Scottish 250 to 197 conversion!

[249XUU]

I've been running my totally rebuilt 250/31a engined 250 Scottish for a year and came to inspect the engine after it started to become noisey over a period of time and discovered that the big end has developed just noticeable vertical play. The engine performs brilliantly through sections but I've never really been happy with the engine at road speeds as it vibrates quite a lot and tends to run hot (pink) as if the carburettor settings have altered despite fiddling with ignition timing (The instructions supplied with the Electrex ignition were quite vague and in any case the thing wouldn't fire at all either side of a 'sweet spot'. Anyway, it always starts easy and never kicks back so the ignition can't be far out!. The S22 carb is set up exactly as it should according to the Carrick/ Walker book but it still pinks like hell at medium revs. Oh, and it's got a decompressor head with a squish band but no identifying marks.
I have a complete (full circle) spare crank with a short conrod which I believe can be used with a 197 barrel with a correspondingly shorter deck height. Will this 197 barrel/crank setup be smoother running?. I think the barrel is 10E ?. I'd really appreciate some feedback as I know diddly squat about these engines.

[John Wakefield]

31A/9E conversion

There should be no vertical play on con rod, any play here is due to big end wear. I would think this is the cause of the noise/vibration, two strokes (at least low compression trials ones) do not usually 'pink' in the same way as a four stroke.
As for fitting a full circle crank, if the con rod is as you say the short one then it should fit, but the balance factor may be different. The vibration on a 9E may be just as bad if balance is out. At a meeting at Cambridge last year Rob Carrick spoke of bad vibration on his 9E racer causing white knuckles & loss of feeling in his hands after a flat out run down the Norwich Straight at Snetterton. The Villiers engines were never designed for high tuning & high revs. The trouble with building up engines from ASP (all spare parts) is that they may not be compatable.
I would suggest that you have the big end of the original crank replaced & try it then.

[Peter Rotherham]

'A' & 'E' engines

Hi,

If you have a 31A engine, this was the 247 version of the 9E, originally developed for the light car market. The 9E was popular as the sub 200cc class had Tax/Insurance benefits back in the '50s. However, more power was being sought and the 250cc Learner limit created a market that Villiers wished to benefit from.Both engines used the same length Con-Rod, thus you can easily change 'top ends'.
Later (32/36/37A) engines had a slightly longer rod and a thicker Cylinder base flange to compensate.
You say you have an S.22 Carb. This is incorrect, you need an S.25. preferrably a /7 or /8 with the 1inch bore for better breathing.
The 10E engine never really existed....it was just the Primary and Ignition covers that were patterned differently to the 9E, as the 10E was intended for 'horizontal' fitting in Francis Barnetts, and a few other uses, thus the cast in 'stripes' would look odd otherwise.
Look on the cylinder base, you should make out an 'E' number. This will tell you what it is.
It sounds as if someone has worked on the engine. To include a squish band and full circle flywheel may seem a power increasing improvement, but in trials type running, it's often better to have a 'flat' or low compression engine as John says. Indeed, Don Smith and other top riders used such for personal reasons, compared to the tuned engines that were around back then.
I confess to knowing nothing about your ignition pack, but as these engines were designed to run on a 'fixed advance' spark, I presume timing advance is being done electronically, thus there will be a low speed 'set point' as on the old Suzuki PEI systems.

Any help?

[John Wakefield]

Villiers ignition

I think you may have hit on something here Peter. If the electronic ignition has a built in advance then this could be over advancing thus causing pre ignition. (and damage to big end)
As you say these engines are designed for fixed ignition timing. Best to re fit the manual system of points.
If you have not got the original set up, Pete Savage (Rex Caunt Racing)
p.savage56@btinternet.com or tel 01827 874015 does a modern setup using car points. Worth giving him a ring as he is very knowledgeable on ignition matters

[dave higgins]

Hi everyone.
Just a couple of points, unless i`ve missed it you don`t say whether you have a full circle or hammer head crank in the 250, i know the old h/head cranks used to suffer from crank pin slippage allowing the flywheels to twist & vibrate, but as a mechanic for over 30 years i would be looking for crank imbalance/ flywheel imbalance, if you have the crank rebuilt get them to check it first, rather than just pulling the pin and replacing.
These engines are so basic, that they will run fairly reasonable a long way off the correct timing either advanced or retarded so if yours won`t run without being bang on i would question either the system or its fitment, if it uses the old flywheel its possible your magnets are weak & don`t generate enough voltage.
Check your earths & as for your pre detenation, as the previous guy said its main causes are timing to advanced, pre ignition by sharp edges, carbon particles, weak mixture. air leaks, hope this helps. dave.

[249XUU]

Hi all and thanks to everyone for the enthusiastic response. The crank in place is a standard (non-full circle type) that was rebuilt 30 years ago and placed in dry storage before I used it in the restoration project. I had it checked out/balanced by an engineer who deemed it perfect. At the same time I had him ream the small end eye to fit the new DMW piston that I fitted. The main aim of this posting is to establish whether I can make the engine more 'user friendly', than it is at present, and better for a mix of uses including green laning and commuting. At the moment it is a very competent trials iron with brilliant handling for events like the Golden Valley MCC March Hare long distance trial.
The Electrex ignition appears to be okay and fires the bike up every time but I can't help feeling that the timing should be retarded a little more than it is at medium revs as it clearly feels a little over-advanced (I know this from bitter experience with a TS185 Suzuki that holed a piston due to an obscure CDI fault that was only cured by replacing said CDI unit with one from a breakers. Some say that variable advance is not generally needed for 2-strokes but the japanese have, for such applications, been building it in to the design of their CDI units for 30 years. If by changing to the full circle crank / 197 barrel, there is no improvement to the rideability of the bike then I will take your advise and try the points ignition. I would be interested to hear of anyone who has used electronic ignition setups and had problems with hot running/detonation/pinking issues. The issue isn't caused by sharp edges in the combustion chamber as I've checked it.

[John Wakefield]

One point that has not been mentioned is the gearing. In standard form the trials gearing is too low for serious road work, my experiance with Villiers singles is that they do not like running light, and will rattle & bang alarmingly if cruised at over 40mph on the road. They are much quiter when they are pulling hard. So you need to put a larger gearbox or smaller rear wheel sprocket on. You need to aim for an overall (engine to rear wheel) top gear ratio of around 6 to 1 whereas the 20TA trails ratio is 7.8 to 1 a big difference. With the wide ratio trials gears (assuming its still got these fitted, the gearbox may have got changed over the years) first & second gear should still be low enough for green laning.

[dave higgins]

A simple test with a good old fashioned strobe light will tell you which way if any your ignition timing is altering at different rpm, but it won`t be able to tell you what its like under load though.
May be worth you giving simon bateman at nametab a bell, hope you find the problem. dave.

[Peter Rotherham]

Hi, Me again....

On the 'point' of ignition advance curves, Suzuki were possibly THE best at 2 stroke ignition systems, having gained most of their knowledge from the old JAWA/MZ racers of the 60's. Anyone who saw the JAWA/Suzuki 4 cyl racer of Bill Ivy can tell you how it was streets ahead of it's time, but tempremental. In the 70's, we had to set up 2 strokes with dial guages.....bloody awful proceedure. Even our Souriau Diagnostic Machine wasn't that precise. The change to PEI or CDI systems was a godsend.
HOWEVER...Factory testing in Japan wasn't as good as real life usage, and many bikes needed changed coils, pick-ups, flywheels, black boxes and plugs, either before sale or at the first service. My SP 370 had 3 such factory changes, going from 8 to 12 to 28 degrees fully advanced!
Nowadays, factory recalls are normal, but back then were rare as they didn't want to appear sloppy.
(Interestingly, the Bulletin book for the Harley Davidson Electra Glide/Road Chief/etc., "Top" model, was over 4 inches thick in just 1 year! All single sheet updates. As a trained H-D Mechanic, you ask me why I wouldn't have one as a gift!!!).
Thus, even Electronic systems can be 'faulty' if set up to advance at unsuitable rates.

[Buzzer]

Happy New Year everybody.

For what it's worth, I remember seeing an article in one of the mags where the owner of a Villiers single engined bike was complaining of vibration. Someone advised him to fit a head steady. He did and said it transformed the bike. Simple enough mod.

Anybody tried it on a Greeves?

[John Wakefield]

I think people forget how crude the old Villiers engines were. In the 60's when we used to ride them as every day bikes there was nothing better. After the Japs started building super smooth performing bikes things changed.
Its only now when younger people are buying these old 'classic' machines that the rose tinted glasses are being put on and viewing the bikes as something they never were, you can't make a sows ear into silk purse. Such is life.

[249XUU]

Yes, I remember feeling quite disappointed when I first rode the Scottish in 2009 on the road as it was far less refined than the 2T engined Sports twin that I restored and rode with great pleasure for several months in 1983. Sure, I remember the 2T engine pinked a bit but far less than this Villiers single and that was with very careful regard to the original needle height setting on the S25. On the subject of gearing - Villiers Services are highly recommended. They got it spot on for my requirements when I told them that I was building the bike for long distance trials like the MCC Exeter as the bike performed perfectly for the long distance 2010 March Hare. Does anyone fancy riding the Exeter with me in 2012 on a Greeves?.

[johnrunnacles]

In the early 1960's, I used to ride my Hawkstone to and from Eastern Centre scrambles meetings, knobblies and all!
I took the mega exhaust in a rucksack, and swopped it for the Scottish version in the paddock, and that was piled up with the speedo, registration plates, my bag of tools, etc., and a can of petroil, whilst I participated (as best I could) in the racing.
A little bit of vibration didn't come into it! That was the least of my worries!
John R