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

[Terrotmt1]

Thank you as ever Colin.
The plug is vertical on this engine, makes things easier.
I use the end of an artists paint brush, about 100mm long. Any longer and the upper end hits the underside of the tank.
It is about 6mm dia and I have 2mm marks along its length.
Poke the length into the combustion chamber and turn the crank until tdc is 'found' best as I can and note the graduation against the land the plug seals to.
Back off the crank by 5mm by using the graduations.
Repeat a million times to average things out!
Place the mag cover on the crank taper so care fully and align the marks, then lightly tap it on and then nip the nut up.
Re check again.
Tighten the nut.

Rotate the mag housing so you can see the points through the small window and that the heel is on the raised cam area.
Set the points to 0.4mm gap which I could only just reach before polishing the points, now best I can get is 0.5mm, hence remove the adjuster screw today which will give me total adjustment from zero to 1mm.

Is there anything wrong with this method?

I had thought to loosely put the flywheel in place, nut just finger tight and rotate to get to the points and adjust.
Then go through the 5mm btdc routine.
Re check again.

[The Artful Bodger]

Usually if the timing is near enough (within reason) things will run, as I said before, too far advanced can be an issue for starting. With small two strokes "fine tuning" the timing will make a difference on the road, I have a short test run route involving uphill and downhill in varying degrees. With the Bantams I rode them over this run altering the timing a little at a time until I had the best all round performance. OTT? At 6 ft. 2
 and 15 stone every fraction of a horse power gained makes a difference on a 125 Bantam! Remember the fuel we're now burning is somewhat different from what was available in the '50s so it makes sense that the original settings for the engine could be slightly different than required now.
  Yours will start if the timing is near enough so don't get overly concerned, finding the fault is the issue for you. Without actually seeing it in the flesh it's really hard to advise, someone with experience with older two strokes might well figure it out pretty quickly........ Then again maybe not??
  If you're somewhere near Essex I could have a look for you but I have limited mobility right now with my broken knee, managing to do a little in the workshop even on crutches though.
Colin
 

[Terrotmt1]

Thank you for your offer, but I'm up in the West Midlands.

Put it all back together, set the points as close as I could to 0.4mm, set the flywheel to 5mm btdc.

Big Chinese carb on, started straight way first kick, just like those bikes on You tube in France.

Removed the carb and fitted the original. Nothing, not a pop or a bang.
Refitted the big carb and inadvertently miss assembled the throttle piston so it was wide open. Kicked it a few times and it started and revvvvvvved it's whatsits off.
Got hot and a lot of the smoke disappeared from the exhaust.

Killed the engine by opening the choke which killed it.
It revved and ran really well for about a minute, seemed an hour.

Let it cool a bit and now refuses to start at all, absolutely nothing.

Decided to tidy the garage up and now focus on my real hobby, hillclimbing my Lola-Porsche race car. First race is on 31 March.
My race car engine is complex, full of adjustment yet I can do everything to it and it works.

This bloody French 2 stroke is beyond me.

[mini-me]

I blame Brexit and Macroneroon.

[The Artful Bodger]

Don't let it beat ya! Thinking logically................. You sorted out the points, re-timed it and it started right away?? Two things occur to me, 1 is the amount of fuel in the crankcase had evaporated to a point where it was ready to run? However my inclination would be to look at the points again. It was running, then running hard so........ Perhaps the points, timing have moved? or if there's a problem with the condenser it wouldn't take long for the points face to get burnt putting you straight back to square one as soon as the engine ran for a short while.
  As a point of interest which might or might not have any bearing. The wico pacy mag. on the D1 Bantams originally had a physically large condenser which you just can't buy anymore, the current ones for sale are about half the original size although they're rated the same. I kill condensers on one of my Bantams.
  My electrical knowledge is limited to say the least but I've formed a theory and a bit of trial and error seems to confirm this. When I first bought my GPO Bantam and got it running I came to the conclusion that it was dangerous to be on the road, at least with 6,2" and 15 stone of me on it. The performance was so slow, especially on any sort of incline, that I had a line of cars behind me all itching to get past. But I loved the look of the bike so decided to do some tuning on it to get a bit more "get up and go"
  Happy days! It's now capable of not being a hazard on the road and I've been using it for 6 years or so, even commuting to work on it some days. But............ The tuning means it revs much more freely and basically when I ride it there are only two throttle positions, on or off.
  My theory with killing condensers is since I'm almost constantly revving the nuts off it the HT coil is over generating and killing the condenser, remember the ones available are only half the size of the originals. I'm thinking they're kind of like a battery, think of an AA battery and a D battery. Both 1.5 volts but one with a much larger capacity, a re-chargeable D battery would stand a much higher input charge than the AA battery.
  A condenser is just two sheets of aluminium foil rolled around each other with an insulating sheet in between them, double the size of the condenser means double the size of the sheets of alli. therefore more able to absorb a higher current flow from the magneto. To test this theory I tried all kinds of different capacitors of the same value but ultimately they all failed. Then I tried two condensers and hey presto it's been fine ever since!
  I have a friend locally who's getting a bit old and doddery, he also has a D1 GPO Bantam which is more an ornament than a rider. Last year we took this and his B 175 down for MOT's booked one after the other. I had fitted a new condenser and points in the D! about a week before and apart from a quick blast up the road the MOT was the first run since fitting them.
  He rides very slowly and cautiously and stalled it at a busy roundabout and couldn't get it started. We swapped bikes and I got the D1 going first good kick, then thrashed it the last 4 miles to the MOT shop. I mean thrashed it! Since he was on the 175 he could keep up.
  About a mile from the shop it started missing and popping, we made it and got the MOT's but I had to take the points out and file them to get it home, about a mile from home it started missing and popping again.
  Basically the new points and condenser lasted about 5 miles. Did he stall it because the condenser was failing after a couple of miles? For me it started straight away and rode off fine for a few miles, or did my thrashing it cause the condenser to fail?
  Condensers are far more important for magneto's than battery coil ignition systems. Battery systems have the power from the battery to create a spark so the condenser is more to stop a fat spark at the points from burning the faces. Magneto's generate only a small amount of power to create a spark, there's a resonance between the coil and condenser which supplies a little more power to the coil to produce a better spark. So with a magneto the condenser is performing 2 tasks one as a spark booster and the other to stop the points face from burning.
  You had starting problems, changed the points face for nice new ones and the engine ran straight away. It revved it's nuts off and now it won't start, maybe I'm biased with the problems I've had with Bantam magnetos, specifically condensers, but........... Taking the points out again and examining the faces might give you a clue, there shouldn't be much going on with the points faces with only such a short running time. If there is anything then suspect the condenser.
  Unfortunately your swapping around with carbs. is further complicating things as none of them are really a known quantity, although you seem to have one which is basically working. However I can't help but think your starting issues are more ignition based.
  Sorry for once again writing a novel, I have too much time sitting around right now with the knee!

Colin

[Rex]

But modern capacitors ("condensors") will be much more efficient than the ones from the 1950s and items which have been hanging around for possibly years in a shop. They degrade whether used or not. Was the plug still sparking after the engine ran and then stopped?
Points burn with a failing capacitor but the engine should run for longer than a couple of minutes even if the capacitor wasn't fitted.
Without physically checking over this bike it's hard to see what the problem might be, but as the ignition set-up has been tested tried and tried again I would think the fault would be on the fuel side.
Simple basic transport like this doesn't need in-depth and precise settings to run in some shape or form, though I reckon the carb-swapping isn't helping.

[Terrotmt1]

Thank you both for trying to sort this thing out for me.
I'm not one to give up, but having a day off from the Thing.

I have a nice new 6V condenser, much smaller in length and a little different in diameter, so will pop the flywheel off and fit it though it is 'waist' mounted and I need a 'base' mount so as ever, so messing about first..

To explain the 3 carbs:
The original AMAC. 903-165 has been cleaned and cleaned again and again with all the holes and drillings open. Some French Mechanic had adjusted the piston by filing it oval so it looked barrel shaped. I have machined a new brass sleeve to restore it back to a cylinder and it slide nicely. The needle mounting to the piston is a bit micky mouse due to the same butchery to the needle...
I would have hoped the bike would start with it. The float gives fuel exactly to the top of the main jet tube where the needle enters the tube. All a bit like a car SU carb.

That engine never ran or popped with that carb. That was October last year.

I bought off ebay a little carb for small 2 stroke bicycle conversion engine, 50 to 80cc 'range', beautifully made for £8. That one never worked either.

Decided to get a larger Chinese carb which has a 19mm dia choke size, the original is 16.5mm. This is the only carb that has had the engine running. I have no idea of the size of the jets etc but it is sold for 100/125cc engines. It has a modern choke, again very nicely made.

The other day after it started on the big carb, I tried the original just to see if it would work, but nothing.

Just tried the bike/big carb again this morning, nothing.

I have noticed on kick starting the bike initially, you can feel a distinct compression, then after several kicks the compression seems to change, it goes 'softer' and each turn over is far less distinct.

[iansoady]

I have just read through part of this fascinating saga......

Surely the key is in post 107 when you say it started and ran well on the Chinese carb. This to me proves that the carb is where your problem lies.....

[Terrotmt1]

I wish it was a 'fascinating sage' to me! A really frustrating PITA for me.

Just come in from a battle with a German leaf blower machine. Cannot believe the terrible design and production engineering, Really Not Very Good.
So, in a bit of a mood and have left the back until later...

I asked Villiers Services about the original carb.
Their suggestion was to replace it with a Villiers carb!

However:

Every now and then the bike starts, only with the Big Chinese carb, and after I stop it (just close the throttle twist grip) it will not re-start, ever, in the same day, even the same week.
When it is running, it is rich, and I feel the jets are simply too big. The drillings in the original carb are very small.
When it is running the engine responds well to the twist grip (for a 2 stroke and in comparison to my Lambretta) and as I found out when the throttle was wide open will rev like a Formula 1 car.

So, if the thing will not start or even show a glimmer of a bang I presume the mixture is way off 14:1.
When it is just right it starts (lottery) and runs well though a bit smoky (maybe too much oil in the petrol) but far more smoky than my Lambretta was.
Thus the condenser, the plug, the points, the timing must be right for combustion and throttling to be sustained for several minutes?

If the basic components were suspect or intermittent then it would not run?

It has never immediately re-started after a period of running. It can be days before it starts, which leads to the idea the crank case get flooded with petrol

So, I bought a used Villiers carb, and it is in great condition. It is a V648C mono block
I've cleaned it and poked some of the holes and now need to turn an adaptor to fit it to the engine stub inlet pipe. It weighs a ton and will just squeeze into the space by the engine.
The throttle cable arrangement is very different but I can cobble something together to test it on the bike.

This is the engine with the big Chinese carb. The Enfield filter is a poor attempt to 'hide' the carb.



And the engine with the Original carb



And off Google, the Villiers carb:

https://www.picclickimg.com/d/l400/pict/112438475682_/villiers-carburettor-v648c.jpg

[Rex]

Can't you knock up an adaptor and temporarily fit the carb off the Lambretta? Looks lie you've got the space there.

[Terrotmt1]

The Lambretta was sold a few years ago and had a Dellorto about the right size and I still have a rough one to try for space.
The 'bretta carb is unusual in design, and I dismissed it last year due to the throttle and choke systems, but they are easy to get so a viable idea.

Any comments on trying the Villiers carb?

[Rex]

It was more about fitting a known working carb than a comment on Villiers carbs in general.
There's millions of Jimmys and Fanny-B's that worked fine with them!

[Terrotmt1]

I'll rig-up the Villiers as the Dellorto I have is a bit knackerd!
It might even fix the problem, but I see you can get different jets for them (etc) which could work out well if it works.

[Terrotmt1]

Turned up an adaptor to fit the Villiers carb on but without any throttle cable for now.
With the piston about 2mm up from closed, and a million hard kick starts nothing happened.

With 4 carbs on the bench I doubt this issue is a fuel one.

Next up is to fit the new condenser, and check the points again, re-gap if required, re set the flywheel to the crank yet again.
If this fails then I am at a loss what to do next except seek professional vintage 2 stroke specialist help and spend more money, good after bad I fear.
I have yet to find anyone in the UK who will/can test and fix one of these magnetos.

Anyone know of a 'good man' for engines such as this?
I might ask Villiers Services if they will spend a few hours on it. They rebuild engines etc but I think they only do Villiers.

This is mad.

[chaterlea25]

Hi

re set the flywheel to the crank yet again.

Maybe I am misunderstanding the above?
The flywheel position needs to be set with regard to the piston position
I would aim for less advance than you have been setting at 2-3mm points just opening
Points gap is not critical but the position of the magnets on the poles of the ignition coil when the points just open
is, (as already mentioned)
You can experiment with various settings and set up a spark gap from plug lead to frame/engine to see where the strongest spark occurs

a million hard kick starts nothing happened.

I have started reluctant engines by using an electric drill with a socket adaptor that fits the flywheel nut
(provided it doesn't undo the nut  )

John