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

[R]

That replacement looks like a pretty fair choice.
Spark plugs back then weren't nearly as fussy as to the heat range as these days
- one or 2 heat ranges covered about everything !

I see some CL1 plugs at an auction in Corunna Indiana. Hmmm. Is that a clue to Corunoite, or a complete coincidence ??
https://s3.us-west-1.wasabisys.com/ebayassets/items_images/163143453941/$_57.JPG_5b4dd78ae41a84.88030634.jpg

The fact that you can play with the jetting and things improve suggests that you are on the right track,
no magical spark plug is going to suddenly burn twice as much fuel as it should be dealing with ??!
Having said that, I notice that those CL1 have a slightly projecting nose - doesn't that make them more resistant to not fouling  ?

[mini-me]

Seems to me you need a much much hotter plug, older plugs, KLG, Lodge etc suit older bikes much better,also the shite that is sold as fuel these days  seems to mess plugs up, I have heard that new plugs once sooty glazed like those cannot be revived like they used to be.

Are you using ethenol free petrol, or have you considered removing the filthy stuff?  The fuel it was originally meant to run on was pretty poor post war  low octane jungle juice.

'best guess'.

..yeeeeeeeeeeeeeeeeesssssssssssssss,........... more likely thats all they had to sell you.   Check out Green Spark Plug co and see what they have on offer

[Terrotmt1]

Thank you both.
There is a big (French) data pile of paper on the Terrot site on Terrot plug types that will need some time for me to digest given on another site on this topic, but it seems there may be something better to try

NGK BH7V
However, the '7' is the equivalent to the Champion '8' that is the plug from Villiers Services.
On the Champ plugs, the higher the number the hotter the plug, so will try to find, say, a '10' numbered plug.

I know this will not be a magic moment, but " every little helps" comes to mind.

Hope to get some time this weekend to carry on with the jets and needle fine tuning to try to get a dry plug and crank case and a start without Easy-Start assist.

The fuel I use is Shell V Max, 99 octane and the ethanol content is quite low compared to their ordinary petrol.
I have a weak oil content, 30:1 where Villiers oil ratio should be 20:1, but I doubt that affects the running, just the risk of seizing....

Another thought is I am doing all this without an exhaust pipe/silencer on the engine, but again, doubt that will make any difference at this stage.....or does it?

[john.k]

I know from mower engines they seem to run OK with an open port,although theoretically a performance stroker does need an exhaust pipe  at least.,and preferably an expansion chamber.......And the other point I made at the start.....can you feel a pop and a pulse of air from the transfer ports when the head is off.......I still suspect the piston may not be right for the engine,and port timing may be astray........i doubt spark plug heat range is any issue at this stage ,as the plug hasnt got hot.

[R]

Another thought is I am doing all this without an exhaust pipe/silencer on the engine, but again, doubt that will make any difference at this stage.....or does it?

Aaaah, you didn't mention that.
We played with a lawnmower engine in a gocart, and without the muffler arrangement AND the aircleaner it was totally useless,
would never run for more than a few seconds.  Once that was established, a variety of such devices could be tried,
the length of such things seemed to be more important than the actual form of them.

This may not apply to a Terrot, but you don't know until you try.....

[Terrotmt1]

Thank you both.

I'll pop the system back on.
The bike, fully 'dressed' never ran a year ago, but that was without the new ignition coil.
There is no filter to the original carb. just a baffle disc.

There is a distinct 'chuffing' with the plug out when you turn the engine over by hand using the kick start lever.

[mini-me]

find a clean crappy old 1950s plug thats as hot as possible and try that, your engine will not be overfussy.

A cautionary tale, I run a 30yr old Peugeot, thought I'd buck up the reluctant starting and went to buy some of those expensive Iridium plugs, don't waste your money said the shop person. old engines really don't like them. Thats just 30 yrs old, not 60.

I have, as I said, heard similar about classic bike use of them.

I have long maintained that trying to apply 2020 technology to a 1930s machine is a waste of time money and effort for usually no result. Except for the owners ego showing off to demonstrate their lack of  real practical knowledge.

[Terrotmt1]

Agree.
Fitted an expensive set in the 90's to my 1973 classic car. Crap.
Fitted normal Champion plugs, grade as per Haynes manual, ran perfectly for years, still have the car.

Tempted just to re-fit the original plug as in the picture. It will fire and run for a few seconds fine with it.

[chaterlea25]

Hi Terrot
If the engine has wetted that Champion  it will be practically useless
In my misspent youth when all I could get my hands on were 2 smokes, you dare not venture far without a fistful of sparkplugs and a plug spanner
That was in the day when plug insulators were glazed and so cleanable  not like the shite available nowadays
A dodge to try that helps keep the plug dry is to fit an even shorter threaded plug from a chainsaw or strimmer / hedge cutter
Yes fit the exhaust pipe too
a bundle of NOS Champions here (3/8 reach)
https://www.ebay.co.uk/itm/vintage-champion-spark-plugs/123988529623?hash=item1cde4ad1d7:g:9UwAAOSwkARd3Bq7

John

[Terrotmt1]

This engine should start reliably, but I take your point.
Always had a spare plug when I ran my Lambretta in the late 60's!

Even those engines started and ran well....

[Rex]

Commuter bikes (of any sort) wouldn't sell many if they weren't basically kick and go. Always makes me laugh when I read about those strange people who cosset some old daily hack as if it was some thoroughbred.
No, your B31 doesn't need 500 mile oil changes..

[Terrotmt1]

Indeed, this bike should be boring to use!

Bloody cold in the garage today, but tried a few things, all to no avail.

Full exhaust on with 2 stroke silencer, all new.
Fresh petrol and modern 2 stroke oil mixed to about 30:1.
No plugs at Halfords, so using the Champion plug I've used for years....

Engine starts, runs for a few seconds and dies. Best run today was 20 seconds.
Plug wet but drier than usual, but not dry just black/damp
This was with #84 jet where the Dellorto data says it should be an #90. Tried a #90 and it floods the plug.
Needle at max weakness position (clip at the top of the needle grooves).

So, absolutely no further forward with this comical situation and this engine.

Last shot is :
to go through all the jets again with the needle on mid-way height.
To re-fit the original carb and try with the silenced engine.

Then, I think I am at the end of all the options at my disposal.

Sell as a Starter/non-runner.

[mini-me]

Halfords??


FFS get a decent older plug thats is clean, if you can't find one pm me and i 'll find you  one in my junk box.

i still think you are pissing up the wrong tree

[R]

Then, I think I am at the end of all the options at my disposal.

You have barely got started !
(pun intended).

Ebay fr has loads of stuff, if you watch long enough ?
Wrong era, but the correct one is bound to come up. ?
https://www.ebay.fr/itm/carburateur-bronze-AMAC-4-012-Moto-Ancienne-TERROT-HST/223766974320

And a suitable lawnmower carb may be better than that Dellorto, which looks somewhat large ??
Small villiers carb preferably - obviously of the 2 stroke variety (4 stroke carbs hate 2 stroke applications)
Something similar off a lawnmower
https://i.ebayimg.com/images/g/yUMAAOSwfCpbGMy9/s-l1600.jpg

hopethishelps.

[R]

P.S. A lot of 2 strokes are allergic to that open carb inlet.
Try a bit of plastic hose on it, at least 3 or 4 inches long
?