Bike carbs

Hello,

I'm sure this has been covered but from all my reading I simply can't quite figure out my issue.

I have a mk1 (with a polo GT 1.3 head/1.4 bottom end) and some GSX bike carbs. I bought the engine with carbs in one unit from another car. I slotted it all in after servicing the carbs and she runs - pretty well too. But start up is very rough and lumpy until a few minutes in tickover settles a bit. Great on full revs but idle is always a bit lumpy and cold/warm start up is like starting a lawn mower.

The manifold is 4 seperate 'top hat' type… no take offs so can't balance the carbs. Is it the balance by the sounds of things? I could tap the 'top hats' and meter/balance… I did relocate the bike pump to next to the tank - was in the bay - which made things marginally better on startup.

Considering sticking a normal carb on - maybe even weber 40s but if it potentially will run smooth i'm happy to keep em so seems a bit drastic. Can carbs be as civalised as a weber?



thanks all,

Tom

Have you got the choke connected for start up on the carbs?

Should be a slider at the front

You should be able to balance the carbs by using a vacuum balancer on the trumpet, no need for take offs on the manifold.

Interesting about the pump move.

I have twin 40's on my Derby, that's got a 1272cc in it. Runs nice.
I think they'll always be a bit rough at tickover and low revs tbh. At the end of the day they are desiged to run

Flat out. Plus they were never designed for these applications really so a compromise is probably to ve expected I suppose.

Thanks for the feedback - you've kinda confirmed my thinking. Having never seen or driven a car on bike carbs i haven't much to go by.

Yes the choke hooked up, and essential I might add!

I've not got any trumpets on the carbs - might be an idea! They are just bare carbs atm.

I thought you monitored the pressure within the manifold so between carb and combustion chamber. I know some carbs have a take off where they connect onto a manifold - not these though. Can you simply monitor the 'pull' into the carb..?

Tom

just found this

- YouTube

I'm assuming it's the same as balancing twin 40's and the carb balancer goes on to the air induction bit of the carb and you make the little plastic thing in the tube thing dance in the same place on each carb.

Hope you like my technical imagery  

i getcha