Wanted: After a Twin Carb setup
Discussion
You won't gain a lot by putting twins on an 850. In fact, a single 1.5" SU on a better inlet manifold will be just as good and a lot easier to set up. Basically, the standard head on an 850 is just so restrictive and a better way of getting some more power is to find a 12G295 Cooper 998 head, have it skimmed to get the comp ratio to around 9.7:1 and put on a 1.5" SU.Typically this will give you a noticeable power increase up from c.34 bhp to, maybe, 44 bhp or thereabouts. A set of 1.5" roller rockers would help if the basic 850 cam is to be retained.
Re-time the dizzy to get a bit more top-end advance, but only a couple of degrees or so.
Re-time the dizzy to get a bit more top-end advance, but only a couple of degrees or so.
Cooperman said:
You won't gain a lot by putting twins on an 850. In fact, a single 1.5" SU on a better inlet manifold will be just as good and a lot easier to set up. Basically, the standard head on an 850 is just so restrictive and a better way of getting some more power is to find a 12G295 Cooper 998 head, have it skimmed to get the comp ratio to around 9.7:1 and put on a 1.5" SU.Typically this will give you a noticeable power increase up from c.34 bhp to, maybe, 44 bhp or thereabouts. A set of 1.5" roller rockers would help if the basic 850 cam is to be retained.
Re-time the dizzy to get a bit more top-end advance, but only a couple of degrees or so.
.Re-time the dizzy to get a bit more top-end advance, but only a couple of degrees or so.
if you take a look at the vizard tuning bible it duz state that if you are running for instance a standard engine with a single 1.5"su you wont get any power increase by slapping on a 1.75"su or twin carbs without modifying your engine. If at standard with 1.5"su you are reaching say 5500rpms a 1.75"su would perform exactly the same, it only comes into play from 5500rpm which is where the 1.5" left off. so twin carbs would be a waste of time and money. Get yourself the vizard tuning manual it has everything you need to know about everything. good look. p.s i will check my 850 head i have spare it is possibly a 12g295.
Edited by dogfather on Wednesday 18th June 18:33
dogfather said:
Cooperman said:
You won't gain a lot by putting twins on an 850. In fact, a single 1.5" SU on a better inlet manifold will be just as good and a lot easier to set up. Basically, the standard head on an 850 is just so restrictive and a better way of getting some more power is to find a 12G295 Cooper 998 head, have it skimmed to get the comp ratio to around 9.7:1 and put on a 1.5" SU.Typically this will give you a noticeable power increase up from c.34 bhp to, maybe, 44 bhp or thereabouts. A set of 1.5" roller rockers would help if the basic 850 cam is to be retained.
Re-time the dizzy to get a bit more top-end advance, but only a couple of degrees or so.
.Re-time the dizzy to get a bit more top-end advance, but only a couple of degrees or so.
if you take a look at the vizard tuning bible it duz state that if you are running for instance a standard engine with a single 1.5"su you wont get any power increase by slapping on a 1.75"su or twin carbs without modifying your engine. If at standard with 1.5"su you are reaching say 5500rpms a 1.75"su would perform exactly the same, it only comes into play from 5500rpm which is where the 1.5" left off. so twin carbs would be a waste of time and money. Get yourself the vizard tuning manual it has everything you need to know about everything. good look. p.s i will check my 850 head i have spare it is possibly a 12g295.
Edited by dogfather on Wednesday 18th June 18:33
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