Jockey Journal Forum banner

Pre unit Triumph 6T bottom end strength? with more pics

13K views 20 replies 11 participants last post by  whittiger650 
#1 · (Edited)
I was recently given a 1955 6T motor and '50-'52 rigid frame project. It is mostly mechanically complete, except for sheet metal. I am wondering what kind of power can a stock 6T crank, rods and single row primary chain handle?
Supposedly it has been rebuilt some time ago but I will be going through it to be sure things are up to snuff.
Right off the bat I would be upgrading to a 9 bolt top end but I am considering some .350 lift camshafts that I have & a set of 10:1 forged pistons, along with some head porting.
There would be no burnouts or other sorts of silly abuse. Pretty much an open hi-way here and am looking for more mid range and top end power.
 
#2 · (Edited)
Re: Pre unit Triumph 6T bottom end strength?

You've got the post '54 motor which has the larger timing side main which is the one you want. The cases will handle the modifications you are considering without a problem if the motor is put together well, a balanced crank will always help.
Has the gearbox got the speedo drive at the bottom of the kickstart/gearchange end?
The gearbox mounting setup on a stock rigid has been known to get a little out of shape when handling more power.

Hell of a nice start though!

Wait a cotton pickin' minute
I've just opened the picture up and that doesn't look like a 55 6T bottom end, it shouldn't have the dynamo drive ear at the front of the timing cover,
Make sure you have this bulge beneath the timing chest;

 
#9 ·
Re: Pre unit Triumph 6T bottom end strength?

You've got the post '54 motor which has the larger timing side main which is the one you want. The cases will handle the modifications you are considering without a problem if the motor is put together well, a balanced crank will always help.
Has the gearbox got the speedo drive at the bottom of the kickstart/gearchange end?
The gearbox mounting setup on a stock rigid has been known to get a little out of shape when handling more power.

Hell of a nice start though!

Wait a cotton pickin' minute
I've just opened the picture up and that doesn't look like a 55 6T bottom end, it shouldn't have the dynamo drive ear at the front of the timing cover,
Make sure you have this bulge beneath the timing chest;

Yeah I was noticing that also, but I went by the engine #s 579XX so I am suspecting mismatched cases. I'll check the #s on the bottom later today and look for the bulge.
Thanks everyone for all the input.
Will post more later, along with some pics of the "goodies" that came with it!!
 
#5 ·
Re: Pre unit Triumph 6T bottom end strength?

Assuming you do have the big bearing case, I'd use the later one piece crank with the bolted on flywheel ring rather than the crank that sandwiched the flywheel between the two crank halves. I think the change was made in '59 when the Bonnie came out.

Bob
 
#6 ·
Re: Pre unit Triumph 6T bottom end strength?

You can modify the earlier cases to use big bearings, too.

Anyway, I have been trying to buy a rigid pre-unit for years with no luck, and here you get one for free. No, I'm not jealous. What's worse than jealous?
 
#8 ·
Re: Pre unit Triumph 6T bottom end strength?

I have been trying to buy a rigid pre-unit for years with no luck, and here you get one for free. No, I'm not jealous. What's worse than jealous?
Ha! I feel your pain. After y e a r s of searching, I finally found a factory rigid titled frame to build. I have a built motor and trans already set aside for this project too. Now I just have to find the time between client builds.
 
#7 ·
Re: Pre unit Triumph 6T bottom end strength?

...hey man, bear in mind that a 6T have the same crankcase of a 500cc; its not a real 650 (T110)

hey Vorhese, in my country most are pre units 1948s 1949s and some up to 54 and a few early 40s
I think less than 30 units (350, 500, 7 750s and 1 T120)
My ride is a pre unit but my project is a unit due to the wearing of those oldies and of course the late 750s are the best Triumph twins, have almost all the racing advantages they fitted in the 50s and 60s.
 
#10 ·
Re: Pre unit Triumph 6T bottom end strength?

I would be curious to know the frame number on the head stock (stamped number). From the looks of the gussett, behind the lower fork bearing, it appears to possibly be a T100R or RR front frame section. If there is an R before or after your serial number, you have something there that is worth quite a bit of money.

Regards,
Dave
 
#11 · (Edited)
Re: Pre unit Triumph 6T bottom end strength?

I would be curious to know the frame number on the head stock (stamped number). From the looks of the gussett, behind the lower fork bearing, it appears to possibly be a T100R or RR front frame section. If there is an R before or after your serial number, you have something there that is worth quite a bit of money.

Regards,
Dave
Unfortunately the frame has been raked and the #s have been obliterated :(

I am going to try and register it under the engine # hopefully.
The cases are a mismatch & no bulge.
 
#12 · (Edited)
Re: Pre unit Triumph 6T bottom end strength?

Just a few more pics of " some" of the parts that I was given.
Sprung hub with extra drum/ sprocket,
2 transmissions (3 in all),
2 oil tanks,
3 front forks & 1 pair of lower tubes,
3 of the 5 boxes of miscellaneous parts,
also a couple of front wheels not shown.
Not trying to brag :p ... but seriously it shows the "deals" are still out there. Although I think this was probably my deal of a life time! and I probably shouldn't bother buying another lottery ticket ever because I know I just used up all my luck! :cool: ...yeah, I'm good with that!!
 
#13 ·
Mismatched half numbers are not the end of the world, there are plenty out there running like that. The lack of the big bearing on the timing side is a problem as it limits the crank options severely. It is possible to fit a later crank to the small bearing cases as there is a bearing available that covers the i.d and the o.d. but is an eighth narrower on the width. Not really worth it in my opinion, as you are just starting out on this build it would be better to get strong foundations sorted out early.

You could figure out what you're going to use, sell some of the rest off and buy a good set of '58 or later cases ( from 011864) these will have the drive side oil seal on the crank, and handle whatever motor mods you want to put in there.

You've got a few choice parts there. The oil tank with the screw cap is a nice thing to have, and the rear brake drum in the gearbox pic has a genuine rigid brake plate, the little boss with the flats opposite the brake arm locates into the frame lug just in front of the drive side axle slot. I've been looking for one of those for a long time.
 
#17 ·
Quaffmeister, I was considering just running it stock with the iron head and it just happened that I had the cams etc. and also some unit cranks and various other unit parts. I'll keep you in mind if I am not going to use the drum and backing plate

Great looking project, if it was me Id be sorting out the rego/title before spending a cent.
I agree with you there Pete, I will be heading next to the MVB to do a title search first.

yep, and my '54 6T eng' No. 50*** is big bearing, I guess I've fallen foul of the 'intersh*te' WWW of missinformation and should defer to Roy Bacon in future.

FRISCO67 that is a nice haul, enough to trade and maybe get best part of another runner. All the best
'59 I agree with you there big time about the "'intersh*te' WWW of misinformation" it makes things really confusing. I have the "Big Bacon" restoration manual , the Clymer reprint '45-'55 manual. definitely will be doing some trading I am sure. Thanks '59

Very nice score of Pre-Unit bits :cool:

Check the top of the center downtube for any possible numbers being stamped into the frame in that area and also, does the center downtube have a large eyelet ...or oval hole in it ?

Check attached pic..arrow indicates where to look for those numbers. Depending on what year that frame is, the same numbers as those stamped on the steering head or neck area were also stamped there.
Whitetiger, the frame doesn't have the opening for a SU carb, I will check the frame over good for any #s, Thanks for the tip!
 
#16 ·
Very nice score of Pre-Unit bits :cool:


Check the top of the center downtube for any possible numbers being stamped into the frame in that area and also, does the center downtube have a large eyelet ...or oval hole in it ?

Check attached pic..arrow indicates where to look for those numbers. Depending on what year that frame is, the same numbers as those stamped on the steering head or neck area were also stamped there.
 

Attachments

#21 ·
Best to start a new thread on this with your question. I guess I would start by taking the timing cover off and inspecting the parts. Then, if all looked okay, taking the Alton off and rotating the shaft by hand and listening and feeling for any grinding, etc..
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top