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Old 05-10-2018, 10:24 AM   #1
vorhese
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Default Best clutch upgrade for preunit Triumph?

I'm fiddling with my clutch right now. I'm currently running a preunit clutch basket with 3-spring unit hub and plate. I'm running 6 steel and 5 friction plates.

I would have thought 6 friction and 6 steel plates would fit if I'm using a unit clutch hub, but it does not. Why? I assume a preunit clutch basket would eat up a friction plate if it went in first?

preunit 4 spring, 6 steel, 5 friction


unit 3 spring, 6 steel, 6 friction


preunit clutch basket


unit clutch basket


Hybrid


Next question: is this the best upgrade I can do to a preunit clutch without going belt drive?
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Old 05-11-2018, 01:48 AM   #2
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Default Re: Best clutch upgrade for preunit Triumph?

don't know the answer but as for upgrades I used the machined billet ali' pressure plate, which may be just bling and I seem to remember suggestion that the clutch springs could be beefed up.

Mr Pete was always the 'go to man' on Triumph stuff also TonytheTorch, I guess you've searched their posts?.
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Old 05-11-2018, 08:00 AM   #3
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Default Re: Best clutch upgrade for preunit Triumph?

I’m assuming here, but just by gazing at the diagrams a PU basket is likely shallower than the unit basket. Ive also never mic’d the plates on either of my triumphs but is there a thickness difference between the plates? When I purchased my PU the previous owner was waxing poetically about how to set up the perfect clutch on these, but alas I was too excited ny the purchase to pay attention. Have you passed this question by Wes at 4 Aces or Hugh at 6th Street?
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Old 05-11-2018, 10:02 AM   #4
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Default Re: Best clutch upgrade for preunit Triumph?

Unf Mr Pete is no longer with us, and I'm not sure which experts post here anymore. I've read a few past threads and some various advice. One was taking 1/16" cork and attaching it to the inside of the basket to act like another friction plate. Another is to weld the outer plate to the first steel plate... not sure about either.

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Old 05-11-2018, 10:17 AM   #5
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Default Re: Best clutch upgrade for preunit Triumph?

I assume this is slipping on you? Don't use ATF in the primary, use engine oil...you could try using Yamaha RD400 springs too...they are similar size, but slightly stiffer.
I would use the four spring pressure plate, but if you're going to stick with the three spring unit, you could try T140 springs

I did the following to my AJS and it seems to work quite well, it might be worth a try:
Machine the friction material off one side of an old plate and stick it into the basket first...this will put another friction surface behind your first steel disc and prevent it from bowing inward when the clutch pack is compressed by the pressure plate, and should not significantly thicken the clutch pack.
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Old 05-11-2018, 10:49 AM   #6
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Default

You said chain so I can’t help.... I gave up on them and put a newby, true love. Great clutch, no leaks.
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Old 05-11-2018, 12:30 PM   #7
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Default Re: Best clutch upgrade for preunit Triumph?

Wondering what you're hoping to get from an upgrade?

I only have experience with one pre-unit trans. Had a hell of time getting it set up to neither grab nor slip. Did achieve peace using 10W-30 and making sure there was absolutely no wobble. Shifts are smooth unless I rush it.

Anyway, just curios what your trying to improve on?
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Old 05-12-2018, 04:35 PM   #8
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Default Re: Best clutch upgrade for preunit Triumph?

There are two fatal issues with pre unit clutches: one is the single row primary chain. That puny chain is not up to the task of transmitting power to the clutch basket without a higher than normal amount of stretch. This is likely why most pu primary covers are chewed up on the inside. I find this means adjusting the transmission back after almost every spirited ride. Too much hassle!

The best pre unit upgrade of ANY kind is a BNR Belt drive. It make owning and riding a preunit a treat. After 5 years of abuse, my '55 has required ZERO transmission adjustments, never had stuck plates, and not leaked from the primary cover (since it is dry). Every pu I build gets a BNR, and I have seen only smooth operation and no fiddling required by the clients in the field.

The second main flaw is the roughly 1.5" loose roller bearing setup these clutch baskets came with. The BNR has a roughly 5" sealed clutch basket bearing. It is SO much more stable than the stock loose bearings. Those less-than-precise roller bearings are what makes the stock pu clutch so difficult to set up: you have to account for the basket's slop when truing the clutch basket sprocket to the engine sprocket. It can be done, but why when there is a product available that is a masterpiece of machining and can make your pre unit a pleasure to own and ride.

Basically you can change whatever you want on the pressure plate, springs, basket, and clutch plates, but if you don't address the single row chain and the basket's roller bearings, you will still have a fiddly, high maintenance clutch system.

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Old 05-13-2018, 10:49 AM   #9
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Default Re: Best clutch upgrade for preunit Triumph?

$800... tough nail to bite.... but probably worth it. I've heard nothing but good things for years.
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Old 05-14-2018, 08:58 AM   #10
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Default Re: Best clutch upgrade for preunit Triumph?

^^^+1^^^
Trying to get "needs and wants" together for my pre-unit build..
Alton gen/alt... $800
Newby belt set up..$800
I may go with the Belt first.. then in the near future get the charging system
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Old 05-14-2018, 11:40 AM   #11
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Default Re: Best clutch upgrade for preunit Triumph?

Quote:
Originally Posted by vorhese View Post
$800... tough nail to bite.... but probably worth it. I've heard nothing but good things for years.
You can order one direct if you want to save a few bucks. This one upgrade will change your pre unit world. Seriously.
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Old 05-14-2018, 11:52 AM   #12
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Default Re: Best clutch upgrade for preunit Triumph?

Quote:
Originally Posted by Rob Axel View Post
^^^+1^^^
Trying to get "needs and wants" together for my pre-unit build..
Alton gen/alt... $800
Newby belt set up..$800
I may go with the Belt first.. then in the near future get the charging system
Rob, I cannot say enough good things about the Alton too. It comes with a Podtronics rectifyer, and makes installing a BNR MUCH MUCH easier. It is recommended to run a battery though, which is not a big deal.

If you use a stock-ish crank-driven alternator, it's best to have access to a lathe to make spacers to move the alternator field away from the crank. The stator field will also need its potting epoxy shaved to fit under the cover. On ALL charging systems, you will need to make at least a 1/4" spacer for your primary cover.

Here is a pic of a 1/4" spacer for an alternator primary.... I keep them in stock for all three types of pre unit primarys. Dave Helrich of HCC designed these spacers, he is your go-to guy if you want one.
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Old 05-14-2018, 03:03 PM   #13
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Default Re: Best clutch upgrade for preunit Triumph?

Yup ... all pretty much "Angry Monkey" standard equiptment...
.. I will be "stealing" a lot of "cues" from your builds...
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Old 05-14-2018, 07:02 PM   #14
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Default Re: Best clutch upgrade for preunit Triumph?

Sorry for straying a little off topic Vorhese, but how did that Bon Ami break-in trick work out for you?
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