Rough idle and a couple of misfires

[tanghonglai]

Hi,

I decided to do the spark plugs and oil/filter change by myself today. After everything's done, the bike becomes kind of rough at idle and I think I heard a couple of misfires at slow speed. It seems to run fine at higher RPM/speed. What could be the problem? By the way, I dropped one of the new spark plugs off the bike, I don't know if that was the main cause.

Thanks,
Tang

[f0r54ken]

Originally Posted by tanghonglai

Hi,

I decided to do the spark plugs and oil/filter change by myself today. After everything's done, the bike becomes kind of rough at idle and I think I heard a couple of misfires at slow speed. It seems to run fine at higher RPM/speed. What could be the problem? By the way, I dropped one of the new spark plugs off the bike, I don't know if that was the main cause.

Thanks,
Tang

hmm. Do you think you might have put too much oil in? I remember I put too much in when I had a Drip from the bolt. it was pretty boggy and chugged down at low rpms. Like I had to keep it alive at 2000rpm with a bit of torque on the handle. after a week or so with oil dripping out daily the bike progressively ran better. and the heat distributed better too.

If you think there might be too much try dumping out the oil again and filling it with the same oil but use that little oil window on the side and make sure it doesn't exceed 3/4s full.

Usually Immediate problems are directly related to the last thing that happened on the machine. I supposed you should make sure your spark boots are shoved onto the plugs really good too.

Also, You had to take the tank off to get to the sparks. So make sure you're pipes are going the right way and non got disconnected accidentally. and that your valve is set to "on" I'll come on and give you some pictures in a sec.

[tanghonglai]

Originally Posted by f0r54ken

hmm. Do you think you might have put too much oil in? I remember I put too much in when I had a Drip from the bolt. it was pretty boggy and chugged down at low rpms. Like I had to keep it alive at 2000rpm with a bit of torque on the handle. after a week or so with oil dripping out daily the bike progressively ran better. and the heat distributed better too.

If you think there might be too much try dumping out the oil again and filling it with the same oil but use that little oil window on the side and make sure it doesn't exceed 3/4s full.

Usually Immediate problems are directly related to the last thing that happened on the machine. I supposed you should make sure your spark boots are shoved onto the plugs really good too.

Also, You had to take the tank off to get to the sparks. So make sure you're pipes are going the right way and non got disconnected accidentally. and that your valve is set to "on" I'll come on and give you some pictures in a sec.

Thank you so much for your reply.

I double checked everything to make sure they were connected/installed correctly, but I did have a little too much oil filled in (a little above the max level when I looked at the circular glass).

I hope having too much oil is the cause. I'll run it for a week and see if it improved.

[f0r54ken]

Hey, Here are those photos I promised. Double check to make sure you're all plugged in, A couple of these aren't cataloged I'm sorry I never followed them cause they didn't need to be removed, but the ones I did highlight are likely the ones you had to take off. I hope this helps The carb has a few puff and vacuum tubes too. Make sure none of those pulled out when you pulled on the fuel plumbing. those would be obvious cause they'll be twisted toward their port not not more than an inch or two away.

I only mention it cause That actually DID happen to me while relocating my radiator overflow tube.

**B is a vent tube or something Don't connect it to anything.**

[Ghostt]

Did you renew the HT leads, and disassemble the caps?

Make sure you disassemble the caps, and clean them, and yes the caps get cruddy.

Here my write-up,

Short explanation: The inside of the hard plastic caps accumulate crud the can short out the spark. This can cause rough running or failure to start. Every time you do any work on the bike: remove them disassemble and clean them and renew the wires or at least the connections.

The long Explanation, Warning engineering information can cause Drowsiness.
The ancient cylinder design of the engine dictates that the spark emanate form the center of the combustion chamber. In order to get it there, the plugs had to be located down deep in a well between the cams. This well is a perfect place for dirt and moisture to accumulate. Then because there is no cooling water at this point the metal around the plug runs very hot. Surround this with the large amount of cool metal and you have a recipe for condensation. Now K did drill a drain hole between the fins to help (a little) but it often gets plugged up.

The moisture boils off the base of the plug and the vapor condenses on the cool plastic cap and the plug insulator. This moisture forms a easier path for the electrons to ground than jumping the gap at the plug to make a spark. Misfire.
This issue is right up there with Pilot jets as a cause of trouble.

Here's some pictures that might be helpful. I took these when I replaced the wires themselves, as it was a good time for a write-up, and the wires were OEM from 1998.

Wires are just 7mm copper core, with clear silicone jacket

[tanghonglai]

Originally Posted by f0r54ken

Hey, Here are those photos I promised. Double check to make sure you're all plugged in, A couple of these aren't cataloged I'm sorry I never followed them cause they didn't need to be removed, but the ones I did highlight are likely the ones you had to take off. I hope this helps The carb has a few puff and vacuum tubes too. Make sure none of those pulled out when you pulled on the fuel plumbing. those would be obvious cause they'll be twisted toward their port not not more than an inch or two away.

I only mention it cause That actually DID happen to me while relocating my radiator overflow tube.

Thanks again!

I was able to remove the tank by removing the 3 tubes (A, B, C) in the third picture and D and E in the second picture. They're all connected and none of the came loose.

[tanghonglai]

Originally Posted by Ghostt

Did you renew the HT leads, and disassemble the caps?

Thanks!

No, I didn't renew the HT leads and disassemble the caps. I didn't know I had to do that. Maybe that's what's causing the misfire? I'll have to take a look again next week.

[ducatiman]

Originally Posted by tanghonglai

Hi,
I dropped one of the new spark plugs off the bike, I don't know if that was the main cause.

Did you check and set the plug gaps prior to installation?

Especially important after dropping a plug on the ground, if I'm understanding you correctly.

[tanghonglai]

Originally Posted by ducatiman

Did you check and set the plug gaps prior to installation?

Especially important after dropping a plug on the ground, if I'm understanding you correctly.

No, I didn't, but I compared it with the other one after the drop and they both looked the same. I guess I'll have to look again.

[f0r54ken]

Originally Posted by tanghonglai

Thanks again!

I was able to remove the tank by removing the 3 tubes (A, B, C) in the third picture and D and E in the second picture. They're all connected and none of the came loose.

Very good!

Something else I did to check the Fuel flow was to take a glass bottle to D after disconnecting it and put that tube into the bottle. and crank the ingition.
don't crank it for long your bike will still turn on. Make sure you're ready to hit your engine's killswitch. You can check the flowpoint to the carb from there.

Mine came out at a decent rate. something equivalent to a low stream from a faucet. Also don't put that gas from the bottle back in Just get rid of it.

[Ghostt]

Originally Posted by tanghonglai

Thanks!

No, I didn't renew the HT leads and disassemble the caps. I didn't know I had to do that. Maybe that's what's causing the misfire? I'll have to take a look again next week.

I recommend doing both at the very least every time you change your plugs, it's easy and cheap to do. I used to do mine twice a season at the very least.

Worse case, go out and by some 7mm solid core HT leads, depending on the age of bike the old ones probably need to be replaced, and when installing the new ones, be sure to leave them long enough for future trimming and renewing the ends to the coils, and caps.

Also a dab of dielectric grease in all areas.

For the above reasons and others is why I converted to coil over plugs from a zx6.
https://www.ninjette.org/forums/blog.php?b=8379

[tanghonglai]

So the gap of the spark plug that I dropped was too small. I am not sure if it was caused by the dropping because it took a little force to open up the gap again. The idle's good again after adjusting the gap.

[Ghostt]

Good deal