Bike carbs on m20b23

[Marcoqm]

Hello, I'm one of many who have given up on keeping the Solex 4A1 running properly on their M20. Obviously, I wanted to install a triple weber dcoe setup, however it's way out of budget. I currently have a few bike carburetor options I'm considering. I could buy three sets of Suzuki GS500 carbs, which would make a fairly straightforward adaptation, but I'm not sure I'd get enough power out of them. My other option would be to buy two sets of four Honda CBR1000 carbs, however I'm not sure how easy it would be to adapt them or if it's even possible. There's several threads on these sorts of adaptations for M10 engines, but I haven't found any info at all on using bike carbs on an M20. Does anyone have any experience or suggestions, or can link me to a thread that could be helpful?

[Wilmo]

For a long time I was planning on using Misumi or Keirin carbs on my M10. In the end I went the fuel injection way, which turned out to be a lot of fun.

I chose the throttle bodies of a 2002 Suzuki GSXR1000 because of the relatively small choke and the fact that I could part them. The new stack of four throttle bodies has now 100mm spacing instead of 80mm.

This is one of the earlier iterations: viewtopic.php?p=317265#p317265

You have to do a bit of engineering in order to get the main shaft as stiff as possible, in order to get the similarities between the six throttles.

[Marcoqm]

For a long time I was planning on using Misumi or Keirin carbs on my M10. In the end I went the fuel injection way, which turned out to be a lot of fun.

I chose the throttle bodies of a 2002 Suzuki GSXR1000 because of the relatively small choke and the fact that I could part them. The new stack of four throttle bodies has now 100mm spacing instead of 80mm.

This is one of the earlier iterations: https://bmwe21.net/forum/viewtopic.php?p=317265#p317265

You have to do a bit of engineering in order to get the main shaft as stiff as possible, in order to get the similarities between the six throttles.

I see, so you took apart the stack in order to space them out properly, theoretically I'd just have to do something similar but adding two more carburetors? (Ignoring the hassle of the fuel rail and throttle linkage of course, that's a whole other issue I'll have to tackle later)

[Wilmo]

Yeah, something like that! Solving the spacing at the carbs/throttles instead of in the manifold saves a lot. The throttle linkage needs doing anyways.

The cylinders on a 2.3 are smaller than on an M10 1.8 or 2.0. I would say something like a choke of 36 or 38mm. Certainly not 'as big as possible'.

Another thing to consider is the length of the runners. Cylinders with one inlet valve with 'limited' rpm need quite some length, a lot more than you see on average.



When you tune this right, quite a lot will happen with torque. A 20" runner is unpractical, but 15", or 40cm, can be approached.

[Marcoqm]

Ended up buying two stacks of '91 CBR1000 carburetors, will have to do a lot of fiddling and learning to get it to work but it'll be a fun little project. Will be one of the few M20s running on bike carbs, so I'll try to keep this updated in case I can provide info for future people interested in doing the same.

[Wilmo]

Cool! Please keep us updated and always feel free to ask questions. Feel free to introduce the car, and yourself, on the forum as well!

[Marcoqm]

Cool! Please keep us updated and always feel free to ask questions. Feel free to introduce the car, and yourself, on the forum as well!

Is there a specific place to introduce myself, or do i just do it here?

[Manitoba]

Please use the 6-cilinder register. You can create your own car topic there for us to follow, read and help.

Greetz,
Walter.

[JuhKu]

Ended up buying two stacks of '91 CBR1000 carburetors, will have to do a lot of fiddling and learning to get it to work but it'll be a fun little project. Will be one of the few M20s running on bike carbs, so I'll try to keep this updated in case I can provide info for future people interested in doing the same.

Propably its too late to propose these Chinise Weber copy carbs DCOE and IDF. I'm running 44IDF copy carbs on my 2.3L at the moment, just and only for budget reasons. But these works surprisingly well. Cost ratio comparing to Webers were 1/3, when i bought these. I have VGS manifold for my "IDF" 's, just little fine tuning with the throttle valve shaft axle width and those fit to the manifold.
If you don't have to work on the mental side to be age appropriate these could be an option.
I must say i have issue with that and i'm going to change REAL Webers sooner or later

[nic65]

anche io uso le copie cinesi sul mio M10 2000cc....vanno molto bene