Mikuni Sizing Advice Needed

Velocipede · 12-12-2012, 05:19 PM

Pardon me if this has been discussed before but after at least a couple of years mulling it over I am finally going to get me a pair of Mikuni VM round slide carbs for my 89 R100 GSPD.

The Bings on my bike are 40 MM's and I'm wondering what would be the best size to go for with Mikuni's.I did read of one inmate who put 36MM's on his R100 and was happy with them.Has anyone used the 38MM's and how did they work.Any advice on jetting would be most appreciated too.

The old girl wont know herself this coming spring,new Endurolast Alternator and Ignition,Progressive springs and Emulators plus a six pot caliper to replace the less than spectacular stopping power of the original Brembo.Also a lowered Corbin Gunfighter to help me plant my feet and oh yes top loading Pelican cases to go with the Pelican top case.Can't wait.

John

Houseoffubar · 12-12-2012, 06:48 PM

the 38mm Mikuni's work great on R100's. The carbs match the ports fantastic when used with San Jose spigots, they have lots of top end, and pull cleanly from idle all the way up. I can't ask for more.

supershaft · 12-12-2012, 07:05 PM

It basically boils down to 36's or 38's. With your small port heads with raised port floors, I would go with 38's. 38mm Mikuni's have a lot more low end response than even 32mm Bing's so it's pretty much a win/win.

Kai Ju · 12-12-2012, 08:22 PM

I'm running VM38's with stock intake spigots and rubbers on the head side and stock elbows inserted into the bellmouth of the Mikunis, sealed with the silicone tape between the outside of the elbow and the inside of the bellmouth.
Better response, power and better mileage.

Velocipede · 12-13-2012, 07:14 AM

Thanks guys for the words I was hoping to hear

.Can you remember if you changed the jetting and if so what sizes did you use.?

John

12-12-2012, 05:19 PM	#1
Velocipede ^OP Gnarly Adventurer Joined: Mar 2006 Location: Kingston Ontario Canada Oddometer: 313	Mikuni Sizing Advice Needed Pardon me if this has been discussed before but after at least a couple of years mulling it over I am finally going to get me a pair of Mikuni VM round slide carbs for my 89 R100 GSPD. The Bings on my bike are 40 MM's and I'm wondering what would be the best size to go for with Mikuni's.I did read of one inmate who put 36MM's on his R100 and was happy with them.Has anyone used the 38MM's and how did they work.Any advice on jetting would be most appreciated too. The old girl wont know herself this coming spring,new Endurolast Alternator and Ignition,Progressive springs and Emulators plus a six pot caliper to replace the less than spectacular stopping power of the original Brembo.Also a lowered Corbin Gunfighter to help me plant my feet and oh yes top loading Pelican cases to go with the Pelican top case.Can't wait. John

12-12-2012, 06:48 PM	#2
Houseoffubar fine beer sampler Joined: Dec 2010 Location: Bothell, Washington Oddometer: 1,533	the 38mm Mikuni's work great on R100's. The carbs match the ports fantastic when used with San Jose spigots, they have lots of top end, and pull cleanly from idle all the way up. I can't ask for more. __________________ Performance Welding Service 1978 R100/7 Build thread 1915 Boardtrack racer replica (Electric Powered) Lots of bicycles Hemp: The strongest natural fiber in the world, and the most nutritious plant on earth.....why is this illegal again?

12-13-2012, 07:14 AM	#5
Velocipede ^OP Gnarly Adventurer Joined: Mar 2006 Location: Kingston Ontario Canada Oddometer: 313	Thanks guys for the words I was hoping to hear.Can you remember if you changed the jetting and if so what sizes did you use.? John

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: .
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

12-12-2012, 07:05 PM	#3
supershaft because I can Joined: Sep 2010 Location: San Francisco Bay area Oddometer: 6,073	It basically boils down to 36's or 38's. With your small port heads with raised port floors, I would go with 38's. 38mm Mikuni's have a lot more low end response than even 32mm Bing's so it's pretty much a win/win.

12-12-2012, 08:22 PM	#4
Kai Ju Beastly Adventurer Joined: Jul 2009 Location: So Cal Oddometer: 1,025	I'm running VM38's with stock intake spigots and rubbers on the head side and stock elbows inserted into the bellmouth of the Mikunis, sealed with the silicone tape between the outside of the elbow and the inside of the bellmouth. Better response, power and better mileage.