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.

[JZ05220r]

Tried the new CDI, wasn’t it. As soon as it happened again, I went right back to the garage and threw an iridium plug in and same thing again. I do have a left hand crank seal leak around the outer bronze diameter, plus a very small base gasket leak. In reality, both of these things have been there since the engine was put back together. I had been keeping an eye on the base gasket and I was gonna get to that, but it was running so good, I never bothered. The symptoms are definitely not lean. I’m at my last leg obviously and seems like reeds are the last thing to try. I’m not going to move forward with and gamble on any other engine work if the problem still persists after I replace the reed petals.

[JZ05220r]

I use boyeson pro series dual stage reeds. Just took a look at them and one of the carbon fiber petals wasn’t seating fully. I didn’t measure the gap, but it was obvious. New reeds in… will test when I have time.

[Chuck78]

You'd said the jet block gasket was NOT the problem, but how can you be 100% certain? Did you pressure test it with the inverted cab body bowl area filled with liquid, using an air compressor rubber tipped blow nozzle at 5-10psi, looking for bubbles???

Just because it may only be 1-3 years old doesn't mean it's guaranteed to be good still.

Also, we have 15% ethanol in our gasoline now, are you running standard pump gas, or ethanol-free?

[JZ05220r]

You'd said the jet block gasket was NOT the problem, but how can you be 100% certain? Did you pressure test it with the inverted cab body bowl area filled with liquid, using an air compressor rubber tipped blow nozzle at 5-10psi, looking for bubbles???

Just because it may only be 1-3 years old doesn't mean it's guaranteed to be good still.

Also, we have 15% ethanol in our gasoline now, are you running standard pump gas, or ethanol-free?

I did pressure test it with the carb upside down in a vice with the fuel mix just above the mating surface of the jet block tower. Also I am using pump gas but I don’t see any labels on the pump required by law to inform of an increase in ethanol.

[JZ05220r]

I did think to just replace it anyways in case I’m missing something. But I have experience checking and finding a failed jet block gasket after seeing bubbles and I saw none when I tested.

[SpruceItUp]

I finally read through the entire thread again so I think I am up to date.
Have you done a leakdown test? Is it possible you are burning a small amount of gearbox oil? Not enough to throw out a ton of smoke, but enough to throw off how the bike is running. Given the fact that gearbox oil won't burn anywhere as easily as gasoline, I could see that causing it to not rev out as much. As for it being intermittent, I don't have an answer for that.

You could also check this by measuring how much gearbox oil drains out compared to how much you put in.
Just an idea, given you seem to be at a loss again, unfortunately.

[JZ05220r]

That is a good question, however my gearbox level has remained dead steady. I did do a leakdown test and have a very minor base gasket leak, and a leak around the outter shell of the left hand crank seal. Both of which were there when put together. The base gasket leak weeped very slowly since put back together, and the shell of the crank seal is obviously not something that would likely suddenly develop.

[JZ05220r]

I’ll add that the leakdown test results were not that great. And I am going to correct them IF I can figure out the current issue. If my issue is related to the poor leak down results then I won’t be fixing the bike because I’m not going to spend that money only to find it still exists. It runs very well low to mid. Had the bike for 5 years and it’s the best it’s ever ran besides that issue.

[JZ05220r]

Reeds didn’t cure the problem. I have just about went through everything at this point. I’ll probably revisit the carb one last time and put in some fresh gas.

[JZ05220r]

OK, so I had already gone down to 142 recently from the 145 main and thought I noticed a little bit of an improvement, but I wasn’t for sure.

Today I was about to go down to a 140 main but I decided to jump up first just to be safe. Keep in mind is it 90 degrees F where I am. Went to a 148 main and the sputtering seemed worse. Then I went to a 140 main directly after. With the 140, even though there was still some sputtering, it had calmed down a lot in the higher gears, actually, my first rip from 2nd to 5th was basically hiccup free. I thought it was over, but it showed up again, just not as severe.

I immediately went back to the 148 just to be sure and it was definitely significantly worse. It fell on its face even earlier in 3rd gear to even consider grabbing another gear.

I’m almost positive it’s running too rich at full throttle in the higher RPMs. I have already swapped my second hand air filter in and made sure it wasn’t over oiled. I almost want to try another batch of fuel. Not sure about going to a 138 because that sounds like more of a mask to whatever the issue it. but I feel more hopeful I will figure it out.

[JZ05220r]

Today I swapped to my spare 36mm (bored by Jeff fredette) 220 carb. I started with a 160 main and kept the needle position the same. Fell on its face badly. Went back and went down to a 152 it cleaned up a lot but still does the same as with the stock 33mm carb I have been running. So what I can conclude based on using both carburetors is that it’s running rich with jets on the leaner side of what others typically run. I am thinking I’m not getting enough air in or I’m not getting enough air out. First thing I’m going to do is switch from my two piece uni, to a spare twin air. Last thing I will do is double check the KIPS valves are fully opening.

[ss109]

You said you're running leaner than most. What elevation are you at?

[JZ05220r]

You said you're running leaner than most. What elevation are you at?

Yes, I’m at roughly 600 ft.