It runs…well sort of

The nice weather and a free morning brought Graham over on Saturday and we decided to have a look at the Cota 123.

I’d spent some time on the Montesa Cota 123 over the last couple of months which basically involved working out why there was no spark, despite a new condensor and a set of points. In the end the stator went of to West Country Windings (who are now in Essex ?) and they changed the energy transfer coil. Not cheap, but there was now a heatlhy spark coming from the bike.

It looks better than it runs (at the moment)

We spent some time trying to kick it over, then stripped the carb (an Amal Concentric) as potentially there was no fuel getting through. The using the Clymer manual reset the ignition timing and the points gap. More kicking and bump-starting still didn’t manage to get it to fire up, so we reset the timing. There was fuel and a spark, so it must be that they weren’t doing it at the right time.

There seemingly was compression, but how good is a bit of an unknown. Anyway on the fourth bump-start attempt, she fired up and I shot off down the road (well sort of)

Getting the barrel off

Pulled ok in 4th (I think) and managed to get it back to the house before it cut out. No idle and difficult to keep running, but it sounded good and the engine seemed to pull well. After more checking, we eventually got it running again for a couple of more laps up and down the road.

Leaking base gasket

It could be compression, and the crankcase seals or barrel/head gasket being possible favourites. Getting the head and the barrel off the bike, showed there had been some seepage across the gasket and a potential cause of the problem. The barrel nuts are 7mm hex bolts and I needed to cut an allen key and fit a 7mm socket to drive it, to get them off.

Will look at the crankcase seals next, though I did change one of them last year in the earlier attempt of getting it to run. Will see what happens

Stator Status

Back to the 123 Cota after a layoff on 6 months or more. as I worked on (I didn’t say focused) on other bikes.

One of the last things I’d done was to look at the electrics as I wasn’t sure if the spark was timed or good enough to fire the bike adequately. Back to the bike now and the first thing to notice was a complete absence of a spark. Checked the gap first, then removed the flywheel and ran some continuity tests

Montesa Stator

There is both ignition and lighting circuits from the stator, but looking just at the ignition circuit, it is like all trials bike; simple [[Compared with the wiring on the Transalp and any road bike with a battery, starter etc]].

So ignoring the lighting circuit, you’ve basically got the condensor, primary coils and points in parallel joined by a common earth (ie the stator plate). These are then joined and connected to the primary coil in the ignition coil. Simple.

So with the continuity test, you would expect to see continuity at all times from the condensor to the ignition coil connecting wire and then also from the windings on the stator. Given the points circuit is also earthed to the stator place it seems that even with the points open, there is continuity to the ignition coil. Looking at the Clymer manual, you should see 0.6 ohms resistance from the black cable to the earth

However, with these checks done, and a new condensor and points in place, still no spark. The points gap is 0.38mm but for some reason, no generated spark. Without having a spare stator plate cannot really determine if I have a problem.

Typical bank holiday weekend

Did manage to get out to the Forest Trophy Trial on Sunday, but the rest of the weekend was bit of write off on the outdoor front. Therefore spent some shed time working on putting the Cota together.

I’ve failed once again to get the engine running correctly on the SWM TLNW project, so decided to switch to the Montesa.

The frame had come back from Redditch Shotblasting who did an excellent job on a fairly corroded frame. Silver is the colour for 1972 bikes, which the frame number indicate [[The dating letter also came through from Roy Bacon to confirm the year]]
So spent some time working on the bike, whilst listening to PlanetRock and the cricket from Manchester, where it wasn’t raining.

-14h00 after ferrying of kids and others around got to the shed around 2 o’clock. Saffron came down also, with overalls, to help. Started by assembling all the bits in the workshop and put the frame on the stand. Checked the engine oil and cleaned it up a bit. The head and barrel really needs blasting and spraying so will get that done at somepoint.
– 15h00 Saffron’s up for some spraying, so painted the exhaust front pipe, the rear brake pedal, as well as the side stand and footpegs. Put the steering head bearings back in the frame. Plenty of grease to hold the ball bearings in place (wonder if there is a taper rolling bearing set for the bike) and put the yokes together. The pressed top yoke looks rather friable.
– 16h30 Front forks into place, which are not exactly massive either, reminds me of the Honda TL125 front end. Not really expecting too much from this bike. It does look rather small.
– 17h30 Need to get back in the van to pick up Tamara, but manage to clean up the ignition coil and connect it in place. No spark, no surprise there so need to spend some time with that later.
– 19h00 Need to prep the Beta ready for tomorrow’s trial, so leave the Cota till tomorrow. Looking good though

Forest Trophy Trial

– 08h30: Its pissing down and blowing a gale, so off down to the shed and start work on the bike. Gavin pays a visit and notices straight away that I’d put the head on back-to-front (I would have noticed when it came to put the exhaust on). No spark from the electrics, so check the earthing and get the meter out of the tool chest.
– 11h30: back from a conference call and a shopping trip. Further debuging of the electrics including trying a couple of alternative coils / plugs etc. Check the connecters and think about removing the flywheel nut; doesn’t want to come off.
– 13h30: back from lunch and continued to look at the electrics. Heated the flywheel nut, but still not keen on coming off, so need to think on another plan. The contact gap was completely out. The listings on Montesaweb indicate a 0.40mm points gap, so set and adjusted them. Also cleaned the faces. The meter shows around 2.5v peaks from the plug gap, but need a little more than that.
– 14h30: still no joy with the flywheel nut; going to need another pair of hands, or an airgun (or both). Decided to fit the exhaust, which is of an interesting design (?) and with a pea-shooter exit pipe. Maybe not getting enough oomph from flywheel, so hence the need to extract it.
– 15h45: England have won the 2nd test at Old Trafford, after a large 1st innings deficit. Still no joy with the electrics, but the rest of the bike is together and now looking the part. Just need to make it run. The stand is a little short (designed for the original 20/17″ wheels) but works. The clutch cable was ok and runs underneath the engine, though is not a one figure pull. Cup of tea and think further about the electrics.
– 18h30 Ended up making dinner. Back to shed, thinking perhaps is an anti-clockwise thread on the flywheel bolt. The bolt itself is only half-way on which seems a little weird. Yep, quick Google [Good reason to have Internet access in your shed]] and it is [clockwise to loosen . Could be a problem with the condensor, handily placed (like SWMs, behind the flywheel).
– 19h08 Flywheel nut off. Now for the flywheel. Not sure about pulling it with a leg-puller, so need to see if I can find right puller (male, right hand thread, 27mm)

Small and in pieces

Latest purchase is something different

Gavin has been going on about the Montesa challenge for a while. The idea is that between us we can re-introduce the Montesa to twinshock trials (when was the last one on a Sammy Miller round).

If there is a handicapping system (lowest power, oldest bike), then a 1972 Montesa 123 wins. I picked it up from Harrogate yesterday.

Montesa 123: I think

It was a donor bike (well really a donor frame in fact), but it is complete. The frame needs powder coating (or painting), as does the swing arm and potentially the front yokes.

Next phase will be a step-by-step run through of the components and getting the frame done. Its a little while away, as work gets in the way. At a glance though it does look good:
– one tank of a good standard, with a spare which needs a little work, but is intact
– engine is complete and comestically doesn’t look too bad. Time will tell on how it runs
– aftermarket NJB rear shocks
– cables and controls all in place

Plenty of people have 123’s so some good references around as well as pictures, including:

Montesa Image 1

[ Montesa Image 2 -> ]

First item for discussion is the frame colour; the 1972 frame colours are silver it seems:

Silver Frame

Whilst from 1974 on, they seem to be black

Black Frane

The frame number seems to be early and I’ve sent a request for dating letter off to Roy Bacon as part of the plan to get the bike on the road see previous article