Terrot MT 1, 100cc 2 stroke: non-starter!

[TGR90B]

Do we really need it all again?

[mini-me]

Don't be hard on him. read through it all again, it's better than Mogadon.

[murdo]

I applaud your persistence and would like to read of you getting it running.
If your saying the plug is wet after the short burst of firing, could the mixture be too rich and just drowning the engine?
Keep going, your nearly there.

[R]

So you have an original carb ?
What is the current status of that.

I'd comment that swapping to other carbs was/is entirely a matter of suck-it-and-see,
and makes you appreciate how well most original carb setups were set up !!
Do any of these carbs have a needle, that you can lower ?
As too much fuel suggests ...

[Terrotmt1]

Yes, the original carb was shot when I first had the bike. I made a new piston from brass and the fit is great. The body was US cleaned and then the drillings cleaned out (some were blocked) using my old BOC gas welding nozzle cleaners. I am sure it is clean.
The needle can be moved , about +/- 2mm just as the float can be.
The float is set so the fuel just starts to come over the jet tube (that the needle runs in) so there is a wet puddle in the bottom of the carb but not flooding into the engine. The intake is horizontal.

The wet plug suggests gross flooding after a short run burst so I expect the fuel air ratio to be incorrect.
However, the jets are the right numbers for the car on this bike, there is a surprising amount of info on the net if you dig really deep.

So, clean clear original carb.
Float correctly set.
Needle at half way height
Jets to factory spec

Flooding.

This might mean the internal dia of the jet tube is worn large so too much fuel will come up from the base and flood any control the needle is trying to meter?
The design of the main jet and the tube it screws into is a bit odd as there are 2 factory cross drillings that allow fuel from the float bowl to flood up the side of the needle so there is a big pool of fuel which the jet is in too.
Sorry, difficult to put into words, but all this is factory spec. so the bike was sold this way.

The carb is an AMAL/AMAC 903 design made in France under license from UK AMAL. There is a good cross-section drg of the carb on Google. AMAL UK have no understanding of this carb and have no info on it at all.

Finally, I'm sorry to re-gurgitate this thread and the same issue which annoyed some a year ago and made me stop the thread while I then wheeled the thing to the shed for about a year.

I cannot get anywhere on the French Terrot Forum, nobody likes this design of bike as it is not seen as a classic 'real' bike there, but I simply am seeking some experienced help from people who know far more than I about these things.

I did a 175 1963 Lambretta a few years ago and that ran great! similar engine but a nice Dellorto carb.

I'll try any suggestions any might have.
I feel this bike is very close to running and starting reliably, light at the end of the tunnel!

[R]

Drop the fuel level, and see what happens ?
Thats sounds too high if it was any common amal ....

[Terrotmt1]

Thank you, will try that, I think I can drop or raise the float needle about 3mm.

Off now to the Nash bike show in Stafford to find a near NOS carb for £10......

[Terrotmt1]

Well, the show was...interesting.

3 miles car queue to get in, same to buy a ticket, 1/2 hour to pass through the tunnel to the show.
4 French bikes there, no bits, coffee @£3.50, £16 in...won't bother again.

In a grump, came home to try the float level and needle level tricks.

Absolutely no difference whatever combo I tried, engine just gets flooded without any choke.
Lower crank case floods (thank goodness I put the drain bolt in there) about a thimble full of black petroil drains out and I think most gets there from a flooded combustion chamber and the fuel flowing from the carb straight into the barrel.

Knackered having kicked the thing about 100 times in all this, so I think I will just leave it outside and hope it gets nicked.

Just to shock you ALL I did actually fit another engine to the bike! A modern 50cc 4 stroke, pull start and centrifugal clutch so twist n go.
Have actually ridden the bike like this just up the road.
Suffers from a Chinese clutch, ie it doesn't fit so it has a lot of clutch slip so difficult to ride up a steep incline but the bike actually gets down the road nicely, brakes are really good.
Might work better when the clutch is bedded in?

Here it is:

[mini-me]

Oh come on,

4 French bikes there, no bits,

were you really surprised?

French stuff like yours is a very niche interest,as you say the frogs don't like them either, a hint perhaps?

Mind you it might be because you are a Brit, they  mostly dislike us and right now are having a sulk.

[Terrotmt1]

Chatted to one UK dealer who had some nice bikes and 3 classic pre '50 French bikes, all small capacity.
Told him of my Terrot and looking for a carb.
He said good luck, and the French have cottoned-on to the British taking the old stuff from dusty barns etc.

Prices have soared, the £ has shrunk so the French Thing has all but died.

Had a shower and a think.

This engine is still flooding no matter what so the actions to weaken are having no effect, so the flooding is well beyond those adjustments to control.

I can only think that the inside diameter of the nozzle/tube is far to big or worn. The piston in the carb when I first stripped it had been attacked with a file and was a great barrel shape rather than a cylinder, hence my repair.

I will strip the new Dellorto and see what the needle dia is and the nozzle diameter to determine a typical relationship between the two and compare it to the diameters in this original carb.

Maybe the inside dia of the nozzle is simply too big and fuel just floods in no matter what when the engine cycles.

Don't know what else to try. If it seems too large I can machine a thin tube to  go inside the nozzle sleeving down that diameter and maybe restoring the 'throttling' of the fuel flow according to the position of the needle taper.

That will be a task on my trusty lathe tomorrow for sure.

The needle is 2.6mm dia so maybe a 3mm hole would be right.

[mini-me]

Just fit a Villiers engine,and be done with it,

[Rex]

That'd look the part especially a 6E or similar, but there's always the engine from a CD200 if you fancy a twin, or a CG125 for a small single.
Then there's those Chinese jobbies on Ebay, Hongshu, Hongdu, something like that?
If you don't hack the frame the mod would be reversible, and at least you'd get some use out of it to recoup some of the money you're clearly spent on it.

[mini-me]

Plenty French makes used Villiers engines.
then you can sell it to some mug as "rare"

[Jean-luc]

I cannot get anywhere on the French Terrot Forum, nobody likes this design of bike as it is not seen as a classic 'real' bike there, but I simply am seeking some experienced help from people who know far more than I about these things.

Are you serious ??

Are you talking about this subject ?
https://500rgas.info/forum/viewtopic.php?f=48&t=1735&p=35100&hilit=MT1#p35100

Maybe that one ?
http://terrot.org/forum/viewtopic.php?f=1&t=19164&hilit=MT1

It's been a pleasure, trying helping you !!

When I see the way you're talking about French.
Hopefully, we are not doing the same with English .... just a question of respect

https://www.vocabulary.com/dictionary/respect

[Terrotmt1]

Jean, I did not mean any disrespect, but the help dried up and I could not get further.
I had hoped that the French enthusiasts could help being a national bike; very few here have heard of Terrot let alone an MT1.

I feel that people have lost interest, and me very soon, this problem seems un-resolvable with my understanding and what I have to use.


As to the engine swap to Villiers, the small Villiers engines are very rare or all put away by others, and I feel the frame would need to be cut to fit one. The original engine is very compact.
I looked at the Chinese Honda look-alike engines, but at £400 too much and it may not fit, too great a risk.  Doubt the brakes would survive.

Sorry for any upset.

 I'll trouble nobody further on this or any other forum.

Thank you for all the help.
Graham.