[rworkman98]

The last few days, I’ve been having a very difficult time keeping my motorcycle running. (Temps between 40 and 55 degrees) For the first five minutes, if I let the revs get below about 2k, the bike dies. I’m aware that carbureted vehicles don’t do as well in the cold, but this is ridiculous. Today, even turning the choke all the way on wasn’t enough. If I didn’t sit there revving the engine, it would die. Every time I would slow down for a stop sign or stoplight, it would die. It has also been dieing every time I start from a stop, unless I really over-rev it.

Is this just indicative of a carbureted bike, or do you think something is wrong? I think my carburetor needs to be worked on, but I’d like to hear other’s opinions too. Are there any adjustments I need to make for colder weather?

 

[No Worries]

The 98 ZX9 is known to have lean jetting off idle. Cycle World magazine and maybe Sport Rider had articles on how to shim the jet needle. That seemed to cure the lag off idle. But it appears your idle jet(s) are clogged. If you are not experienced with carbs, I would bring it to a good mechanic and have 'em clean the carbs. The choke passages may be clogged too.

 

[Gas Man]

Not sure about what NW says...but he does know his stuff!

This is not normal. You need to have the carbs looked at. They may need a cleaning and most likely need a sync as well. How mechanical inclined are you?

 

[bumblebee]

I agree, carbs are starving, start at carb bowl and work way back to tank, looking for "gunk" that may be clogging lines with colder weather here.

 

[rworkman98]

This is not normal. You need to have the carbs looked at. They may need a cleaning and most likely need a sync as well. How mechanical inclined are you?

I'm pretty good at mechanical things. I work on my cars in my spare time, but have never touched a bike before. Would spraying carb-cleaner into the carb inlets be useful?

 

[rworkman98]

The 98 ZX9 is known to have lean jetting off idle. Cycle World magazine and maybe Sport Rider had articles on how to shim the jet needle. That seemed to cure the lag off idle. But it appears your idle jet(s) are clogged. If you are not experienced with carbs, I would bring it to a good mechanic and have 'em clean the carbs. The choke passages may be clogged too.

I've done work on engines and cars before, but never worked on a carburetor. Are there any good step-by-step guides for motorcycle carbs?

 

[Gas Man]

A few of the guys here are carb profient...they will be able to steer you in the right direction. However, I would also suggest getting a service manual!

 

[rworkman98]

A few of the guys here are carb profient...they will be able to steer you in the right direction. However, I would also suggest getting a service manual!

Excellent. I will most likely have a number of questions if I decide to clean them myself. I'm trying to get a service manual, but no luck yet. I did get one for the ZX-7R on .pdf, so it may be close enough to work...

 

[jeeps84]

:readng:
:here: Did you try to simply increase the idle rpm first? :here:

 

[Gas Man]

Well keep us advised...

 

[rworkman98]

Well keep us advised...

Update: I purchased a service manual, and decided to do it myself. I took off and disassembled the carburetors. As recommended, I cleaned them in a carb cleaner solution, then washed them and dried them. While I had the bike apart, I re-gapped all my spark plugs as well, and also cleaned and re-oiled my air filter. While the carburetor was apart, I also inspected the floats and needles for any visible wear, but could not find any.

After that, I put the carburetor and the bike back together, taking great care that everything went back exactly as it was removed. (I took about 200 digital pictures during removal, and referenced these pictures during reinstallation.) Well, the bike runs much worse than it did before. It has a VERY rough idle, and is running roughly at any engine speed as well. Also, the idle won’t stay very steady, especially when the bike isn’t yet warmed up. Before yesterday, I didn’t have any problem with a rough running condition; only a problem with the bike dieing excessively before it was warmed up.

Any ideas on what I may have done wrong? One thing I noticed was that all 4 spark plugs had gaps that were significantly over spec. I re-gapped them all down to .76mm, as noted in the service manual. I wonder if the specs in the service manual were wrong, and this contributed to my problem.

 

[jeeps84]

Make sure you don't have a plug wire crossed.

 

[ShanMan14]

And that is why I will let someone else deal with my carbs. I sprayed some carb cleaner in mine this weekend, but that's as far as I'll go.

I haven't a clue what's wrong but I know what it's like to spend hours "fixing" something only to make it worse. Sorry, I feel your pain. :sorry:

 

[jeeps84]

And that is why I will let someone else deal with my carbs. I sprayed some carb cleaner in mine this weekend, but that's as far as I'll go.

I haven't a clue what's wrong but I know what it's like to spend hours "fixing" something only to make it worse. Sorry, I feel your pain. :sorry:

:iagree:

 

[Gas Man]

And that is why I will let someone else deal with my carbs. I sprayed some carb cleaner in mine this weekend, but that's as far as I'll go.

I haven't a clue what's wrong but I know what it's like to spend hours "fixing" something only to make it worse. Sorry, I feel your pain. :sorry:

:iagree: but I think you should have replaced your plugs instead of re-gapping them. I have never re-gapped my plugs... if I'm going to take them out, I replace them... just a rule of mine.

Other than that, I would find a compitent mechanic and take it to him. Much better than screwing around with it.

 

[No Worries]

Kind of late now, but when I work on my bike or any vehicle, I will only work on the ignition or the carbs. Never both at the same time. Now you don't know which one is screwed up. If the plugs were "over gapped" they were probably well worn. I would try new plugs first and then do like Jeeps says and check that the spark plug wires are going to the correct plugs.

If you took off the float chamber covers, took out the jets and sprayed carb cleaner through each one and all the non-removable jets, they should be good. But that's only half the cleaning.

On top of the carb, the piston slide has the jet needle attached and pulls out of the main jet according to differential air pressure. The slides and walls get sticky and the air passages get clogged. The tops (another 16 screws) have to come off. There will be a spring and thin rubber diaphram attached to the piston, which is probably plastic. Don't bend the needle. Spray carb cleaner on the piston without getting any on the diaphram. Also clean the walls where the piston slides. Spray carb cleaner through all the passages till clean.

Now to assemble it here is the trick. Use a little Vaseline petroleum jelly and put it in the groove where the lip of the diaphram goes. Now you have to get the piston in the cylinder and the needle in the main jet without forcing it. And you have to put the diaphram in the groove. The Vaseline keeps the edge in place while you put the spring and cover back on. The vaseline also prevents air leaks. One down, three to go. After you finish, you should get the carbs synchronized.

 

[Gas Man]

That's a good idea... never both! I'll have to remember that!