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

[Terrotmt1]

Time will tell John!

Jets arrived 30 mins ago, so off to see if the Dellorto can be persuaded to work.

Surprised nobody has suggested the final resolution idea for this 'Worthless French Article' and that is to go electric.
I nearly did this before trying the 50cc push bike motor conversion that is in the bike now, and if the centrifugal clutch stopped slipping (common issue on these) then I would not be pestering you all.
My thought was to fit the 50cc 4 stroke and sell the bike as a motorsport Paddock Bike, so popular in historic meeting today.

Pulling an electric conversion together was quite complex, but only due to getting the right mix of 48 volt parts which would give about 30mph (remember these brakes) and a range of around 30 mins, so about 1.5 hours of country riding.

This bike lends itself to this, a motor in the place of the engine, batteries atop the panier frame and speed controller under the tank.
Lots of satin paint and some deceiving aluminium parts to kid the first glance.

Still saleable as a bike or a paddock bike.
Cost would be about £300 all done.

Any polite comments?

[TGR90B]

Yes, I just think you're a serial poster/keyboard warrior - call it what you will.

[Terrotmt1]

I am simply trying to get to the bottom of this problem. I feel there are many who are far far wiser than I about this subject that I am tapping into to help.
Just noticed about 43,000 views so it must interest a few.

The jets have been a bit disappointing, the smallest being 0.7 which I believe to be simply the metric size, 0.7mm.
The jet dia in the original carb is approx. 0.48 or 0.5, hard to measure with the wires I have.

It did however fire and run for a short time, again with little throttle response and a wet plug, but not flooded, after it self-stopped. The needle is in the weakest position.
I have ordered some drills of the right sizes. By soldering up the jet hole I can drill the jet to a size closer to the original.

The engine fires quickly though from cold with a good spray of Easy Start. Previously, it has never had any effect.

[TGR90B]

Over two years on the same problem and you bat back every suggestion. I stand by my remarks. Your entertainment would come to an abrupt halt if you sorted the problem.

[Terrotmt1]

But what have I batted-back?
What have I missed?
If you will list them I can maybe move forward.


Yes, 2 years have gone by.
This topic is not my primary interest, just something to try. I do not give in easily on anything I take on, but it would be good to finish this, I have other things to do.

If the solution is simple, let it be detailed.
If anyone finds this protracted thread irritating etc, then simply do not watch it, it is not compulsory to do so.

[murdo]

I like your idea of the modern engine, but I am still interested for you to find the answer as to why it wont go as everything I would have done has not produced results. I will keep watching to see what you find.

[chaterlea25]

HI Again
Main jet size will not affect starting or slow running they only affect approx 3/4 to full throttle
the engine should start on more or less any carb that will run another engine
If not there is some other problem
Way back I suggested wiring up a battery and coil ignition system using the existing contact breaker
Did you try a known good capacitor? New old ones cannot be relied on
Another idea might be to try a currently available version of the "atom" ignition module that bypasses points and capacitor
https://pickersyard.weebly.com/atom-universal-electronic-ignition-module.html

Assuming there is plenty lube inside the engine? try running it for a few minutes on gas from a propane blowlamp
pointed into the carb inlet
(do not light the blowlamp  or it might be an end to all your woes)

John

[Terrotmt1]

Thank you both.
Yes, I recall your ignition suggestion and I did it!
The capacitor is a new one, well, a year older now, but fresh.

I have also tried fuel for a petrol powered chain saw that is more than 100 octane, didn't start at all!
I have thinned out the oil to 30:1 which is quite weak, BUT...

When the engine get flooded by the rich mix the lower case starts to fill. After each run it makes (about 45 seconds) I remove the plug and wash the wet mix off using a shot of brake cleaner aerosol. I also remove the lower drain and the mix will trickle out (or pour out) and it is always black. Never clear or green like the fuel supply.

I either have a VERY clean crank or the primary seals have dissolved/are dissolving.
This will be my next check while waiting for the drills to arrive late next week.

I can pressurise the lower case via the inlet and listen for hissing.
If the lower compression is weak then I have another problem.

Having said this, it would not affect the mixture but would effect the draw through the carb.

Murdo: indeed, it is a nut to be cracked and I'm trying as hard as I might. My enthusiasm waxes and wains as I'm sure you all understand.
Have to walk away at times or that blow torch will be used to full effect.
 

[john.k]

You mention black staining in the drain fuel......it does sound like the seals are dissolving.This would not surprise me ,as modern unleaded does have many constituents in common with  older type paint thinners.Not running on aerostart is pretty indicative ,IMHO.My old chainsaws are impossible to start after sitting for years,but a good spray of aerostart ,they fire up ,and the added suction pulls any oil blocking the jets out,and away they go in a cloud of smoke....The newer saw I bought to compensate for my advancing years had a very big warning about fuel,no alcohol,and be sure to drain the tank and then run the motor dry while still hot,no matter what fuel is used......I know of an Ariel Leader engine rebuild where new seals were found to have cracked after the performance went right off in a short time...........but didnt the Terrot have metal face seals?.like a Scott.

[john.k]

Seals are somewhat colour coded as to material ,for instance dark brown is fluorocarbon.

[Terrotmt1]

Yes John, and I modified the case to take Lambretta case seals, lip type as used in car crankshafts etc.
Still suspect them though.
The original seals were a felt disc on the clutch side and a plane sleeve with a deep spiral grove machined in such that crank rotation 'screwed' the oil back to the case innards.
Crank bearing wear saw that sleeve worn oval, so no seal.
I'll strip the engine down, I've made all the tools to hold this and that so no big deal, remaking the gaskets is a pain.

[Rex]

Pre-war simple two strokes often used to rely on a nice thick 20:1 petroil ratio to achieve crankcase sealing when designed with those long main bearings, so don't lean it out too much.
 I've never heard of modern lip seals being affected by ethanol.
Rather cataclysmic for two-strokes if it is the case.

[Terrotmt1]

The seals should be good, I will try to get some air into the bottom of the engine, it can only come out of the 2 seals or the piston rings.
Not sure what pressure to use, but will try 10 psi.

After that I will remove the head and cylinder, v easy, and pour some thinners down into the case and see if there is a flood out of the crank seals.

If tight then the seal of the case is a red-herring.

[Terrotmt1]

Strikes me the seals are all ok after some simple pressure tests.

I looked into tuning Dellorto carbs, bike carbs and they say to find a starting jet size you simply take the choke diameter (18mm in my case) and x by 5. Thus '90'
You then compensate for sea level, so where I am the compensation is '0.9'

Thus the starting jet size is #81
The jets I have are all # 74 to 98 so tried a #80 with a rich needle position.

It started and ran badly, but the plug was not soaking wet and the case was not full of fuel, but had a trickle.
There was some degree of throttle response and the engine nearly idled (this carb has a pilot jet).

So, instead of weakening the carb by jet size I've opened it up from #48 to #80.
Still some more trial and error to go, but I hope to find a sweet spot.

The 'x 5' multiplier ignores filter restriction etc so it a simple starting point.
The super fine drills arrived today, so  that may help.

Try to find time tomorrow to tweek it.

[Terrotmt1]

The trials with the new Dellorto jets continues, and I seem to have a black damp plug so far, but with 'easy' starting (ish) so some more tuning required when time allows, but a thought occurred to me about the plug.

I know nothing/little about the heat ranges of plugs, but know the wrong heat can cause issues.

Thus anyone know which plug might burn better in this engine?

The new plug I have used came from Villiers Services, for this engine as their 'best guess'.
The code is Champion L82C.
I wonder if a different heat range might give a better burn?

The original plug still works:
Code is KLG Corunoite (KLG CL1)

Any thoughts please?