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dr nosh

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  2. Cota 348 cracked engine case

    in Montesa

    Posted · Edited by dr nosh

    Engine through bolts are M7 (as are all the engine outer casings).

     

    I did not torque mine up. Just used flat washer, spring washer, drop of thread lock.

     

    You might have to resprt to the  Dremel method to remove the bearing race out - 3 or 4 surgical cuts....

  3. Cota 348 cracked engine case

    in Montesa

    Posted

    Very common problem.

    That lug on the kickstart shaft always causes this damage if rotated too far round.

    Seen it lots of time, and search posts on here for other pictures etc.

    Will need proper welding - preparation is key. If the case is oily welding will be difficult. Casting will need thorough degreasing.

    So, engine out, head and barrel off, split crankcases etc, etc.

    Otherwise the timing case will fill with water, mud, oil etc and spoil the Electrex electronic ignition that somebody (you?) have fitted.

  8. MH 200

    in Montesa

    Posted

    Last on here a lot when building a 248.  

    Now that has gone, I am looking at a MH200, year 1983. (According to the VMCC dating cert for the V5).

    So, one key question. It has a plastic tank under the cover. What is the current position with modern, ethanol fuel with the plastic.

     

    Do you need to use a 'special' additive in the fuel?

     

    Does the tank have to be lined?


    Is there an alloy fuel tank from another Montesa that fits as a replacement?

  12. 1981 Montesa cota 248

    in Montesa

    Posted

    Your gear change problem is the dimpled plate held in place by the M6 nut. Its an eccentric adjuster. Has to be i the right pace to get all the gears.

     

    Its a 40 year old bike, laid up for 20 years.

     

    I would budget for:

    Crankshaft seals (can be replaced without splitting the cases). You need a special puller tool to get the pinion gear off the crankshaft. Dont try to use anything else, you will damage the pinion gear.

    Have a look at bore and rings. You might get away with honing the bore.

    Flush out the fuel tank (alloy under the f/glass cover).

    Clean carb and jets. (Its a mkII concentric)

    Ensure float and shut off needle are E10 proof. (Go to Surry Cycles for carb parts.

    Replace the fuel pipe tank tap to carb. E10 will eat the old rubber.

    Replace air cleaner.

    Swinging arm bushes check

    Rear shocks - check damping

    General lubrication - cables

    Check grease in wheel bearings,

    Lube chain.

    Tyres - Probably perished, replace + tubes

     

    Could go on. 

     

    Hope this helps.

     

     

     

     

  14. Cota 247 Removing Rear Wheel

    in Montesa

    Posted

    Yes. The arrowed part is the chain/wheel alignment device.

    It acts as a cam, rotating about the spindle and bearing against a peg just forward of the wheel axle.

    The position should be the same on both sides.

    Judging by the postion of the cams, it looks like either the chain is badly adjusted, or more likely the chain and both sprockets are worn out.

    Photograph below is from my later 248 model, but the same principle. Note the notches in the outer diameter. 

    This is the position with brand new chain and sprockets.

     

    SAM_1202.JPG

  15. 349 rebuild take 3

    in Montesa

    Posted

    Looking good.

     

    Bars. 22mm = 7/8".  The original bars would have been 1". You will probably need a set of shims to go into the standard clamps. I have a set available. PM me.

    Rear sprocket. What locking have you got on the nuts? Spring washer or thread lock?

    M8 pinch bolt in the bottom of the r/h fork leg?

     

    Agree, I had good service from Bike Revival UK.

  17. 349 rebuild......slowly!

    in Montesa

    Posted

    Make sure that you 'flat' all the gloss to a matt finish with 1200 grit or the clear coat will not adhere and will eventually lift.

    Clearcoat is 'thinner' than paint with colour pigments, so don't layer on too thickly, just light coats and a few of them.

    Dust control is very important with clearcoat - it will show all the inclusions and imperfections.

     

    Good luck.

  18. 349 rebuild......slowly!

    in Montesa

    Posted · Edited by dr nosh
    Added Pictures

    When I did mine, I used a rattle can for the primer/filler build up, then rattle can brilliant white. Flatted it back to matt (500 and 1200 grit), applied decals (last original set from Vallmoto), then had an aquaintance with a body shop apply 2k clear coat in his painting booth.

    That was petrol proof.

     

     

    Finished 05.JPG

    Finished 11.JPG

  19. Fibreglass Fuel Tanks

    in Montesa

    Posted

    As has been said above, its not going to be the use of a f/glass tank at a twinshock trial, but rathermore the E5 and E10 ethanol containing fuels that will be effectively be 'eating' and destroying the fibreglass. (Along with fuel lines, plastic carb floats, rubber tipped and plastic float needles).

    Its a well documented fact.

     

     

  21. Cota 247 Standard Gearing

    in Montesa

    Posted

    Marky16.

    What kind of help are you looking for?

    You dont know how many teeth on front or rear sprocket?

    You dont know where to buy standard sprockets?

    You have purchased some standard sprockets but they dont fit the rear wheel or the gearbox shaft?

    Your 520 chain does not fit the sprockets that you already have?

    Your 520 chain is slipping/jumping on the sprockets that you already have?

    etc, etc.

     

    Be a bit more specific or descriptive to help us help you.

     

     

     

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