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Will cv carbs fit a '79 with vm carbs

  • Thread starter Thread starter cacker
  • Start date Start date
C

cacker

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I have been having a heck of a time with the carbs on my '79 gs850g. Completely cleaned, rebuild kit, new air box and head boots, airbox sealed, new filter etc. Complete top end job with new valves, rings, etc.
Can't get the bike to run lean enough on the low jets. Have the fuel pilot jet at 3/4 and the air jet at about 2. Also get only about 30 mpg, but it does ride smooth and engine is great above 3k rpm.
My question is, can I put CV carbs in this bike without modifications?

Thanks
 
You'll need to do some mods - cylinder mounts, airbox, cables etc. In my opinion you're much better off with the VMs. If it's running rich have you checked your float levels / valves for wear plus the choke plungers to make sure that they are sealing off properly?
 
If you used a rebuild kit, the crappy jets in there may be your problem

Do you still have the stock main and pilot jets?

Cv carbs would require a new head as well as all that other stuff
 
Tried the old jets

Tried the old jets

I replaced the jets from the rebuild kit with the jets that were in originally (don't know if they were stock or from another rebuild kit) didn't make any difference that I could tell. Put the jets from the rebuild kit back in.
 
What indications do you have that the bike is running rich on the low speed circuit?

Your first post says that you have the air screws set at 2 turns and the mixture screws set at 3/4 turn. These may not be right. Each carb will need to be adjusted seperately from that starting point. There is an article somewhere on this forum or Basscliff's site that explains it. But, I would start with the air screws on each carb one at a time and adjust them for best idle. Then do each mixture screw for best idle as well.

During this process keep adjusting the idle speed to keep it at the book recommended RPM. If the idle gets too high you could come out of the low speed circuit which will make it hard to see the changes you are making in the mixture.

Chris

ETA: BTW, the VM carbs allow for more/easier adjustment and I believe you are better off sticking with them and getting them adjusted. I also agree that to use the CV carbs with larger throats you will need to replace the head with a later model that uses the CV's.
 
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To go to CV carbs, you would need to transplant a cylinder head, along with the carb boots, carbs, and airbox.

It would be much easier to get it running right with the VM carbs. Is there anyone local who might be able to drop by and take a look?
 
cacker said:
I replaced the jets from the rebuild kit with the jets that were in originally (don't know if they were stock or from another rebuild kit) didn't make any difference that I could tell. Put the jets from the rebuild kit back in.
Click to expand...

So, what are the sizes of the jets - be sure that all 4 are the same size?!

The stock ones will have the Mikuni stamp on them as well as the size

Also, where is the needle(s) set ?
 
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