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Discussion Starter · #1 ·
ive got an old 640 alpine motor i wanna get running. tons of compression and its got spark. i dont have a tillitson or mikuni, but u have a walbro wf style carb. anyone know what i should set the adjustment screws at? thanks.
 

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Just my 2 cents, between tillitson and walbro I'd rather burn them and put on a Mikuni. Starts easier and runs a lot smoother with a Mikuni IMO.

I have done many tillitson to mikuni conversions on old Rotax engines, which also includes drilling the case and adding an impulse nipple for the fuel pump, and they always seem to run better with the Mikuni (There's a reason they went to Mikuni, haha, tillitson is basically a big chainsaw carb :biggrin_old: ). Not much experience with Walbro, but I just like Mikuni because parts are very plentiful. I did a 640, tillitson to mikuni conversion a couple years back, drilled the case, added an impulse nipple and a fuel pump, and if I remember correctly, I used a VM-32mm or 34mm Mikuni, and the thing ran great.

If you're looking for a Mikuni, I can sell you one, I have a lot of them. Is your 640 the newer style with the impulse port?
 

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Discussion Starter · #3 ·
i have a mikuni, just not the right jetting. i just wanna see if this engine runs and keep it as a spare. it is from a 1975 alpine. it has an impulse port, which i believe is stock. what are the stock tillotson settings, as i think i might have one of those
 
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