TR5MX Avenger restoration

[YK55]

Hi all, Rickard suggested I post about my TR5MX Avenger restoration project so here's a bit to start with.......

I've always liked BSA unit singles, I owned a C15 when I was a kid 40 years ago but what I really, REALLY like are the square-barrelled 441s and 500s for me they are one of the best looking engines of all time
My TR5MX motor is currently sat on the kitchen table and I'm quite happy to just sit and stare at it with either a beer or glass of red in my hand

Last year I decided I wanted a B50T so I started looking in the usuak places and placed a bid or two Ebay, then one day I saw a TR5MX and had to have it! I've always loved Triumphs and I already had a TR5T so the TR5MX would make a nice addition. Anyway, I became the new owner and I brought it home and began collecting parts for the restoration. There were quite a few bits missing, including the front wheel and my plan was to put it on the road as a Triumph version of the B50T. However this soon changed into making it into a single-cylinder TR5T.

Here's a couple pictures in 'as bought' condition.

[HPbyStan]

I like it in the "as bought" condition.

[YK55]

The TR5MX is basically a badge-engineered BSA B50MX, when BSA went out of business the remaining parts were built up as Triumphs. As far as I know they are identical to the B50MX except the Triumph had a 21" front wheel, a full alternator with Lucas MC2 capacitor ignition and the 2 gallon Triumph-style fuel tank. Triumph also sold a 570cc tuning kit as an optional extra. There is a nice road-test article in the March 1974 issue of 'Cycle' magazine comparing the standard and kitted bike which makes interesting reading.

It's a full matching numbers bike, engine and frame, crankcase halves and inner timing cover are all correct. The engine number gives a build date of July 1973 and this date is also engraved on the oil pump however the crankcases are date-stamped 31. 1. 73.

It's a one owner bike, I have California title from August 1973 and it was re-imported back into the UK in 2011 when I bought it. I assume it's unusual for a competition bike to have a US title? It certainly isn't normal in the UK.

The most obvious error was the front wheel which was from a H*nda, I believe a 250 XL Motorsport. The bike wasn't in running condition and looked like it had been standing for many years.

For about 6 months I didn't do anything other than gather parts and information and then I started the strip-down. The bike had obviously had a hard life during it's latter years and had suffered from a lack of maintenance. It was on + .040" rebore but the crankcases had obviously never been split and the bottom end was in remarkably good condition although I have replaced the big end and the main bearings. In fact I have replaced every bearing and bush on the whole bike, those Torrington layshaft bearings are an absolute PIG to remove! I had a new cylinder liner fitted and bored to standard as I had a New Old Stock std Hepolite piston. I have also fitted new valves and Colsibro guides.

I have replaced the close-ratio gearbox with a standard ratio cluster from a low mileage B50T and I have converted to a 3/8ths drive chain using a 17T gearbox sprocket and 47T rear wheel sprocket from a BSA A65. The engine is now ready to go back in the frame but I need to fit a tachometer drive first. I bought a New Old Stock one but it turned out to be for the earlier B25/B44 models and it won't clear the frame so if you know where I can get the later type I'd be very grateful!
Andy.

[YK55]

I like it in the "as bought" condition.

It was worse than it looks! It wasn't useable at all as it was, everything needed overhauling.
Andy.

[koncretekid]

I give up! How did they get a 670cc kit out of the B50? I want one.
Tom

[YK55]

I give up! How did they get a 670cc kit out of the B50? I want one.
Tom

Oops! My error, it was 570cc, (I've edited the original post)

There is a copy of Cycle magazine on Ebay at the moment :-

http://www.ebay.co.uk/itm/CYCLE-MARCH-1 ... 45f7f3f98a

[2manyrides]

In the days when there wasn't a whole lot happening down at the triumph shop, (late 70's early 80's), I bought the big bore kit from my local dealer who had it in the bargin bin.
New piston, rings, wrist pin, liner...
Price... $40.00

I could not pass that up!
I never did put it in my TR5MX, but did install it in a B50 motor. I was pleased with the results. It's like the C/W article states. I have that issue of C/W.

But if you talk to Ed at EV he'll tell you this is not the "ideal" method for boosting your umph!

[b50root]

Magazine here http://b50.org/phpBB2/viewtopic.php?f=87&t=3765

Rickard

[HPbyStan]

That sorry a$$ed piston belongs in a tractor not a motorbike.

[Michael Moore]

Are the side panels under the seat still available? If not, I can take some photos of mine for you if you need to replicate them.

cheers,
Michael

[B44R]

This place in the UK does side panels

http://www.cmf-engineering.com/

Chris...

[YK55]

Are the side panels under the seat still available? If not, I can take some photos of mine for you if you need to replicate them.
cheers,
Michael

Hi Michael, many thanks for your very kind offer, I have a pair of reproduction side panels ready for fitting
Andy.

[YK55]

Just to update this thread, I sold the TR5MX a couple of years ago to a good friend of mine and it now resides in the in the Transport Museum at Jurby in the Isle of Man. I've re-posted the original pictures thanks to Photobucket playing silly buggers.

As bought.





When finished.

[beat]