Topic: K 7 K8 750 carb rubbers to roundtops ?

[754]

Do they work ?
Putting a 78 in an early frame,  and want to run the roundtops..
Looks like I may have a very hard time getting early rubbers onto the later head.

[seanbarney41]

It can be done.  I know because I have roundtops on my 78f.  Weird thing is, I don't remember having much trouble fitting the boots.  I wonder if I somehow randomly used an old set of boots that had been trimmed to fit?  Try warming them and lots of lube first.

[Jerry Rxman Griffin aka MuthaF'er]

Frank, the 78 K (not F) head spigots are the same as all the others so the early boots should be fine with round tops. However the 77/78 F spigots are larger and all the 77/78 carbs F and K are 1mm larger so avoid the boots for any 77/78.

[seanbarney41]

Jerry, do you know how much bigger the 77/78f spigots are than other 750s' spigots?

[754]

2mm on the lip and same on the flat hehind it.
 Just picked up late boots for f3

[seanbarney41]

man, I would think with lots of lube and boots heated so they are pliable, the early boots will go on with some muscle

I don't know if the f3 boots will tighten down on roundtops enough to seal, plus I have never found a useable original f3 boot, and Honda doesn't have 'em anymore

[Jerry Rxman Griffin aka MuthaF'er]

I'm fighting to get a new set of K7/8 boots to use with my +1mm Webers. CruzinImage for $50. US for $100. Cruzin's got "lost" in shipment then he shut me down after the refund so I had a friend order a set for me. Hopefully they won't get "lost" too. I've been told they are all from the same supplier anyway.

Frank did you get a new set for the F3?

Yeah, lube works wonders 

[ekpent]

 Wonder how many people Cruz has on his blocked list. Your in good company Jerry cuz I know other members are on his blacklist also.

[754]

 I got a few used sets, and I  have the GREEN WUNDERGLOVES.. so I will get r dun..
 And if that fails I bet the silicone rubber hose with my Webers will fit on..

[BPellerine]

early boots fit on the 78 k head.bill

[754]

Someone said  not sure , thatvthe late K heads may have same spigot as early.  . Not sure
 The motor I am using has a 410 head, and I measured bigger spigots.

My early style rubbers are sort of hard, I got z good way to get  them off.
 I stick a socket and extension down Inside the rubber,  don't go too far  like not in the port....
 Gets them off easy. 

[Jerry Rxman Griffin aka MuthaF'er]

410 head does have larger spigots. 391 head is the same size spigot as all the K's and early F's.

[Mr. Mike]

I had a set of ‘74 roundtops fixed onto my 78CB.
The only thing I needed to do was get an air box from an earlier year to fasten the boots to. Boots and proper clamps came from Vintage 750, and the replacement carb holders for the head were OEM replacements. I love it.

[754]

Mike those rubbers are shorter than the earlier round top style.
 And you say the early air box still lines up to the K7 mounts..

[Mr. Mike]

Yes it did line up. The original air box boots were just a wee bit to large. But the earlier box with the matching boots fit perfect, and of course the box hanger bolted right up too.

I’m not sure if the rubbers are shorter, because even the original 78 air box and boots although too bigga boot slipped onto the carbs perfectly.

[seanbarney41]

Mike, those are 69-76 carb boots in your picture. The 77-78 boot are radically shorter and different shaped.

[Mr. Mike]

Thanks Sean. IIRC everything carb related is mid 70’s.