Help with stumble

[flyingace]

Electrical things tend to happen to 2&3 and 1&4. You can still make plug wire swaps to see if the problems change cylinders - change wire #1 with wire #4 and wire #2 with wire#3. If the issue remains with 1&2 - forget electrical. If it changes to 3&4 - it is electrical.

I think the stumble is fuel delivery related. That model probably has the CV carbs and as such the idle/off idle circuit can get fouled with crud if water has ever sat in the pilot jet screw recess (front of carb). The spring corrodes and gunk fills the circuit. You need to clean the circuits out with spray carb cleaner and compressed air. Dipping isn't enough.

[Skievryday]

I think it is probably carbs too.

If you are having this much fun with electrical have you thought yet about doing the coil relay mod?

My bike hardly needs choke anymore, and idles smooth as glass. It was fine before, but was finicky on start-up. I did the mod as an added bonus to a decent running bike, and I am so far impressed.

Might help you if one is misfiring, but obviously won't solve the problem.

[JTsGS650]

Actually, anything over 12.6V is going to charge a 12 volt lead-acid battery. The question is how well and how quickly. 13.9 volts is perfectly acceptable.

Just for your own education, start with a fully-charged battery. It should read 12.6-12.8 volts with no load. Start the bike, let it idle. Note the battery voltage at idle. Increase the engine speed to 1500, 2000, 2500, 3000, note the voltages at those speeds. You will likely find that somewhere around 2000 rpm the voltage will peak, then slowly come back down. That is the point where the regulator starts to kick in. Now that the regulator is doing its thing, the increased firing rate on the coils draws a little more, which brings the voltage down a bit.

Let us know what you find.

.

Thanks Steve. I'll give this a shot and report back.

I had to pull my carbs yesterday to diaganose and clean my pilot jet in carb 4 and I was dreading it. I am happy to report that this being the 3rd time pulling my carbs in less than 4 months, I managed to due it with ease (grain of salt) . All in all, the whole procedure took me about 2.5 hours. The wrestle of getting the carbs in and out is becoming less and less and I spent more time, taking my time, opening up the bowls and cleaning the jet. That said, I'll be quite happy not having to pull the carbs for a while, but it's night and day from when I first pulled them.:-D

Well done maro. It really does get easier every time you do it.

Electrical things tend to happen to 2&3 and 1&4. You can still make plug wire swaps to see if the problems change cylinders - change wire #1 with wire #4 and wire #2 with wire#3. If the issue remains with 1&2 - forget electrical. If it changes to 3&4 - it is electrical.

I think the stumble is fuel delivery related. That model probably has the CV carbs and as such the idle/off idle circuit can get fouled with crud if water has ever sat in the pilot jet screw recess (front of carb). The spring corrodes and gunk fills the circuit. You need to clean the circuits out with spray carb cleaner and compressed air. Dipping isn't enough.

I did switch wires 1 and 4 and the problem stayed with 1, I guess this answers my question as to if it's fuel or electrical... CV carbs correct. I'll check the pilot screws and jets this weekend. But when I cleaned the carbs I did clean all the circuts, including the mixture screws with spray carb cleaner and compressed air after dipping them for 24 hours. Those orings were replaced and the spring was in good shape. I think the carbs are clean, maybe the floats need to be re-set? This is the only other adjustment I'm aware of.

If you are having this much fun with electrical have you thought yet about doing the coil relay mod?

Might help you if one is misfiring, but obviously won't solve the problem.

I have not looked into the coil relay mod yet but it sounds interesting. I'd like to get this thing running right first and then I'll start researching the crm.

Thanks for your help guys.:-D

[ironb12s]

GS650G Carb removal and install

A buddy of mine has a 1982 GS650G that we're doing some maintenance on. We're replacing the screws on the intakes with allen bolts, and replacing the intakes, as they were destroyed taking the carbs out. Yup, we slid the front plenum back as far as we could, still didn't leave much room. So, I wonder if there is a specific method to getting the carbs out and then back in? :?

I recently cleaned up everything in the intake system of my GSF1200S by pouring 7-8 oz of Berryman's B-12 fuel system cleaner (very similar to Sea Foam) into the 5-gal tank and running it empty in less than 12 hours. Filled it up with fresh fuel, and it improved the idle significantly, in fact I lowered the idle setting by 3 full turns on the side adjuster. Powerband came back thru the full range and the stumble disappeared. Rode thru a T-Storm and put the remaining B-12 into the fuel to dry it out, and rode it again to empty in less than 24 hours, and filled again with fresh. Bike is right as rain again, pardon the pun... 8-)

As always, YMMV...

[JTsGS650]

Pulled the carbs this past weekend and raised the floats on carbs 1 and 2 by 0.5 mm. Went for a test ride and the change made a marginal difference (I think). The stumble is still there after warming up. Definitely a rich condition. It smells like its running rich. Damn, I wish this thing was running right. This is really frustrating me. Any other ideas?

Carbs looked good with nothing stuck in the needles or seats.

[rustybronco]

If it smells rich, it's rich.

did someone mess with the jets that you may not know about(p.o.?), i.e. drill, change/swap?

make 4 adapters that thread into the carb drains, attach some clear tubing to them and run it up the side of each bowl. then check the fuel levels.

I checked out the spark plugs and they appear as follows: #1 is black and sooty, #2 looks rich (possible leaky petcock), #3 and #4 look perfect.

is the exhaust the same both sides with no crushed pipes, baffles missing, holes drilled?

replace the spark plugs for cylinders 1 &2.

3&4 plugs too lean? post up pictures please.

[JTsGS650]

Stock jets in the carbs. When I cleaned the carbs it looked like someone had been in there before since there are a few scratches etc. But the jets looked undisturbed and original. Exhaust is in really good shape with no dents. The only thing I did not verify is the position of the jet needles since I didn't have a pair of snap ring pliers.

After riding the bike in to work this morning, I can say for sure that there is a difference. The stumble is still there but it is better after raising the floats 0.5mm. I'll check the condition of the plugs again and try to get a pic of the plugs up.

I have also been meaning to pick up one of the Suzuki fuel level gauges to check the fuel level in the carbs. Seems like there's never enough time to work on a motorcycle.

[JTsGS650]

Better! and a few ?s

Been a while. I finally found time to pull the carbs off again. I raised the floats a full 1mm to 23.4mm set the air screws to 2 turns out and the stumble is all but GONE. It is still there but only ever-so-slightly only when fully warmed up.

I talked to a guy at the local 'Zuk dealership about this issue and he said that it may be "heavy floats". Meaning that the floats had absorbed some of the gas over time and that they would be heavier than they used to be which caused them to not float as well, causing the rich condition. It seems logical (I think?) and would explain why I'm rich on the cylinders in the left side of the bike and good on the right side since the bike was parked on the side stand for a few years with gas in the carbs. What do you guys think?

I also noticed that the pilot air jets in the carbs were 150s and my suzuki manual said that they were supposed to be 160s. What effect would this have on driveability. Is this part of my problem? TIA