Fuel problem?

[James1217]

Hey guys...

I am having a slight problem with my 2009 GS500F. A few weeks ago, I noticed a slight decrease in power, and I noticed that if I went over around 6k RPMs the engine felt different. Rougher, I guess. When it started to get colder (35-40 degrees), I could not start it even with full choke. However, once it warmed up, it started right up with no problem. I changed the oil/filter/spark plugs (I was due anyway), but it didn't help at all. Now in about 50 degree weather, will full choke, it will start and idle at regular speed. Last winter, in 15 degree weather, I didn't even need to use full choke.

So, I am not entirely sure what is wrong with that. Could something in the fuel system be clogged? Could it be bad gas or something?

Any advice or opinions would be fantastic.

Thanks,

James.

[jestercinti]

How many miles? 
Has it been sitting for a while?  Bad gas?
Probably fuel related such as a dirty carb, air leak, or valves.

[James1217]

Sorry, I meant to add all that. I've been riding it every day for the past few months, it's at exactly 4800 miles right now. Has not sat at all since I got it. The gas is less than a week old.

Would you happen to know how I could check for an air leak? I'll probably put some cleaner in the tank later, in case the carb is dirty or something. What could I do to check the valves?

Thanks =]

[jestercinti]

At 4000 or so miles, the valves should be OK for now.

I'd spray some carb cleaner around the intake boots.  If the engine speed increases, you have an air leak.  Make sure that the clamps holding on the carbs are tight also.

Try some seafoam through the bike.  May clear it up before tearing into the carbs.  Your bike is pretty new, so I would not tear into it quite yet.

[BockinBboy]

I'll offer my thoughts on this one.  Vacuum leak possible and since its worse when cold(Air is more dense) that offers support to the theory... Carb boots are a good bet if it is a leak.  They may just need tightened up.

As with any suspected fuel problem, a quick float height check is in order to rule it out since its quick and easy using the U-tube method.  Procedure can be found with a quick search or on the wiki.

I'll add that my bike at just over 5k miles shows the tell tale signs of tight exhaust valves (winter project for me), and takes more to warm up and is finicky while using the choke as a result.  So I wouldn't entirely dismiss the valves, but there are other things to check first.

Although this truly shouldn't affect our 20 year old designed engines, gas stations are transitioning to a 'winter blend' which is known to cause rough idle in some engines. But this is highly controversial topic for a forum, so don't dwell on it.

-  Bboy

[bigfatcat]

When u spray carb cleaner for the vacuum leak test, adjust idle screw up to about 1700. Pay particular attention to the area where the intake pipes bolt to the head - o-rings seal this area and if hardened and mashed out of shape may not be sealing.

Don't go crazy with the carb cleaner - don't soak it down,  just a spritz here and there as you go about the motor/carb looking for a leak, and there will be a slight delay as the motor revs in response (if u have a leak).

[craigs449]

Check valve clearance,.......and USE A TORQUE WRENCH WHEN PUTTING THE VALVE COVER BACK ON..

[gsatterw]

DO NOT USE A CHEAP TORQUE WRENCH, if you don't have a decent one, youre better off doing it by hand. Ask me how I know.

[craigs449]

DO NOT USE A CHEAP TORQUE WRENCH, if you don't have a decent one, youre better off doing it by hand. Ask me how I know.

I have a Craftsmen one and also one from HF.......I have used both and tested them both against each other...the HF is spot on!  The HF one is better than "Feeling it" without one IMO..

[gsatterw]

i used a 3/8" Pittsburgh torque (10-80 ft-lb) wrench i got on ebay for like $25. Clicked at 10 ft-lb on a 22 mm bolt, but snapped a 10 mm test bolt rated at 9.5-11 ft-lb at the same setting. Getting a 1/4" in-lb torque wrench from the same company, which is probably stupid, for the lower register torque ranges.

[craigs449]

Also keep in mind that all torque wrenches (even the high dollar ones) are most accurate in the middle 2/3 range, and least accurate at the bottom and top end of the range listed on the wrench........I.E., I wouldn't use my 10-80 ft/lb torque wrench for a bolt that called for 10 ft/lb.....I would use the other one that is rated at 20-200 inch/lb's and set it to 120 inch/lbs for that application......which is kind of in the middle range of that wrench.

[James1217]

Thanks for all the replies...I'm going to check for an air leak and hope its that and not the valves or something else. I rode the other day with the fairings off, and I don't know if I was imagining this, but when idling in my driveway I thought I heard a hissing noise. I asked a friend, and he said he heard the same thing. But I could still be imagining it. =P

[gsatterw]

Thanks for all the replies...I'm going to check for an air leak and hope its that and not the valves or something else. I rode the other day with the fairings off, and I don't know if I was imagining this, but when idling in my driveway I thought I heard a hissing noise. I asked a friend, and he said he heard the same thing. But I could still be imagining it. =P

hmmm...there is this little hole in the gas cap to let air into the tank as the fuel level descends, so a vacuum in your tank doesnt form. it could be clogged, which would cause fuel flow problems. just a suggestion.

Edit: maybe start the bike with the gas cap open, see if that helps. If it does help, clean out that lil hole.