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Hello David, Thank you for the time and effort that you are putting into helping me work my way through this. I have the standard airbox and a new, oiled filter. A new rubber connector for the carb, and as far as I am aware no restrictions in the exhaust (though I will whip it off and have another look). Ignition timing is set BTDC, though I am a little intrigued by the fact that I do not seem to be able to over advance to the point of getting it to kick back. Over the thirty years that I have worked on bikes I have sometimes used this ploy as a starting point when I did not know the timing spec, just another little mystery. I cannot vouch for anything inside the motor though as far as I am aware everything is standard 348. As to the oil ratio, everyone I know here in the NE USA uses at a minimum 50:1, and friend who is an aknowledged Ossa expert, plus a Montesa dealer of many years tell me 80:1 for the 348. I have run the TY on 50:1 for the last six years without any problems or signs of wear on its annual strip down. Anyway, thanks again for all of the help, it is much appreciated. Mike

Hello and thank you for the rapid reply. The Mikuni is new from Sudco the US importer and was fitted with the slide, needle and jets as quoted to me by a US Montesa fellah. The engine has new points, condenser and spark plug all set as per Montesa specs. New crankcase oil seals, and shows 125 pounds secondary compression. I am running 80:1 with synthetic oil. It seems to be running rich as I do get a fair bit of blue smoke and a wet plug. It may be that I am expecting something that I will not get with the 348 with its extra drive side flywheel etc. I use a TY 250 at the moment and the performance of that, particularly off closed throttle, is my point of reference. The 348 will not pick up the front wheel and the exhaust note sounds a bit flat. Basicaly I am being lazy and hoping that someone can give me a closer carb spec to save me some time. We all live in hope. Mike.

I am restoring a pair of Montesas and need some help with the jetting. I have new Mikuni VM26 carbs for each and have been given jetting for both from a couple of sources here in the US (expat Yorkshireman), but the 348 which is finished would not pull the skin of a rice pudding. Any one have any experience of putting Mikunis on the 348/349. Thank You.