FIXED - Cutting out at high RPM - electrical, other issue?

[billwill]

Been dealing with an issue lately with my vertical build with it cutting out at high RPM, specifically between 1/2 and WOT up near 10-11k rpm. 

The issue: for the life of me I cannot seem to get the thing jetted correctly on the main jet. The low and mid range sound and feel spot on but no matter the main I use, she sputters and is either missing or cutting out at about anything more than 10.5k-11k RPM. 

What's strange is I had the bike running pretty well with the exact same setup and Yasuni C16 exhaust on the same day this video was taken.

I've leakdown tested recently and it held 6psi for over 45 minutes so an air leak isn't the issue.

Build details:
- '99 Zuma
- MXS race cylinder 
- MXS intake and vforce reeds
- b9hs plug
- stock ignition (I know this isn't ideal. I have an MVT dd ignition ready to go on the bike but wanted to get it dialed without it first)
- SCR Corse exhaust
- Malossi CDI
- motoforce coil and plug wire/cap (only running this because I thought the issue might be the stock coil and NGK plug wire and cap I was using)
- polini 24mm PWK (have tried a 30mm polini PWK too, but the 24 is on the bike now)
- jetting: 42P, 132M, JJN Needle set to middle clip

I have tried main jets all the way from 124 (this ran lean) up to 148 (very rich) and I just can't shake the high RPM breakdown. The sparkplug cap is tight and secure, fuel flow seems good with my gravity fed, vacuum deleted setup... I'm stumped.

My current thoughts are that it could be the polini PWK carbs. Both the 24mm and 30mm behave similarly. Or, it could be that I need to upgrade the ignition, although others have run similar builds without it.

Or, maybe a deeper underlying electrical issue? The Trailtech cutting out like it does in the video is nothing new to me. It has done this before although just started acting up again. This is the second one I've had with the issue and Trailtech sent me a second one (this one) free of charge a while back.

[billwill]

More data for consideration…

I just tried a 128 main and the issue persisted. Then I tried swapping back from the malossi cdi to stock and the sputtering was still there but the trailtech didn’t flicker.

[sckanksta]

Have you checked that the grounding are 100%? Clean and nice / tight connection?

[billwill]

May 28, 2024 4:55:26 GMT -5 sckanksta said:

Have you checked that the grounding are 100%? Clean and nice / tight connection?

I went through it last night and this morning a bit. CDI ground is good. As is frame and engine.

I'm thinking the stock ignition just doesn't have enough juice and the plug gap needs to be taken down. The iridium plug I was using prior to that video was set to .030 in/.75mm gap and the one in the vid was using a .026 in/.65mm gap. I've set the plug gap to .016 in/.4mm and going to test later today.

[billwill]

Welp, time to swap out the stock iggy for the MVT I guess.

I gapped the plug down to .016" and she runs like a champ now.

Probably going to start bumping it up in steps of .002" to see how wide of a gap I can push.

Also, a buddy on facebook was saying how resistor plugs should keep the Trailtech from flickering. Sure enough, I gapped the Iridium plug I was using (BR9HIX) down to .016" and tried it and the flickering is gone. Something about the resistor plugs removing noise from the wire.