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I decided to go for a little easy ride close to my house with my son. About 15 minutes in I opened it up on a straight away. It pulls good through the bottom but then when it should hit it sounds rough so I just shift up. Normally it will do that after riding really slow in first gear following my son. I wasn't concerned yet so I turned around to do it again. Usually after the first try it clears out and rips. Well it didn't do it again. I attributed it to the really hot weather (hottest it's been since I've had the bike) making it run a tad rich.

So I decide to take it easy and play around with Jackson. We're riding along and come to a stop and the bike didn't want to idle. I had to give it gas to keep it running. I rode a little more and when decelerating it always makes a ring ding sound, but today it was slower. More like ring.........ding..........ding. I don't know if that matters but I figured I'd mention it.

So I decide I'm gonna go back home before something happens. About that time it quit on me. It would restart and run for 5 seconds and die. After a minute or two the same thing again.

I pushed it home and took the carb off, I blew everything out with compressed air and cleaned it. I didn't see any obvious signs of dirt or trash in there. It's the first time I've had the bowl off of it.

It has a 145 main, 42 pilot, air screw 2 turns out, and needle 3rd from top, FMF rev pipe and powercore 2. It has about 5 easy hours on a Wiseco piston and I let it warm up until the radiators are hot before I flog it.

Oh after cleaning the carb it seems a little better but still doesn't seem right. It will stay running but the idle is turned way up and it sputters if I give it gas.

Any tips or ideas?

I just remembered right after the bike died the first time, I started it and had to open the throttle a little to keep it running. When I did this there were several loud pops from the exhaust. Then one really loud one and it died again.

What does the plug or air filter look like? reeds?

The plug was black but not wet. I've never fouled a plug before. I know I need to go down to a 40 pilot but it's never run bad before.

I don't clean my air filter after every ride, but it's only been about 2 hours since I cleaned it last and it hasn't been dusty. It was still nice and clean.

I just came back in actually from pulling the reeds out and they look good. No light showing and they have a good seal all the way around.

I'm going to put a new plug in it tomorrow. The only other possibility is I changed from Amsoil Dominator to Yamalube 2R. I used 93 octane but now that I think about it I got it at a gas station I normally don't go to.

Today was the first ride on that gas. I'm gonna drain the tank and try a new plug tomorrow. I'll report back. I'll probably take the carb back off and go ahead a change to a size 40 on the pilot. I know the 42 is is a little big and probably the reason I have to clear the engine out sometimes.

Stuck needle in the float?

I don't think so it all looked normal earlier.

Vent tube on the tank collapsed? This happens when they get old and hot, try taking it off and see if that helps.

Water in the tank? Happened to me once (old gas and rain water somehow got inside). Ran a bit rough until it died. Then it would start up now and then and eventually wouldn't start up at all.

First things first ....

New plug & cap .

Fuel cap?

No.....

Spark plug cap ( NGK rubber waterproof are great )

I'll go with my standard flywheel key sheared answer.
Happened to me once and was just as you described.

I'll do a search but is there an easy way to check the flywheel key? I've had the top end apart but never taken anything off the bottom.

You could check with a timing light, but I think pulling the flywheel is easy. You might have to scrounge up the tools.
Pull the cover, loosen the nut (an impact gun helps) and use a flywheel puller.

I've got everything but a timing light and flywheel puller.

I could hear a slight knocking sound in the engine but couldn't tell where it was coming from. Maybe it was detonation.

I'll see if I can borrow a puller somewhere. I'm not in a huge hurry it's 91 outside and probably 95 in my garage.

Ok I went out and took the carb apart again, did not find anything inside wrong. I went ahead and put in a size 40 pilot jet and a 148 main. It seemed decent up top but I'd rather be a little rich at WOT.

I took the flywheel cover off just to get a quick look and started the bike. I don't know if it means anything but with it running it turns perfectly straight.

It will sit and idle now but it's kind of erratic.

Here's a quick video I took, should I be able to do this?

Kdx220:

I'm guessing it's ok, the kickstart feels the same.

I also took another video of it running. I was holding the throttle steady when I had it revved up and it's hard to maintain rpm. After running it it seems like more heat is coming off of it than normal but that could just be me being paranoid. I'll upload that one shortly. It was making that knocking sound in the next video, but I'm not sure it will be audible. You can feel it when it makes the noise.

I'm thinking it is very lean and that I might have an air leak somewhere. I forgot that is used the same gas in my Lawnboy and it didn't miss a beat. My father in law also accidentally poured some in the CRF50 and it was fine as well.

KDX220:


At about :24 you can hear the knocking sound.

The knock sounds like "detonation " possibly down to poor fuel.... My 220 used to sound the same if I ran old fuel.....I since mix up fresh 98 or higher octane fuel & the sound has gone away, the only problem with running 98 or higher octane fuel is the ethanol , it breaks down quicker & will overtime eat away at rubber components.... I always drain my fuel if I know I won't be riding for sometime .

Spray starting fluid around the intake manifold with it running if the idle changes you have an air leak

OK guys I checked pretty much everything on the bike.

Finally stopped and got fresh gas, and put in a new plug. She runs awesome. It's even better than before with the jetting changes.

I appreciate the replies and help. I feel dumb for not doing those two things first but it was running so bad I just knew it was something else. It's nice to know this community is here when a question comes up. Even better is that I learned a little more about my bike through this process.

Thanks again,
Joey