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Monty 248 possible bsa 250 motor swap?


2xmonty
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Hi all

I have a 248 that I cant get to run clean after much effort so my engineer pal suggested fitting a 250 BSA engine in it.

Has anyone had an had a Monty with a four stroke motor fitted, I know it may be sacrilege but will be using it for green lane work and after having new forks (chromed and new seals) new rear shocks new headlight and frame paint wheels rebuilt mudguards it seems too good to stop here.

Maybe not the best choice but I had a 348 years ago that was good for trail stuff, if not could sell and look for a 4 stroke.

Cheers Noel  

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I'm taking he's saying a BSA motor as you have one under the workshop bench at home or his place what job to swap motors in a frame and the hard job is to make it look like it came from the factory like it. I can think of lots of motors I would pick up before going for a BSA c15 top first on the list would be a 350 Triumph twin.

Hears a pick of my Honda XR with a twist it's a 84 with a 82 cb250rs motor running a xl head gets used for Green lane work the pic belittles the time it took to get that motor into that frame lets just say the frame is now 25mm longer than before and has no bottom rails

should you go for the motor swap do a build post on hear I love a good build

The things you have to do to get a bike with a comfy seat for that all day ass is ok thing on a Honda

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Edited by pug
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That looks a pro job...

I did not think of a C15 motor its just my mate has rebuilt several small brit single engines with higher quality bearings and upgrades. He did suggest a Triumph 350 saying it would fit in fine, he has built Tribsa's and the like in the past. The alignment is out of my league so only going on advice really. The Montesa 248 engine is difficult to get some parts for (common bottom end with 349) so looking to use this long term, I would buy a 348 or 349 engine if one was going but you dont see them often.

Thanks for the reply 

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As Said a Triumph 350 twin as it's what I would put in it and I have seen one in a Montesa before there are lots of Jap motors around the 250/350 size you could play with. I go with what I have in the parts pile and what's cheap and close by on Evil Bay

Best of luck with the Build

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The C15 is probably a bit tall to fit in the Mont frame, and the triumph engine a bit heavy and wide. Unless you are in for the long haul try again to get the original engine going, it's probably not a huge issue and if you don't like it at least you can sell it on reasonably easily

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The sound of good reasoning thanks I would rebuild it but the parts are hard to get hold of. I should have looked for a 4 stroke engined bike in the first place because I would be using it on road throughout the winter months as well as a bit of light trail riding. The 248 starts 2nd kick has good compression but smokes a lot which is not too good for the road, the bore is good carb rebuilt with original spec parts just cannot get my head around it so will probably sell on.

Thanks for the reply

 

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The sound of good reasoning thanks I would rebuild it but the parts are hard to get hold of. I should have looked for a 4 stroke engined bike in the first place because I would be using it on road throughout the winter months as well as a bit of light trail riding. The 248 starts 2nd kick has good compression but smokes a lot which is not too good for the road, the bore is good carb rebuilt with original spec parts just cannot get my head around it so will probably sell on.

Thanks for the reply

Got a pair will fit and try again.... Cheers

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