Ok my bike has receantly started spitting and chugging when I ride it on the freeway. In top gear it does it the worst at around 55-65 mph. Speed up and it almost completly goes away after 70mph.
It does it in all the other gears accept 1st at around 5500rpms.

The first thing I thought is fuel starvation. So I started at the fuel strainer. perfectly clean :dunno:. So I check ny spark plugs, both look pretty good, and are gaped properly. The right plug was nice and cocoa brown at the tip and fadded to a little more white. The left plug was more white, but not to bad at all.

So at this point I am stumped, and seeing as the bike is my only form of transportation this sucks!!
Does anyone have any ideas??

Also I think I have a very small exhaust leak in my can. I was thinking this might contribute but didnt think it was "the problem".

Any help would be great!! I really cant afford to pay $72 just to have it diagnosed. (standard 1hr shop rate).



Micah

Have you changed anything on the bike?
Check the carb to make sure all the jets are tight.
Also, check the ignition rotor plate to make sure it is tight.

air filter :dunno:

What year bike you are riding? On my 93 GS500 I encountered exactly the same problem as yours,  after consulting the board I tought it was fuel starvation or dirty fuel tank. Nope. Problem was caused by an erratic valve float inside one of the carb, causing the mix of the fuel to be too rich especially when riding at low speed causing the engin to splutter and backfires. A blast at high speed (open throttle) will burn the fuel off and the engine power returned to normal. I have not planned to changed it yet coz I was told it is damn expensive.  Dun know if you problem is the same as mine tho.

Sorry I havent replied in a more timely matter, but wrk has been a little busy, and makes it hard.


My bike is a 99 first of all.
And second I was thinking it might be my float bowls. What you described kyzee is exactually the same problem I am having.
The damn expensive part is kinnda scary. Can anyone shed any light in the subject?

If you think the actual floats might be flaky, you might ask in the For Sale section if anyone has a spare carb or two lying around.

But before you can install a new float you need to get into YOUR carbs anyway.  You didn't mention whether you had opened them up yet or not.  If not, I would recommend giving them an inspection and a cleaning.  You should be able to see if one of the floats has a hole, or any gas INSIDE.

If you have reason to suspect any of the parts that you see in the Carb Rebuild Kit that's available online, you could go the $12.00 route and try some new parts.

I would be remiss if I didn't point you to my Float Height Check page.  It shows you one possibly useful check you can make without disassembling anything.

About the "very small exhaust leak" - is it underneath, close to where the pipe meets the can?  If so, it's a design feature.  There is a small hole there to allow moisture to escape.

Good Luck!

EDIT: Changed link from sisna.com to bbburma.net

Now, I'm not claiming to be a master mechanic, but I've done well so far with the whole "start cheap"  routine.  I would change the air filter, plugs, and run an entire tank of gas (don't run out) with some stp or equivilant carb cleaner...  for the most it'll run ya 20-30 bucks I'm thinking, and it wouldn't hurt matters, and in my experience, whenever you think the problem it catastrophic, it's more often then not minor.

I think that I am going to go ahead an end up taking my carbs apart, as this is the only thing really left to check. Unless of course my bike is really trying to piss me off and its sometihng in the ignition.



I just replaced my spark plugs, and have run about 4 tanks of gas though, with about 1oz of MMO. The air filter is about 3000 miles old, and still in very good shape.