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Jetting problem/question

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Posted by: downhill---------------------

OK, I've read Dave's article on jetting but still have some questions. I live in Iowa and have a 2001 KDX 200 with a Gnarly torque pipe and a swiss cheese type airbox lid.

I just put the pipe on it and thought I should check the jetting. It had been running a little on the rich side though not real bad, just a dark chocolate. WOW! good thing I checked it. After a WOT throttle chop the plug was whiter than it was new. That was with a 158 main, stock needle and a 42 pilot. So I put the 160 in it that it came with and ran another chop. Still white as can be. I don't have anything richer than the 160 so will have to wait until Tue to pick up some more brass. It looks to me like I'll probably end up at least at a 165 or so. This sounds really high on the main to me and everything I see on the board here peole are talking about 152s and 155s. The air temp is around 85 and the humidity about the same. Clean airfilter, FMF Powercore silencer other than that I don't even know what else to check. Any ideas?

Thanks.


Posted by: 23jayhawk---------------------

Are you using a new plug for each test? As in, right out of the box? It's usually suggested to get a little 'color' on them (like 15 to 20 minutes run-time) before running a check. Otherwise, there is nothing to burn away at WOT.

Are you leaving contrails at WOT? Or is it just a light haze?


Posted by: downhill---------------------

I am using a new plug, maybe 5 minutes on it, as that is the way I understood the article by Dave. I will try it with one that is colored and see where I end up.

I ma not sure what a contrail is? The plug appears to have no haze of any kind on it just white as white can be all the way to the base. Same color all the way around also.

Thanks for the reply.

Downhill

KDX 200
KX 125 (sons)


Posted by: 23jayhawk---------------------

When you're running wide open, is the exhaust plume kind of heavy? Or just a light haze? If people are asking you for exterminator estimates, you might be a bit rich.

On the other hand, if there is no smoke, or worse yet kinda white, that would support lean.

Contrail = CONdensation TRAIL (like on jets)


Posted by: canyncarvr---------------------

Oh oh.....don't let SOME moderators see this:
"It's usually suggested to get a little 'color' on them..."

Not to get into a huge debacle yet again on this thread..but opinions (read: 'facts according to them') abound. I think a bit of carbon on a plug (used a bit) shows 'color' better than a brand new plug. But, a brand new plug will show the slight 'ring' around the insulator way down next to where it meets the shell.

From gordon jennings:
Quote:
Look far inside a plug, where its insulator joins its shell, and what you'll see there if your engine's mixture is too rich is a ring of soot. If this ring continues outward along the insulator to a width of even a millimeter you can be sure the mixture is rich enough to be safe, and too rich for maximum output.


You can 'read' mixture on the thread flat, too. Should be 'medium brown' on a 2-stroke.

Yes, it does sound like you are needing a bit more jet than most. Still, everyone's bike is different..and before I'd entertain nightmares about splitting the cases to replace the crank seals, I'd jet it to run...and run it.

Might check your reed cage gaskets, bolt tightness, carb boot integrity a bit.....just for fun?

BTW...at sea level a 160 main on my bike is marginally lean (I run a 36mm carb with a -30 pipe on the coast). You don't mention your elevation. Isn't eye-oh-wah kinda low in that regard?

You don't say where your needle is? Or which needle?? Raise the needle (lower the clip) and check it.

Probably a good idea to keep your WOT chop tests short..don't wick-it-wicked for miles! 10-15 seconds on a plug in good shape will let you know what's going on.

Better white than a bunch of shiny aluminum bits...or the dull grey ash-of-death (vaporized aluminum that used to be a piston crown)!!

Note..you have a powercore...not a S/A. Most trail/woods riders would have an S/A (I hope!). That'll make you want to run a bit richer.


Posted by: downhill---------------------

canyncarvr, thanks for the input. My thread flat is showing no color at all. I am located at around 800 - 900 feet altitude and have checked for any place that might be leaking air. Everything looks OK. I also have moved the clip on the stock needle (I don't remember the # off hand) to full rich and it did not make any difference in the WOT reading. I am then rich in the midrange it seems. Overall the bike seems ot run pretty well and does not 'feel' lean, it feels pretty good, though I have not ridden it much and won't until I get this sorted out.

I agree white is better than some possibilities. I have been somewhat careful in my WOT testing and will continue to be so.

One thing I thought of is that here in Iowa almost all the gas is 10% ethanol. As a matter of fact it is hard to find gas with no ethanol where I live. I remember when I used to be involved in IMCA modified car racing that our motors we ran straight alchohol in were always spotless when you tore them down. Abosolutely no carbon anywhere. I am wondering if this is having an effect on the plug reading also. Any comments on experiences with that would be appreciated.


FWIW I am running Yamalube R2 at 40 to 1.

I'm going to pick up some more brass today and try a few more setting tonight if I get home in time.

Downhill

KDX 200
KX 125 (sons)



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