Valve Problem?? MXC400

I have a 2001 MXC 400 and it started making a strange noise this weekend and I wanted someone's opinion on the matter. You know the sound a bike makes when its running and the kickstarter is in engaged- the tikky/tapy noise? Well I was riding along and it started making that noise and I thought it was the kicker but it wasn't. I was thinking maybe the kicker mechanism went bad or is stuck on/in position? The other thing it sounds like is the valves are needing adjustment. So I can't tell if its the valves that need adjusting or "piston slap" or what so if anyone has any idea on what it might be it would be most helpful. As for the valves, it seems like the noise would be more gradual and the noise would increase as they needed more adjusting instead of just making noise in the middle of a ride. Thanks-Thomdogg

you would normally hear the valves when idling, probably not when riding with your helmet on. people have been posting that the primary drive nut comes loose and makes noise.

Where is the primary drive nut? and is it difficult to get to/repair or replace??

When is the last time you checked the valves? Only adjusting them if you hear a problem is not a good maint schedule. They need to be checked regularly. Not saying you don't, but just saying.

Primary nut is a left hand threaded nut on the clutch side of the crankshaft.

Another possibility might be cam bearings. Have you ever replaced the cam bearings or the auto-decomp stop bolt?

I haven't had to replace the bearings or any thing internally and I have been keeping regular maintenance on my machine. Is the primary drive nut easy to get to or should I have it taken to a shop and do you think that could be the problem/is that common?? Also, I checked the valves and rocker arms to see if anything may be broken or damaged but they were fine. Thanks for the feed back and all info is a great help.

Primary nut is easy to check. Just order a clutch side cover gasket in case you tear the old one. Then drain the oil, pull the sidecover off (kickstarter and possibly brake pedal will have to come off first) and it's right there.

From the discription of the problem and what the post made by that other guy said, do you think thats what it could be?? I have never herd of that part backing out and making noise. If its not the valves than it makes sense to think that it is the primary drive nut. Thanks again for all your info-thomdogg :naughty:

It could be, sure. It's worth checking as it's not very hard to get to. And it has been reported in the past. Haven't seen it much lately, though.

Thanks Jeb! I will check it out this week. Also, do you know any good on-line shops where I can get a gasket set for my bike??

You said you checked the rocker arms? How much valve clearence did it have? Per your manuel you should be way past due for cam bearings and the cost to update is minor before they fail, after? It can be big.

Also, do you know any good on-line shops where I can get a gasket set for my bike??

I get most of my parts from the good guys at Cycle Zone KTM. But this website has a store, too, so check that out.

i've seen this problem with the primary drive gear twice, it really does sound like the motor is history, its simple to fix. As a rule I change my cam bearings every 180 hrs, i know of two instances of bearing failure, again its a simple fix but i think the dealer should do it because its a little complicated

I took my machine to the shop today and the mechanic there thinks it sounds like something in the bottom end-maybe the rod? Just have to wait and see I guess. I will let you guys know as soon as he calls me when they get in side of it. I'm new to ThumperTalk so thanks for all the input and help everybody. Keep tear'n it up out there- thomdogg

p.s- "you gotta rev that sucka! Just rev it up!" -Elvis :naughty:

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