a1200 and a1500 standard carby

[pieman]

can any 1 tell me if the jet sizing throughout the carbies of standad factory fitted carbies are the same. I feel they should be due to although there is 25% difference in volume of air/fuel mixture per minute the fuel ratio would be consistent or am i missing something with this theory.

[philip1]

physically they are the same jetting they are not

[ggzilla]

They are all 26/30carburetors.

* The A12 carburetors are jetted richer than the A15 carburetors

* A12 carburetors have 20/26 primary/secondary venturis

* A15 have bigger 21/27 or 23/27 venturis

[pieman]

So swap the venturies , main and idle jet and all should be sweet? If your wondering one is manual choke other is electric. the top of one is cactus both hitachi but not interchagable. The other jets and plugs in the body of one have been butchered although both run fine on there respective engines however if I muck around trying to remove the other juts may render one of the carbies usless

[ggzilla]

Don't swap any parts. A12 carb runs on A15, and vice-versa.

 

1971 carb has manual choke, all others are automatic.

[pieman]

I beg to differ. the 1500 carby made the 1200 run smoky (yes float level is fine as it runs the 1500 fine). I'm running the motors in vanette's (C20) manuel choke std in the 81 mod they seem to go electric in 82. well thats how my lot are configured anyhow. 1 x 81 mod , 3 x 82 mod. (we are a little behind the times over here on the other side of the pond (Aust.)

[ggzilla]

Well if you already knew it, why'd you ask? I have run large carbs and stock carbs mix/match with no problems. Not the optimal jetting, but not observedly smoking or anything like that.

 

In USA, A15 carbies are all lean-jetted for emission control, even catalytic converter. By contrast 1971-1973 A12 had minimal emissions and richer jetting. Your KMs may vary in Australia.

[pieman]

Didn't know until I swapped them the other day. I asked the question before I did the change. The motor where set up originally for leaded fuel Aus didnt stop leaded fuel until about 5 years ago, however have been running them on 98 octanr(our premium unleaded) for some years now.

[ggzilla]

We've been running ours on unleaded since the late 1980s, no problems. The sintered valve seats work good, even though they were designed in the back in the 1960s.

[pieman]

Yeah we had the stories going around at the time phasing out the old fuel the valve face angle had to be changed (cast iron heads maybe) however looks like the good old y2k bug story for computers. Only trouble I've had with the valve seat is the odd one comes loose. eventually makes a mess other than that my old girls run all day everyday doing about 30 starts a day5 days a week year in year out. one thing I like about the whole design is I think they were totallly over engineered. I hear a 1500 go past my place each day i'm sure dosn't have a much of a shell in one of the big ends but still bangs away each day. It will be a said day when corrossion has destroyed all the heads.