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I have latley been trying to figure out whats going on with my bike. It's the '84 KDx 200. It recently has been not running right on the top end. It will take off great, but once it starts to "rap out", it seems like it's missing. It used to ping at high rpm's but the richer jetting helped that out. I've tried several different jets to no avail for the missing type problem. I did put a set of carbon reeds in some time back. I don't know if it was doing it before the new reeds or not because I put the new reeds in before the first time I took it out for a good ride. What else could be causing those symptoms? I have no idea how long the rings have been in there or the last time they had been changed. I do know that I personaly have put 30 to 40 hours roughly on the bike myself, hard hours too. My next step is to try some VP racing fuel and see what that does.

Jon.

I would check for air leaks around the carb boot... the older bikes tend to leak air there. Does an 84 even have a KIPS? Sorry, just not familiar with them. On a later model, this is usually the cause of cutting out on the top. It could be electrical too, but hard to tell without seeing the bike. Jason should be able to tell you more about the earlier models. I started in 92 and worked up to a 95...

When I was your age...

I have heard of failing ignition systems (failing, not failed) that may cause lack of spark at high RPM's.

No KIPS on an '84. The first KDX with KIPS was the 1986 KDX200.

Any chance to buy a gasket kit and get all the necessary top end parts measured to make sure they are in spec?

I used to own a '84 KDX. There are several things that might cause this. If you have done some of these already, that's fine. If you think that there's no way one of the items I mention could cause this problem, then check that one out for sure!!!

Replace the plug. I know, you probably already did. Do it again. Sometimes they are bad right out of the box. Handled poorly in shipping, there could be a crack in the insulation that shows up as a short when under high rpms.

Check the sparkplug wire. My cap came loose one time. At upper RPMs it would cut out.

Check all the electrical wires, including the coil. Those connections get corroded over the years and cause all sorts of intermittants.

Start with clean gas and oil

Clean the petcock. There's a small screen filter inside the tank and it could have a bit of crud on it.

Remove the carb and use some carb cleaner to blow out all the passages.

Be sure the float level is set right.

Check to see the air filter is clean and has no tears.

Like Jason said, the ignition CDI box can fail. Mine did. It started out with cutting out at low RPMs though, not high. It cost over $350 to replace!

I also agree with Jason on getting that gasket kit. My '84 was the easiest bike to tear down the top end of any I've ever had. It is an hour job, tops.

Perhaps your CDI is starting to fail at high rpm/high load?

-Maurice

Ok guys, thanks for pointing me in a direction. I'll try to check all these things out.

Jon.

OK, I went to the garage and pulled the coil off. It had numerous wires with ampeyes on them that grounded to the coil bars. They were alittle rusty and corroded. I cleaned them with a small file. I also cleaned the bar that goes through the coil, it was particularly rusty. I took the NGK sparkplug boot off the plug wire and cut about a 1/4" off the end and screwed it back on to the plug wire boot. I then took it out and tried to start it. It backfired once and then i used the choke and it fired up. I let the engine warm up alittle and then took it for a test ride and got the engine hot. It seemed alittle better. I noticed that it only does it in first and second gear. I don't seem to notice it at all after I'm in third gear. Am I shifting to late????? I tried short shifting and I did'nt notice the miss like problem. I pulled the plug out and it looks great. It's a lightish brown on the porcelin.

Jon.

Are you saying you took the ignition coil off the bike? Ignition coil, meaning the thing that the spark plug connects to? I have found that my frame gets a little rusty there after a while. I don't know if it helps any or not, but whenever I have it off, I use some 400 grit sandpaper and sand the frame right where it connects on each side. If yu haven't already done that, it might be worth a try.

Yeh, I forgot to mention that part. I noticed that when I was cleaning all the other connections. So, yeh I did clean the frame where the coil mounts to it. I cleaned every connection there was around the coil.

Jon.

Another obscure item to check is the kill button. I've had mine act up and cause me to go on a wild goose chase. Easy to check, just unplug it and see if the problem still exists. You're making progress, sounds like.

Can someone explain what pinging is, i dont think my bike has ever pinged but i wouldnt be sure

Check your stator. Mine was bad when I got it. Is it getting harder to start?