PanzerAce Posted June 10, 2008 Share Posted June 10, 2008 The Mikuni motorcycle carbs shown in the image above are aflat slide, smooth bore design. They are excellent and very tunable carbs. Generally they would be set up for use on an inline 4. For someone with the skills and access to machine tools, making the linkage to set up for an inline 6 would be fairly simple. They use a common throttle shaft running through all of the carbs and a single bell crank for the throttle cables. You're right, after looking at the picture I posted, it actually doesn't look like it would be very hard, assuming there is the space. The biggest issue I guess would be getting them all synched up the first time *shrugs* Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted June 10, 2008 Author Share Posted June 10, 2008 I figured that for the 2 vs 4, and as far as it went, for the inline multis as well, thats why I was thinking multiple bike cars rather than lots of car carbs besides a L20 has 333.33cc per cylinder up to a L30 stroker at 500cc. it's easier to find bike carbs for 750cc twins to 1200 twins etc. to handle similiar cylinder sizes than to find small enough car carbs off little wee econoboxes and link them Quote Link to comment Share on other sites More sharing options...
Guest Scooterpat Posted June 11, 2008 Share Posted June 11, 2008 Synchronizing the carbs really isn't that tough. One vacuum gauge per carb/intake pipe and turn the adjustment screms until they are all the same vacuum. One carb, usually the with the bellcrank attached to it, is the base carb and the others are adjusted to match it. Quote Link to comment Share on other sites More sharing options...
Gareth Posted June 11, 2008 Share Posted June 11, 2008 I don't think it's that important to have a set of carbs from a motorcycle that has similar cylinder displacement to the L-series. Remember that bikes operate at MUCH higher RPM than car engines. I'd imagine that a car engine at, say, 6000RPM and a bike engine at 13000RPM (these figures are only exemplary) should need an equal amount of air to operate properly. Am I wrong? Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted June 12, 2008 Share Posted June 12, 2008 I don't think it's that important to have a set of carbs from a motorcycle that has similar cylinder displacement to the L-series. Remember that bikes operate at MUCH higher RPM than car engines. I'd imagine that a car engine at, say, 6000RPM and a bike engine at 13000RPM (these figures are only exemplary) should need an equal amount of air to operate properly. Am I wrong? Well, really what needs to happen is for the math to be done. Compare the TOTAL amount of air through the intake for say, a minute, at the redline (ie: volume of cc at TDC * rpm/4), and compare what you would be doing on a Z engine (say, for a 3L, 500cc*7500rpm/4 or 937500), and find a carb for a motorcycle engine that would be using the same amount of air per minute at the redline. Quote Link to comment Share on other sites More sharing options...
Xnke Posted June 12, 2008 Share Posted June 12, 2008 Well, for starters, carb throat diameter for a single-intake-event system should be Piston Diameter/3. in the L24, that means a 27mm throat is the minimum carb size for that engine. 30mm is the next largest common size, and would be adequate to start with. If it was me, i'd go with a 36mm carb, per cylinder. But that's still gonna be a pain to tune the first time round. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted June 12, 2008 Share Posted June 12, 2008 Well, for starters, carb throat diameter for a single-intake-event system should be Piston Diameter/3. in the L24, that means a 27mm throat is the minimum carb size for that engine. 30mm is the next largest common size, and would be adequate to start with. If it was me, i'd go with a 36mm carb, per cylinder. But that's still gonna be a pain to tune the first time round. I would love to see where you get that equation, as it COMPLETELY ignores that actual air requirements of the engine. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted June 13, 2008 Share Posted June 13, 2008 Certainly the per cylinder displacement and the RPM are the primary factors in determining the carb size. Motorcycles with a similar cylinder displacement (and stroke) to the 240Z (260Z?, 280Z?) will have a similar RPM range and therefor a similar carb size what we need. Cycles with a smaller cylinder displacement but a higher RPM "might" have a suitable carb size. This is where one must be savvy. I need to determine the size needed for my application and then go look for "it" rather than look around and say "I hope that will work". Quote Link to comment Share on other sites More sharing options...
brokebolt Posted June 20, 2008 Share Posted June 20, 2008 Hey I noticed that nobody mentioned that motorcycle carbs have two types (or I just didn't see it). Like the SU carb their is a slide bore carb (as I heard a bike guy call them) and a open bore carb (again his terminology not mine). I would think the open bore carb would be the better of the two types as the slide bore would be using engine vaccum to open the venture. I would think the vacum would be different between the two engines simply becuase the RPM range is different and the fuel requirements would be different. But if you figured out the fuel curve on either set up it should work. The bore size, if larger than like 32mm should be fine; what does the SU meassure??? 38 or something. After all the magic of the carb is the bore size vs. the ventrue size...the rest is just fuel metering. With a smaller bore carb you may not gain any performance advantage over a twin SU set up or 40mm triple carb set up but that picture posted here sure looks like a nice set up. And if your a bike guy you may have everthing you need to tune them which in multi carb world is a HUGE advantage; six bores means six sets of everthing; huge expense their. Kiwi303 I say try it and if it works...great!!! Just post your results for others to follow and sponge off all your hard work! Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted June 20, 2008 Author Share Posted June 20, 2008 well... update is I lost out on a bid for a set of carbs... Untill I get a motor and carbs together in one place this is going to be in limbo Quote Link to comment Share on other sites More sharing options...
Racer Z Posted June 20, 2008 Share Posted June 20, 2008 "hey wanna go to the beach today? its nice out... lets go for a cruise" --- "nah, maybe next weekend, this weekend im adjusting and balancing my carbs... all six of them" I can't ever decide what's more fun, wrenching or driving. Quote Link to comment Share on other sites More sharing options...
83zed owner Posted June 20, 2008 Share Posted June 20, 2008 I was talking with a garage guy recently who buys old bikes and scraps them for parts. he mentioned running a Toyota 3Y engine in a hilux with 4x 600cc bike carbs, one to each cylinder instead of the stock piece of crap autochoke carb toyota fitted them with. That got me thinking, what would a L series motor be like with individual carbs? straight line equal length tubes out to a motorbike side draft carburettor... If two SU's are good, and 3 Webers are better, what about 6 of them? Anyone done this? should I round up a set of six carbs and hook them up? That's a pretty sweet idea good luck if u dicide to do it and keep us updated. Quote Link to comment Share on other sites More sharing options...
Careless Posted June 20, 2008 Share Posted June 20, 2008 I can't ever decide what's more fun, wrenching or driving. starting to wonder myself :-/ Quote Link to comment Share on other sites More sharing options...
supertip Posted June 30, 2008 Share Posted June 30, 2008 Just purchased 2 sets of 3 carbs from a 850cc 1979 Yamaha bike at Bent Bike in Lynwood, Washington. I will update when i install them. I plan on cutting down a webed efi intake manifold and linking them to that, like this guy did http://forums.evolutionm.net/showthread.php?t=241327 anybody see any problems with this Quote Link to comment Share on other sites More sharing options...
Guest Widebodys30 Posted December 13, 2008 Share Posted December 13, 2008 http://forum.ratsun.net/showthread.php?t=8017 Quote Link to comment Share on other sites More sharing options...
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