Montesa Cota 247

[turbofurball]

You've been busy!

[oldaz]

Wheels all rebuilt, new tyres, tubes, bands, rim-locks, brake shoes modified and fitted, made new spacer to replace the knackered speedo drive and fitted the wheels to frame, the fitted up the brake levers, etc - all fixings are stainless steel, even inside the plates. I'm very pleased with the way it's coming together.

[oldaz]

Bash plate made and fitted, (picture below) details are in a separate post, it came out OK, so that's the end of the "frame" work.

In process of stripping engine further. The barrel and head are back from hydro-blasting, a bit more tidying up and finish the new head studs and it will be ready for some engine enamel. 

New flywheel puller arrived, so started into pulling the magneto flywheel - no joy for 2 days - soaked in penetrant, applied heat, still no go. Got more serious with it today, more heat while under pressure to the point where I've probably compromised the crank seal on this side, tried impact gun, still no go, breaker bar on the puller and promptly sheered off the M12 bolt in the new puller - more heat and more penetrant while I repaired the puller with a new hi-tensile M12 set screw, got back into it and lay the engine on it's side on the steel bench so it was supported on the crank weight on the clutch side - a good belt with the 4 pounder and it popped - FINALLY!!! 

Shut down the workshop and quit for the day.

[oldaz]

Got the clutch cover back from welding yesterday, they did a nice job, shouldn't leak oil when it goes back together.

Finished off and installed the 2 new head studs to replace PO's M12 cap screws and started tearing down the bottom end. Finally found the cause of the slack in the final drive shaft - the bearing is full of rusty water, probably trapped in there from when the bike was lying on it side all those years. Another "interesting" one is the inner bronze bush for the kick-start shaft is missing about three quarters of the flange, but so far no sign of bronze bits in the gear case, so unsure what's going on there.

Looks like I'll have to fully strip the bottom end and try to find the missing bits of the bush, then make a new one. Will replace crank seals while I'm at it, so progress will be slow for a while. New final drive shaft bearing and seal on the way from InMotion.

[turbofurball]

It'll be worth it, awesome bike when it's done

[oldaz]

2 hours ago, turbofurball said:

It'll be worth it, awesome bike when it's done

I sure hope you're right :-) Did some measuring and seems all the kick-start shaft bushes and seals will have to be replaced - also need to figure out what's going on with the kick-start mechanism - at the moment it looks like the shaft has been only going part way into the inner bush when the spring should allow the ratchet to slide on the shaft instead of the shaft sliding in/out - this added to the play in the middle bush has caused the inner bush to fail.

At least I found the missing bits of the bush, some of it was ground up by the gears and caught in the drain hole and the biggest chunk was jammed into the top of the drain by one of the gears - took some getting out. In case anyone is interested, the drain hole in the bottom of the case is only about 8mm, then opens up to about 12mm where the plug is - no idea why it wouldn't be 12mm all the way through - it will be when it goes back together. Picture of the remains of the inner bush below.

[turbofurball]

Maybe so people don't use a drain bolt that's too long (?)  On the 349 you can swap the standard plastic one with a ford oil drain bolt, which is a little harder wearing (I need to grind a little off it though, as it sits slightly proud of the bash plate)

[oldaz]

Got some more done over the last couple days. Completed the kick start settings/clearances and timing, repaired the case damage from kick start over-travel and tidied up where the chain had hacked the side of the case, fitted the new seals and bearings, modified the oil drain and assembled the two engine halves. I was pleasantly surprised how easy it was to reassemble.

When the kick start timing is correct and the lever is in the right place, the mechanism is quite good and it becomes difficult to over travel the shaft and cause the damage - there's even enough room to get a thin metal plate on the side of the damaged casing web. Pictures show the aluminium patch on the kick side and the JB Weld on the flywheel side. I veed both sides of the hole in the case web, screwed the patch in place, then completely filled the hole made by the kick start shaft stop. Now when the timing cover and gasket goes back on there shouldn't be any water ingress into the magneto.

Does anyone have a wiring diagram for the ignition on one of these? I won't be running lights, so only need the ignition circuit.

[deleriousdave]

Here’s a shot from my manual (73 247)

[oldaz]

Thanks deleriousdave, most helpful, made it so much easier to figure out which wire I need to keep.

[oldaz]

Finally finished the engine/gearbox rebuild and fitted back to the frame this evening. Also took some pictures of the remains of the steel clutch follower I replaced - shows what happens when you run steel on steel without oil - or not enough oil.

Now have to rebuild the exhaust system and tank unit, then all the fiddly bits.

[potto]

On ‎2‎/‎3‎/‎2018 at 6:17 PM, oldaz said:

Thanks deleriousdave, most helpful, made it so much easier to figure out which wire I need to keep.

Brilliant work,went back in your topic and read all the way through,hell that bike was rough..wow look @ it now.

I have my wiring to sort out and a condenser relocation is on my list.

I noted with interest your frame repair,do you feel if you just welded up the cracks they would come back?,appears cracking around the steering head is common issue with the older Montesa's.

Careful reinforcing of these area's is as you have done appears the only way,I have cracks at places on the edge of repairs because the haven't been done right .

I do suspect my steering head angle has been changed @ some point...not a lot I can do about that.

Keep up the good work,you must be getting close to a test run ?.

[oldaz]

The frame repair meant fully grinding out the tubing cracks to expose the extra tubing inside, then welding to the inner, welding it shut, dressing the weld, repairing the edges of the original gusset/s where cracked and welding them back to the down tube, fabricating the "wrap" reinforce, tack on one side and clamp tightly to the repaired area and finally fully weld in place and clean up. Where it was cracked at the rear support, simply grind out the crack, weld and clean up. By "grind out the crack" I don't mean V it out, I cut the crack right through, then rebuild - extra work, maybe not really needed, but there's no crack left to maybe start over - yes, it could crack beside the weld, but stress relieving it should minimise the risk.

Cracks in the head-stock area appear to be caused by a combination of dropping the front end heavily (imagine coming down suddenly off a wheel stand and you get the idea) and poor design in this area. The internal reinforce ends almost exactly where the gusset/s end creating an area of flexing, so a weak spot. It could have been much stronger by either extending the gusset/s another 50mm or so, or extending the internal reinforce a similar amount. A different material may have also been a good option.

Test run won't happen for some time yet, lots of little things to sort out yet and some extra little bits to make and fit to help with maintenance. Exhaust system to rebuild - need to burn out primary muffler, open it and repair inside, same with rear non-original silencer, then the fuel tank. I'll probably strap on a temporary tank to test things before I finish the fuel tank.

[motosolex]

On 12/13/2017 at 4:51 PM, pro sport said:

Hi Oldaz

Been following with interest your refurbishment of your UKR. I have a mk4b the version before yours and have found similar problems to what you have come across. Your timing cover might have been damaged by the chain but pay particular attention to the inner case around the Kickstarter shaft, in a lot of cases the Kickstarter itself has been positioned to far forward on the splined shaft in the miss belief it would give a longer throw to the kick, unfortunately all it does is allow the stop on the shaft to punch a hole through the inner casing allowing water/moisture into ignition.

The correct position of the kickstart should be the ' one o clock ' or 30 degrees, or looking side on parallel to the frame down tube.

Hope this helps, here's mine.

 

[motosolex]

On 12/13/2017 at 4:51 PM, pro sport said:

Hi Oldaz

Been following with interest your refurbishment of your UKR. I have a mk4b the version before yours and have found similar problems to what you have come across. Your timing cover might have been damaged by the chain but pay particular attention to the inner case around the Kickstarter shaft, in a lot of cases the Kickstarter itself has been positioned to far forward on the splined shaft in the miss belief it would give a longer throw to the kick, unfortunately all it does is allow the stop on the shaft to punch a hole through the inner casing allowing water/moisture into ignition.

The correct position of the kickstart should be the ' one o clock ' or 30 degrees, or looking side on parallel to the frame down tube.

Hope this helps, here's mine.

Interesting. The 349 we are restoring has a hole too at kicker shaft area. So, this is caused by a miss positioned kick lever? I dreaded that something in the mechanism close to the case may have been the culprit.