K series carbs on 750F2

[royhall]

Am going to try a conversion from the horrible PD carbs on the 750F2 to a set of K4 carbs I have spare. These are 20mm shorter than the PD's so am going to need to use the isolator rubbers off the K series to get the airbox back on.

Does anybody have a spare K head that can be measured. I need the diameter of the inlet spigots. Not sure if they are the same on the F2, I have a feeling the K's are smaller. The F2 spigots are 35mm. The K's carbs don't fit the F2 rubbers as the carb outlet  bosses are smaller. If the head spigots are smaller it could be end of game before I start so don't want to waste money buying parts that are not going to fit.

Have searched the internet and unbelievably cannot find anybody that has done this before. Have found a guy that has PD's on a K2 (Why) but not the other way around. He's also running pod filters that I don't want. So I guess its all in the spigot size, if they are the same I can just use K series isolator rubbers and it should all fit? Jetting is then anybody's guess.

Thanks Guys.

[royhall]

Am going to try a conversion from the horrible PD carbs on the 750F2 to a set of K4 carbs I have spare. These are 20mm shorter than the PD's so am going to need to use the isolator rubbers off the K series to get the airbox back on.

Does anybody have a spare K head that can be measured. I need the diameter of the inlet spigots. Not sure if they are the same on the F2, I have a feeling the K's are smaller. The F2 spigots are 35mm. The K's carbs don't fit the F2 rubbers as the carb outlet  bosses are smaller. If the head spigots are smaller it could be end of game before I start so don't want to waste money buying parts that are not going to fit.

Have searched the internet and unbelievably cannot find anybody that has done this before. Have found a guy that has PD's on a K2 (Why) but not the other way around. He's also running pod filters that I don't want. So I guess its all in the spigot size, if they are the same I can just use K series isolator rubbers and it should all fit? Jetting is then anybody's guess.

Thanks Guys.

Thats a lot of words, here's the short version.
Does anybody know the size of the intake spigots on a K4 cylinder head.
Thanks.

[martin_uk]

Hi Roy
This may be of interest as guy in US doing same thing.

http://forums.sohc4.net/index.php/topic,141761.1200/topicseen.html

I thought the intake stubs were the same as my K8 looked similar, but carb outer is larger.

I have an old K8 rubber and can measure.


"For anyone else considering doing this, you'll need different A & B throttle cables (possibly not one of them but the longer one (A?) doesn't go around to the far side like it does on the 77's and 78's.  Also, the carb boots that match up to the 78K carbs seems to have a larger front end (the side that connects to the carbs)"

[martin_uk]

Just measured my 392 F1 head.

Inlet spigots are 36mm at lip and reduce to 34 after lip.

Inside is 28.5 and outer depth to head is 18mm

F carbs are 37 engine side and 40mm air cleaner side.

F rubber is 33mm head side (old one) and 36 carb side.

K8/PD carb rubber is 34 head side and 38mm carb side.

Hope this helps.

[royhall]

Thanks Martin your a star. Shame there's not a bit more info or a picture on the link. Was expecting to change the throttle cable for K's. If it measures up okay I'm hoping to just be able to use K rubbers to get them to fit. Might up the jetting one as well, but I will get them to fit first of all. Cheers.

[martin_uk]

The rubber connectors/velocity stacks to air cleaner on my K8 are marked 405 and are bigger, so you will need the smaller ones if your carbs are 40mm at intake.

I have a  flat spot at around 4k rpm on my PD carbs on K8, but will get a few more miles on it before messing with jetting.

[royhall]

What I'm hoping for is to change all the rubbers (both sides) and the cables to K series and they will just fit. Maybe a big ask as its an F2 with its bigger valves. Should be interesting.

[martin_uk]

You may find air box openings are different, I will have a look at mine.