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H2B RH cylinder misfire
http://www.kawi2strokes.com/forum/viewtopic.php?f=14&t=12996		 Page 1 of 3
Author:  DGA [ Thu Aug 03, 2017 10:33 pm ]
Post subject:  H2B RH cylinder misfire
I am still working on getting this H2B to run cleanly. Partly it's difficult for me because I have never ridden one before and don't know how it should run, how hard it should pull etc. It does pull hard at 5,000 and over, but under that it's a bit erratic. At low revs I think I feel a cylinder jumping in and out again, and the motor does seem a bit lame under 5,000, almost like it's only on two cylinders. Also confusing me is the fact that I have expansion chambers, and maybe these are hurting the bottom end, but my experience tells me they shouldn't hurt that much. SO, when I checked the ignition timing, the RH cylinder seemed to have a misfire, the strobe light would cut in and out. Also, because these are new pipes, the LH and center headers are going a light straw colour, but the RH one not so much. Also when I shut the motor off, I can notice the RH head is a little cooler than the LH one.
So this question is, what ignition part would cause something like a misfire? Could the CDI do this or do they typically just quit? The coils and plug wires are original, as are the pickups and windings. The wire harness is also original, but seems to be in good condition, I cleaned and checked the connectors for tight connections etc. I don't see any cylinder base gasket leaks or head leaks, no oil present, all clean. The crank and bores and rings and pistons are all new, and it starts and idles great. So it seems like it's idling on 3 cylinders, but when I load it, it drops the RH one, which does point me to ignition.
Author:  Jim [ Thu Aug 03, 2017 11:25 pm ]
Post subject:  Re: H2B RH cylinder misfire
DGA wrote:
So this question is, what ignition part would cause something like a misfire? Could the CDI do this or do they typically just quit?

The right cylinder CDI unit could possibly be doing this. If you swap the white wires between the right cylinder and another one, and also swap the same red output wires, you effectively swap the units. If a CDI unit is the problem, the problem should now be on the other cylinder.
Author:  DGA [ Mon Aug 07, 2017 6:47 pm ]
Post subject:  Re: H2B RH cylinder misfire
I swapped the CDI wires around, no real differences. I started playing with the idle mixture, went a quarter turn richer, no real difference. So I started going leaner, that had an effect. I am at 3 turns out now, with 37.5 pilot jets, and it still seems like it needs to be leaner still. The H2B came with 40s in it, so I'm guessing the small transfer port changes and the chambers make it not want much low speed fuel, and when I think about it, it makes sense. It won't make more power at very low speeds with porting and chambers that don't work until maybe 3500. So, when is it considered to be out of the idle mixture screw range, how many turns out, to need to go to a leaner idle jet, a 35?
As a side note, I think the RH CDI might be weaker, and the low speed fuel was so rich it couldn't fire it, while the center and LH CDI were able to marginally. I think I need to order one of Jim's CDI boxes.
Author:  usernameandpassword [ Mon Aug 07, 2017 7:08 pm ]
Post subject:  Re: H2B RH cylinder misfire
If you have the timing light cutting in and out when it's idling, that's pretty much pointing you to the ignition for that side. If you have stock carbs, it would surprise me it would be rich on a 37.5 with the screw all the way out. Without the air box and filter, the stock needle is lean just off idle with a 40 to where it's noticeable.

Have you checked the pickups on the side, air gap timing, grounds, and the wiring from the pickup to the ignition box for solid connections? How about the coils.....got a spare you can throw on it, or swap a couple around?
Author:  DGA [ Mon Aug 07, 2017 8:50 pm ]
Post subject:  Re: H2B RH cylinder misfire
Forgot to add, there does not seem to be any spark erratics with the timing light now. All are consistent, I did have to tweak the timing on one cylinder a bit. My thought is that it's not missing a spark, that it has a weak spark on the RH cylinder, and that it was that rich off idle that it couldn't fire that cylinder always. I will possibly have to go one size leaner on the slide cutaway as well.
Author:  DGA [ Mon Aug 07, 2017 10:32 pm ]
Post subject:  Re: H2B RH cylinder misfire
But back to the question, when is it considered to be out of the idle mixture screw range, how many turns out, to need to go to a leaner idle jet, a 35?
Author:  mraxl [ Tue Aug 08, 2017 6:01 am ]
Post subject:  Re: H2B RH cylinder misfire
I can't tell you for sure what your problem is but I can tell you FOR SURE that anything less than #40 pilots for VM30 on an H2B is wrong and going to a leaner slide is also wrong. H2's are inherently lean at low throttle positions and the fix is going to a RICHER slide. NOTE: Carb sync is critical.
If you are truly too rich at idle with #40 pilots I would look at restricted air supply... maybe over oiled filter?
A misfire is typically and ignition problem. An intermittent misfire is likely due to a problem with the pickups... air gap not correct, poor solder at pickup, etc. CDI could also be at fault.
If you are using resistor plugs or plug caps that might also be a problem as would bad/arcing plug wires.
Author:  DGA [ Tue Aug 08, 2017 9:13 am ]
Post subject:  Re: H2B RH cylinder misfire
I am not getting a misfire anymore after I went leaner, I think it was a rich stutter miss and was throttle dependent. I have 37.5 idle mixture jets in it now. I see the stock H2 idle jet was a 35, and my H2B should have been a 40. I have raised the transfers a little, but my chambers are radically different from any I have seen on any H2, much longer, much larger diameter, so this case might not be a typical one. I also have an H1 intake manifold, which is shorter and smaller diameter which is probably killing bottom end as well. I have a new foam filter that is not oiled.
Author:  mraxl [ Tue Aug 08, 2017 9:41 am ]
Post subject:  Re: H2B RH cylinder misfire
Quote:
I also have an H1 intake manifold, which is shorter and smaller diameter which is probably killing bottom end as well.
I assume you are talking about air canister, etc. If so, the canister, itself, can kill you... making it rich.
I'm also assuming you have the stock oil system setup.
Chambers of any kind won't affect how rich/lean you are at anything <3500rpm or 1/4 throttle.
Author:  DGA [ Tue Aug 08, 2017 10:16 am ]
Post subject:  Re: H2B RH cylinder misfire
No I mean the rubber intake manifold, its for sure not an H2 one, I can get a pic of it later. I also don't have the canister, so have an aftermarket 4" mushroom shape foam air filter I adapted to the inlet of the rubber manifold. I have the stock oil setup mostly, but have different check valves and lines.
I just know that as I open the idle mixture air screws, it runs better, the misfire I talked about was I think a rich miss, 4 stroking, and not bad. But it had no power under 4k or so, and now does as I go leaner. I do also have higher compression, removed the head gasket and used a Viton O ring, and is part of the reason I wanted to start out rich to avoid detonation.
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