Need help in why I'm only getting 25mpg

[Duffy]

Hi all. Okay, I posted this on the R6 Forum as well. I need as much input as possible. Hope someone can help.

I bought my new to me R6 ('99) with a little over 6k miles over the
winter and I had a mechanical friend look it over and get it ready for this riding season. Unfortunately this poor bike was NOT taking well care of from it's previous owner and I had to bring it back from the dead. It had/has issues and he did what he could but I may have to go further in fixing it up but, I would like to know what direction I should look into. Your expertise would be appreciated.


I am getting almost 25 mpg. I know that's not good. so where does the problem lie? Engine temp (with fan on, comes on around 210 or so) runs a constant 210-220ish temp, is that too high? It HAS been hot outside when I been riding, 85-92 degrees outside. Soooooo, other than shit mileage and maybe higher than normal temp I think those are my only 'bigger' problems I have (left) that I would like to immediately rectify before I possibly damage the bike more.

Now the results of when I got back from mechanical friend...

1. The Carbs were/are in bad shape. He did what he could (cleaned, synced) but told me I "could" get a rebuilt carburator...or I could just take it easy with what I have. No racing, no riding hard. Should be fine for putt putting around and for this season. And honestly bike runs strong. No loss in power. No pauses. I don't hear any knocks, pings, nothing, sounds smooth. So not sure if that is contributing for bad mileage, but I'm no mechanic.

2. Bike DOES have a yoshi slip-on and it doesn't have jet kit. Friend said I wouldn't even notice unless I was racing bike in higher RPM's and it would only be a slight pause in power. But could this be the reason my mileage sucks? Would it be prudent to get a jet kit instead of filling up every 100 miles or so?

3. Is this engine running temp higher than normal?

4. Oh, and fuel light usually stays on, So, I have been gauging my mileage from resetting my trip odometer. Haven't lifted the tank yet to see if sensor is dirty. But, other than a possible dirty sensor, could it be reading something more about my fuel consumption? Does it even have the capability, or it does it merely let you know you have low fuel?


Friend told me to not to bother putting in any more money into this bike. Get a few seasons out of it and then trade it in for a fuel injected bike. But I LIKE this bike. I Love this years look. It's in great shape outside. I think he was just thinking that its just not worth throwing money into an older bike, or he just knew that it was just in rough shape and it could be a money pit. Not sure. So, what do you guys think could be possible problem(s)? Thanks in advance.

-Jen

[butcher bergs]

What you were told about the carbs as far as "taking it easy" isn't exactly accurate. Either they flow fuel or they don't, there's no in between or "babying" them, so to speak.

Jet kit ain't gonna make a lick of difference other than fattening up the power (meaning "more fuel consumption"). Bike is likely running a bit lean with just the slip on installed at the moment.

Normal engine temp operation is typically within the 180 to 220 range, respectively for any given machine.

I'm inclined to ask what RPM range to do you usually cruise in? If you're riding at 7k (for example) every time you ride then there inlies your fuel consumption problem.

Also, how's your air filter look?

[naked-daytrader]

[Duffy]

The kid told me that he had to replace a slider because one was broken. He didn't even know how it could have happened. Apparently at one time someone was in there tinkering around and really messed it up. I don't even know how you mess something like that up He said it was a bitch to clean, that he did the best he could and it has cracks everywhere. Now, I never saw it and I don't know what it looks like now or what it looked like before he dug in. All I know is I don't feel or hear any problems. Only info I have is a bunch of "he said"


I'm going to adjust my riding style. Make sure I put it in the highest gear possible before bogging and see if it increases mileage.

I had fuel filter replaced and I think the air filter was just cleaned....or visa versa. All fluid was changed. New plugs..etc.

[butcher bergs]

The kid told me that he had to replace a slider because one was broken. He didn't even know how it could have happened. Apparently at one time someone was in there tinkering around and really messed it up. I don't even know how you mess something like that up

Other people's botched jobs....yeah, been there "once" before.......and it's called "hamfisting".

He said it was a bitch to clean, that he did the best he could and it has cracks everywhere.

Cracks everwhere where? The carb slides?

I'm going to adjust my riding style. Make sure I put it in the highest gear possible before bogging and see if it increases mileage.

I wouldn't go to the extreme of lugging the engine but you should be able to motor along just fine within the 3k to 5k RPM range and return, at the very least, hi-30's/low-40's for fuel mileage on that bike. If not then there is something else going on.

Did your friend set the air mix screws and balance the carbs after the cleaning?

[Cerberus]

i can't imagine what would cause cracking of carb components, unless someone tossed the slide in a big coffee can with a strong solvent and shook it like a maraca(sp?)..

ok, regarding the slip on..
most slip ons are basically a straight through can with perfs and packing.
this is a significant difference from the way most OEMs design their cans (wave reflection/cancellation, and long path with more backpressure)

the importance of this is as follows; all engines benefit from a bit more back pressure at lower rpm and throttle position, to utilize the weak power pulse made in those conditions and not let it slip out of the chamber so easily, instead using it to push the piston down.(better usage of the power pulse= more efficiency)
Also, all engines benefit from a reduced back pressure but an increased amount of inertial chamber scavenging to improve volumetric efficiency.
*this is true unless the engine in question has variable cam timing to optimize flow dynamics across the RPM range(and almost no bike engines do).

NOW, by putting a slip on on, you remove back pressure throughout the RPM range which can realize a few HP at the top end, but usually costs a few FT/lbs of torque at the lower end because of the reduced back pressure and reduced inertial scavenging.

it should be noted that the exhaust system consists of at least 2 major components, each of which serves its own purpose but works symbiotically with the rest of it. the header is designed for great flow and utilizes the inertia of high velocity exhaust pulses to initiate the new fuel/air charger flow into the chamber during overlap(when both valves are open for a short time while ex is closing and int is opening(commonly called inertial scavenging)). the muffler usually is designed to cancel the pulses as much as possible while minimizing restriction of flow(not canceling out the inertial flow from the header). the examples given below are in reference to the whole system, but primarily the muffler, the header is assumed to be the same.
(4-cycle engines)
low RPM/TP(throttle position): low back pressure = excessive loss of the weak power pulse(reduced torque), & ineffective inertial scavenging, so the resulting chamber mixture can be effected

low RPM: greater back pressure = minimized loss of the combustion power pulse(greater torque) and improved inertial scavenging(i know this seems counter intuitive)

high RPM: low back pressure = effective venting of exhaust gasses in the short window of time available, and effective inertial scavenging

high RPM: high back pressure = exhaust does not properly vent, and no inertial scavenging resulting in significant loss of power and engine over heating is likely.

Because of the fact that the exhaust volume (quantity, not sound) changes hugely throughout the range, the exhaust system is always a compromise, unless of course there is a valve in the system in make back pressure when it is helpful.. like most modern bikes have..

oh crap.. i sort of went off on a rant there.. sorry bout that..

[Wishbone]

Cracks everwhere where? The carb slides?

could be the ports that connect the carbs to the engine. I know the outside of my ports have small dryrot looking cracks but they are only on the surface and don't go threw.

I wouldn't go to the extreme of lugging the engine but you should be able to motor along just fine within the 3k to 5k RPM range and return, at the very least, hi-30's/low-40's for fuel mileage on that bike. If not then there is something else going on.


Did your friend set the air mix screws and balance the carbs after the cleaning?

3-5k????? I was unaware these machines operated bellow 5-7k


I would check the air mix screws. but probably still have the stupid brass plugs covering them.

How does your friend know that there is no jet kit installed? Some one may have just switched out the jets with larger ones. Increasing gas flow, reducing mpg.


Also if the plugs were changed, what did the old plugs look like? Spark plugs will tell you a good bit of info as to how the engine was operating.

[Duffy]

I know they replaced the plugs. Bike ran like shit, something about how it wouldn't go past idle (I don't know if they meant it had no power or stalled or whatever, they didn't elaborate) and they said it was backfiring.

They also changed the jet(s). What I gathered was original one(s) were not letting any fuel through.


All I understood was that the bike only had 6k miles. It is 10 yrs old. Sat a lot, not used, not maintained. Fair amount of corroding, oxidizing. They said it looked like it was on its side for awhile they way old congealed, lacquered fuel was all pooled to one side and that it appeared that at one point someone "tinkered" with the bike and really had no idea what they were doing and messed it up. No one really knows the history of the bike. They think it was maybe a theft recovery because ignition was replaced and it was in lowspeed crash on its left side. They said you should never have to replace the ignition. But we are only guessing here. Only thing for sure is that no one took care of it till I came around and picked it up and dusted it off. This is a learning experience for me, I'm out of my element. I usually buy new....with a warranty.

But hey, whatever. Thanks for all the input so far.

[richw]

FLOAT LEVELS and float valves

Note on every carburettor I ever saw the floats were level with the operating position.

If they are tilted down on the engine then float would start letting fuel in when rear of float is below horizontal


If one float was off you could get that bad gas mileage