2k-4k RPM Missfire/Stumble

[MrOzz]

I had a set of the mikesxs High Output Replacement Ignition Coil Part# 17-6803. They seemed to of died out after a few months of riding. My brother in law sold his bike and had a set that he never used, so he gave them to me. I put them on my bike and I am having the same issue as before. Seems like I am getting a missfire between 2k-4k rpms.

I know when switching to to the mikesxs coils you want to remove the ballast resistor so the coils get full voltage.

If you use the NGK Resistor Spark Plug Cap (5K Ohms), could that limit the voltage to the spark plug? I am using NGK BP6ES plugs.

I have checked the plug color and they all look good.

If I remember correctly that the needle jet affects this range? So I might want to lower the clip on position on the needle?

What do you all think?


Thanks,
Ozz

[natemoen]

I had a set of the mikesxs High Output Replacement Ignition Coil Part# 17-6803. They seemed to of died out after a few months of riding. My brother in law sold his bike and had a set that he never used, so he gave them to me. I put them on my bike and I am having the same issue as before. Seems like I am getting a missfire between 2k-4k rpms.

I know when switching to to the mikesxs coils you want to remove the ballast resistor so the coils get full voltage.

If you use the NGK Resistor Spark Plug Cap (5K Ohms), could that limit the voltage to the spark plug? I am using NGK BP6ES plugs.

I have checked the plug color and they all look good.

If I remember correctly that the needle jet affects this range? So I might want to lower the clip on position on the needle?

What do you all think?


Thanks,
Ozz

I know its been a common thing with those coils that they burn out after a couple months or so and every now and then you find someone who has had them work for a couple years. So I would check them and make sure they are not burning out as well!

You shouldnt have to change any jetting just because you have hotter coils. Did you have this problem before you put on the hotter coils?

The main jet is going to begin to over take the pilot jet at around 3500 give or take. So if you were to raise the needle (lower the clip) It would lower the RPM that the mains would begin to feed the engine and if you lowered the needle (raised the clip) it would raise the RPMs that the mains began to feed the engine. What is your needle set at now?

It also seems to be a common problem with a lot of these bikes that without the stock pipes there does seem to be a pretty pervasive stumble in roughly that same range. It is possible to get rid of it with good tuning but it takes time and effort!

[MrOzz]

I checked the primary and secondary resistance on the coils before I put them on the bike, and the are in spec. I know some members have had issues the with black mikesxs high output coils, the ones I have. I dont think there has been any issues with the green ones yet.

I did not have this issue with the stock coils, only after changing to the high output ones.

I have it set at the second grove down per the instructions with the dynojet kit. Float is set at 23mm.

I am running stock pipes.

[natemoen]

23mm is a bit on the lean side. but i dont know how it would work since it sounds like you have a dynojet kit in it.

[motoman]

Might double check the pick-up wires.......had same issue. Can read my latest "what did U do to your bike"........surprised me as I knew on the 81's Yammy supposedly resolved the issue relocating the wire hold-down bracket.......nay on that as I found out. JAT....

[MrOzz]

Might double check the pick-up wires.......had same issue. Can read my latest "what did U do to your bike"........surprised me as I knew on the 81's Yammy supposedly resolved the issue relocating the wire hold-down bracket.......nay on that as I found out. JAT....

Thanks for the idea on the pick up wires. That was the first thing I checked when I noticed the stumble.

[MrOzz]

On the coils the red/white is + and the orange and grey wires are -? I just want to double check.

thanks

[bikerphil]

On the coils the red/white is + and the orange and grey wires are -? I just want to double check.

thanks

That is correct. I've had those black Mikes coils fail on me too. When you checked your pick up coil wires, did you remove the wire crimp clamp? They sometimes fail in that area.

[MrOzz]

That is correct. I've had those black Mikes coils fail on me too. When you checked your pick up coil wires, did you remove the wire crimp clamp? They sometimes fail in that area.

Thank You bikerphil,

Yes I did. I had already done the pick up coil fix. I double checked them today and they are good. I have a feeling there is something else going on. I have 4 of the mikesxs coils. 2 old, 2 new never used. No mater how i mix and match them I am having the issue.

Now I have noticed its not just between 2k-4k. I am even getting a stumble at idle. Almost a misfire type of sound.

When I hooked up my carb sync I noticed that the vacuum will drop, but only on the #2 carb.

All the carbs are at 22cmHg. The #2 carb will drop to 14cmHg then rise back up to 22cmHg. This is when the stumble happens.


Any ideas?

Thanks all

[motoman]

Very well explained issue going on here. Of course, the vacuum drop is due to not firing at that moment. Of course, sure you already kew that. IMHO, primary not secondary ignition would be the source of the problem based on the well explained issue and how you have thus far tried to resolve it.

[bikerphil]

I'd try the simple things first. Change out the #2 plug and make sure the connection at the plug cap is solid. When I'm checking for a misfire, I like to hook a timing light up to each wire so I can visually see which cylinder is misfiring with the flash of a light. When doing this, plug wires (2+3 and 1+4) can be switched around to see if the problem moves around.

[MrOzz]

I'd try the simple things first. Change out the #2 plug and make sure the connection at the plug cap is solid. When I'm checking for a misfire, I like to hook a timing light up to each wire so I can visually see which cylinder is misfiring with the flash of a light. When doing this, plug wires (2+3 and 1+4) can be switched around to see if the problem moves around.

Ha you must of been writing that while I was doing it, lol.

Well I think I found the problem. 3 out of the 4 mikesxs high performance black coils, the 2 new and 1 of the old are junk.

I am glad that I did not pay for 2 of them. But my brother in law did. I told him what was up and he is happy he never used them on his ride or sell it with them on it. Unfortunately Mikesxs has a no return policy on the coils. We had bought the coils at the same time so I think he had a batch that were no good.

So in conclusion, I put the stock coils on and it runs fine. No stumble or miss fires. I would also never recommend the mikesxs black coils to anyone.

But on the other hand, how are the green ones? Anyone having any problems with them?


Thanks all for your help with this.

Ozz

[bikerphil]

I put the stock coils on and it runs fine.

Glad you found the problem. Don't forget to put the ballast back in line. AFAIK, no problems have been reported with the green coils.

Yep, those black mikes coils left me running on 2 cyl, had to limp the bike 7 miles home.