[Slippery Sam]

The Golden Rule in any restoration is to start with the most complete and authentic bike you can find. Even a project that's described as 95% complete will take a lot of time, money and effort to find the missing pieces. I knew this. I knew it from previous experience and yet I still thought it was a good idea to build a bike starting with just a front frame section and the numbers matching crankcase halves. My reasoning was that it was never going to be a Concours standard show-winner so what could possibly go wrong? Here's what I started with, 1967 T120R frame and crankcases bought off Ebay Motors and shipped to the UK with all the associated costs and paperwork.

 

[Slippery Sam]

The frame was in good shape apart from the usual broken side stand mounting lug, a bent zener diode mount and broken steering lock lug. These were either removed or repaired by means of an angle grinder and MIG welder.

 

[Slippery Sam]

The crankcases were also in need of some attention. At some time the rear chain had snapped, wrapped around the gearbox sprocket and punched a hole through the top of the drive side crankcase. Another common problem found on old Triumph twins.

 

[Slippery Sam]

The oil seal for the drive side main bearing had also been butchered at some time and was siliconed and centre-punched to hold it in place. This didn't overly concern me as I was intending to delete the timed breather and convert the engine to 1970 spec with crankcase breathing via the primary chaincase. The crankcases were rather grubby after 50 odd years of use and abuse.

 

[Slippery Sam]

My original plan for the bike was to build a 'resto-mod' replica of the 1967 Thruxton Production Racers with the engine tuned accordingly so originality wasn't the main concern. Perhaps the most famous Thruxton Bonneville is MAC 232E

 

[Slippery Sam]

However, once the rolling chassis was built, complete with period flanged-alloy wheel rims and ventilation holes cut into the front wheel hub, I decided that I didn't want another bike with rear-set footrest and clip-ons and decided to build it as a standard T120R but subtly modified as a bit of a street sleeper.

 

[speedrattle]

whats up with the triple next to it?

 

[Slippery Sam]

whats up with the triple next to it?

That's another restoration project, a Slippery Sam replica. Mechanically it's done, just needs tank, seat, fairing and electrics.

 

[Slippery Sam]

To repair the chain damage to the crankcase I cut a piece of ally casting off a scrap gearbox casing, shaped it to fit and had it welded in at my local welding shop as I don't do Tig myself. When dressed back is almost invisible and is hidden under the new breather outlet anyway.

 

[Slippery Sam]

I had to source everything other than the front frame and crankcases which took about 3 years whilst I was doing other projects. I found really good lightweight crank from a 1966 bike, it was on standard diameter journals which were probably ok to use as they were but I had it reground to - 0.010" and fitted a new sludge trap. I like to ride my bikes hard and don't generally use standard conrods which are all getting on a bit now anyway. My favourite rods are made by Arrow in the UK, I've had four sets in my T150s but they don't make them for twins and so I went with R & R billet alloy rods. I have to say they are rather nice.

 

[Slippery Sam]

New big end shells and main bearings completed the crankshaft.

 

[Slippery Sam]

As I didn't have any transmission or clutch parts I decided to go with a conversion to a 5 speed gearbox as I've done on my T150s previously. This means opening up the clearance hole for the 5 speed high gear to go through the drive side crankcase. I also blocked off the breather tube in the lower crankcase and fitted an elbow from a TR5T to run a breather pipe to the end of the rear mudguard.

I fitted a belt primary drive with alloy clutch basket and I run the primary case dry so I drilled the three oil return holes as low as possible. I also removed the primary chain tensioner pivot which increases the breathing between the crankcase and primary case. (it's still in place in this picture) The crankshaft oil seal was left out. With new cams, fitted without the timed breather disc, the bottom end could be reassembled.

 

[Slippery Sam]

The new cams.

 

[Slippery Sam]

View from the other side showing the new crankcase breather arrangement and also a new Morgo oil pump and not shown is a new SRM stainless steel oil pressure relief valve.

 

[speedrattle]

youre running a dry belt but you drilled the three oil holes. youve left out the crank seal?

what kind of belt is it?

 

[Slippery Sam]

youre running a dry belt but you drilled the three oil holes. youve left out the crank seal?

what kind of belt is it?

It now breathes through the main bearing into the primary case and out through the new breather pipe so the crank oil seal has to be removed. The three holes are to let any oil that blows through the main bearing return to the crankcase so the primary case doesn't fill with oil. The belt can be run wet or dry, it's a 'Megapower 2' AT110 800

 

[StuartMac]

Hi,

SRM stainless steel oil pressure relief valve.

Currently, these have a rep. for sticking because SRM made both body and piston from stainless. Your first-hand experience?

Regards,

 

[Slippery Sam]

Hi,

Currently, these have a rep. for sticking because SRM made both body and piston from stainless. Your first-hand experience?

Regards,

I've had 6 in total, I had a problem with one on a T150 which I solved by polishing it 1200 grit wet and dry. That was about 5 years ago.

 

[Slippery Sam]

With the engine back in the frame I assembled the top end. The cylinder head is from a 1969 and has had some porting work done. The pushrod tubes are billet alloy from TriCor. Carbs are 32mm Amal Premiers with the stainless steel inlet stubs bored out to match, also from TriCor. Cylinder barrels are new Aerco as per original and I sourced a pair of NOS genuine Hepolite standard size pistons and rings.

 

[Slippery Sam]

Due to the cost of having parts painted I decided to have a go myself. I found a very good tank on Ebay which had the tank badge holes filled with solder. These cleaned out quite easily with a bit of heat and then re-tapped. Lots of rubbing down left me with his.