TR7v Tappet Gaps

Woollybandit

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My Ride
T140V, TR7V, Guzzi V7ii, Harley Dyna FXD
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1974
I was reading through the 'up to and including 1978' workshop manual for the TR7V 750cc (published May 1973) and noticed the rocker gaps were given as Inlet 0.008” & Exhaust 0.006” which seems the wrong way around as the exhausts run hotter than the inlet and expand more. The specs for the1972 T120 650cc were 0.002 & 0.004 inlet and exhaust respectively.

T140/TR7v 1973-1978
B10482FE-BFB0-49E4-A137-E81F4A921741.jpeg
T120 1972
694F3E16-B585-45F6-A545-41AEEDE09FBE.jpeg

Does this look like a typo or am I missing something?

Cheers
 
Not a typo. The 750 twins were fitted with an inlet cam with quietening ramps and a mild exhaust cam without, to try and prevent owners thrashing them for high top speed. Try "t140 tappet clearance" into Google.
 
Not a typo. The 750 twins were fitted with an inlet cam with quietening ramps and a mild exhaust cam without, to try and prevent owners thrashing them for high top speed. Try "t140 tappet clearance" into Google.
Now I look at it I have a question over which gap I should use.
The bike is registered '74 but has an engine number CH28*** which puts it Marich '73.
The manual states it is for KH17124 onwards which is later than my engine. I can’t find a manual for a '73 750cc. This bike seems to sit between two stools.
What to do, what to do?

The bike has been rebuilt by PO from ground up with other personalised mods so I don’t know if they are the original cases.


CFC7B2A7-FECC-4615-B017-9998F35D829A.jpeg
 
question over which gap I should use.
The bike
has an engine number CH28*** which puts it Marich '73.
The manual states it is for KH17124 onwards which is later than my engine. I can’t find a manual for a '73 750cc.
This bike seems to sit between two stools.
View attachment 53374 indicates a manual for a 1973 model year 750 twin. CH28*** does not "sit between" any "stools".

How can 17124 be "later" than 28***?

At least part of your confusion is you are making the common mistake decoding KH, thinking "year" is a calendar year; it never was, always the model year; model year and calendar year might coincide in some months but that is as far as it went.

Only the date code month letter indicates a calendar month.

Like most motor manufacturers all over the world, even today, Triumph began producing a new model year during the previous calendar year. Some well-known authors will have you believe all sorts of silly rubbish but, from the company build records, a model year could begin/end any time between July and October in the previous calendar year (when Triumph was part of BSA, the financial year ended in June) and could be different for different ranges. However, when BSA finally collapsed during 1973 and Triumph became part of NVT, the 1973 model year ended and the 1974 model year began during calendar June 1973.

1973 model year - date code second letter H - production began in calendar August 1972 at JH15101 (the first of a batch of 265 T65 - 4 speed Triumph TR6R with BSA badges). The 1973 model year month sequence is JH, KH, NH, PH, XH, AH, BH, CH, DH, EH, GH; as in any model year, the number increased sequentially throughout the year, ending during calendar June 1973 at GH35466 (the last of a batch of 79 TR7P).

"KH17124" on the manual page might be a misprint - afaik, KH17124 was actually the third engine of a batch of TR7RV beginning at KH17122 built during calendar September 1972; this was the first large batch of 750 twins built during the 1973 model year, all others since JH15101 had been 650 or 500 except 40 T140.

What View attachment 53374 essentially says is that workshop manual applies to all 750 twins; however, "T140E" means it is a 1978 or later update, and a complete new manual was issued for the 79 on twins.
 
Thanks Rudie,
How can 17124 be "later" than 28***?
I have a 1972 Bonnie with sequence number **30701. Numbers can be confusing.

As the model year starts 2/3 through the calendar this table is tricky to read isn’t it.

B89E5ECF-697D-4313-A4B1-A262424E5AFB.jpeg

According to this
 
I have a 1972 Bonnie with sequence number **30701.
Different number sequence - 1972 model year used the number sequence started for the 1971 model year with KE00001.

"**" is HE or HG?

As the model year starts 2/3 through the calendar this table is tricky to read isn’t it.
View attachment 53375
A lot of that table is either misleading or completely wrong:-

. It is not correct that model years always ended at the end of a month or began at the beginning of a month; as in my previous post, the last 1973 model year bikes and the first 1974 model year bikes were all built in calendar June 1973.

. Also in my previous post is that the model year could begin/end at different times for different ranges:-

.. The first 1969 model year production were T150 engines built at BSA Small Heath during calendar May 1968, complete bikes assembled at Meriden during June 1968 (all Triumph triple engines were built at Small Heath; until the Meriden sit in from September 1973, they were then trucked to Meriden for installation in cycle parts and dispatch). Small Heath began stamping date codes and five figure numbers on T150 engines during September 1968.

.. Otoh, Meriden did not first stamp date codes on twin engines until sometime in October 1968 (T120R NC00100) but the 1969 model year began there during July 1968, Meriden continued to use the separate 650 DU and 350/500 H prefixed number sequences from the 1968 model year.

. 1970 model year, Meriden continued to use the number sequence started during calendar October 1968. Small Heath did not build any triple engines before calendar April 1970 and started a new number sequence (T150T DD00101).

. 1971 model year - due to the problems fitting the 650 engine in the new oil-in-frame, 1971 model year production began with 500's in September 1970 (KE00001) while 650's with separate oil tanks continued to be built and numbered in the 1970 model year sequence until sometime in October 1970 (ND60540?). I have it in mind the first 1971 model year 650 (T120R NE?????) was also in October 1970.

. Not only did certainly Meriden's 1971 model year end during July 1971, the 1972 model year also began (HG30870 documented) but without restarting the number sequence.

. While Meriden began its 1973 model year in August 1972, Small Heath continued to build T150 engines date coded and numbered in the 1972 model year/number sequence until sometime in October 1972; otoh, the X75 Hurricane engines also built there from calendar September 1972 also have the 1973 model year H and had their own number sequence; from December 1972, Small Heath built more T150 engines, but with the 1973 model year H and using the same number sequence as the Hurricane engines ...

. 1974 model year - while begun at both Meriden and Small Heath during June 1973 (T140V GJ55101 and T150V GJ40101), production stopped at both Meriden and Small Heath shortly after the sit-in began during September 1973. Production of complete T150's resumed at Small Heath during March 1974 and continued until early November 1974; shortly after the GJ date code was reused in June 1974, Small Heath began stamping the K year letter, so the last T150 are PK45nnn.

. 1975 model year:-

.. The first T160 engine (XK00101) was built at Small Heath also in calendar November 1974 but date coded XK probably because the last T150 engines were date coded PK.

.. "April 1974" is a misprint and only for the first 1975 twin engine (DK61000, by the then new Meriden Workers Co-operative) in April 1975.

. 1976 model year - again, "July 1975" applies only to the twins; T160 continued to have the K year letter until sometime in October 1975, after which Small Heath stamped the 1976 N year letter until the last (CN07203) engine built in March 1976. :(
 
Thanks Rude
Very interesting and informative.
 

Attachments

  • 3CB752CE-FF3A-436E-9A48-FF5F9C8FA4D6.jpeg
    3CB752CE-FF3A-436E-9A48-FF5F9C8FA4D6.jpeg
    109.6 KB · Views: 2
Now I look at it I have a question over which gap I should use.
The bike is registered '74 but has an engine number CH28*** which puts it Marich '73.
The manual states it is for KH17124 onwards which is later than my engine. I can’t find a manual for a '73 750cc. This bike seems to sit between two stools.
What to do, what to do?

The bike has been rebuilt by PO from ground up with other personalised mods so I don’t know if they are the original cases.


View attachment 53374
The T.O.M.C.C. have a copy of the original factory records which show details of your bikes history. For example my CH prefix Tiger 750 had the VIN allocated on 21st March 1973 but wasn't completed/despatched until 19th July 1973. My bike was despatched to Sports Motorcycles in Manchester where it lay until 7th December 1973 when it was registered.

Interestingly Sports Motorcycles were a well known BSA, Triumph, Norton dealer but are best known for supplying Mike Hailwood's TT winning Ducati.
 
Thanks David & Bloodknot,
both helpful posts. Will follow up on your suggestions
 
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