Carburettors Vergaser Types on Sandcast/K0 Bikes

[kp]

We know of two distinct types of carbs fitted to Sandcast bikes. The early type is the straight brass vent tube type and the 90 degree cast alloy vent tube type.
I have 2 questions
Can anyone give some information on what type is fitted to what engine number. We know early Sandcast bikes  (let's say to at least E650) had the earlier brass straight vent type, whilst the 90 degree cast vent type was fitted from an unknown E number. The best way of finding out this info is for members to check what they have fitted to their respective bikes or for anyone with the knowledge to add to this thread
The other question relates to the long choke arm. I am pretty sure that the long choke arm was fitted to both types of carbs but it would be also of some benefit to know about what Enumber  the short choke arms started to be fitted.
Wood ya all have a look 👀 at what you have and give some feedback. I have E1771 and it has short choke arm and 90 degree cast vent tubes. KP

[kp]

Hey Bo, you have a nice collection of bikes, can you help with this. Thanks

[bojje]

Hi!
Both #388/407 and #609/636 has 90 degree pipes and long choke arms. I'm sure both has their original carbs. Now we have to see who is answering next to find out when changes appeared.
Looking forward to information, Bo.

[kp]

Hi Bo
Thanks for that feedback. Wow! I would have thought both those E numbers would have had the straight vents. Makes these early carbs made of gold

[Steve Swan]

fwiw, the "Distinctions" thread shows the highest vin having straight horizontal brass tube insert vents being F302/E338.  of course, if we have more participation, then we will learn more. 

i suggest the brass vent tubed carb bodies were fitted for only a brief time in early production.  i can't hazard a guess when the brass vent was last fitted.  i've always believed these brass tubed vent carb bodies had a short production run.   the 4 hoses leading venting these carbs have to lay horizontal with the carb rack, the hoses cannot go over the airbox like the hoses leading from the 90' cast elbow vents.

[Steve Swan]

ok.  KP unearthed an interesting find from Mark's #97 thread.

reply #673, from Sam Roberts, "Interestingly, I have straight vents on #836 and not on #410. Note sure why and I am sure both are original to the bikes. Perhaps another example of early sandcast randomness?"

assuming the straight vent type carbs on 836 came with the bike from the factory and did not come on 410, then the "early sandcast randomness" we see, does not allow us, at least in some cases, to make assumptions of how late in a vin range we can expect top see a certain distinctive part.  at least from a consecutive numeric standpoint, we do not know how many vins between 410 and 836 the early brass vent carbs appear.

that being said, 836 having brass vents and 410 not having brass vents, for only the sake of example, we can say 836 was last vin for brass vents to be seen, but this is not accurate, because it leads one to assume, all vins before 836 had brass vents.  in the case of Sam's two vins, we know this is not the case.

what would be interesting to know, consecutively beginning at vin #1, how many vins had brass vents and at what vin did the 90' elbow vent start being seen ?  Then, after the 1st 90' vent seen, at what vin did a brass vent reappear ?

or i suppose one could ask how many angels can fit on a pinhead.......

[4pots1969]

But in fact maybe some of the carburetors with brass vents remained in the bottom when they replenished the stock, they used the new production that was on the front for 410 without the brass vents which would explain why 836 is found with brass vents because they have taken again the bottom of the stock... Just my thought...
At the time these details did not matter to them, the main thing being that the bike is equipped with carburetors....

[Steve Swan]

But in fact maybe some of the carburetors with brass vents stayed in the bottom when they replenished the stock, they used the new production for 410 without the brass vents which would explain that 836 finds itself with brass vents as they have again taken the bottom of the stock.... At the time these details did not matter to them, the main thing being that the bike is equipped with carburetors....

Agreed.

[kp]

We do know from photos posted here that the engines were installed into frames with carbs attached so carbs were obviously fitted away from the main production line given they are complete in their crate. Poses several questions. Were the engines stamped after assembly. I doubt they were stamped with carbs attached so I think the randomness of carb installation is not so much possible but more likely probable.
I do know of an engine in the mid 6xx that was fitted with straight brass tube carbs. My understanding is that this bike was original.

[kp]

fwiw, the "Distinctions" thread shows the highest vin having straight horizontal brass tube insert vents being F302/E338.  of course, if we have more participation, then we will learn more. 

Dementors

[Steve Swan]

We do know from photos posted here that the engines were installed into frames with carbs attached so carbs were obviously fitted away from the main production line given they are complete in their crate. Poses several questions. Were the engines stamped after assembly. I doubt they were stamped with carbs attached so I think the randomness of carb installation is not so much possible but more likely probable.
I do know of an engine in the mid 6xx that was fitted with straight brass tube carbs. My understanding is that this bike was original.

KP, do you have the factory picture of frames being fitted to engines w/ carbs ?

[kp]

Posted by Ujeni

http://cb750sandcastonly.com/smf_forum/index.php/topic,1582.0.html

PS Actually it was Tom Courtney who first posted these pics, not that it matters but thought I should acknowledge that
http://cb750sandcastonly.com/smf_forum/index.php/topic,1354.msg9479.html#msg9479

[benjixt]

Hi Evrybody
on sandcast VIN 323
horizontal tube .

kind regard.

Benji

[cb7504]

sandcast motor VIN 181 horizontal brass tube.

[hondasan]

I too have seen an engine with serial number in the 600's, appearing original, and fitted with straight vent long choke lever carbs.
Interesting factory pictures showing engines with carb bodies already fitted prior to installation in frame. Suggests that engine serial number would be expected to be the more reliable indicator as to which bikes should have straight vent carbs. That said, we know that engine / frame  pairing was random so probably also engine / carb pairing. Little wonder then that the relatively rare straight vent carbs seem spread over quite a large serial number range.

For myself, I need information as to the appropriate carb type for #1120 / E1106. I am thinking that long choke lever / 90° vent carbs are probably correct?
More data needed to confirm this view please, before I remove the long choke lever from my spare straight vent carbs (pictured below for those members out there who may not have seen these before) carbs to fit to a set of later 90° vent carbs?


Chris R