Sammy Miller Highboy Bultaco

[David Lahey]

I'm on a quest to see if I like riding a Sammy Miller frame .
I know already that I love riding trials bikes and have spent many years getting my 1968 model 49 Sherpa T to feel wonderful in trials sections and today I've been doing some testing and measurements so I know how to set up the SM bike so it feels how I like, based on the current setup of the model 49.
The SM frame in the photo came from a friend in the UK and from what I can tell is one from the second series which I'm thinking would have been made around 1975/76. If anyone knows different, please let me know.
The main things I was checking for today was what length shocks and what handlebar rise to use, so I set up the two bikes so that the fork tubes were at exactly the same angle, because this should give the same excellent steering that I'm accustomed to on the model 49. This was straightforward because even though the fork clamps look very different between the model 49 and the model 198, they and the fork sliders and fork tubes share the same geometry. It turned out that 340mm shocks on the SM frame gave the same fork tube angle as 360mm shocks on the model 49 . I also checked how far the rear wheel comes up with 340mm Falcon shocks bottomed and the tyre will be very close to the rear guard.
The handlebar clamps are the same height off the ground for both bikes but the footpegs are a bit lower and lot further back on the SM so I may need lower rise handlebars on the SM .
The wheelbase is the same on both (52.5")

[Bully fanatic]

Good to see you have decided to go with a Real Trials Bike David!

[David Lahey]

Good to see you have decided to go with a Real Trials Bike David! :Bultaco: :Bultaco: :Bultaco:

Yes indeed. I'm very much looking forward to the riding.
Doing this sort of thing reveals lots of things about different models so I'm loving it. This morning a learning was about the differences between the header pipes and cylinder head finning on models 49, 80 and 85.
Yesterday included a learning about the differences between the airbox designs and the angular offsets of the inlet manifolds on models 49. 80 and 85.

[David Lahey]

It's my RDO so I'm hoping to do some more on the SM Bultaco.
This photo of a series 1 (1968) model 49 Sherpa T and a mid-1970s Sammy Miller Sherpa T illustrates a few things:
The increased ground clearance under the motor. It looks a lot, but the difference would not be anywhere near as much if the bike on the left was a mid-1970s Sherpa T.
Footpeg location. The footpegs are lower and further back on the SM frame bike. The distance rearwards can be judged by looking at the positions of the footpegs relative to the swingarm pivot location. Both bikes have the same length swingarm and wheelbase. As for the footpeg height difference, it can't easily be seen here because the swingarm pivots are different heights, but the SM frame has the footpegs about 20mm lower than the model 49 frame.
I noticed today how much the SM frame design around the top shockie mount looks like a SM TL125 frame.

[David Lahey]

There are lots of little things to do so I can have a test ride on the SM to see if I like riding it.
One thing was to set up some rear brakes.
The brake pedal had been extended and was was quite bent so last weekend I removed the ugly extension piece and did some straightening. The pedal is made from thin-wall steel tubing and is held together with bronze welding so I couldn't use heat to soften it for straightening, so it's not as neat as I wanted but at least it should work OK for the test riding.
Before

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Before

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The brake pedal is now ready for the test riding

20230722_140457.jpg (1.43 MiB) Viewed 14292 times

[David Lahey]

No progress on getting the SM frame bike ready to ride, but today I had to move some bikes around and decided to do a comparison photo of the SM frame bike with a model 80 Sherpa T.
I've put housebricks under them to better show up the difference in clearance under the motor. As expected, the SM frame bike is a bit higher than the model 80 bike.

[don.howison]

Miller frame looks to have a slightly steeper head angle. Is that the case?

[David Lahey]

Miller frame looks to have a slightly steeper head angle. Is that the case?

It is steeper than that M80 Don. I suspect that the Konis in the photo that are on the model 80 are a bit shorter than ideal.
I put 340mm shocks on the SM frame bike so that it had the same steering angle as my model 49, which I had set up to feel lovely in the steering. I think if I fitted 340mm shocks on this model 80, the steering angle would be very close to or the same as the SM frame bike. Maybe that could be something to check next time I need to move the bikes around in the shed

[David Lahey]

I took some annual leave from my paid job and managed to fit in some quality workshop time, working towards test-riding the Sammy Miller .
The final jobs to get to test-rideable stage were to fit some sort of exhaust, make a bashplate and sort out a chain tensioner.
Due to some minor complications resulting from using a model 49 motor in a 1975 SM frame, I am using a header pipe which puts the outlet of the mid-muffler in the wrong spot to fit one of the famous triangle mufflers. As well as the mid-muffler outlet being in the wrong place, a triangle muffler won't fit anyway because of the shocks being laid-down compared to a standard frame.
Being keen to have a test ride, but finding the raspy tone a bit too much even for my motorbike, model aeroplane and brass band-seasoned ears, I added a tubular rubber "muffler" and did some test riding. I found I can ride around my test sections for about 15 minutes before the exhaust starts smelling like burning rubber. Ah the joys of living far from the madding crowd.
Can anyone recognise the type of rubber hose I have used here? This type of hose was quite a leap in technology in the early 1980s and a quick Google search told me that it is still being produced.

(and yes the rolling test bed is fun to ride)

[tat ty]

I've absolutely no idea what the pipe is ... but I just love the combination of ingenuity and impulsiveness.

I recently realised that the internal diameter of a left over roll of flexible ag drainage pipe would fit neatly over my car exhaust and the external diameter fitted perfectly down a particular rabbit burrow.

Haven't seen any bunnies leaving that burrow for a while.