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

[mini-me]

[Terrotmt1]

Because that's how I feel as above!
Not really ready to spend ££££ with a specialist to go over the same ground, but I expect he knows a lot more than me (obviously).
Got to find a new angle on this thing.
Just do not know which way to turn, so trying to go back to basics, compression, fuel, sparks.
 

[mini-me]

But you have done that so many times already, over and over again.

It's upsetting me because I have run out of sarcasm now:o

Put a cap on it and cut your loses.  There's a boat near you needs  an  anchor.

[Rex]

I posted a while back that I thought the basic problem was a degraded flywheel magneto and suggested (as others did also) that you rigged up coil and points. I don't know why it didn't work/you didn't persevere with that set-up?

[Terrotmt1]

When I rigged the 12v battery and coil the timing was smack on at 5 mm btdc, and I tried to start the bike several times but not a single pop in many kicks.
I tried that several days, same result.

It has only run on the magneto.
Going back to basics, I am taking the mag back to Villiers Services for another check and re magnetisation if needed.

[TGR90B]

But did you check that you had a good spark?

[The Artful Bodger]

The battery / coil set up with a different plug lead and plug, completely does away with the magneto side of things except the points and condenser. If it doesn't run with this set up then taking the mag back to Villiers is a waste of time.
  So on the ignition front, using the battery coil, that only leaves the points and condenser to look at. You have fuel, either directly down the plug hole, or by the plug getting wet so it should go BANG.
  I don't know you so have no idea about your experience and knowledge, please don't think I'm being insulting to ask if the timing is 5 mm before TDC not 5 mm after TDC? although it does run on occasions which suggests otherwise. I have seen engines running after TDC and an exhaust manifold glowing like Rudolf's nose!
  Actually I do remember looking at two bikes for people in the past with a very similar problem as yours. One had a standard sized piston in a +40 bore, the other had no piston rings.  Both were bought as "should run with a little fettle-ling?? Although I thought you'd  had the engine apart? You do mention the compression, have you tried a compression tester? Remember with these the throttle must be wide open for a compression test. But............... I seem to remember you riding it a bit last year?

 Colin
 

[Terrotmt1]

Thank you as ever for the interest and suggestions about this 'issue'.

The bike with a strong 12V car battery, a good 12v coil, a new HT lead (but this was a length of heavy duty wire, not real HT lead), all other leads were new automotive loom wire, all connections were soldered, not crimped.
As I said at the time, when I connected the ground wire there was a light sparking with the points open or closed at the -ve battery terminal.
The condenser was the original one.

I turned the engine flywheel by hand until the plug sparked. The spark 'intensity' was much the same as the spark from the 6v magneto.
The timing marks on the static and flywheel parts were in line, the engine was 5mm Before TDC, points @ 0.4mm

The spec for the engine is 5mm btdc, a figure found in various Terrot handbook pages. Most 2 strokes are 2mm btdc?
Away from this set-up I have tried 10mm btdc, 5mm, 2mm and TDC.

In all cases when the engine has run it has been @ 5mm btdc.

OK, with the 12v system attached I tried to start the engine with the large Chinese carb (used because the engine last ran with it) and some mighty hard kicks, about 20. Nothing happened.
Out with the (wet) plug, clean with brake cleaner, rub the electrodes with fine W&D, tea spoon of 30:1 in the hole, fit plug pdq and kick hard, 20+ times, nothing, not a glimmer of a fire-up.

Next day, remove the 12 volt kit, remove plug, clean etc and after some hard kicking it fired and ran. I stopped the engine by closing the throttle, and after 10 seconds tried to re-start it. Nothing at all.
So, the 12V test showed the timing to be right, the plug sparking outside the engine, no combustion.
The only times this bike has run has been on the original magneto.

I have very limited 2 stroke experience, and what I have is around Lambrettas.

The engine is all original, the bore is really good, piston is standard size and a nice fit, rings are new. When I stripped the engine the rings were solid in the piston due to carbon.
There was a lot of carbon build up in the lower crank case which must be evidence of blow by.
I know I can get a new piston, I think about 0.5 and 1mm over size are available, so if I have to I can have it rebored to suit a new piston, cost would be about £150

My back ground is in mechanical engineering, new products, 5 year classic indentured apprentice, and I did my first Lambretta when I was 15.
I have built several cars, restored 6 and have raced  cars for 27 years.
I have a full bike licence, but after doing 3 hours riding on a modern 175cc bike 2 years ago I realise I don't want to ride these things due to the current breed of car drivers around here...

Thus I restore bikes for winter fun and sell them, not to make a profit, but to make room for the next one!

Below is what I normally work on, and proves I know enough to be dangerous! 



And my last 2 restorations:

[Rex]

I'm losing track of what's been done and not been done, but have you tried substituting the capacitor (as you call it the "condenser")? You could always just disconnect it to try the engine, it won't matter in the short term.
It seems to be the one component common to the mag and battery+coil set-ups.

[Terrotmt1]

I almost feel the Same!
The capacitor is the original. Easy to disconnect and see what happens.
I'll try anything.
I have a new substitute which needs a different mounting tab to use.
Neworiginalones Ive never found.

If it was broken, what effect would that have in the short term?
It stops erosion of the point's contacts and not much else?

[cardan]

The engine is all original, the bore is really good, piston is standard size and a nice fit, rings are new. When I stripped the engine the rings were solid in the piston due to carbon. There was a lot of carbon build up in the lower crank case which must be evidence of blow by.

Very hard to contribute on issues like this from a distance, but since it's getting desperate...

1. Re the bore, how do you define "really good"? Wear in a two-stroke bore is often not just at the top (as it is on a 4-stroke), but also just above and just below the ports. This is hard to measure, but on a little bike like this one even 0.005" wear in the wrong spot might correspond to "worn out". A worn out 2-stroke is hard to start - possibly why the bike was put into retirement? Certainly carbon in the crankcase sounds pretty grim. New rings won't help with wear near the ports because the bore here is no longer circular. The bore can be good at the top, and good at the bottom, but if it's worn out around the ports, the cylinder will need a rebore.

2. Replace the condenser.

Good luck.

Leon

[chaterlea25]

Hi Terrot,

The timing marks on the static and flywheel parts were in line, the engine was 5mm Before TDC, points @ 0.4mm

This is incorrect!
At 5mmbefore TDC the points should be just separating not .4mm which will be the maximum gap later in the rotation

If it was broken, what effect would that have in the short term?
It stops erosion of the point's contacts and not much else?

The capacitor or condenser is critical to ignition,
It absorbs the current from the collapsing magnetic field in the coil core, This prevents arcing on the points
If the points arc the current continues to flow through the arc, so the magnetic collapse time is longer and the transformer effect in the coil is lessened to a detrimental degree

Old condensers or capacitors degrade with time , so a NOS one is not a good idea,
If a new capacitor will not fit inside the flywheel , simply run a wire from the points connection to outside and fit it somewhere convenient,
A lot of modern replacement condensers are poor quality
have a read here
http://www.distributordoctor.com/distributor_condensers.htm

and here
http://www.nonlintec.com/sprite/cap_failure/

John

[john.k]

A capacitor thats easy to fit inside the flywheel is one of the little ceramic ones sold by the magneto repairers......I havent been following this lately,as the yard is turning into jungle,and just thinking about it is tiring......anyhoo    .....has the crankcase sealing been restored.....without crankcase pressure no 2stroke will start under about 3000 revs,when exhaust depression pulls mixture thru the engine.

[The Artful Bodger]

Re the condenser, with a battery coil it might be possible to run without a condenser for a very brief time but the points will burn almost straight away. With a magneto it probably won't work at all as the condenser sets up a resonance with the coil to produce a spark. My electrical knowledge is too limited to fully understand this resonance but I know it's there, and after much trial and error with Bantam magnetos trying different capacitors I know it's essential.
 As suggested a condenser can be externally mounted (to ground) with a wire run to the points. Or look at http://www.brightsparkmagnetos.com/easycap/index.htm they do a universal one.
  I bought some of these ceramic units through an electrical friend after looking at Bright sparks site and was very impressed something so small would do the same job. I fitted one on a friends Bantam and it was fine, unfortunately it didn't solve the issues with one of mine which required two condenser in the end to cure it.
 A bit of time spent browsing through their site, especially looking at the videos is very informative!
 By the by, throttle dampers were standard on about all British bikes to hold the throttle in a set position, I hate riding classics without them! Try indicating to make a right turn, without one every time you stick you arm out to make a right turn the bike slows down.
Colin

[Terrotmt1]

This is great!
Just to clarify, the points are 0.4mm gap with the heel on the 'cam'.
If it tires to contemplate this issue, its killing me!

I have a small new condenser from V Services and with a simple mod it will fit in the magneto.
I've seen those solid state ones and they look good
The original is 25 pico farrad.
Will swop it over today.
I can't measure the bore for local wear, I only have simple callipers.
Please keep following this! You all know I need all the help I can get.