Shovelhead Clutch Shudder / Slip Under Load

[HogsRear]

I think I've read through nearly every different shovelhead clutch thread on here (and other sites) and I can't find an answer for the issue I am having with my bike. It's a ratchet top 4 speed with bearing support plate added and tin primary cover, foot clutch hand shift. New five finger clutch hub, BDL 1.5" belt drive, Ram Jett style retainer, Blue Barnett clutch springs. I have tried swapping friction plates and metal plates (all new and in good shape) and nothing changed. I've tried adjusting spring tension, clutch arm position, aluminum pressure plate, again no change. Everything is set up to spec, my primary belt if anything might be a bit loose (can move it up and down a good inch) which I think is better than too tight but the trans is currently all the way back on the plate.

The issue I am having feels like it should be clutch related. The first part is I'm getting a good amount of shudder taking off from stop in first gear, a problem that I've heard is fairly common but can be addressed with a tamer typically. Second, when riding and especially under load in 3rd and 4th gear, I get another shudder that feels to me like the clutch it slipping. Again, I have tried and tried again every clutch adjustment I could think of and I'm at a loss. Any info or ideas on what could be happening here would be appreciated.

[JBinNC]

Yes, a shudder on takeoff is a common problem with open primary clutches. I have the same problem with mine. A softer lining will fix it, but without using asbestos as a component of the lining material, it's hard to formulate one that is soft enough, and still give some life. I have tried every lining/clutch kit I can get my hands on, and all will shudder, at least sometimes.

If your clutch seems to be slipping in third and fourth, IT IS. Add more spring, check the clutch pushrod adjustment, or change lining material or add a plate and steel. Those are the remedies. I like the Barnett foot clutch springs, the orange ones, for hand or foot clutch. You can also tighten the adjustment on your existing springs as long as they do not coil bind when the clutch is disengaged.

Jim

[Dragstews]

Auto Clutch ..... Whoa .. !!!

[HogsRear]

If your clutch seems to be slipping in third and fourth, IT IS. Add more spring, check the clutch pushrod adjustment, or change lining material or add a plate and steel. Those are the remedies. I like the Barnett foot clutch springs, the orange ones, for hand or foot clutch. You can also tighten the adjustment on your existing springs as long as they do not coil bind when the clutch is disengaged.

Jim

Thanks Jim, I'll try tightening the springs again, and maybe swapping friction plates with the other set I have. It does feel like it's slipping, but I was curious if that feeling could be caused by anything else that I might be missing.

[HogsRear]

Auto Clutch ..... Whoa .. !!!

?

[Dragstews]

Let me tell you a story ...
Was living in Vegas at the time ...
Every Friday night, H ( . Y . ) ters would put on a Bike Night.. I showed up on the 52 and parked it in line with about 25 other bikes.. Guess there was three or four lines of bikes in their parking lot ...

I was there about three hours and was getting ready to head home ... Well all Hell broke loose in the parking lot ... What happen was a Guy had the same idea I had ... Fried up his bike, which was new to him, had a shop build it and like the Titanic was out for his first ride around town on it...
Seems that he didn't understand the function of a Auto Clutch very well, it took off dragging him along side of it and right into a line of parked bikes it went... Knocked over at least 8 or 10 of some super nice Customs ... He broke his wrist and a bunch of Fellas was wanting to add his neck to the list of broken bones .. !! I stuck around till the Cops showed up to make a report ...

Something like this went down ...

.../// https://youtu.be/gyhy7Z71qzE \\\...

[HogsRear]

Update on this. I've gone through the clutch adjustments several times now and while I think I have figured out the initial shudder taking off in first gear, I still feel the same thing as before when the bike is under load. Like I said, to me it feels like the clutch is slipping but I've adjusted the springs pretty tight (4+ threads showing on the clutch hub fingers) and have felt no difference. They are newer blue Barnett springs, should be more than enough pressure. I've tried the aluminum pressure plate and switched back to the stock one again. No difference. Could any other issue on the bike cause this feeling? Something in the transmission? Belt? Going crazy trying to figure it out.

[JBinNC]

The only other possibility that comes to mind is that the clutch hub key is sheared, and the clutch hub is slipping on the mainshaft taper. It will weld itself to the mainshaft over time, so it kinda fixes itself.

I will again suggest the Barnett orange foot clutch springs.

Jim

[Tattooo]

It's hard to guess what your feeling on my computer but...........

I'm gonna go out on a limb on this one too.................. Bent shift fork not letting the gear totally engage..........

Is it a chatter or slipping????????? You can't really feel slipping..............

[JBinNC]

You most certainly can feel a clutch slipping. Accelerate up a hill in high gear and when the motor hits the torque level that the clutch can't handle, the clutch will start slipping and will continue to slip until you back off the throttle. If it's real bad, you can feel it on level ground. My stroker FLH will slip the clutch on the hiway with my wife as passenger, because I've got it adjusted a little too close to the limit.

Jim

[Davestune]

Can you add another fiber plate?

[Tattooo]

You most certainly can feel a clutch slipping. Accelerate up a hill in high gear and when the motor hits the torque level that the clutch can't handle, the clutch will start slipping and will continue to slip until you back off the throttle. If it's real bad, you can feel it on level ground. My stroker FLH will slip the clutch on the hiway with my wife as passenger, because I've got it adjusted a little too close to the limit.

Jim

Jim what does it feel like? Like a spinning tire? I'll bet you hear it more like the motor revving etc......

But you can feel chatter...........

[JBinNC]

Jim what does it feel like? Like a spinning tire? I'll bet you hear it more like the motor revving etc......

But you can feel chatter...........

Yes, the motor will rev freely, but the bike ain't gaining any speed.

Jim

[Davestune]

This shits hard to do over the internet
Could be key ciuld be a number of things

[HogsRear]

It's more of a vibrating/chatter feeling when the motor is under load vs a smooth slip but I guess I thought if the clutch was just barely slipping it would maybe shudder like that? If someone on here who has felt a big twin clutch slip before says that it's more of a smooth slip and lack of power translating to the rear wheel I can rule that out.

I guess it could be the key but I had the clutch hub off a few weeks back and everything went back together smoothly. I wouldn't know where to add another fiber plate as there's one on each end right now per the stock setup. If it were the shift forks would it still be able to shift fine through all the gears?

[JBinNC]

If it's jerking under load in one particular gear (usually third in a big twin box) that is the transmission jumping out and back into gear. That will cause real damage, and is an indication that the transmission needs to be rebuilt. The jumping out of gear will cause a bent shift fork, but not the other way around. Replacing the offending gear, shift clutch, and shift fork is the cure.
If that is your case, the transmission rebuild is a must. There will be other worn out stuff in the box to be dealt with, and it can get expensive $$$.

Jim

[HogsRear]

If it's jerking under load in one particular gear (usually third in a big twin box) that is the transmission jumping out and back into gear.

It's not really jerking as in engaging and disengaging throwing me around while riding but more of a chatter/shutter. Sounds like it could still be an issue in the trans though?

[JBinNC]

It's not really jerking as in engaging and disengaging throwing me around while riding but more of a chatter/shutter. Sounds like it could still be an issue in the trans though?

Could be. The gear will skip dogs and you will definitely feel it. It will only be one gear, though, and the other three will pull normally. If it's happening in more than one gear, it's probably something else .

Jim

[Tattooo]

This shits hard to do over the internet

You know Dave I was thinking about what you said........ Yes it is in a way.....

I think the biggest problem is most people don't know how to describe there problem accurately..... So the key is, how to ask the right questions to help........ And that's hard as hell sometimes.................

[Whoremonger]

Has anyone ever experienced the cluthch chatter with a PRIMO RIVERA clUtch setup? I have that clutch chatter also on my stock clutch. Only happens on take off in first gear. Cleaning the clutch pack helped to eliminate most of it but not all of it. I have learned to live with it being its my beater 78 lowrider.