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

[Terrotmt1]

At the first strip down, I tried to remove the bush to replace it with a close fitting sleeve, but it will not shift and that is with the case really hot.
The crank journals are round and clean, the bearings are 'ok' but new ones will be better.
The lip seal is tolerant of some movement as it obviously conforms to small variations.

I've made up my mind to lip seal the crank just as my Lambretta was.

As to the cylinder bores; I will attack them tomorrow and see if any carbon I thought/think is steel comes free!
It is hard to photograph them but I will try again after my attack.

The transfer passage (single from the lower case) splits into a 'Y' within the barrel, my pic above is of the smaller of the Y passages, the main inlet is much larger, maybe 3 x the area.

If a good 2 stroke is a knacker'd one, mine should be hypersonic in performance (and start on command)!

As I said before, I fear there is nothing I can do to improve the barrel/piston fit, the rings are new and the ring gap is about 5 thou (2 rings).
A fresh standard dia piston would be better, but there are no score marks on this piston, no obvious wear marks etc.
The step at the top of the bore is extremely light now all the carbon is off.

I believe the barrel is original. The model (up to 1949) of this bike had a very different barrel, twin exhausts pipes, single carb, same spec as mine.

I will ask Chambrier if they have any oversize pistons, they have been good in the past to me, but none show on their site.

Hope to get several hours on the engine tomorrow. Thanks for your continued patience.

[Terrotmt1]

Chambrier have oversize pistons with rings!
Std is 48.5, 49/49.5/50mm dia are available, 90 Euro.

Been busy.

The piston I have is 49mm so the engine has seen a rebore of +0.5mm in the past.
Went to V Services, and the Man was not impressed by the bore, "stepped and scored", "it's French so probably crap" (must be Colin's son)
He thinks a 50mm piston is best and that will get everything fresh assuming Chambrier have a NOS 50mm as they advertise. I await a reply from them.

The bearings and seals arrived from Simply Bearings, a 24 hour service for £18, not bad.

VS cannot machine the case for the lip seals on the (brass bush) magneto side, so the case will have to be machined somewhere here.
The new lip seal is 22mm OD and the brass bush about 21.3mm OD, so all can be done.
Wish I was back at work so I could DIY this in the proto shop.

So, my plan is to get the case machined and put the engine back together.
It is nothing to slip the piston/barrel/head back together and see if it will start/run.

If it does, then it gets sold.

If not, then I will get the piston and the barrel sorted and back together.
If this works, then it gets sold and someone gets a bargain and I get my life back.

If I do this what clearance is right for the piston/barrel?
Does 0.003" sound right??

Here are the pics of the ports.

You lot WERE right about the one port. There was an edge of hard grey crud on the edge or the port (exhaust) so I've clear the lot, not a lot came out to be honest, about 8 grains of sugar if that.
All are nice and open now:

Inlets: The port with the 'v' shape in one edge is from the carb. the other port is from the case under compression, transferred up the single port in the barrel base.





Exhaust (previously questioned)



Piston:

free photo hosting

[john.k]

Lawnmower technology all the way..not even loop scavenge.....certainly not going to be a rocket ship.....on the bright side....you wont be getting any speeding fines.

[Terrotmt1]

Yes indeed, something of an obstruction on today's road, esp around here where bikes are invisible.
I won't ride it, restore and sell is my objective.
Wish the machine shop would hurry up!
Gasket cutting today.....   

[Terrotmt1]

The case is back today from the local machine shop, so I now have:
Lip seals on both sides of the crank
Lip seals on the kick start shaft that leaked gearbox oil all over the place. No wonder the case was dry when I had the bike.
Drain plug incase of flooded lower crank case.
New crank bearings
Gaskets cut

Note the 'seal sleeve' pushed out whilst machining the bore for the lip seal, but I'll leave it there for now.

Can't get to re-assembly for a few days, but hope to get the engine back together and in for testing next week.

As said before, going to try the current piston and barrel for now and if it starts great, if not a new 50mm piston, fresh rings and a re-bore at Villiers Services.

[cardan]

I'm a bit amazed that the timing side bush is unchanged, and that you're intending to leave the bore as is. But I guess you know when "the man" described it as "stepped and scored" that this is not good. Many restorations are like this: very pretty but rubbish mechanicals. Pity, as there is real joy to be had riding a machine that runs as it should. Measurement and fit are words just-about lost to motorcycle restoration these days.

Make sure you put the piston in the right way around. Was it correct before? The motor won't start if it's back-to-front.

Good luck.

Leon

[Terrotmt1]

In this work, I want to find what was wrong.
I felt the step was ok, your nail can hardly feel it.
If the sealing to the lower case was at fault then it will show when I try to start it.
The upper compression does not seem to be poor, but if the engine will not start then I'll look to reborn once I have the £100 piston in my garage.
The piston shape fits the chamber in the head, the head won't go one if the piston is wrong orientation.
Got the basic engine back together now, clutch and magneto next.

All done now, even the pre-loading of the kick start spring went well, that's a first.
Thought you might like to see the guts of this powerhouse.

[Rex]

Great set of "mangle gears" there!
You seem to have a great machine shop on tap.... let's hope it's all good now.
When you take it racing you'll have to make up some big old crankcase stuffers!

[iansoady]

Yes, the crankcase compression will be very poor.

[Terrotmt1]

2nd speed has certainly seen far better days, lots of clutchless crunching I think.
I stuffed the crankcase on my hot Lambretta back in the late 60's, bloody vibration!

Hope this works...

[chaterlea25]

Hi All
I do not think the condition of the remains of the original bronze crank (sealing) bush will matter as the ball bearing supports the crank ? leave it in or remove it ??

John

[Terrotmt1]

Agree John, and it is already out, simply pulled out of the casting using pliers.
Stuck for a bit of time to spend putting it back in the bike frame for testing.
Thinking of making a simple engine stand so I can kick start it out of the bike and once reliable fit it in the frame.

[Terrotmt1]

Everything back together in the frame.
Kicks galore and swear words, some in French and very little action.

There was a whiff of combustion at times, even a pop, but no running.

This is with the Big Carb that it has randomly run on before.
Tried a fair bit og choke and removed the new crank case drain plug expecting to see a flow of petrol, but nothing.
The plug was dry after the first 20 kicks.
Petrol down the plug hole made no difference.

I think now I have to rebore the engine using a £150 NOS 50mm (max rebore) with Terrot rings.

What I have noticed is the ring ends are very very highly polished and the ring 'diameter' either side of the ring gap is grey.
Thus there is a high spot where the ring gap is.

Upper compression is obviously being lost.

The only way to true the lot up is a fresh bore and new piston. Just talking the wife round to throwing more money at this bike. (going to cost me...)

[iansoady]

If the ring ends are polished they must be butting up. I assume there is a pin to stop them rotating?

[Terrotmt1]

Yes, 2 simplerings, bothhave anti rotation pins in the  same place.
The ends are cut at 45 degs.
I'll take the barrel off and look harder, but resigned to a full rebore.

When will this end?