Clutch overheating on 86 KDX

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pkenney
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Clutch overheating on 86 KDX

Post by pkenney »

This might be better in the Air Cooled section but I'm looking for help on a strange clutch problem that a broader audience might have seen.
I have an 86 that overheats the clutch after ~30 sec of hard work on hill climbs.
The clutch works fine most of the time but on long hills I tend to intentionally slip it quite a bit.
After a short time the lever comes into the bar and the clutch locks up (is fully engaged).
It cools down quickly and returns to normal but it is a repeatable problem.

I originally thought it was the 30year old plates but I have replaced the clutch with an EBC kit over the winter and get the same symptoms.
The EBC kit was from a KLX300 but the P/Ns matched and I can't find anyone selling a performance kit for the 86.
I have also tried ATF , synthetic motorcycle oil, and currently Maxima MTL with no improvement.
I can find nothing obviously wrong with the clutch after repeated inspections.

I assume the clutch should be able to handle some abuse but am I expecting too much?
I have lengthened the lever at the case about 1/4" for 1 finger pull but everything moves fine.
I am considering trying to run higher transmission oil levels or trying to find a way to allow more oil into the basket.
I have a spare basket that I don't mind drilling.

Any suggestions would be appreciated!
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Re: Clutch overheating on 86 KDX

Post by bufftester »

I have had issues with the EBC springs being too short, or at least shorter than spec (if you used the EBC springs). How much oil are you running? On long uphills the clutch can get starved of oil due to the orientation of the motor. Similar to the later models you can run a full quart with out any issues and it puts a little more volume of oil in there. On a side note, how long are these hills? :blink:
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SS109
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Clutch overheating on 86 KDX

Post by SS109 »

I would definitely add more transmission fluid just because you can. However, how much are you slipping the clutch. A little bit on a hill climb shouldn't be a problem. Are they very long and/or steep hill climbs? Are you using the correct trans gear when climbing? What is your final gearing? Is your engine down on power?
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pkenney
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Re: Clutch overheating on 86 KDX

Post by pkenney »

The hills are typical southern Ohio and Kentucky hills. If I can keep it on the pipe with momentum I have no problem.
If the hill gets technical and I can't keep good forward momentum I have to slip the clutch with the motor revving pretty high like an old 125.
In that situation I'd prefer to be in 2nd gear but can drop down to 1st if I come to a stop.

I do feel like the power is very soft off the bottom and even in the midrange but I have not been able to tune it with needle or timing to gain anything.
If I'm stuck on a hill and need to get moving I can't just rev it a bit and feather the clutch, If it isn't on the pipe it won't pull through.
It pulls cleanly though and has decent power once it is on the pipe, I've only ridden one other KDX (2002?) and it had much more grunt.
Gearing is 1 tooth up at the wheel but we end up on the rode sometime and 50mph is really revving so I don't want to add more.

Engine problems aside, the confusing thing to me is the nature of the clutch problem.
The clutch operates normally but after hard use the lever comes to the bar and I lose the ability to disengage the clutch.
It returns to normal after it cools which does not take very long.
It is like something is mechanically binding the push rod in but instead of disengaging the pressure plate it causes it to engage.
I need to take the cover off and try to get a better picture of how the clutch operates.
I'm used to Yamaha where the clutch shaft is hollow and a push rod runs through it to push the pressure plate out but I need to visualize this system better.

For oil level I have it 1/2 way in the window (0.7L) but will add the full quart.
Also, I found a Barnett Kevlar kit directly from Barnett that I might try but at $165 its not cheap
The popular online retailers don't have much for the 86.

Appreciate the feedback and any other thoughts.
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Clutch overheating on 86 KDX

Post by SS109 »

Weird. The clutch problem you describe defies everything I know about how a KDX clutch works. Let's make sure we are understanding each other. You said "The clutch operates normally but after hard use the lever comes to the bar and I lose the ability to disengage the clutch." So, what I'm hearing is the clutch is still applying power to the transmission when it overheats, yes? Is the cable loose at this point? What is your free play set at when the clutch is working correctly?
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Re: Clutch overheating on 86 KDX

Post by pkenney »

You understand the problem, its like the cable stretches 1" but returns to normal.
When this happens I typically stall it and after I restart it has some lever back but it takes a while to return to normal.
If I make it up the hill without stalling it recovers also so the motor does not have to stop for it to return to normal.

I do need to frequently adjust the free-play while I'm riding also.
I always keep 1 finger on the clutch and it varies quite a bit, once I start to hit my knuckles with the lever I adjust it but then it gets tight so I adjust it back.
I actually thought that was normal but it may be related.

Back to power delivery, do newer KDX's have the motor to pull a technical hill at low revs?
I'm talking about 2nd gear low ground speed where you have to navigate obstacles.
These are where I struggle, I need to be on the pipe feathering the clutch.

I'm going to disassemble and inspect the clutch and will take some photos.
Any other ideas would be very welcome.
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Re: Clutch overheating on 86 KDX

Post by KDXGarage »

tire choice?
age of tire?
width of tire?
expecting too much from a 24 HP machine?
any mods to intake, engine or exhaust?

How were you able to tell that KLX300 plates would work in a 1986 KDX?
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Re: Clutch overheating on 86 KDX

Post by pkenney »

I use a Kenda 774 IBEX, 110/100-18 - awesome tire!
I have 3 rides on it and I don't think 24HP is enough to get it to spin, traction is not my problem.
The only mods I have done are the reeds, air filter, and spark arrestor. Stock chamber and carb.
The KLX clutch showed the same P/N on BikeBandit's microfiche so I ordered the EBC kit and they fit just fine.
I'm curious if 4 stroke clutch kits are designed differently than 2 stroke kits though.
I had the same symptoms with the stock clutch though which is why I put a new clutch in so I don't think it is the plates themselves.
I'm starting to think something is wrong in the basket, hub, or pressure plate.
Is the basket a helical gear? Could it be climbing the crank gear?
I need to take it apart again this weekend.
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Clutch overheating on 86 KDX

Post by bufftester »

SS109 wrote:Weird. The clutch problem you describe defies everything I know about how a KDX clutch works. Let's make sure we are understanding each other. You said "The clutch operates normally but after hard use the lever comes to the bar and I lose the ability to disengage the clutch." So, what I'm hearing is the clutch is still applying power to the transmission when it overheats, yes? Is the cable loose at this point? What is your free play set at when the clutch is working correctly?
Yeah, after rereading the OP I was puzzled a bit as well. Pulling the lever pushes a rod in and separates the plates. Releasing the lever lets the rod travel back out due to the clutch springs and the plates re-engage. Either something is assembled wrong or broken to allow the clutch actuator to rotate (giving you cable slack) without engaging the push rod. Have you replaced the clutch cable at all? All the parts in, in the right order, in the clutch assy?
pkenney
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Re: Clutch overheating on 86 KDX

Post by pkenney »

Update: I took the clutch apart over the weekend and found a few things that might make the clutch act strange.

First thing was the frictions were reversed from what the manual shows.
Instead of the angled grooves running towards the center they were the opposite.
The normal orientation would tend to fling oil out from the center.
Wonder if these grooves control oil flow into/out of the pack?
Maybe with them reversed I was filling the gap between plates with oil and locking the clutch???

The other thing I found was that the basket was very worn where the frictions contact.
I had a better basket with very little wear so I put it back together with that one.
Also filled it up with fresh Maxima MTL (whole quart this time).

Another odd thing I noticed was that 1 steel plate was much more blue than any others.
It was in the middle of the stack, I wonder if the wear on the basket was not allowing a full release.
I had a good looking spare set of steels that I put back in.

I will update after the next ride if these changes fixed the problem.
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Re: Clutch overheating on 86 KDX

Post by KDXGarage »

Hmm! I hope that does it for the bike! Thanks for the follow up information. :bravo:
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