Author Topic: Terrot MT 1, 100cc 2 stroke: non-starter!  (Read 158279 times)

Offline The Artful Bodger

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #90 on: March 16, 2018, 11:46:23 AM »
You've kind of shot yourself in the foot here? If the crankcase is flooded you have an excess of petrol, therefore putting more petrol down the plug hole is putting you back to square one. If you plug is wet when you take it out then putting extra fuel into the equation is a non starter (pun intended!).
 What you need to do is dry the engine out, hence the dozen kicks to blow the excess out of the plug hole. With the plug replaced you need to use no choke and a good twist of throttle to get extra air into the engine to offset the excess petrol. Putting a wet rag over the inlet is once again making things worse.
 As already suggested any plug will work as a short term replacement just to get it started, I've even used long reach plugs in a short reach head half screwed in just to get it banging.
  As already suggested using a battery coil will bypass 90% of the mag, the only parts still in use will be the points and condenser. Also a battery coil will give a much fatter spark at whatever speed the engine is turned over at.
  If I was looking at this I would start by removing the points and have a look at the faces, anything less than perfect I would clean the faces with an oil stone, the wipe them with de-greaser. If the points faces are anything but a silver colour I would look at either oil contamination or a faulty condenser. You describe poor oil seals hence the possible oil contamination, I just put new bearings in one of my Bantams as the timing side main had play in it and was allowing oil to foul the points. Every ride I got about 10 miles before it started missing and I had to clean the points, this was more than just a wipe with a rag as the oil caused the points faces to burn.
  If there's no oil there but the points faces are blue, purple or black (any slight discoloration) then the condenser has failed. Never assume that fitting a new condenser takes it out of the equation! I have a box of brand new in the packets condensers for various '70's - '80's cars and had to go through 6 before I found one that would hold a charge. They fail with age even still in their packages.
  By using a battery coil with the points cleaned any ignition issues will be bypassed, as has already been suggested. Even if the condenser is shot the engine will still run until the points face gets burned, this is not the case using a magneto coil. Magnetos work differently and there needs to be a resonance between the coil and condenser during the spark to produce enough energy for a good bang.
  A 6V or 12V coil wired independently from the bikes electrics (with clean points) will test the ignition for you. Use a suitable battery for the coil's voltage with the negative going to the engine as earth. The positive goes to one side of the coil and a wire from the other side of the coil goes to the points. For a short test it doesn't matter which way the positive and negative are wired to the coil.
  So the points will have the coil wire and the condenser connected to them, now you will have a good spark to try with. I have played around with Bantams for years now and have found several magneto problems they suffer from, several of these faults will give a good spark but the engine won't start. Two of these are; the main shaft of the crank has turned slightly in the crank web (this is very common on Bantams) so now when the ignition is timed up the magnets in the magneto are not in the correct position to produce the maximum generation of electrickery to create a spark from the coil. Kicking the bike over with the plug out gives a false impression of a good spark as the engine is spinning so fast with the plug out that the mag can generate a spark at the plug. As soon as the engine has compression and turns over much slower there is no spark inside the engine. This can sometimes be compensated for by altering the points gap to get the timing nearer the correct magnet position at the time of firing. There's other methods with a Bantam but I won't go into detail here.
  The second one is if the timing is too far advanced. An engine will, and indeed, wants to start with the timing retarded, still BTDC but more retarded than the best running position. Most small two strokes have fixed timing, ie. no manual or auto advance as the revs build up. This means the timing gets set in a compromise position.
  Too far advanced and they just won't start, however if you manage to get it going on a bump start you will notice the engine has more pull and top end. Too far retarded (without getting silly about it) and it will start really easily but lack power, go a little further with retarding it and you could heat seize it as it will run hot when reving.
  Flywheel magnetos can be fussy and everything wants to be "just right", some are fussier than others. They can be not quite "just right" and one day will seem to work fine and the next give nothing but trouble despite nothing being altered, bad starting is the main "show" of a not quite right magneto. Don't get me wrong I love magnetos, but I've had to spend a lot of time messing with them to learn their foibles! Battery coil ignition is a lot less fussy, I would be running it on my Bantams but the charging coils on a D1 don't produce enough electrickery to run a coil and the lights. I did fit later charging coils to one of them and this worked fine but I changed back to a magneto coil after several flat battery issues.
  Remember if you have magneto trouble the engine will become flooded since fuel is going in but not getting burnt, so you now have a double issue to sort out. Remember this if you try a battery coil as it might not work straight away due to the flooding. At least if it runs on a battery coil you will know where to start looking for your problem, I have a small 6V one I keep purely for mag. testing.
 If nothing else the length of this post might put you to sleep so you can wake up refreshed and ready to have another go?

Colin
 
1926 Magnat Debon, 1953 Bantam, 1955 Ariel Huntmaster, 1961 GPO Bantam, 1979 GS 850, 2001 Burgman 400, 2004 Burgman 650

Offline Terrotmt1

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #91 on: March 16, 2018, 02:07:58 PM »
Thank you very much for taking so much time to help me.

I'm getting nowhere at the moment, now time to start again.
The engine is dead, and shows no life at all.
I can re set the magneto to 6mm btdc or maybe 8mm to see if something happens.

I don't have the parts to try all these things, you cannot get points for this engine anywhere and such like.
I'll pull the mag out and have it checked at Villier Services
Maybe I can use Lucas points to repair the French ones.

Final option is to sell as a non runner just to be rid of the frustration and move on.
Again, thank you for your help.


Offline mini-me

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #92 on: March 16, 2018, 04:33:31 PM »
final offer, £125.

Non starter no problem, I'll get it running. :o

Offline mini-me

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #93 on: March 16, 2018, 04:36:50 PM »

Constant fiddling with ignition timing is a waste of time. If it won't start on 6mm it won't start on 8 or whatever,

the french spec sheet says 5mm but I think you are barking up the wrong tree,also it might take days not over night for the excess fuel in the sump to evaporate.
I'll drill and tap crankcase  for a small drain plug after I take delivery of it.

replacement points for magneto france on ebay.fr......253433399224

chambrier has three different sets on offer

macadam deux roues has two sets. and one complete volant magnetique NOS 90€

anyhow ,cash waiting
« Last Edit: March 16, 2018, 05:06:20 PM by mini-me »

Offline mini-me

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #94 on: March 16, 2018, 05:08:09 PM »
even more here


ttps://www.pieceallumage.fr/equipement-france-morel-b1540.html

Offline Terrotmt1

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #95 on: March 16, 2018, 05:59:56 PM »
Ah, been looking at that lot this afternoon.

The Mag is made by Magneto France, model 18/2S.
The CB sets on those sites are nothing like the set in the Mag, but the riveted point replacements look good as those will be the perished parts, so thank you for all info esp those parts.(NOW PURCHASED)

Here is a pic of the points on this bike:

« Last Edit: March 16, 2018, 06:05:16 PM by Terrotmt1 »

Offline mini-me

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #96 on: March 16, 2018, 09:25:13 PM »
Bon chance is all I can say now.

After looking at some of the french pages I am wondering if, although there is a spark, and you think you have timed it correctly is there any chance the actual flywheel is not opposite handed?

I see the NOS one for sale is for a left hand rotation, and another page makes mention of the direction of rotation for these bikes as "gauche"; so it would seem there are RH versions?

do you know if this bike was run by previous owner at all?  was the french owner glad to see the back of it?

don't ask me how to determine which is which.

« Last Edit: March 16, 2018, 09:53:26 PM by mini-me »

Offline mini-me

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #97 on: March 16, 2018, 09:59:03 PM »
this  magazine carries the only kind of workshop manual the french had at that time.

https://www.ebay.fr/itm/Revue-Technique-Motocycliste-N-60-Annee-1953-Salon-de-bruxelles-essai-TWN/252673723698?hash=item3ad4870d32:g:lzgAAOSwzJ5XX7Xk

page 29 et seq covers MT1, they are quite good articles.

Offline Terrotmt1

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #98 on: March 16, 2018, 10:19:26 PM »
The bike was rust free and very original, the engine I feel had been taken out and cleaned.
The box was oil dry, the rings stuck in their grooves with carbon and the head and piston crown had a good carbon coating, so not a complete job..

The flywheel was on almost impossibly tight to pull off so doubt it had been removed.
There were no renewed parts on the bike inc the tyres and tubes.
Even the headlamp bulb is original as much as I can tell.

Viewed from the flywheel side, the engine works counter clockwise, there is no marking for rotation, so I think it is the original mag etc inc the points and condenser.

Offline Terrotmt1

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #99 on: March 18, 2018, 02:03:33 PM »
Magneto out and stripped the points down.
The lead from the coil was rimpy, so replaced that. So cold in the garage I had to pre heat the brass block which has the new lead soldered to it as the soldering iron quenched in seconds..

Cleaned the points to a good shiny surface and re assembled.
I can't get the gap to less than 30 thou now....
Going to leave it at that and see what happens.

Before putting it all back together will test the coils as much as I can.
There are a few video clips on YouTube to help me.
Need to scour the internet for resistance values etc.

Offline The Artful Bodger

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #100 on: March 18, 2018, 06:39:43 PM »
One thing to bear in mind as I mention in my previous post. Altering the points gap will both alter the timing and the timing of the magnets in relation to the stator fingers. You might be able to time the engine to BTDC correctly if you have enough timing adjustment, however beware of the magnets not being in the correct position when the points open to produce enough electrickery for a good spark.
  One way of testing you have enough spark to run the engine is to leave a plug in the 'ole to have compression and another resting on the head with the HT lead to test the spark. Kicking over the engine with the compression has you turning the engine over at normal kick over speed which is much slower than kicking it over with no plug in the hole.
  This magnet alignment has another issue which I learnt about the hard way. Since the crankshaft has moved on one of my Bantams I figured I'd be clever and take the key way out of the flywheel and alter the flywheel position to get the correct magnet position. To find the best magnet position I pushed the kick start by hand watching the spark, then altered the flywheel position a few degrees at a time until I found the position where I had the best spark at the lowest possible engine turning over speed.
  Sure enough at normal the kick over speed I had a monster spark and the engine started really easily. However going down the road it was missing and popping as soon as the revs got up. It turns out there's a magnetic curve which alters the magnetic flux the faster the magneto's turning. This curve means that at higher revs the magnets effectively went out of alignment with the stator fingers  loosing the ability to create a good spark.
  I had to change the position of the flywheel a few degrees to get a reasonable spark for starting and still have one at higher revs. Many small two stroke engines run with no points and condenser, they use a small unit which senses when the magnetic flux is at maximum and cause the coil to spark. With most chainsaws etc. this unit is part of the coil, you can buy the separate units off eBay to use to replace the points and condensers on magnetos. Unfortunately they don't work with multi magnet magnetos, ie the type with charging coils, only magnetos which have the HT coil.
  It's possible to use them with multi magnet magnetos but the points need to be retained for the HT spark, they will stop most of the burning of the points face though. One of these is marketed as the "Rooster Booster" and sold for Bantams (the bikes, not the chickens) but myself and others have had mixed results with them.
  Anyway enough waffle, just a warning due to your larger points gap now.
Colin
1926 Magnat Debon, 1953 Bantam, 1955 Ariel Huntmaster, 1961 GPO Bantam, 1979 GS 850, 2001 Burgman 400, 2004 Burgman 650

Offline Terrotmt1

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #101 on: March 18, 2018, 10:14:35 PM »
Food for thought!

I can get the factory spec of 0.4mm on the points by removing the eccentric adjusting screw and move things until I get th gap and tighten.
Thought about that doing the washing up!

The crank and flywheel have no keyway so you can set the flywheel timing absolutely anywhere.
There are timing Mark to b aligned when the engine is 5mm btdc.
I have wondered my the engine has no mechanical registration, and that in production the factory can't have spent ages getting everything aligned, they would need to slap them together pdq to keep costs down.
Thus this engine should be easy and quick to get in a running order?

The Terrot owners in France say turn the crank to tdc and then rotate back 5mm using a probe resting on the crown of the piston. It is very easy to do, but judging actual tdc is hit and miss so that 5mm could be +/_ 2 mm.....

Hope to get it all back together tomorrow and try again.

Offline Rex

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #102 on: March 18, 2018, 10:18:49 PM »
You should get some signs of life even at 2mm + or -.
Can you not determine TDC by using the time -honoured "bolt down the plug  hole and degree disc" method?
Google should bring it up...too late for one-fingered typing a missive at this time of night!

Offline Terrotmt1

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #103 on: March 18, 2018, 11:09:58 PM »
The big and little end bearing could be better on this engine, the tdc is more a wide plateau than a precise point...

On my 62 Lambretta you could index the mag stator round to get exact timing which was by degrees rather than piston travel. Here the stator is in a fixed position which is why I guess the flywheel is not keyed to the crank.

Offline The Artful Bodger

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Re: Terrot MT 1, 100cc 2 stroke: non-starter!
« Reply #104 on: March 19, 2018, 12:09:19 AM »
To post pictures on forums these days I do them through my own website, however my son does all my web site stuff for me and right now he's in Austria. So I'll try to describe a simple tool I made for timing engines from the piston.
  I used a length of welding rod (wire coat hanger etc. would be fine) , one end I hammered and filed to resemble a small screw diver but with a working edge sharp like a wood chisel.
  Around 3/4" from this chisel end I bent the wire with a sharp bend at a right angle so the flattened end is at a right angle to the wire. Basically an L with the chisel end being the shorter bit and around 8" on the long bit. Putting another piece of wire down the plug hole with the piston near enough at TDC I used this wire to measure from the top of the piston to around half way up the nearest cooling fin on the top of the head.
  Using this measurement I marked the long side of the L from the right angle bend and bent the wire 180 deg. totally back on itself so the wire is now like a double barrel shot gun with the 180 deg. bend at one end and the chisel end sticking out at a right angle.
  The idea is that the 180 deg. bend end sits on the piston crown, the chisel edge will be able to scratch a mark sideways on the cooling fin about half way up the fin. The excess long side of the wire is bent at a right angle well clear of the plug hole to act as a handle in use. Any excess can be cut off.
  You now put the tool in the plug hole with the chisel end resting against the fin and rock the flywheel back and forth until the highest point is observed, there are always a few degrees of crank turning at which the piston doesn't appear to move. Now use the chisel end to make a small but clear scratch on the fin. Remove the tool and now measure whatever the timing height is (5mm - 6mm whatever) below the TDC mark and make another scratch.
  On my Ariel the plug holes are angled outwards, on my Bantams they are angled backwards, but because you only have the thickness of the doubled wire, the plug holes have enough diameter for the tool to stand up vertically from the piston meaning any measurement is accurately the vertical piston movement.
   I always time engines by starting before TDC and turn the crank the until I see the points start to open, the old fag paper trick works pretty well. A gentle pull on a small strip of fag paper clamped between the points face, as soon as the paper starts to pull out you know the points are just opening. I then put the tool down the plug hole and see if the chisel edge is in line with the timing mark, if not then make an adjustment and try again.
  I time engines by turning the crank in the direction of travel rather than turning the engine backwards to the timing point so that any backlash in the timing gears, timing chain, advance-retard etc. is taken up in the same way it would be with the engine running. Not that this is an issue with your mag, just a handy way to learn to do it for when it does matter.
  This tool takes less than 5 mins. to make, every one of my classic bikes has two small scratches on a cooling fin and their own piece of wire in their tool box. As we all know pattern parts vary in quality greatly, so whenever I fit a new (or cleaned) set of points, as well as gaping the points I whip the plug out and check the timing as well. A slight difference in several parts of the points will alter the timing.
  Remember though, this times up the firing, it does not time the magnets to create the spark!
 
Colin
 
« Last Edit: March 19, 2018, 12:11:08 AM by The Artful Bodger »
1926 Magnat Debon, 1953 Bantam, 1955 Ariel Huntmaster, 1961 GPO Bantam, 1979 GS 850, 2001 Burgman 400, 2004 Burgman 650