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Old 04-18-2017, 03:32 PM   #1
[JP]
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Default juddering at low speeds?

Hi all..

wonder if anyone can shed some light on this.

What is happening is when trying to maintain low speeds, say 30mph or 40mph riding through town at constant speed, the bike judders quite a bit

It's on my 76 Shovel.
I've changed my clutch hub for the big fix kit with 52 rollers at the weekend, nice bit of kit and very smooth, but I didn't have new steel plates, forgot to order, so just fitted the old ones.
They had a bit of scoring on them... could this be the case of the juddering?

I believe timing to be right as I followed the many how to's on here. Mainly the set at BTDC and advance weights and use the light bulb method.
when running at speeds she's fine and sounds spot on.

I've also adjusted the clutch as per so many tutorials, however, going from 1st to second is still a case of having to blip the throttle or it won't go to 2nd

When the bike starts to judder, if I open up a tad on the throttle, it goes away as I'm gaining speed slowly.
If i then try to maintain the speed I got to it starts to judder again.

hope someone can give me some ideas where to start trying things out, hope I've given enough info.

thanks
JP
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Old 04-18-2017, 03:57 PM   #2
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Default Re: juddering at low speeds?

I'm going to go for the obvious first.. Have you checked your wheels are properly laced? I just had to get mine looked at as I laced it (first one I've done) and it was out by 2 mm, the bike was almost throwing me off.

Secondly for timing, I can only talk for my pan, it's done off the rear TDC and the line for full advance (running a mag).

If it was the clutch I would imagine it would be all the way through the gears not just at a speed. Are you certain the tranny is all good? Also clutch adjustment is the other thing.. but I would again imagine it not being so specific to a speed.
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Old 04-18-2017, 04:30 PM   #3
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Default Re: juddering at low speeds?

I corrected my post, I meant the advancing the weights method is using the BTDC mark, which on mine is the line in the middle. the TDC is a small dot.

would a poor gearbox cause this symptoms?

everything else is fine, all the gears go in smoothly, even 1st to 2nd go smoothly when I get the adjustment spot on.

also, if I put in first and grab the clutch she kind of start juddering forward, therefore why I keep thinking it might be clutch and something to do with the steel plates?

if the steel plates were warped, would it cause this juddering? any ideas?
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Old 04-18-2017, 05:31 PM   #4
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Default Re: juddering at low speeds?

[QUOTE='[JP];1957746']I corrected my post, I meant the advancing the weights method is using the BTDC mark, which on mine is the line in the middle. the TDC is a small dot.

would a poor gearbox cause this symptoms?

everything else is fine, all the gears go in smoothly, even 1st to 2nd go smoothly when I get the adjustment spot on.

also, if I put in first and grab the clutch she kind of start juddering forward, therefore why I keep thinking it might be clutch and something to do with the steel plates?

if the steel plates were warped, would it cause this juddering? any ideas?[/]

Definitely sounds like clutch adjustment to me man, if the plates are warped that's what's causing it I'd bet. Maybe try changing them first of all. If it's juddering forward in gear it points to that!
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Old 04-18-2017, 06:26 PM   #5
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Default Re: juddering at low speeds?

Did you change the trans or rear wheel sprocket by any chance? By what you describe it sounds as if the bike is geared too high. If the you have ridden the bike with this drive ratio before and it now started to do the judder the problem is most likely in the clutch.
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Old 04-18-2017, 07:03 PM   #6
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Default Re: juddering at low speeds?

If it were a Triumph I'd say the clutch damper rubbers were slutted out. What kind of damping arrangement does a big twin have -- all metal?
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Old 04-18-2017, 07:56 PM   #7
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Default Re: juddering at low speeds?

What you have is what a compensator sprocket is for. Are you running a solid engine sprocket or a belt drive? Even with a compensator at low rpm you will get the surging.
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Old 04-18-2017, 09:53 PM   #8
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Default Re: juddering at low speeds?

^^^^ What he said.

Another thing that happens with some of those old compensators is that spring gets weak and can cause a surging at speeds where it normally would have no effect.

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Old 04-19-2017, 02:21 AM   #9
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Default Re: juddering at low speeds?

Quote:
Originally Posted by VonWegener View Post
Did you change the trans or rear wheel sprocket by any chance? By what you describe it sounds as if the bike is geared too high. If the you have ridden the bike with this drive ratio before and it now started to do the judder the problem is most likely in the clutch.
nop, didnt change anything on the drive train at all, so it points to clutch then.

Quote:
Originally Posted by joe49 View Post
What you have is what a compensator sprocket is for. Are you running a solid engine sprocket or a belt drive? Even with a compensator at low rpm you will get the surging.
No, didn't have compensator sprocket, solid sprocket on the front, its a BDL kit, been running it for the last 3 years or so.
So I think what might be happening here is the steel plates warped..

Going to order some this morning and should be here by tomorrow. See how that goes.

by the way this the big fix kit... 52 bearings of pure goodness.
and my belt setup



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Old 04-19-2017, 02:34 AM   #10
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Default Re: juddering at low speeds?

I had a juddering on take off .
i have a thread on it somewhere
i replaced complete clutch pack in the end with a quality one.
solved problem(i would like to do the big fix anyway at some point)
"Flathead clutch jumping and screaming"
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Old 04-19-2017, 06:28 AM   #11
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Default Re: juddering at low speeds?

Are you lugging through town in high gear? When the bike is juddering, does the exhaust sound normal and even or is the sound erratic ?
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Old 04-19-2017, 07:48 AM   #12
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Default Re: juddering at low speeds?

My Shovel will do that sometimes, if the chain is a little out of adjustment and I'm putting around at low RPM in a high gear. I just take it as she's telling me "don't do that" and down shift, it goes away then. In my case it's the drive train lash due to chain slack that's causing it. After adjusting the chain it goes away for quite a while. I just figure it's telling me time for an adjustment.

Loose primary chain can cause it too, but you're running a belt so that shouldn't be an issue.

Last edited by WhizzbangK.C.; 04-19-2017 at 07:49 AM. Reason: add statement about primary
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Old 04-19-2017, 09:01 AM   #13
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Default Re: juddering at low speeds?

Quote:
Originally Posted by Truckedup View Post
Are you lugging through town in high gear? When the bike is juddering, does the exhaust sound normal and even or is the sound erratic ?
nah.. not in high gear, I'm not that dumb lol
any gear dude, if I change gear to the speed I'm doing. so say for examply.. 45mph, i'm in 3rd... once I hit a constant speed she judders.
if I'm doing 30pmh.. i'm in 2nd, once I try to maintain that 30..she judders.

I'll check the final chain drive, that's a pretty good call, I completely forgot that!!! On my firebalde (pocket rocket) she complains with a juddering when the chain gets too much slack.
It's usually the simple things that I tend to overlook and go for the cahotic worst case scenario first... duh!!

New steel plates are on order and should be here tomorrow anyway, I wasnt happy fitting the old ones when I fitted the friction discs at the weekend, so at least I'll get that peace of mind of everything new in that clutch basket.

I'll keep you posted. Will only have a chance to ride the bike again on Saturday and will be a long one to a party, so I hope I get it all right as no time to test ride before setting off. (dad commitments come first)
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Old 04-19-2017, 09:39 AM   #14
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Default Re: juddering at low speeds?

i'd check chain adjustment on both secondary and primary drive and to be honest from that first shot the rear drive chain looks dry and as if one of the rollers has seized by the angle in it, or is that just slack where gearbox eased off for primary belt remval.

Last edited by Thunderbird; 04-19-2017 at 09:41 AM. Reason: cuz i can.
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Old 04-19-2017, 10:14 AM   #15
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Default Re: juddering at low speeds?

yeh dude.. on that first shot is the slack to move gearbox forward. the chain is not dry as the gearbox just leaks enough to keep the chain oiled, doesnt leak a drop on the floor though and i'm always on top of gearbox oil.
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Old 04-19-2017, 10:32 AM   #16
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Default Re: juddering at low speeds?

I still think it's clutch plates! Keep us updated!
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Old 04-19-2017, 10:49 AM   #17
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Default Re: juddering at low speeds?

Quote:
Originally Posted by rhysmort View Post
I still think it's clutch plates! Keep us updated!
yep.. that was my initial thought as well.

until you scared the shit out of me this morning talking about laced wheels and fked tranny
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Old 04-19-2017, 11:46 AM   #18
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Default Re: juddering at low speeds?

Quote:
Originally Posted by [JP] View Post
yep.. that was my initial thought as well.

until you scared the shit out of me this morning talking about laced wheels and fked tranny
Haha sorry! my wheel was off and my bike did similar!! Yeah I'm sure your tranny is fine!
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Old 04-19-2017, 04:23 PM   #19
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Default Re: juddering at low speeds?

If you want to finish off the details of making a good clutch, great, get one of those Tamer Clutch Insert kits. They hold the basket true to the hub, and stop the tugging when you are in gear, with the clutch pulled in. It will be the best money you can spend, and it cures half the clutch problems everyone has. Pretty simple to install too.
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Old 04-24-2017, 04:41 AM   #20
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Default Re: juddering at low speeds?

update..

with the new steel plates is much much better! I think still needs some adjustment, but is much better!
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