section swept

Runaway 2T the quickest way to get back control is to get the thing in a high gear and feed the clutch in pretty sharpish ( time wise) and ‘stall’ the engine with the back brake held on lean over the bars and hold the front down and the brake on. So what if it burns the clutch thats better than the alternative?

Just looked on Google its all there for you plus other specs you bound to need!

Glaze bust the drum braking surface. Use wet and dry 600 grade and a little water. Rotate the rubbing action around the drum to produce a clean grey effect on the surface. Clean thoroughly with damp cloth. Don’t chamfer the brake linings too much as this reduces contact surface area. They should already have a very slight chamfer which just needs cleaning lightly with fine emery cloth or scotchbrite pad. Montesa front brakes (348) are quite good when compared to Ossa-Bultaco type. Tony27 method is an excellent way of centralising the brake plate?

Chrome rings will be shiny just like chrome. Plain rings will be greyish to polished grey where they rub against cylinder wall. Chrome bore will be easy to spot as it will be much shinier than cast iron bore. You will also see where the plating finishes on the bottom of the barrel/bore. Obviously chrome bores cannot be bored out, unlike a cast bore which can be oversized by reboring. Nikasil and other types of surface hardening processes are harder to define, try a Google search ?

Cylinder intake/inlet stub leaking allowing weak mixture due to excess air by passing carb jets etc.

I can add a little info here. John used a Yamaha YZ80 front hub on his development 320 Majesty. The motor had various piston/cylinder configurations during development, torque was amazing (go up the side of a house) but the clutch needed to be stronger, tended to be overcome by that motor. What ended up being used in the final works motors depended on the type of trials going, and the riders preferences. As these are all old tech now it would be really interesting if more details could be found......?‍??from the horses mouth perhaps....gents.

Provided the piston rings are suitable. You can’t run chrome rings in a chrome bore, they’ll eat each other! You can run chrome rings in a cast iron bore. The top ring is usually chrome to deal with the high heat of combustion.

Best thing since sliced bread. Allows easy starting, controlled descents and easy engine stopping. No need for a kill switch. Makes a loud chuffing sound when spectators step into your path.

Most probably easier to locate rocking horse ****. Some info on Google...why does no one look here first?bikezone

Do you mean decompressor?

Nothing wrong with feeling a bit of a ****! Its when you feel a bit of a @#£& thats when you need to worry?

You’ll need child bearing hips to ride comfortably.....no welder can help you with that! The old original Crusader seat would have been quite wide in this area but as the rider would have been less inclined to want to stand up the width issue would have faded away. Reshaping the top outer tubed to move inwards by about 2 inches either side but curving out to meet the original damper mount positions could give a better (slimmer) seat base area. Considerable cutting and reshaping will be needed, potentially new frame tubes required. Sifbronze welding would be better for strength.

These engines were designed when the oils were what was available at the time. Now modern oils can be used more sparingly, so the mix ratios can be reduced. However those newer ....technical.... oils can still be mixed at the old ratios 40 or 50:1 purely for peace of mind....I run my 348 on 50:1 synthetic.

What atmospheric pressure do you have at your location. If you have lots of sun and are quite high up altitude wise then that could have a bearing on your issue. Inspect that carb and ensure both pilot and passageways are clear. Two strokes do react to the air temperature and altitude. Higher you go the thinner ( less dense) the air.....hence detonation.

Its usually too much pressure washing close or actually onto the wheel bearing seals/dust covers call them what you will, that causes wheel bearings to wear rapidly. The same can be said for gearbox output shaft seals. Wheel bearings especially on trials bikes don’t turn at very high speeds. Adding more grease especially waterproof grease can only be a good thing. Certainly overpacking a bearing that rotates at high speed will cause the grease to be centrifuged out passed the sealing mechanism, but these bearings are running at much higher speeds than wheel bearings. Steering head bearings will also suffer rapid wear if the pressure washer gets to close, sealing of these bearings is marginal to almost non existent. These bearings to should be the subject of a time based service plan or planned maintenance. Blow drying with compressed air will also force water and other crap into the seal lips and create corrosion and wear. Wash these areas and wheel bearing areas with a soft bristle brush ( paint brush).

Anything appears to be fair game at the moment. Catalytic Convertors on cars gone in under 60 seconds. Van doors pose no threat to opportunistic arseholes who cant be bothered to earn their money and actually pay for their own playthings. You find out who stole it and they then threaten to burn your house down. Cops aren't interested far too busy appearing on TV shows.

Ah pond life will go for anything ‘spangly’.

Strimmer will be good for ‘cleaning sections’ ?

Yes you can drill a small hole centrally into the filler plug. I then inserted a plastic tube with superglue. Measure the plastic tube for drill size, try for a really snug fit. Then attach a clear plastic tube and run this to where ever you think fit, my breathers are routed up to the top frame tube and are then held inside the open end of the top frame tube with cable ties.

Is there not a Dabbalot already on Trials Central? I could be wrong?

Check gearbox oil quantity as well. Check gearbox breather is clear.

Can’t add any useful information bit it looks as though you may have a nice piece of ‘trials bike history’. Get it all cleaned up but don't change anything. Restore it certainly....you may have a very rare bike, I’m very envious...John Shirt and Mick Andrews are the guys to ask for advice as you have mentioned. John Lee could also be helpful too.??

If you have a good spark, fuel and a clear airway and adequate compression the bike should start. Start again and work methodically. No fuel in crankcase, drain (if drain plug fitted) or turn fuel off and leave to evaporate Choke operating correctly, on and off etc. Good plug, cap as well. Good compression. Clear airway, air filter not blocked. Kill switch working correctly, possibly by-pass to eliminate. Fuel flowing to carb, float stooping fuel from flooding. Carb overflow pipes routed correctly, not blocked/ kinked etc. Throttle (handlebar) set up correctly. Throttle cable fitted accurately and free movement. DO NOT ATTEMPT to tow start this proves nothing and is dangerous to both you and your bikes engine. With everything set/working correctly bike should start after second or third kick. Others have pointed to the woodruff key allowing the flywheel to move on the crankshaft, entirely possible and an area that should be inspected. If the woodruff key has sheared then a straight forward replacement is normally all that is needed. However if its happened a few times ( you won't know this as the bike is new to you) then the woodruff keyway in the crankshaft may be seriously compromised. Not an impossible repair if you are handy with a welder and Dremel type cutters. Glue is not a way to go it will not last the test of time. Hope this is helpful and you solve the issue??

There is a whole raft of info on the Cotas and the 348 especially. Do a search through the Montesa area of Trials Central. I use automatic transmission fluid in the alclutch ( Actually a Mercedes Benz fluid) but most ATF fluids will do. In the gearbox EP 80 will be ok. There is no level plug so its an overnight drain down and then fill with the correct amount. The amount you will find on this site, I cant remember the exact quantities but 300cc and 600cc might be ok but CHECK as too much oil will cause the breather to pass oil out. The gearbox is a ‘dog box’ so you can change gear with out the clutch (as are nearly all bike gearboxes) so a strong oil is best. ATF in the clutch will help prevent clutch sticking and dragging. Mont 348’s with a proper set up on the clutch are very reliable. Do not rely on the old sealing washers on the drain plugs fit new if you can, otherwise they ‘will leak’! If not already done it is a good policy to turn the clutch filler into a breather, also the gearbox filler. Or purchase ready made. Either way allowing the clutch case and the gearbox to ‘breathe’ allows any gas pressure build up due to the oils getting heated and creating vapour (gas) which will need to get out. This usually means the oil seals or a gasket weak area. The Montesa 348 has a breather hole in the gearbox casing but it is well hidden and can get blocked....not good! I have tried to show these in some pics....hope you enjoy your ‘tractor’ an endearment for the lugging ability of that motor.??

Are you doing a plug chop or just riding about and then when you stop pulling the plug and viewing. The latter will not give you a true reading.