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happycyd

Help needed

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OK - it’s time to bite the bullet. With much trepidation dragged out the 349 montesa from under the bench in the garage . Yep it’s a box of bits.

  The frame isn’t the issue - it’s the engine - I’ve an owner’s manual - it has exploded diagrams which are helpful. However, I’m looking for a strip and rebuild manual for the engine ( along with all the associated wrinkles to make the rebuild a smooth experience ) . I’ve plenty mechanical experience , but it’s always better to read a manual/ article before starting. ( many years of experience has taught me this is a wise way go! ).

  Apparently the montesa has interesting shimming!!!
Any advice would be greatly appreciated - to point on the way.

 Many thanks for reading - stay safe and well.

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Slide it back in under the bench and buy a fantic a guy in our club used to call them multi gyms for good reason

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Sorry to be the bearer of bad news, but there is no service manual for the 348, 349, or 350 series Cota's. Closest you'll find is the Clymer Service Manual for the 1965 through 1975 125 - 360 cc singles. They come up occasionally on Ebay.

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They are the same basic layout as every other motor of the era but there are features that some people haven't come across before. Here are some things that spring to mind:

The conrod is held centred on the crankpin by spacers on the gudgeon pin.

The primary drive crankhaft gear is mounted on a taper which needs a special puller to remove without damaging the teeth.

The cylinder is held on with 7mm internal hex nuts.

The positioning (and side play) of the crankshaft is set using shims behind the crank seal carriers.

The kickstart travel stop is a weak design and very commonly broken which allows dust and water into the magneto casing.

Take note of how the shift mechanism is set up before you pull it apart.

Yes the side play and positioning of the gearbox shafts is important but if you use the same shims in the same spots and use the same thickness centre gasket 0.5mm it will probably be fine.

Pistons are very expensive.

 

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 Hi , 

I have bultaco , montesa , think montesa little more care patience , gears like to fall all over the place , , you shop around find exp montesa repair dude , have  him do short block , just a suggestion  maby at bike show ,,,,,

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Having just finished my 348 rebuild, all i can say is yes its a bit of a challenge but interesting, buy more than one crankcase gasket (i used 3) as the shimming is awkward to get spot on,  i lost my free play when fully tightening up the cases, then found i hadnt got the gear selection right as the shafts tightened as well, the clymer manual isnt too good to be honest but better than nothing. Soak the barrel nuts well, i used a ground down oversize allen key and then bought new nuts ohh and dont lose the little washers underneath. Need any help along the way just ask ?  cheers Mark

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The 7 mm allen key you need for the head studs is easier to get these days.

It certainly isnt in any standard key set but lots of german cars use them in the brakes.

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I got a 349 rebuild article which was a copied from an old TMX, The rebuild was done by Sandiford's and is pretty comprehensive. Pops up every now and again on ebay. I go the 7mm allen keys of ebay as well. Hope that helps...

cheers Guy 

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Hi Sparkieb,

Just sent you a message on shimming, keen to understand the setup

Cheers

Guy

 

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If the engine is still together, when you split the crankcases do it carefully and try and keep the gears located on the shafts with the shafts still located one of the halves (r/h side I think from memory)  If it's like the 247 Cota (I think it is but it's been years since I split one)  some of the gears run on individual rollers (three per gear)  They are different lengths and If they fall off the shafts and onto the bench when you split the cases you won't know which has come from where. Being careful also means any shims will stay in situ on the shaft or stay stuck to the bearing face so you can refit in the same place when reassembling as Feetupfun mentioned (same for crank shims)

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