keychange

https://www.speedandsport.com/index.php/parts/ignition-lighting/ignition-coil/ $18USD - I have one and it works perfectly. It took me 6 months to get my Cota working reliably, very frustrating but that was 10 years ago and it has been fantastic ever since. I haven't touched the points since then either. PS - make sure coil is bare metal to metal earth

I cut all wires from auxilary stators just in case they were shorting. The engine seals would have to be totally stuffed for it not to fire at all.....again compression and leak test would confirm. Likewise timing would have to be out to buggery like 180 degrees. So almost certainly you have electrical issue causing very weak spark. There is only a few parts involved, remind me did you replace the coil - pick up a cheapie on ebay.

Did you try the starter spray ? Aerostart or whatever as that will decide if problem is fuel, or electrical

Personally I think 50:1 is not a good idea on an old engine - the old bearing aren't remotely comparable to modern engines. You may have to lean off the mixture as you are delivering 2% more fuel ..not sure if that is significant or not. That oil "is for use in modern, high speed, high performance 2-stroke engines." I would seek advice as to how suitable for an old, low performance, piston port engine.

Ok so you have spark and even if the timing wasn't perfect it should fire unless it is too advanced so err on retarded if you check again. The 247 doesn't have much if any gear reduction on the kick starter and is notoriously hard to kick and easy to bugger the starter gear ( which you cannot find replacements for ). I use a decompression valve on the spare plug. I have an old Yamie XT250 with no decompression valve and Cota takes twice as much kick as the Yammie .. So your assumption that compression is good just based on kick strength may not be correct. I assume you have tried a fresh plug - even if it looks perfect and I repeat the gap is critical 0.4mm as the old ignition system can't throw a spark any further when under compression - so just because you have spark with plug removed does not mean it will spark when installed. My 247 can be hard to start when cold - so after a couple of tickles I turn fuel off so as not to soak the plug. It can take 20 kicks to fire when cold ( decompression valve invaluable ) but once warm will generally start first kick. Why not try some starter spray just to see if it fires - then you will know if fuel/carbie is the issue.

Does it run at all or completely dead? They are very basic machines - so start with the basics - is it fuel or is it spark. If it is spark - is there any spark at all? If there is spark is it strong enough - make sure yo have gap correct ie: standard plug setting is too wide If it's fuel and it won't kick at all - then what have you done already ... the Amal is notorious but once set up correctly it will run for years Other things to check are compression and leak down - engine seals are a common problem.

You asked " should the wire that runs to the live side of the coil read as shorted to earth at any point? " well yes when the points are closed ...that's why they are called breaker points.

If the points are ok then check condenser ( just disconnect from frame ) as a faulty one could short to earth as could a buggered coil.

Make sure your points aren't earthed when open - if they are you haven't installed the insulator on the pivot correctly

Well that'll do it

Forgot to mention many owners including myself have removed the condenser from the timing area to underneath the tank mounted with the coil. Much easier to get at ...in my case I just left the old one in situ with wire removed and installed a new one but remember to ensure a sound earth which can require scraping paint or powder coating

Agree with lineaway - with no spark at all first check the condensor and make sure it is earthed to bare metal. I had a hell of a time trying to get timing right with spark advance TDC measure. Timing disk 21 degres BTDC was the solution for me (see attached). Points gap 0.4mm .0157 inch - spark advance on TDC 2.5mm timing.disc.pdf

Could be ignition timing - if you move the timing plate you have to reset the points gap. Check valve timing and valve clearance and don't ignore possibility that timing chain has jumped a tooth.

dadof2 - as I said it was several years ago - I have a 76 Cota 247 I am pretty sure it was ATF - I currently use Castrol EPX 80W90 and apart from jumping out of first it is otherwise excellent

That is not my experience - when I went to lighter oil the gears were terrible - it was several years ago and I can't remember the exact issue but I didn't stay with the lighter oil as the bike was barely rideable.

Yep you do learn to double check before launching up a steep bank ... some oils appear to make it better or worse. Mine mainly jumps out of first and occasionally when going into second. No issue with the other gears.

Yep my 247 was terrible with ATF - just a nice 10/40 works so much better.

Persevere and you will get so used to it you won't even think about it

Hasn't happened with my Monty but did happen on an old Yammie AG175 I restored for a charity ride. Stopped to open a gate - kicker her over slipped her into gear and woooo backwards

Lots of twinshock riders will tell you not to bother with the clutch - these old piston port engines can be almost running backwards

I had similar issues years ago took me 3 months to fix - revs would climb and she would run lean and get hot then impossible to restart. After checking all else it was the timing so check your timing - it is critical. 21 degrees over flywheel. I gad tried setting the timing countless times with light etc - eventually just printed out a timing disc and set it with that ...fixed! As feetup says it could be air leak but it sounds very similar to my issue. As for other common things to get wrong - check your plug gap as the Monty spark is not strong and the gap is small so has to be on spec manual says 0,4mm - not a bad idea to change the condensor ( just cut wire on old one and fit new one under the tank metal on metal). right side engine seal if you have a non spec muffler - get a new replica one it made heaps of difference to my performance

not sure about older models but I know my 76 model is not to be messed with ...I do have a spare shaft locked away in my safe

Not that high

I fitted and easy pull adapter on mine and it does reduce the pressure. One other consideration for you is the kick start gearing is very high ...the shaft is almost unobtainable - you can reduce the stress and wear in this with a simple compression release. Not sure about the 72 but mine has two spark fittings I use the top one for the decompressor.

Looks like a pretty easy job to tidy it up ...I have three bodies - trail, trial as per yours and this more dual purpose body . Most of the time I leave the trials. tank on as it is pretty knocked about and I don't have to worry about it