Hard starting and possible misfire

[Drewski51]

Hey guys, just wanted to run this by the group and see if anything stands out as obvious to anyone. I can’t work on my bike until this weekend and can’t stop thinking about this problem. I’ve been working on cars and small engines since I was a kid, used to be a Dodge auto tech a while ago, so not new to mechanical problems, this just isn’t dawning on me as to what it is obviously yet.

Bought my 97 220 about a year and a half ago and did a resto on it minus any motor work because it had good compression (I think around 130-140) and ran well. It’s my first 2T and didn’t have a good impression as to what’s normal running I guess.

I put a Lectron carb on it and a good set of stock reeds. Got that dialed in and ran great for about a year. It has since I took it for its first ride had kind of what seems now to be a misfire at low RPMs. Cruising around it seems like every 20 or so strokes it drops a stroke. If you get on it, it runs great with good power and idles fine. Always started on first or second kick hot or cold.

Recently it’s become really hard to start. My buddy will pull start me on his bike and it takes a really long distance to fire up, like a few hundred yards. Once it’s running it runs like it used to. I pulled the plug and it’s wet but otherwise normal, so it’s getting gas. Air filter is fine. Pipe is too new to be plugged up. Bike maybe has 20 hours or less since I put it together.

I put a torch to the plug to dry it out and it started much quicker than it has been. So it seems like it’s been running rich. I adjusted the carb leaner on another day and put a new plug in and it started up after about 10 kicks but is idling high and won’t start up quickly once warm. Also getting it hot doesn’t make it run worse.

I’m thinking it’s an ignition problem but I’m not sure what exactly it is. Gonna start with inspecting the stator and put a multimeter on it, check ground bolts. Just kind of looking for some confirmation from anyone with more knowledge than me if it sounds like stator, CDI or coil. Any thoughts? Thanks in advance.

[SpruceItUp]

If you think it's running rich I'd do a plug chop with a new plug in it and see what the plug tells you.
Given your description of the miss (and that you think it's rich) it sounds like it's 4 stroking from a rich condition.
I would check your Lectron and make sure it isn't clogged or anything of that sort (though my guess is that would cause a lean condition... but it's worth a clean). Did you leave gas in it over the winter (specifically ethanol)? I always had a problem with my Lectron where I would get it set and it would randomly go to a lean condition after I had set it many rides after.. Unsure why, but it always runs fine on my Keihin... so I just gave up for the time being.

[tosaw]

All good advice from spruce - I'd add doing a compression test and a leak down test. Sounds like low compression symptoms to me, and every time I've changed reeds I've found an air leak at the intake no matter how careful I am.

[SpruceItUp]

Good idea!
Also, if you do detect an air leak at the reeds, use a tiny bit of yamabond (or equivalent case sealer, needs to be fuel resistant)
around the gasket. Not too much, you do not want it to end up inside the intake. That should fix your air leak. I typically do that by default whenever I have the reeds off.

[Chuck78]

In order to get the mid-range adjusted properly on my Lectron power jet carb, I was always a touch rich on the low throttle range, resulting in significant pipe bang on closed throttle or very light throttle engine braking deceleration. The Billetron Pro Series modern Lectron version fixes that considerably.

I would first look at the compression though, I think you're a touch low on compression and I wouldn't bother tuning until you at least put a new piston ring set on that piston if not measuring the bore to see if you are better off with a Wossner 69.01mm bore B-size piston or 69.02 C. It sounds like the piston/rings or cylinder plating had considerable wear on it a year ago even if it only had 130-140 PSI, which is towards the lower end of acceptable. Still run good and give you adequate power, but when you have 170 - 195 psi, they run CONSIDERABLY stronger after proper fuel metering adjustments or jetting.

Usually an electrical problem will worsen when the bike is hot, because the resistance in the state or windings will become greater and you will have a lot of trouble keeping it idling or starting it hot, from my experiences with other ignitions not necessarily the KDX which has never failed me yet beyond spark plug issues.