e21 on bike carbs????

Is it a carb engine? If so, sunday afternoon job using your current ignition system.

I haven't done it on one of those, but i put CBR600F-X carbs on an '80s VW Polo with 1.6 bottom end, set up was effectively a 1.6 8v carb engine with stock electronic ignition, and i didn't touch the ignition - just swapped the downdraught carb for the bike carbs and it ran great.

The carbs will obviously need a tune, ideally on a rolling road, those particular carbs would need the mains to be about 155-160 mmm but it varies between carbs and engine designs obviously.

Fuel line, throttle cable, and choke cable is all you need (and a very low pressure, but fast feed fuel supply - simple T-piece on a return line an ideal fuel distributor, though the bike pump is obviously best - i don't like regulators with bike carbs).

If it's an injection engine, then i don't know the best route (although if it'll take a dizzy, then you can go down the above route).
Custom ignition is obviously preferable if you're gonna change the cam or do other work to change the curves, but otherwise the carbs will be fine as a straight swap and merely amplify what you have.

Bogg bros seems to be everyone's proffered choice

Simpleton make tho, I just made mine today with a few 45 degree exhaust bends and a flange cut to the correct size


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No-one does an off the shelf bike carb manifold so will need to make one yourself

There was a chap on ebay selling laser cut flanges for the M10 in either small-port (which will suit your engine) or later large-port(injection M10) heads then just get hold of some tube the correct diameter and weld it up

Fraid not dude I bought a large-port flange to go on the E30 M10 I was building up for my E21 but decided to go turbo instead so didnt use it....but might make a custom inlet to suit that depending on how the turbo performs its a pretty simple flange layout so could just take a template off your existing manifold and cut it out of steel plate for proper cheapness

Cheers for all the help! I was thinking of scribing round the existing manifold on some quarter plate or summert? I'll let you know how I go on!

mikey you are a legend sir! I'm going to a bike breakers at weekend to find some suitable carbs? on with the fabrication!!!!

retrorides.proboards.com/user/7826

This gentleman - very nice guy by the name of Rob - had an M10 running bike carbs in an E30.

I had zx9r carbs on my m10 e30 1.8. I re-spaced the carbs to match the inlets which made making the manifold easier. I bought a laser cut flange off eBay and made the runners from mild steel pipe. I used a fuel pressure regulator and the standard fuel pump. I think I have a spare flange in the garage if you're interested?

I'll see if I can dig it out this week.