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36mm Mikuni Flatslide rennsport back to Dellorto phf 32mm

across

across

Just got it firing!
Joined
Apr 14, 2014
Messages
7
Location
Southern California
I am currently taking my T-3 back from some rennsport mods (for good or bad) but currently I have a pair of big ugly 36mm flat slide mikuni carbs on there. Could I go down from 36mm size carbs to 32mm Dellorto phfs with the bell cranks on top or would that just be a rat nest of re jetting and a step backwards, or should I just go with a 36mm PHF?
 
Not knowing the other engine mods it is difficult to say. Originally the bike had 30mm square slides, but it depends on the mods you will leave in place which carb would work best.
 
It has a dual plug head a has been bored out to 1000 cc. all done by the previous owner who had a lot of rennsport mods done.
 
The dual plug heads have no impact on carb size, just ignition timing. As to carb size, either the 32 or 36 would be OK and you shouldn't need a bunch of jetting changes. I'd start with jet and atomizer sizes near the factor delivered for a 1000cc bike from Guzzi. You may find the Mikuni used jets of similar size. All the carb size really changes is the RPM of best efficiency. There is a spreadsheet in the Download section where you can enter bore, stroke, and carb size and it will tell you the approximate best RPM for efficiency. Then select the size you want based on that. The smaller the carb, the lower the optimum RPM. https://www.guzzitech.com/forums/resources/carb-sizer.188/
 
ok I will begin the research on this. Thank you very much for the information!!! This will probably be a slow process, but I will post any results in hopes it helps another member if they decide to do the same. Cheers
 
across said:
I am currently taking my T-3 back from some rennsport mods (for good or bad) but currently I have a pair of big ugly 36mm flat slide mikuni carbs on there. Could I go down from 36mm size carbs to 32mm Dellorto phfs with the bell cranks on top or would that just be a rat nest of re jetting and a step backwards, or should I just go with a 36mm PHF?
Click to expand...
Hi,
Wonder if you still have the 36 Mikunis and, if you'd like to sell/swop?
Carlo Guzzi
 
I would think that your inlet tract has been enlarged to fit the 36mm Mikuni's, so I would go for 36mm Dellorto's. A 1000cc engine runs fine with that size carb, in fact you could run 38 or 40mm without problems. I know there are Mikuni VM round slide kits with filters and cables for sale, I believe Sudco has them for classic bike upgrades? They might be a little easier on the throttle hand than the Dellorto's as well.
 
jr1967 said:
I would think that your inlet tract has been enlarged to fit the 36mm Mikuni's, so I would go for 36mm Dellorto's. A 1000cc engine runs fine with that size carb, in fact you could run 38 or 40mm without problems. I know there are Mikuni VM round slide kits with filters and cables for sale, I believe Sudco has them for classic bike upgrades? They might be a little easier on the throttle hand than the Dellorto's as well.
Click to expand...


38 or 40mm could be to large if the heads don't have the large valves like the MK IV and MK V LeMans engines.
 
jr1967 said:
I would think that your inlet tract has been enlarged to fit the 36mm Mikuni's, so I would go for 36mm Dellorto's. A 1000cc engine runs fine with that size carb, in fact you could run 38 or 40mm without problems. I know there are Mikuni VM round slide kits with filters and cables for sale, I believe Sudco has them for classic bike upgrades? They might be a little easier on the throttle hand than the Dellorto's as well.
Click to expand...
Thanks for the technical advice but, my inquiry was whether you still had the Mikunis and, whether you would like to sell/swop.
 
john zibell said:
38 or 40mm could be to large if the heads don't have the large valves like the MK IV and MK V LeMans engines.
Click to expand...
For a stock bike I agree, just not for a bike that has been worked on. I ran a 992cc LM2 with 40mm Dellorto's that had 90% of it's torque from 3000 up to 8000rpm. No bogging at lower rpm's. It ran fantastic plus it did a real 46.5mpg at 100mph measured over a few months of 230 mile/day commute. Apart from the heavy throttle I would recommend it. Could the same result have been achieved with 36mm's? I don't know, mine were worn out and they were unavailable at the time, so they gave me a deal on the 40mm's.
In case of the bike of the original poster here, I'd go with the manifold size, not smaller.
 
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