Can VM carbs be swapped out for CV carbs?

[Roadwarrior]

I've got a 1978 GS550 with the stock VM carbs. I was wondering if it would be possible to swap out the carbs for a set of 1980 - 1983 CV carbs. Im hoping the CV carbs would offer better fuel economy, better drivability, and better warm up. Has anybody tried this? What would I need other than the carbs, rubber manifolds? Choke cable?

 

[earlfor]

Re: Can VM carbs be swapped out for CV carbs?

As far as I know, none of the early GS models that used VM carbs have head castings that can be mated to later model CV carbs. You cannot replace a 26mm VM carb with a 26mm CV carb because the flow is not the same. It takes a 32 mm CV carb to provide the flow of a 26 MM VM There are no 32 mm spigots that will mate to a 26 mm head intake and if there was, it wouldnt work because it would change the throughflow characteristics due to neck down.

For the average backyard mech, it isnt doable. If one is a machinist with skills in fluid dynamics, its doable, but probably not worth the effort.

My opinion is that the VM carbs are more tunable/adjustable than the CV.
I find the VM's easier to set up since there is more flexibility. Changing from VM to CV is not a quick and easy fix anyway, as the CV style still needs to be tuned. A clean, well set up rack of VM's will run as good if not better. Its all in the guy on the end of the wrench.

Earl

I've got a 1978 GS550 with the stock VM carbs. I was wondering if it would be possible to swap out the carbs for a set of 1980 - 1983 CV carbs. Im hoping the CV carbs would offer better fuel economy, better drivability, and better warm up. Has anybody tried this? What would I need other than the carbs, rubber manifolds? Choke cable?

 

[AOD]

My thoughts are with Earl's. I don't think you would see a vast improvement in fuel economy or warm-up by switching carbs. If the VM carbs you have are cleaned good and set up properly, they'll warm up plenty quick.

~Adam

 

[SqDancerLynn1]

Plus the 550 probably has 22mm VM's