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  1. #1
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    Default Pre Unit Primary questions

    Hey, I have a question about a primary setup. So I have a 56 thunderbird motor and a rigid transmission maybe a 51 or 52, and a 52 frame. What clutch/ drive parts do I need to make the primary all work? I have a random and what looks to be some old racing clutch (alloy tech) on it. Itís complete with a clutch hub and rollers, but not sure if it will work with the rigid trans or if itís meant for a swing arm trans. And in the front I have a crank drive with the spring but from what Iím aware of thatís for a rigid crank because the nut is too big. These are all parts Iíve had laying around or found and am open to buying the right stuff or even going a belt drive if thatís easier. My main question is just what do I need to make a swing arm engine/crank work in a rigid frame with a rigid trans?
    Attached Thumbnails Attached Thumbnails EF819A72-EA21-4110-A14C-F629C10C4B4A.jpg   1A53D61A-5068-4AE3-BDEB-B26F2766E407.jpg   0AEB9CF4-1230-4864-96C4-56394FEE26C5.jpg   CE45B40F-C94E-4BE4-AF4F-5A9754088DFB.jpg   0C36372F-B357-4CFD-8895-5560CEB27BE9.jpg  


  2. #2
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    You need to look carefully at the parts books for each one. There is a lot of small but significant differences. First of all,, there is a pretty big difference between the rigid and swing arm primaries -inner & outer (Length and bolt up, as well as features).

    Start with the parts books for a range of years,, Say 52 and up to 62. Then you can narrow the list of what you have vs what you need. You can download such manuals all over the internet with just a few minutes search. 1st item on any agenda is the factory parts manuals. If you cant find any then PM me for literature.

    I have a lot of these parts, but same deal, I compare the parts books because even allegedly stock bikes are full of mismatched bits. Some of these bikes are 70 yrs old. But if you get in a pinch I can take some pictures.

    To answer your root issue/question is YES! You can run later PU parts and motor/trans in a rigid. Many reasons to do so if you are not doing a #s correct restoration.

    IE: early motors ran weaker rods and crank, as well as babbit bearings, Also the crank ran smaller/weaker bearings on the ends. (Unit crank style with upgraded ball on timing side and heavy duty roller on timing side is the way to go)

    As well, Purists will cringe but its nearly impossible to keep oil in the stock primary, there is no seal at the trans mainshaft on the primary, Just a friction disc, So running a dry belt drive is a huge improvement in my book, as well as removing a LOT of weight from the stock drive train, Its worth it as you CAN feel the difference, more power.

    Depending on the nature of your project and how comfortable you are with custom/mods, I can show you how to use a later unit crank, rods and then modify it to run a Alternator and Digital ignition instead of the Mag. Solves 2 issues. Upgrades to ignition and charging.
    Ive done a few of these as well as hotrodding the motors. 750 long rod big bores, 750 short rod race engines. A 500 all alloy motocross racer for AHRMA. 2 TRIBSAs as well.

  3. #3
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    On primary covers: Your Tbird motor uses an alternator. Most rigid frame Triumphs used a generator (dynamo.) The only ones that used an alternator were the '53 and '54 5T (speed twin) and the '54 6T (Thunderbird.) The stator bolts to the outer primary cover. The covers are pretty hard to find, and pricey when you do. If you're going to look for one, familiarize yourself with the difference between those and the TRW primary covers, which look similar but will not work.

    I was looking at putting an alternator equipped engine from a '61 T110 into a stock Triumph rigid frame at one time. My plan was to take a swingarm alternator primary cover set and a generator rigid frame set, and find a way to splice the two. I started to do a little layout work on it but I stumbled upon a '56 TR6 engine (which uses a dynamo) to put into the rigid frame instead, saving me all that fabrication.

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