Clutch issue, RD400

SoCal250 · May 26, 2025, 09:44:36 PM

As you may have read in the other section I've been refreshing and updating my Daytona and just did the FZR clutch upgrade. I've done clutches before and there's not much that can go sideways because there's not many parts involved. However...
Something isn't right. After getting my clutch reassembled and the left engine cover replaced I have almost no resistance on the lever on the bars and the pressure plate barely moves. Previously the clutch had very firm pull. It has to be something simple. Tomorrow I'll double check the two covers just to compare them, but I doubt that's it.

The only parts that were exchanged were:
Removed:
7 RD400 clutch frictions measuring 2.95 to 3.0mm each
Left engine cover, polished stock 2V0
Installed:
7 FZR1000 clutch frictions measuring ~3.0mm each
Left engine cover, painted stock 2V0

Everything else was reused, including the 7 rubber cushions. I've pulled the pressure plate to confirm it was clocked correctly so that the arrows align and that there were no other issues there, and everything looks good.
The push rod was never removed, and the same for the ball and the push "hat" on the clutch side.
I took off the left cover to ensure that the ball was installed on that end of the push rod and it's there.

I'm leaning toward maybe something to do with the push lever (#20 in the image) in the left cover. Maybe it's not oriented correctly or assembled into the housing right, but it's not really shown or detailed in the factory manual. When that assembly was moved from the old cover to the new one the cammed lever arm fell out of its housing. I thought I got it put back the same way and I think the angle of the arm is the same as it was on the old cover. I think currently the arm is at about 9 or 10 o'clock when looking at the inside of the cover with the cable installed and the tension spring connected. (I'll get a pic tomorrow of how it's installed now.)

Any ideas or suggestions?

klaird · May 27, 2025, 12:41:21 PM

Is your pressure plate clocked correctly? If its like the later 350s the pressure plate needs to be clocked correctly to get the clutch to fully engage.

SoCal250 · May 27, 2025, 12:57:11 PM

Quote from: klaird on May 27, 2025, 12:41:21 PMIs your pressure plate clocked correctly? If its like the later 350s the pressure plate needs to be clocked correctly to get the clutch to fully engage.

Yes, as I mentioned above the arrows on the pressure plate and the basket are lined up as per the shop manual.

RDnuTZ · May 27, 2025, 01:50:07 PM

There's a 2nd ball bearing #13 that goes between "t hat" and long pushrod. Is it there?

1976RD400C · May 27, 2025, 02:01:02 PM

The new clutch plate stack may be thicker than the old so the adjustment will be off. Did you turn adjustment screw #24 in some?

RDryan · May 27, 2025, 02:27:03 PM

I recently rebuilt the clutch in my RD250 and one problem I had that kinda sounds like yours is...So I did take the clutch actuator off the left side cover and reinstalled but I did it before replacing the clutch plates and thought it OK to leave as such and adj. the pushrod adj. screw as necessary. Well that didn't work out too well. Somehow literally after start up the clutch cable came off that clutch actuator (this even after multiple pulls of the lever to feel pressure, ad. etc.).....So off came the left cover to reattach. Once I reattached the clutch cable,reinstalled left cover and reset the adj. screw at the clutch actuator then adj. at clutch lever all was good to go. Maybe try retracing all those steps?

Also and it probably means nothing but I used the cheap FZ600 plates and discarded the rubber damper rings.

SoCal250 · May 27, 2025, 08:28:50 PM

Quote from: RDnuTZ on May 27, 2025, 01:50:07 PMThere's a 2nd ball bearing #13 that goes between "t hat" and long pushrod. Is it there?

Yes, it's there. s I mentioned above, the "hat" and push rod were never disturbed. They remained installed in the tube the entire time.

Quote from: 1976RD400C on May 27, 2025, 02:01:02 PMThe new clutch plate stack may be thicker than the old so the adjustment will be off. Did you turn adjustment screw #24 in some?

Yes, I was assuming the new clutch stack would be a little thicker than the old one but since I has measured old frictions and new frictions during the exchange I didn't expect much adjustment would be needed since each friction was only 0 to 0.05 mm difference. In previous clutches I've done the adjustment required afterwards at the linkage screw was minor. And no, I hadn't touched it yet, but something else is causing it to be way off.

Quote from: RDryan on May 27, 2025, 02:27:03 PMI recently rebuilt the clutch in my RD250 and one problem I had that kinda sounds like yours is...So I did take the clutch actuator off the left side cover and reinstalled but I did it before replacing the clutch plates and thought it OK to leave as such and adj. the pushrod adj. screw as necessary. Well that didn't work out too well. Somehow literally after start up the clutch cable came off that clutch actuator (this even after multiple pulls of the lever to feel pressure, ad. etc.).....So off came the left cover to reattach. Once I reattached the clutch cable,reinstalled left cover and reset the adj. screw at the clutch actuator then adj. at clutch lever all was good to go. Maybe try retracing all those steps?

Also and it probably means nothing but I used the cheap FZ600 plates and discarded the rubber damper rings.

At first I thought that the cable coming off the push arm could be the issue, but it was still in place when I checked and I've had the left cover off 3 times checking things.

Thanks all for your suggestions and input. It's appreciated! That's why I posted my "stupid question" here. I was hoping you guys would be able to get me on the right track. When you're the only one working on something and deep into it, you can get tunnel vision and ignore the obvious things that are right in front of your face.

So here's what I ended up doing earlier today:
I pulled apart the clutch pack again and checked everything. Nothing looked out of place. I considered installing the old frictions again just for a sanity check to test function but decided against it. This time I reassembled without the rubber cushions. And Eureka! Problem solved! I now have a firm clutch lever and just need to make some fine adjustment at the linkage set screw in the left cover. In my previous clutch rebuilds I've always reused the cushions (although this is the first RD400) and never had an issue. Usually the final adjustment required is minimal. Now it's performing as was expecting it to after swapping plates.

In my engine build notes I have saved comments from Chuck and Lyn Garland from way back, both of them said "toss the rubber rings". I ignored that advice, thinking that it was working fine with them in there and Yamaha put them there for a reason, so why not just leave them. Lesson learned!

Striker1423 · May 28, 2025, 09:39:07 AM

That was going to be my suggestion, because my RD had a weird clutch until I ditched those old rubber dampers.

Twill864 · June 03, 2025, 08:17:13 AM

I would do some math on the entire stack. Assume every friction and steel is at the max spec. Figure out the max stack size. Do the same for the min. Does you stack fit inside those parameters?

SoCal250 · June 03, 2025, 11:32:32 AM

Quote from: Twill864 on June 03, 2025, 08:17:13 AMI would do some math on the entire stack. Assume every friction and steel is at the max spec. Figure out the max stack size. Do the same for the min. Does you stack fit inside those parameters?

Yes, this was done. If you read my previous posts, the steels were reused and the difference in old vs. new frictions was between 0.00 and 0.05mm, so the stack height delta was negligible. At first I was thinking the problem was being caused by the push lever assembly under the left engine cover, but as it turned out it was caused by the cushion rings.

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Clutch issue, RD400