Terrot MT1 Motorcycle restoration project

[911hillclimber]

Thanks, I will. It is soaking in paraffin right now in bits to open the hole up a little before a dose of U/S cleaning if I can get the threads 'back' on the slider top.

Somebody has had this bike part apart at one point as so many screws are finger or factory tight.
The gearbox and clutch share the oil bath except there was NO oil in there or any sign of it, it was all washed-out before I had it, not drained, but washed out and very clean.

It would be good to know the history, but no chance of that. It will be a real test to rescue the carb, but the engine looks ok esp once I get the mounting bosses all welded.
I need to get this all essentially done by the end of Feb! ('17)

Carb looks like this:

[911hillclimber]

After a 2 day soak in clean paraffin and a good blast of carb cleaner I have sort of rescued the carb.
It is quite a mess despite all the attention with a major threaded area crossed and re-crossed a dozen times but sort of cleaned up with a needle file and the brass throttle cable top soldered over 3 cuts made to its mating threaded collar to tighten (when crushed) onto the multi crossed body thread. Nasty but hanging on by a thread, literally.

The carb was made by AMAC under licence from AMAL so I'm hoping I might get some new parts from AMAL, but no luck so far...

The jets all cleaned-out well, the float and needle are fine and the last horror is the piston!
The carb design is very much like a miniature (16.5mm choke diameter) SU car carb but the sliding piston is so butchered I cant see what the French man was seeking to gain from files and solder and gouges on its surface.

I'm tempted just to replace the carb for a new similar size AMAL carb as I have little hope this one will seal and work.

Lastly, I can advise you NEVER to get an eye-full of Carb Cleaner in your eye.
The swelling is still sort of deflating slowly.

[smallspeed]

Sorry, I replied before but I think it was victim to the "no post mode" bug!
The amal carb I have is a lot bigger than that, I think it might be from one of the old 500's or my gramps old 350..

If its just the piston that's knackered could a new one be turned up? If you want me to have a crack at making one let me know.. Will be a month or so until I cab get around to it as desperately trying to finish off my car for an mot, but happy to give it a shot after that..

[911hillclimber]

Thanks for the offer!
I have an old school lathe ad if I need to I can try my hand at one also.
A milling machine would be a very nice thing to have as there are several intricate sloths to the piston..
I have found out this carb, an AMAC 903 165 was used on a lot of French small 2 stroke engines so I need to search deeper into French EBay to see if I can find another for parts at least.
An alternative cab might be Plan B
The D1 first BSA bantams used a simple AMAL carb, and some Lambrettas, the Cento, have easy to get carbs for their 100 cc engines.
The one I have might work, but I'm not sure, but some weeks to go before I can find out!

[Kneeslider]

Can you post a picture of the carb slide, and the bore inside the carb, and the butchered threads on the top?

Usually, I try to gauge wear in the carbs for small motorcycles by inserting my finger into the inlet, then wobbling the slide back and forth. There are people out there who can bore a carb and sleeve it if you are desperate to retain the original carb. I once reclaimed a scrap Amal from a 350 Ariel W/NG which had the carb top badly and irretrievably cross threaded by turning off the old threads, and turning up a sleeve to go over the outside, which was then shrunk onto the top. It worked, and was neat, but took a good couple of days of careful machine setting. It would probably be better just to get another carb body.

Would it be the end of the world to replace it with an Amal?

[911hillclimber]

Thanks, I'll send the pics later today.
No prob replacing with an Amal but would need it to look period, this why I looked at the BSA bantam d1 carb, also early Lambrettas.a carb for 100cc ans 2stroke really.
The amac 903 was used on a lot of bikes of this period but are very rare to find!
Graham.

[911hillclimber]

Bit tricky to photograph, but I hope these will show the state of the piston.
The bore in the body measures well (inside callipers) and is 19.1 max

The piston is a very loose fit at about 18.6mm dia and is not particularly round or cylindrical!
The body thread where the brass conical top 'screws' looks better than it is.

[911hillclimber]

Right, this has made me to stop being lazy and to get on with the carb restoration!
The bore of the carb is just over 19mm so I have just ordered some 19mm do brass tube with a wall thickness of 1.4 mm.
My plan is to turn the rough and damaged and filed and soldered piston down to snugly fit into the tube and solder it in place.

I can then cut the slot for the piston guide pin and the slot for the throttle cable using the original slots as a position guides.
This will maintain concentricity and roundness and be within the capabilities of my lathe!
How I miss my Myford Super 7 lathe when I used to work!!

The thread on the body I think will hold good.

[Kneeslider]

Thanks for posting the pic. Looks like that slide is well used, re making it oversize could be a good plan, but the only issue is going to be getting the gap between the slide and the tube sufficiently filled with solder. Capillary action should do it, but I guess you will only find out when you try to machine it back to size.

Would an Amal slide not fit? It's a long time since I played with Amal carbs, but aren't they owned by Burlen who re manufacture SUs? They are probably the sort of company who hold spares from the last 100 years or so.

Is the bore in the carb OK? A lot of the time, if the slide is that bad, then it has usually worn the mazac body of the carb oval too.

[911hillclimber]

I hope to get the original piston tuned to a transitional almost fit to the inside of the drawn brass tube and flood the one end of the pair and heat will do the rest.
Obviously when I cut the guide slot it will turn the tube into a C so I hope the solder will be complete so stopping the C from opening up.
I have 100mm of tube on the way, piston is 24mm long so 3 chances!

The piston has bee filed and filled with solder on some faces, and the guide screw has been turned into the slide grove rather than the piston replaced when the screw is in place, all in all a mess.
I have been in touch with AMAL about the carb, but they do not have anything to offer (over the net) so a visit to a bike show or even a visit to them with the parts might yield something I can adapt.

Oddly, the bore is quite good. not perfect, but I hope with a good piston diameter I will have about 0.15mm clearance.
The carb is quite crude as you would expect for a 1950 item designed after the war if not before so I think it is all a bit of a compromise.

If ALL fails then I think an AMAL 361 will do the job but also a Dellorto carb off an old 100cc Lambretta might do as a last resort, and parts are easy for them.

While I wait for all this lot I have 2 of the 3 engine mounts to replace/repair on the engine cases. Going to try Lumiweld. Looks like it actually works and has been around for years.
Those done I can re-assemble the engine and get it in the bare frame.
It was a bugger to get out, nearly as bad as my Honda CB175 was.

[911hillclimber]

Took the case halves to be welded today to restore the missing/broken-off mounting lugs.
£30 later and they were all welded ready to be flattened and drilled to the correct positions for the frame mounts.

All done and to my mind a job well done! I must have been in a good mood!!





Decided to look at restoring the carb's piston slide using a piece of cold drawn, thick walled tube, 19mm diameter. The outside is 19mm so after a light polish it slides in the body of the carb nicely.
Next is the machining of the piston to a round and reduced to fit the inside diameter of the new tube.
Not finished as I need to take VERY light cuts as it is very hard to hold the part and turn it.
I'm using the true hole for the floating needle (1/8" dia!) mounted on a new drill shank to hold it central....wish me luck.

[911hillclimber]

So pleased to say the piston is restored and slides well in the carb's body!
My 1937 lathe can still do a good job!
Not shown, but also made the carb/head spacer sleeve from solid nylon which was quite a tricky thing as the wall thickness is 1mm...
Waiting now for the paper sheet to arrive for the engine gaskets to be made and I can re-build the engine.

[smallspeed]

Awesome

[Ashley James]

Splendid work and fun even to this spectator.

[911hillclimber]

Thank you both.
My humble Drummond 4" lathe was made in 1937 I think, and is a wonderful little thing to control.
Not exactly a Myford Super 7 but a cracker.
Doing the piston restoration on the carb typifies what I wanted in this project.
So much better than buying parts, not that I can as none are available. I have really enjoyed sorting it out.
DIY is best!

The restoration cost me £3

The lathe came from an old school garage in Cumbria. Bet it has done lots of similar work in all its 70 years.