Sudden rough running

[JZ05220r]

Have you inspected the reed petals? How's your air filter condition and sealing, as well as oil content?

I just cleaned the air filter and oiled it before the problem began, but I do that often so it could easily just be a coincidence. And I installed my spare filter, cleaned that thoroughly and oiled it making sure to avoid over oiling. Same problem. I haven’t removed the reed cage. I just got a view from the inlet side. I do have a brand new set of petals. I may try that.

[JZ05220r]

I have been hesitant to mess with the jetting as everything had been good for the last 45-50 hours when I suddenly noticed this misfiring at the beginning of a ride. I also have to keep in mind that I’m riding the bike a little harder this year than I was prior. Still doubt this is something that had been going unnoticed prior.

A few things I can conclude about the problem
1. Less common in 2nd gear at high rpm
2. Commonly happens in 3rd gear and up
3. Load dependent
4. Stator source coil is not the problem
5. Ignition coil, spark plug wire and boot are not the problem
6. Over-oiled filter not the problem
7. Clogged/restricted silencer not the problem.
8. Jet block o ring not the problem

I just recently decided to go down one size from 145 to a 142 main jet and my first impressions were that the problem was minimized…. to the point where I can sometimes a rev out entirely without any hiccups, other times, it’s very minor and you can hear faint pulses through the intake in unison with very brief sharp cuts in power. Other times it’s much more significant like my video above.

Basically on average, out of three different runs, one will be clean, one will be harsh, and one will be very minor in terms of the misfiring. I’m curious, yet very hesitant to go down another size on the main.

[SpruceItUp]

Given the fact that it is intermittent I would maybe start to suspect the CDI? Also, there isn't a whole lot else it could be given the list you gave here. They tend to fail either entirely at once or in very weird ways from what I have experienced. You can get a cheap replacement one from RMSTATOR. I got one a couple months ago from them for my 92 200 as it was not revving out at all and it was the issue. I ended up going through pretty much everything just as you did, and the CDI was my last resort, and it turns out it was bad.

Unfortunately I don't think you can really test them, at least not without special tools from what I understand. The CDI was like 35 bucks. In terms of what I tend to spend on repairs for my bikes, it was chump change, so if there is not much else to try, I'd say throw a new CDI in it. I hate to throw parts at repairs if I am not certain it is the problem, but after a certain point what can ya do, y'know?

[Chuck78]

Spruce, I believe he has ordered that exact PeakRPM CDI from RMStator after we talked Friday or Saturday. It was either that or I was to ship him a CDI off my spare bike that's disassembled, but for $35(+shipping) that's a bargain compared to shipping my CDI there and back for a loan...

James, I still would insist on getting a couple new NGK spark plugs from an auto parts store, BR8EIX or BR8EGV (or EG/EV). Those are not copied by the cloning factories so much if any vs the standard BR8ES, so you're more guaranteed to get a genuine NGK. Still, ohm out the 5,000 ohm resistor spark plugs, because even genuine versions come out often at 7000, 22,000, or even 32,000 ohms as I have found with firsthand experience on my own brand new genuine NGK plugs. I might start switching to Denso (IW09???) again in hopes of finding better quality and further lesser chances of fakes. The Denso iridium equivalent of the NGK BR8EIX

[JZ05220r]

OK, I’ll try a new iridium plug and the CDI. Thank you guys.