Author Topic: Skipping (Read 5234 times)

Dhastings1954 · **on:** June 12, 2018, 06:22:50 pm

I have a 1998 Bullet 500. I have installed a mikuni carb and an electronic ignition system, along with a lot of other things.
The bike skips intermittently. Usually at the same place on the throttle, which is at the higher end of revs. It does not do it all the time, though it seems to be getting a little worse. When it is not skipping, it runs very smooth.
Any ideas? I was inclined to think carberator issues, but now not so sure.

mrunderhill1975a · **Reply #1 on:** June 12, 2018, 06:32:23 pm

Hmmm.....That is a puzzle.....is there any correlation with vibrations? If so, I wonder if there is coil wire (usually red/black) that vibrates on the frame which occasionally touches the frame at the same instant as the electronic ignition is firing. Just a thought.

If it were a carburetor problem, I would expect it to happen consistently at the same RPM. So, I think it is most likely an electrical bug.

Dhastings1954 · **Reply #2 on:** June 13, 2018, 03:26:15 am

Good thought. I will check those connections and wires. I have had some issues with crud in the gas tank clogging up the screen on the fuel filter where it was actually starving for gas, it I don’t think that is what this issue is.
I adjusted the valves today and took the plug out to find TDC. I noticed the plug was kind of carboned up. Not a nice clean brown, but more black and sooty. I don’t think it has been running too rich, but....

Spitting Bull · **Reply #3 on:** June 13, 2018, 03:23:46 pm

Are you finding that the engine skipping starts when you're holding the bike at a steady speed?

tooseevee · **Reply #4 on:** June 13, 2018, 03:58:58 pm

Quote from: Dhastings1954 on June 12, 2018, 06:22:50 pm

I have a 1998 Bullet 500. I have installed a mikuni carb and an electronic ignition system, along with a lot of other things.
The bike skips intermittently. Usually at the same place on the throttle, which is at the higher end of revs. It does not do it all the time, though it seems to be getting a little worse. When it is not skipping, it runs very smooth.
Any ideas? I was inclined to think carburator issues, but now not so sure.

You don't say what model Mikuni you have.

Float level is a possibility, I suppose, if your "skip' is only at WOT.

If your petcock has a filter inside the tank, that might also be a possible.

Dhastings1954 · **Reply #5 on:** June 13, 2018, 07:20:19 pm

Yes, the skipping seems to be at the same rpms regardless of the bear I am in. If I throttle up or down from the point it smooths right out. For a while it did not happen all the time, but now it seems to be doing it more times than not....getting worse in other words.
Not sure what model mikuni carb I got! Got it from Classic Motorworks as a listed replacement. Will try to post pictures.
Did not know there might be a filter on the inside of the tank. Worth a look, as I have had some issues with crud in the tank. The petcock has a removable filter on the bottom. Any way to know about the filter inside the tank short of taking the petcock out?

Spitting Bull · **Reply #6 on:** June 14, 2018, 01:51:19 pm

If your bike had points ignition, I would say that the battery isn't holding a charge and needs replacing. I don't know if this will hold true for electronic ignition, though. My 350 did the same thing. When held at a steady speed, the battery wasn't holding enough power to run the ignition system. With the added charging of acceleration, the hesitation and missing ceased. Charge your battery and leave it overnight. Then test the voltage. It should be between 12.4v and 12.6v. It only has to be a little lower than this to have lost quite a bit of its power. For example, if it reads 12v it will have lost half its charge overnight. How old is your battery?

Dhastings1954 · **Reply #7 on:** June 14, 2018, 03:26:05 pm

Good idea of something to check. Battery was new last year and I brought inside and put a trickle charger on it all winter. It tests good at 12.5v.
I was having problems with (original) rectifier and regulator with fluctuating ammeter charging, but there was no correlation that I could tell between the ammeter going negative and skipping issue. Have replaced the regulator and rectifier with a single unit. That cured the ammeter fluctuations, but has not helped the skipping issue.
Do you think the coil could be bad or in the process of failing?
The puzzle for me is that it seems to skip at just one place in the rpm spectrum. If I had a tach I could check it for sure.

Dhastings1954 · **Reply #8 on:** June 14, 2018, 04:01:50 pm

An earlier post question was what mikuni carb did I replace the original with. As far as I can tell it would be a JRC 30 mm. On the float bowl casing it says PWK 30.

Spitting Bull · **Reply #9 on:** June 14, 2018, 10:43:50 pm

We may have different symptoms, then, DH. When my 350 did it, I didn't notice it happening at a certain rpm. It was usually when the engine got up to speed - when it had stopped "pulling" and started "cruising" if you know what I mean. A battery check won't do any harm, though, and if it's something else, I hope you find it.

tooseevee · **Reply #10 on:** June 15, 2018, 12:36:10 am

Quote from: Dhastings1954 on June 14, 2018, 04:01:50 pm

An earlier post question was what mikuni carb did I replace the original with. As far as I can tell it would be a JRC 30 mm. On the float bowl casing it says PWK 30.

I think what that is is a copy of the Mikuni flat slide 30mm similar to the Mikuni TM 32 I put on my AVL.

If you Google PWK 30 you can find out all about that carb.

tooseevee · **Reply #11 on:** June 15, 2018, 12:46:54 am

Quote from: Dhastings1954 on June 13, 2018, 07:20:19 pm

Did not know there might be a filter on the inside of the tank. Worth a look, as I have had some issues with crud in the tank. The petcock has a removable filter on the bottom. Any way to know about the filter inside the tank short of taking the petcock out?

No. You gotta remove the petcock to see the filter.

Be very careful with that pesky little external plastic filter. Don't remove it unless you Must.

I could not reseal the little bastard no matter what I tried. I finally removed the tiny filter and permanently sealed the filter housing to the petcock with Seal-All (this was many years ago). It can never be removed, but It Does Not Leak

ace.cafe · **Reply #12 on:** June 15, 2018, 02:09:35 am

The JRC is a copy of a Keihin 30mm D-slide carb.
They take an OKO 30mm and install a mounting flange. The OKO is a copy of a Keihin PWK 30.

Dhastings1954 · **Reply #13 on:** June 15, 2018, 12:16:24 pm

So I took off the carburetor and gave it a total cleaning, removing all the Jets, blowing everything out and liberal use of carb cleaner. Doesn’t seem to of made much of a difference. Seems like I may be back to an electrical issue? Going to try a new plug wire . Checked all the connections from my electronic ignition to the Kyle which seemed good. Anybody think it could be the coil??
I still need to take the petcock off and see if there is a filter up inside the tank.

Dhastings1954 · **Reply #14 on:** June 15, 2018, 12:18:03 pm

Coil, ot Kyle ....auto correct

tooseevee · **Reply #15 on:** June 15, 2018, 01:16:40 pm

Quote from: ace.cafe on June 15, 2018, 02:09:35 am

The JRC is a copy of a Keihin 30mm D-slide carb.
They take an OKO 30mm and install a mounting flange. The OKO is a copy of a Keihin PWK 30.

Boy, was I wrong

blasphemous · **Reply #16 on:** June 15, 2018, 06:56:43 pm

I have the same problem, I put in a new airfilter and pipes, so I put new jets on the 0 to 1/4 throttle(pilot jet?) and left the main jet stock. Since then I have had this problem. Does it 3 times out of 5, when I transition from pilot to main jet , it skips a beat. By skipping I mean the engine behaves as if it is ready to stall. I am thinking that maybe it is because there is not a smooth transition from pilot to main jet at the transition, throttling the supply of fuel. I am going to go up on the main jet 1 level and see if it helps. Will keep you posted.

Dhastings1954 · **Reply #17 on:** June 16, 2018, 03:38:43 am

Took the petcock out and there was a screen filter but it was not clogged.
After riding several hours today I would say the carb cleaning helped but did not cure. When it is NOT skipping it runs great. When it does skip I can find a place on the throttle above or below where it runs good. WTF.
Going to put in another new plug, change the plug wire and maybe a new coil and see what happens. Pretty sure the coil is original, so 20 years old.

Adrian II · **Reply #18 on:** June 16, 2018, 06:01:51 pm

Quote from: blasphemous on June 15, 2018, 06:56:43 pm

I have the same problem, I put in a new airfilter and pipes, so I put new jets on the 0 to 1/4 throttle(pilot jet?) and left the main jet stock. Since then I have had this problem. Does it 3 times out of 5, when I transition from pilot to main jet , it skips a beat. By skipping I mean the engine behaves as if it is ready to stall. I am thinking that maybe it is because there is not a smooth transition from pilot to main jet at the transition, throttling the supply of fuel. I am going to go up on the main jet 1 level and see if it helps. Will keep you posted.

Transition from the pilot jet is not directly to the main jet, you need to consider the size of the throttle cut-away, the needle size and position and the size of the needle jet itself.

A.

Dhastings1954 · **Reply #19 on:** June 16, 2018, 10:26:00 pm

Another symptom. My plug is black with carbon buildup. It used to be nice clean Brown. I would have thought this a symptom of too Rich a mixture. Could it also be from poor spark and failing coil??