TOPIC:

Working on a 1984 GPz550.

It was running totally fine for about 5 rides (10 hours or so). Then, all of a sudden, it didn't want to get up and go anymore. It will start real easy and idle just fine with no hiccups. When in neutral, you can rev it and there are no pops or backfires and there is good throttle response. But when you put it in first gear, the engine all of a sudden doesn't respond the same way.

The engine wants to die when you put it in first without revving it. If you blip the throttle and shift, it will get into gear. You can't get the bike to go unless you are revving the engine a couple thousand RPMs when you're letting out the clutch (much higher than normal).

The carb has recently been disassembled and thoroughly cleaned, all rubber lines have been replaced, and the pod filters have been replaced. I checked for air leaks all over and couldn't find any. I checked cylinder 1 and cylinder 4 spark plugs for fouling. Cylinder 1 was so hot that I had to hold the plug with a rag so I didn't burn my hand. It was also pretty white in color. Cylinder 4 was cooler to the touch and fouled. I don't know how long these spark plugs have been on there.

Could this be a carb sync issue? It doesn't seem like it to me since the bike was taken on a rides of 1-3 hours multiple times with no issues at all. Could it be a clutch issue? On the first ride, I tested the clutch multiple times and couldn't get it to slip. Maybe it's not disengaging now? I dunno.

Does it act the same way with the kickstand up or down? There is a safety circuit that relies on the neutral switch to let the ignition work in neutral, and a kickstand switch when the kickstand is up while in gear (out of neutral). A flakey kickstand switch might kill the motor when it's put into gear, but vibration might let it run intermittently with coughing etc.

You can bypass the safety system by grounding the brown/white wire on the igniter.

I'll look into that! Thank's for the quick response. It's gonna take me a day or two to get to that (not my bike, it's a friend's) so in the meantime if anyone has any other suggestions to help me troubleshoot, please let me know!

If the problems started right after the carb work, its more like the carbs. Maybe the choke ball is missing?

Sync, by itself, wont cause this problem.

I only mentioned the kickstand safety because it has caused problems like this in the past.

Ahh I understand. I did the carb work because the bike had been sitting outside for about 2 years. It was dirty and gunked up and had been run with pod filters for years.

I guess I should clarify that I didn't disassemble the carbs from the rack. To clean them, I removed the jets, gaskets, diaphragm etc... and soaked them in a pinesol/water mixture for a day. Then I rinsed and dried them out and sprayed carb cleaner and compressed air thru them. Then I reassembled them with new gaskets and did a bench sync to get all the butterflies open to the same amount.

So there is no kickstand switch, it's been removed long ago it seems.

The left side of the engine (cylinders 1 & 2) are running way hotter than the right side (cylinders 3 & 4). That to me says that it's a carb balance problem, right?

Any imbalance in the carbs at idle will disappear when you open the throttle. The difference, as a percentage of throttle opening. is too small to affect anything when you open the throttle.

So any imbalance at idle might be causing the temperature difference if you spend time idling, but it won't cause the non-running or rough running when you open the throttle.

Seems like you are running lean on 1and 2. Rich on 3 and 4. Check your float levels.
Syncing your carbs won't solve this.

I tried checking my float levels, but it seemed gas kept leaking out of the screw area so I wasn't able to get a good measurement. I checked all of the float bowl screws and the little rubber gasket on each screw was all chewed up. Could that cause any problems? The bowls don't leak gas or anything.

In float bowl for cylinder 2, I did find some jellied-gas. The bike had been sitting with old gas for a while, so this is not totally surprising. I had filled the tank up with fresh gas, but I had not drained the old gas. Would fuel stabilizer dissolve any jelly in the tank? I didn't find any jellied-gas in any other carbs and I sprayed the jet passages clean with cleaner and compressed air. I think this definitely could be contributing to the issue.

The diaphragms looked free of tears except for on cylinder 4. The very outside edge of the diaphragm is cracking:

I don't think this a particularly big deal, but I'd like your opinions!

Additionally, I was able to check the spark in cylinders 3 & 4 before the battery died from cranking it too much. I was getting good, consistent spark on cylinder 4. On cylinder 3, I wasn't getting consistent spark, but that may have been from the battery dying. I'm going to check again tomorrow. I wasn't able to double check the cylinder pressures because the battery died.

I didn't run the bike at all today, I just wanted to take a look at everything to make sure it was all copacetic.

Seems like you are running lean on 1and 2. Rich on 3 and 4. Check your float levels.

Not quite sure how float levels affects running rich. I thought the richness was determined by the jets and the balance.

I worked on the bike today and checked that there was spark on all 4 plugs. All were good. I couldn't get the bike to start tho...

I checked the float level on all the carbs and only carb #1 was low. I took the carbs off, bent the tang a tiny bit and now the float level is way too high. The bike would start, but it ran terribly.

It had no throttle response and when you gave it gas it immediately bogged down. I find it hard to believe that one single float bowl would cause that.

Additionally, the left side of the engine and the left exhaust are still running way hotter than the right.

www.kzrider.com/forum/3-carburetor/59856...cleaner-in-cv-carbsg the

Also check and make sure those pods arent blocking the air jets feeding the carbs .Sometimes you have to cut out a bit so they dont block the air coming in .

The pods aren't blocking the little bean if that's what you mean.

Is there any other way to set float height other than: measure, drain, remove, adjust, reassemble, measure, repeat? If not, that's a horribly overlooked design consideration for carburetors on these inline 4s. Harleys are nice because you don't have to remove the carb to remove the float bowls or even measure the gas for that matter. The float just needs to line up with the gasket by a certain tolerance.