not very good.

When I got the 650, I barely got 50 miles out of the first tank of gas I put in it. With most of the newbie maintenance done, the situation hasn't improved much.


144 km and I'm switching to reserve. That's about 86 miles That's been the last four tanks of gas.

Filled up the tank, and put in 14.7 L (for those of you keeping score...4.1 US gal). So, I'm a hair over 21 mpg. This is freaking ridiculous, and I know that I can make this better.

I am turning to the collective yet again after reading up on this as best I could.

My stats:

- all valves between 0.003 and 0.002"
- no petcock leaks (crankcase oil holding steady volume)
- larger than OEM main (115 installed)
- plug chops look good: not lean/rich/gas fouled
- vacuum synch done
- idle mixture adjust at 2 3/4 turns +/- (sounds a little "wet")
- 4 into 1 header with stock airbox and filter
- no detected leaks around the carbs/on the petcock seal
- slight rub on rear caliper...wheel rotates freely in neutral on kickstand but is a little warm after riding. Front calipers are cold to touch after a casual ride
-no clutch slip that I notice
-almost all of my riding has been around town 30-50mph, with brief stretches on the highway at 60-70 mph

EDIT- tire pressures were quite low, but I fixed that up before the last fillup)

Despite the plug chops, the bike smells rich when running so I've been suspecting a weak spark, but the spark on all four plugs is nice and blue when grounded against the head. If I remember correctly, there is about a 0.3V drop across the coils. I also have a little bit of an issue with the choke rail hanging up ever so slightly, but this is a new problem since the last time I had the carbs off.

Where do I go from here?

[tom203]

Yeah, this is ridiculous mileage- I get about 50 mpg (35 to 60 mph, lots of hills, seldom steady throttle. At those low speeds ( 30 to 50), I'd suspect the needle/main jet sizing to be critical- maybe the fit ain't right and it's running rich at this point.
Make sure choke is fully off at carbs.
My rear brake gets warm to touch also- I just assumed the disc didn't wooble enough to push pads back into caliper

[koolaid_kid]

Have you rebuilt the carbs yet? New o-rings and fuel bowl gaskets, dipping per Nessism's tutorial?

[tkent02]

115 main jets are how much bigger than stock?
Why so many turns out on the mixture screw? Are you using the stock size pilot jet?
If it smells rich it is very rich, you can't smell just a little bit rich.
Have you checked your fuel levels?

[razor02097]

Check for fuel in the crank case.

[BigD_83]

Have you rebuilt the carbs yet? New o-rings and fuel bowl gaskets, dipping per Nessism's tutorial?

Welcome back, Koolaid Kid!

That is a big affirmative on the cleaned and re O-ringed carbs, including the intake o-rings.

[koolaid_kid]

Thanks.
The next thing I would check is fuel in the crankcase as already mentioned, plus I would look for fuel in the airbox. It has to be going somewhere, obviously, if not through the cylinders then somewhere else.

[BigD_83]

115 main jets are how much bigger than stock?
Why so many turns out on the mixture screw? Are you using the stock size pilot jet?
If it smells rich it is very rich, you can't smell just a little bit rich.
Have you checked your fuel levels?

115 is two sizes larger than stock 110s which were there until I changed the header

The mixture screws ended up at where they are currently using the highest idle method, and the plug chops were showing the stock 1 1/2 turns to be a little lean

I still have the stock pilot jets

Fuel levels: floats were set on the nose and the needles are not worn. I am not getting any fuel out the fuel tees, so I have not yet attached a fuel level gauge to see. I do have one, though. Is it possible to get it attached to #2/3 carbs and get an accurate reading without removing the rack?

This reminds me a bit of MisterCinders Two faced symptoms problem, which I know he traced back to a gasket holding a float from rising and closing the needle

[tkent02]

I am not getting any fuel out the fuel tees, so I have not yet attached a fuel level gauge to see. I do have one, though. Is it possible to get it attached to #2/3 carbs and get an accurate reading without removing the rack?

I don't understand this fuel tee part, you check fuel level by attaching the gauge to the float bowl drain and then checking the level while the engine is running. You can get to all four drain plugs easily enough.

[BigD_83]

Thanks.
The next thing I would check is fuel in the crankcase as already mentioned, plus I would look for fuel in the airbox. It has to be going somewhere, obviously, if not through the cylinders then somewhere else.

It sure does not smell like there is any fuel in the crankcase and the viscosity feels right. There has been no change in the oil level. There is a new OEM petcock on now, which tests fine. I had some earlier conerns about fuel possibly running down the vacuum line to #2 carb, but I was just seeing a mist with the vacuum draw.

The airbox is not wet like I would have thought it would be. When is the best time to check? Cold, during a ride? Or after, bike not running but still warm?

[BigD_83]

The fuel tees and vent lines have come up a couple of times in other threads where people were looking for leaks and/or possible fuel level issues. MagicMArker is one that comes to mind with a smelly bike issue. Not sure if his was running rich or if that was resolved to a bad gas cap seal.

I guess it is time to get that fuel gauge on.

[tom203]

I guess it is time to get that fuel gauge on.

Auxiliary tank might be more useful- you don't have any friends who like to torment you? With that much gas "disappearing", you'd either see it in crankcase or on shoes, or be into mosquito control from the fumes.

[MisterCinders]

115 is two sizes larger than stock 110s which were there until I changed the header

The mixture screws ended up at where they are currently using the highest idle method, and the plug chops were showing the stock 1 1/2 turns to be a little lean

I still have the stock pilot jets

Fuel levels: floats were set on the nose and the needles are not worn. I am not getting any fuel out the fuel tees, so I have not yet attached a fuel level gauge to see. I do have one, though. Is it possible to get it attached to #2/3 carbs and get an accurate reading without removing the rack?

This reminds me a bit of MisterCinders Two faced symptoms problem, which I know he traced back to a gasket holding a float from rising and closing the needle

I also had a dodgy washer on one of the needle valve seats that contributed to the overflow. But if you were overflowing, you'd see signs of gas in the overflow tubes, airbox, crankcase, etc.

[hampshirehog]

Leaky tank?

[koolaid_kid]

That fuel has to be going somewhere. It can't merely cease to exist. And there is no way a 650 should only get 21 mpg. Thimk!