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

[Terrotmt1]

Thank you for the reply.

The original has a plastic sleeve and a 360 deg clamping ring and is tight on the inlet which is a direct spigot cost into the cylinder, but I will add grease to fill any small gaps and try again.
The large Chinese carb (Delorto copy) is jetted for something, not sure what, but was a cheap (£12) experiment to see if the carb was the issue to non-starting.
It proved to be so.

The original AMAC 903/165 carb is very simple, hard to see why it does not work which adds to the frustration.

I have emailed AMAL to see if they sell a new 'equivalent' carb to the AMAC. I'm not hopeful though...

[Terrotmt1]

AMAL do not make a carb this small, so dead end there.

Put the original carb on and raised the needle to the max position, hand kicked it over a few times and it almost fired continuously (!), one of those 'so close-so far' feelings.
But, the first time this carb has shown any interest in running, so some progress.

Raising the needle increases the mixture for a given throttle position, so will try some tinkering about later.

I guess the way to kill a running engine with this carb is to close the twist grip and the point of the needle bottoms out on the main jet, so killing the fuel supply, hence needing the throttle a bit open to get it to run.
Any suggestions as to how high the slider needs to be for 'tick-over' position?
1 or 2 or more mm??

Trying to find a starting position.

[Terrotmt1]

After a lot of trying and changing choke and throttle position the bike started. (big Chinese Carb on).
Even odder it responded to opening and closing the twist grip and ran for a good minute or longer. First time this has happened!

The engine got really hot, disconcertingly so with the down pipe a dull purple!

I stopped the engine.

This might signify the carb is far too weak.
IIRC when a 2 stroke down tube starts to colour it is too weak.
If this is so, then maybe this is why it is so hard to start?

It would not re-start after cooling down...

Found another carb on ebay.fr but for 125 Euro. Looks like it has been in a shed for a long time, but I need to progress somehow!

[chaterlea25]

Hi
Wrongly timed ignition will cause overheating very rapidly
I would aim for points just opening 2-3mm before top dead centre
Have you checked this already??

John

[Terrotmt1]

Just had the same 'conversation' on another forum about this bike, thanks for your response.

The Terror spec is 5mm BTDC, about 28 deg btdc. It is measured/set by locating tdc and winding the engine back until the piston drops 5mm, that is the factory method.

I tried 2mm btdc but that was before re-magnetising the magneto flywheel.

I will pop the flywheel off and re-set at 2mm btdc, about 14 deg.

The heating was rapid and quite disconcerting, certainly cured the heat resistant paint on the cylinder head...

Can't get to the bike until Wednesday, so will re-set to 2mm and try again.

With the  timing at 5mm and if too advanced, wouldn't the engine kick back when trying to kick start it?

Fingers and spanners crossed!

[chaterlea25]

HI,
2-3mm was just a base line figure to see if the bike runs
if 5mm is the book figure stick with that
If the timing was retarded, ie after TDC then unburned fuel continues to ignite in the exhaust system causing
the pipes to discolour or even glow red hot
Its best to go turn the engine back more than the book figure then rotate it in the running direction to the desired figure
Fresh paint can deceive as it cures giving off smoke and fumes giving the impression of lots of heat 

John

[Terrotmt1]

Take your points.
Modern 2 strokes seem to run 2mm btdc.
If I run it at 2mm then if anything the spark arrives a bit late and the piston is on it's way down before the combustion.
5mm is to allow time to get the spark through the magneto and to the plug 'just' after tdc, more power per stroke.

At this point in time I'm looking for an easier start and a reliable one too cold or hot. Right now at 5mm is is luck it runs.

The head smoked which I expected, but the mild steel unpainted (natural steel finish) turned dark purple (450 deg C?) inside of a minute, for a length of about 150mm from the pipe retaining collar which was unpainted and certainly dark blue in that time.
30 secs later (ie 1.5 mins of tick over and rev up/down action) it worried me to a point I thought the engine might seize, so I killed the engine by closing the throttle completely.

If it won't start readily at 5mm then 7mm would be worse?

[chaterlea25]

Hi,
With a flywheel magneto the "window" to get a good spark is quite narrow
The points need to just break when the magnets are evenly sat over the coil pole pieces
So in reality the magnets, piston and points position in relation to each other is fairly critical
The points opening position is more important than the fully open gap (in most cases) depending on the limitations of the points adjustment design
In my youth I struggled with various 2 stroke engines, even to resorting to converting to battery and coil in a bid to get good running

John

[Terrotmt1]

In later years a battery version of the bike was the norm!
This little Terrot is a touch crude, or minimalistic to be kinder...

[murdo]

Most two strokes I've had anything to do with start (but not always run) better with a bit more advance. I would be putting it to what the manual says and try that.

[Terrotmt1]

The engine is at 5mm btdc as per the info I can find.
Tic is very vague, bit of play in the rod bearings.
I will drop the piston by 10mm btdc and come up so taking the back lash out of it I hope.

I need to make some progress, I have something wrong here, but it is nearly right.

In one data page they time the engine at 5mm or 28 degrees.
I timed my Lambretta with a protractor.
If I can get a true tic if the crank, I can set the crank back 28 deg easy.
Trouble is getting a true tdc!

[chaterlea25]

Hi,
To get true TDC make up a piston stop tool
I have made several and keep each one for different bike engines I set and lock them to the before TDC figure after setting up the protractor (degree disc)
This means all I have to do the next time to check the timing is screw in the tool
If you make one from an old sparkplug body and use 6mm rod, then its easy to set the desired figure as the thread pitch is 1mm.   (Of course this only works when the sparkplug is vertical with the cylinder

https://www.google.ie/search?q=piston+stop+tool&ie=utf-8&oe=utf-8&client=firefox-b&gws_rd=cr&dcr=0&ei=0hDeWbOEIJHLwALb-7kQ

John

[Terrotmt1]

Good thinking!

Spent some time on the bike today.

Tried 5 different timing positions and on 4mm the engine started after a fair bit of hand kick starting and ran quite well, certainly no massive heat up.
Stopped it and tried to restart.
Got going after a while...

Tried 2mm through to 7mm and no luck. Back to 5mm and no luck!

Thought I would check the points gap to find the points are closed.
Moreover, the heel of the points 9the plastic part) that runs on the 'cam' on the flywheel hub is suddenly badly damaged. Probably count it after replacing the flywheel.

I know there are no spares, searched before, so I need to make a new heel from delrin.
Not exactly the largest part to make by hand (and my old lathe) but needs must.

When will this ever end.

[Terrotmt1]

Before a fresh air outing in the Boxster this morning I had a go at making the plastic 'heal' for the points.
Bit of lathe, bit of drilling, bit of hacksaw, bit of filing and a bit of scraping with a razor blade and all was done in 20 mins!

Installed and could only get the points gap down to 20 thou (should be 14) but put the flywheel back on at 5mm BTDC, added fuel and swore at it (sort of John Cleese style) such is my relationship with this French Fancy.

Several dead pan kick starts, wide open throttle, 3/4 choke and it started. That is the quickest it has done it so far.
Stopped the engine by fully closing the throttle (this is how to kill the engine).

Paused for thought, and kicked it several times, and it re-started, full throttle, 3/4 choke. Stopped the engine and went out, slightly pleased.

Came back this afternoon and it did it again!
I think I'm making some progress and refining the starting technique, full throttle opening, 3/4 choke and swear at it!
If this repeats itself tomorrow, I will tidy the mounting of the carb and find a period style air filter to 'hide' the modern carb.

I will also re-fit the original carb, just in case that works....

[murdo]

Good work. Do you swear in Gallic? Might help.