fuel starvation problem????

[northwoods]

I got this gs550l running after sitting for 12 years, cleaned everything up, soaked and cleaning and rebuilt carbs, coated the tank, installed an in-line fuel filter. I got it running and it was running really good. The only thing was I couldn't get the idle set right, it seemed that when I had the bike running and I would turn the idle down to 1500 then later when I started the bike the idle would be to low and so I had to crank it up only to find out later that it would be set to high. Anyway, now for some reason I'm running into a problem where I can get the bike started but when I try to rev it, it kind of chffs or bogs and won't rev. If I stop the bike and let it sit for a minute I can start it and take off for about a mile until I lose power, unless I'm high up in the rpm band, but as soon as I slow down, the bike will die. Any suggestions????

[Nessism]

Did you change the carb boot o-rings? If not, you need to.

[almarconi]

After you rebuilt the carbs, did you vacuum sync them? The bike will run like crap until this is done. Before you sync, make sure airfilter is clean, airbox is installed and no leaks around carb boots.

[northwoods]

Why after letting it sit a minute does it idle fine then? My o-rings are in good shape. It will idle fine and then when i get on the road after 30 seconds it will lose power and when I try to rev it just bogs, unless I can coax it up past 4k rpm. I thought that maybe it was an air leak but now I'm not so sure. I have an inline filter and it will go from being full to empty to full to empty so maybe there's something wrong there as well. Figures, just when I was starting to enjoy the bike.

[flyingace]

Many old-timers here suggest you remove the inline fuel filter. Not a bad idea to try it. The other problem may be the petcock vacuum valve is going out on you. Try running the bike on prime and see if the symptoms go away.

[northwoods]

I'll try taking the fuel filter off and running on prime to see if that could be the prob. Keep my fingers crossed.

[ryonker]

I don't know how the timing works on your bike (electronic ignition), but my 79 750 did the same kind of bogging down thing until....I adjusted the valve clearance, changed the points and condensors (not on your bike, mines older ignition) and set the timing.

I had cleaned the carbs, synced the carbs, made sure there were no air leaks (new o-rings like nessism pointed out). But it wasn't until I did the above things that it really began to run like a bat out of hell ! No hessitation, no backfire...just power

Good Luck!

[ryonker]

The other experts will know more about this, but I guess another factor to consider would be power to your coils. I found I only had about 9 volts running to my coils and they like 12 to really run correctly and get a good spark. So I did a coils re-lay modification and now they get 12!

Go here for the mod:

http://members.dslextreme.com/users/bikecliff/images/coil_relay_mod.html

Or here:

http://www.wgcarbs.com/index.php?option=com_content&task=view&id=12&Itemid=26

I also took my inline filter off. I put a new pet-cock on that has a really good filter on it so I do believe I get better gas flow.

Good Luck!

[Suzuki mad]

You say that it 'boggs' down till after 4,000rpm. That is when the main jet comes on line.

You have a blocked jet or passage way on the pilot circuit. Have you had all the parts out of the carbs and cleaned them as per the carb cleaning papers on this site?

Suzuki mad

[tfb]

Nine times out of 10 these are fuel problems, not electrical... so make sure you eliminate the first before pouring money into the second. (Many a poor punter has forked out for a new set of coils, only to find they still have the problem. )

The first thing I would do is ditch the inline fuel filter. Now I know there are many who will disagree, but IMO inline fuel filters are about as useful as an udder on a bull. For one thing, you already have a very fine nylon filter that is mounted on the fuel tap, where it pokes into the tank. For another thing, that pesky rust sediment will get through to your carbie bowls no matter how good the filter is. As it is, you have lined your tank, so you shouldn't get any more rust sediment through.

So you have nothing to gain by using an inline fuel filter (unless your nylon fuel tap filter is missing). What you usually do get, however, is a large fuel bubble sitting in the filter, which can lead to the bubble 'locking' the fuel flow. Kinked fuel lines can be another cause. Yet another possibility is that the fuel line goes down from the tank, rises, then goes down to the carbs, thus creating a place for a bubble to lodge, and 'locking' the fuel flow in the same manner as an inline filter.

One easy way to test if you're getting fuel starvation, is to open the choke while the engine is bogging down. If you suddenly get a surge of power as you open the choke, bingo, fuel starvation is your problem. As I said, it is often caused by inline fuel filters. Another possibility is if the fuel cap breather hole is blocked with grime or whatever.

I also think that 'Suzuki mad' might be onto something. Above 4-5000rpm your main jets come into play, so I would doubly check your pilot jets and needle jets. (A common source of jet-blocking gunk is bits of sealant from well-intentioned attempts to seal leaking fuel bowl gaskets.)

I hope some of this helps you eliminate stuff, if not curing the problem.

Cheers,
Mike.