Britbike forum

Classic British SparesKlempf British PartsBaxter CycleThe Bonneville ShopLowbrow CustomsGirling Classic MotorcycleLucas Classic MotorcycleHepolite PistonsIndustrial tec supplyJob Cycle

Upgrade your membership to Premium Membership or Gold Membership or even Benefactor

New Sponsor post
Triumph 650/750 High-Output Alternator Kit
by The Bonneville Shop - 01/13/23 11:29 pm
New FAQ post
Missing edit button
by wrench136 - 05/30/22 2:57 pm
News & Announcements
Premium members! 🌟
by Morgan aka admin - 01/31/23 2:14 pm
Buy BritBike staff a coffee ☕️ or pint 🍺
by Morgan aka admin - 01/15/23 9:29 am
Benefactor ✅
by Morgan aka admin - 01/08/23 8:38 pm
Gold members! ⭐️ ⭐️ ⭐️
by Morgan aka admin - 01/03/23 6:30 pm
How to guides - Technical articles
British Fasteners Specs
by Morgan aka admin - 01/03/23 1:29 pm
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Member Spotlight
Wangi Wangi, NSW, Australia
Posts: 25
Joined: November 2022
Top Posters(30 Days)
Lannis 77
DavidP 74
Top Likes Received (30 Days)
Kev. 36
DavidP 25
Newest Members
BSA A65 rebuild, Dan Haggard, Padsdad, sam keller, Raz
12,386 Registered Users
Forum Statistics
Most Online204
Jul 10th, 2022
Random Gallery photo
Photo posting tutorial

Thread Like Summary
Denis J
Total Likes: 1
Original Post (Thread Starter)
by Denis J
Denis J
Hey All
I have scoured the factory service manuals, the Recommended Triumph service manual by Masters, watched every last second of the Hancox video (holy whoa) and searched this forum and the net with lots of recommendations, but no specifications. Here is where I am at:

1950 6T Thunderbird - Restoration of the engine back to stock
I have the correct valves, springs and guides
The seats are so deep in the head that the exhaust valve contacts the guide before it contacts the seat - excessive cutting and service over the years has caught up
I am getting ready to install new seats and correct the valve and rocker geometry.

The 1949-62 6T valves are shorter by .030" (Intake) than the T110 and TR6 stuff of the same pre unit make. The T120 pre units are .095" longer still . Trying to use Unit-construction specifications puts the valve up against the rocker arm itself with no room for the adjuster to adjust.

Is there anyone who has experience with this and some specifications? I can discern the stem installed height if I have a fitted spring length, but I have no specifications at all. Help!

John Healy! I scoured all your write ups on Vintage Bike magazine. Thank you again for taking the time to document this. Where I am coming up short are the specifications for the springs and valves in the engines not described in your write ups. Maybe I need to convert to later valves? Maybe the thickness of the cylinder heads are different and that is the reason for the different springs (unit/pre-unit) and shorter valves?

Picture for fun
[Linked Image from]
Liked Replies
by Stein Roger
Stein Roger
Great information as always from Pete. Thanks for digging it up, it's been added to my archives!
Mr.Pete went by Pete R on this forum. His name was Peter Russel and was a veritable fountain of experience with Triumph in particular, but also other makes. I understood he was a machinist or engineer by trade, and he seemed to have a solid grasp on physics and mathematics as well as the practical application of it. He had the patience to answer dumb questions by the likes of myself, without resorting to sarcasms or rolleyes...
As you understand he died a few years ago and he is deeply missed.

Lash caps is a good idea to adjust the rocker geometry, or you could use Porsche/VW "Elephant Foot" ball and cup adjusters. Their metric thread of 8mm X 1mm pitch is so close to 5/16" X 26tpi as can be. Run a metric tap through the rocker and you hardly remove any material at all. You may still struggle with the space under the rocker, but it's OK to remove some material from it. Shortening the push rods slightly is another possibility, or use thicker rocker box gaskets. Pete wrote about these too, I can send you a copy of it if you wish.

1 member likes this
British Cycle SupplyMorries PlaceKlempf British PartsBSA Unit SinglesPodtronicVintage MagazineBritBike SponsorBritish Tools & FastenersBritBike Sponsor

© 1996-2023
Powered by UBB.threads™ PHP Forum Software 7.7.5