Problem starting/running when hot, still trying to solve(2 1/2 months)

[DrDoot]

So, I've been at army training for a good bit of the summer, and just got back a little while ago. I posted this same problem a couple of months ago, and have been working through the suggestions one at a time. No luck so far.

What I've found:
1. Even running with gas cap off, still has the problem. Very suddenly loses power and dies, then won't start until completely cool.
2. Have replaced the Ignitor with one from my parts bike(it doesn't get hot). Problem persists.
3. Fuel petcock flows when turned to prime, which I believe means that it's working properly(even if there is a problem on "Run", the problem with the bike persists even running on Prime, which flows).
4. In-line fuel filter replaced. Problem persists.
5. Pulled off the 2-3 ignitor coil and replaced with one from my parts bike. Problem persists. (I didn't try the 1-4 coil because the one on the parts bike was damaged, but I can do that if it's a possibility?).
6. Pulled the tops off the carbs, and the big thing that goes up and down(which, using my college education, I assume is the float, but don't have much experience with carbs) seems to go up and down smoothly.

So, the problem persists. I can get the bike to start and run fine if it's cold, but as soon as it warms up and runs for 10 minutes or so, it loses power and slows until it dies, and will not restart until it cools down again. The problem started as running fine when cold, until I stopped the bike myself when I got where I was going, then couldn't restart until cold, and now has progressed to dying on it's own while running and not being able to restart until cold.

Any ideas?

Old post(http://www.thegsresources.com/_forum...t=93931&page=3)

[justin caise]

Subscribed.
Well, I've got the same problem, but no answers yet. Just down the driveway and back and it starts to bog.
- then looses power and eventually stalls.
The fuel tank was a bit rusty inside. And, as the PO told me, the carbs weren't completely seated. I have since inspected and reseated the carbs, but the tank is still off awaiting sealing ($).
This wkend, if time allows, I'll try to run fuel from a seperate source to see if the problem persists. This will allow me to check other things I've read on your threads; coils etc. while the tank is out of the way.
Check your rubber boots and airbox etc.

We'll get it.

[DrDoot]

Another fact that I forgot to mention is that the bike had been running fine and regularly for over a year and counting before this problem started.

[Nessism]

Next time the bike stalls take a plug loose and confirm if you have spark or not. Assuming you have spark, open the carb bowl drains and see if fuel comes out (most likely there will be no fuel).

About 3/4's of the problems with these old GS's are carb related. My advice is to take them off and clean them out before doing anything else. You need to make sure all the small orifices are open and the float/needle is functioning properly. Sudden stalling is most likely due to fuel starvation. Fuel filters can sometimes cause a problem because they cause the delivery line to loop too high and/or the filter creates a restriction by itself.

Good luck.

Ed

[rustybronco]

After it stalls and you pull a plug wire to check for no spark, get some component cooler and spray the coils to cool them or substitute known good ones. quicker with the tank removed first.

[Cyg]

6. Pulled the tops off the carbs, and the big thing that goes up and down(which, using my college education, I assume is the float, but don't have much experience with carbs) seems to go up and down smoothly.

Had too chuckle at that one. The thing going up and down inside your carbs is your slide and needle going too the main jet. Floats are on the bottom of the bowls.

Ok, you start it up, and then it dies after 10 minutes. why do you insist its a heat issue?
So too me like it starved for gas. If you get spark too the coils after it starts up then its going too keep sparking as long as the points are turnign over in and the codensors are firing. Did you check your timing? Time will throw off a plug cause it will misfire and explode before the right amount of gas get in there.
Pull of your plugs after it runs for ten mintues and read what they say. are they black and sooty? its too rich. are they white hottish? then you have the wrong plug in there and its buring too hot. are they wet with fuel? then its flooded and then I would start looking for problems with spark.
Do you know how too check for spark against holding the plug against the block? Make all ur plugs are new and set too right gap 23 ths. i think.
try those suggestions first.

[DrDoot]

Alright, after reading the Haynes manual a little more carefully, I went after the carbs today. Pulling the float bowl off showed the entire bottom was covered in fine rust dust. Pulling the petcock off of the tank, it was looking pretty rusty too, but the strainer on the petcock looked fairly clean.

With enough dust in the float bowl to make two or three pennies, would this be a likely cause by itself for the problem of dying when it's hot? I only got to one of the carbs, and the float seemed to be moving alright, but if the other one is stuck does that mean that it's not letting enough fuel in? or is it that the fine dust has clogged the jets(which I didn't have time to get to because it started to rain)? Which should I focus on?

[koolaid_kid]

Well, you definitely have an issue there. Is it the cause? Hard to tell, but you need to fix this one for the time being. Short term solution is to put a fuel filter inline from the tank to the carbs. Longer term solution is to remove the rust from the tank. Either way, you need to clean out all of the float bowls prior to any more tests. The strainer in the petcock is for larger items and would not have caught the fine particles you have described.
Also, if you have access to an air compressor, blow air through all the jets and orifices to clear out any particles that may be present.

[Cyg]

if its dust and not wet then that means that carb is starved for gas. and you are running on just some of your cylinders. that float bowl should be wet with gas. The filter is your best bet now. inline too the tank and carb.

another trick is too take your air hose and attach a long length of hose too the end of and let it whip around in there cause any loose rust too break free and then you can blow it out.

[DrDoot]

There was a good bit of fuel in the float bowls. I'd say 1/3 cup of fuel came out of each, but I didn't measure.

Any suggestions on the bigger problem?

I will be spraying carb cleaner and pulling out the jets tomorrow to use a wire and clean. Anything else I can do while I'm in there? (with carbs still attached to bike?)

[DrDoot]

Raining today, will try again tomorrow.

While I was in there yesterday, I broke off the head of the screw retaining one of the main jets. Will just spraying carb cleaner in there clean it enough(if the jets are blocked) and if not, will the bike run alright with only 3 jets completely unclogged?

[Cyg]

you break off the main jet? I dont understand what you mean by the head? Dont try too take out the main jets body. The one with four holes in it that is seated in . That is the long stem part. That part is a pain too get out even with pbblaster.

[DrDoot]

The main jet (in figure 5.8a on pg 107 if by some chance you had the Haynes manual) "can be unscrewed for cleaning". Well I broke the screw head off on one. Do I need to take the others out (using the wooden dowel method from the technical section on carb cleaning here at gsresources) or will spraying carb cleaner in there be enough?

What is it that I should be concentrating on cleaning if this rust powder is what has been causing my problems of dying and not restarted when it's been running awhile?

[Clone]

I haven't taken the carbs apart on the zuke, but above the float valves is there a screen filter? Take out the float valves and check the screen filter. I know that the Yamahas do, but I don't know about the Suzukis.

[DrDoot]

Yes, the screen filter was clear(on the one carb I got to).