PR: Proprietary Items TT carb

[LoneStar]

I think if you use a more buoyant float in order to increase needle pressure against the seat, you will also lower the fuel level. The more buoyant float will need less fuel to hold the needle up against its seat. Being it's a remote float bowl, though, you could possibly compensate by changing the height of the entire bowl relative to the carb. The viton scheme sounds promising if you can figure out how to work it.

 

[litnman]

Yes a viton needle would be an improvement. The float bowl can be raised or lowered by spacers between the bowl and carb body.
Bouyant force has a definite effect on seat pressure so while changing the seat out for a smaller one I can adjust its location to get the
fuel level correct.

 

[oexing]

Well, I have been running motorbikes for 50 years, all without Viton needles and no problems with standard needles. But if you think it will cure your troubles, get some from Aliexpress for putting them onto top feed needles. I cannot see how to have them in bottom feed types.

Vic
Viton float needles

6.4mm needle

5.2mm needle

 

[litnman]

As I mentioned before, this setup (type 14 bowl) is not by choice, it is correct for this Lightning. I'm not trying to reinvent the wheel, just
improve it.

 

[Cyborg]

If using viton, it might be easier to put in the seat? I haven looked closely at one to see if it’s feasible.
I would think the smaller needle would be worth a try just on its own. Try that first?
I’m definitely interested to see how you make out.

 

[litnman]

I noticed your photos of the seat inserts, that's a possibility. What source of information do you have on the seats you show in post 83? Next step will be inserting a .125 seat and trimming off the excess portion of the needle to reduce weight.

 

[Cyborg]

I don’t have any real solid info on them… I did a search for viton v-rings and looked at images until I saw one that looked interesting. I didn’t have much luck finding a supplier for ones small enough. I “think“ it was SKF that had the small ones listed in their catalog, but the local vendor listed it as special order. I’ll keep looking and let you know if I find anything interesting.
I have new slides, needles, and needle jets, but couldn’t find float needles on this side of the pond. Just for sport, I’d like to try making a couple, but will be up to my armpits in the KVFTT knockoff for the next while.

 

[Cyborg]

No idea if these would work. The ”V” would need to be supported so it wouldn’t move.

SKF

www.skf.com

 

[oexing]

Cyborg, these v-rings are meant to go on rotating shafts for axial sealing with their soft lip. You could use them in primary chain cases when there is a need for chain adjustments by shifting the separate gearbox. In those cases you cannot have common shaft seals as they will no longer be concentric to the shaft once you tension the chain. I wonder how you think about using v-rings in float chambers. There are lots of viton float needles plus their separate seats to go with them at Aliexpress. Just how to install the lot is another topic.
I don´t know about your idea of using o-rings, depends where they would go. Common NBR o-rings are quite allright with modern fuel, don´t dissolve BUT swell a bit and get softer. So in many places no problem from that and no real need for Viton types. But when you look into Ebay.cn in my link, you can select lots of sizes in FPM/Viton . Seems many forumites tend not to use Ebay for unknown reasons - scared about gangsters ?

Vic
float needles plus seats

Ebay Viton

 

[Cyborg]

Vic,
Yes I understand these seals are meant for shafts. I don’t know if my suggestion makes sense and I realize the lip is flexible and would need to be supported to maintain a good seal and consistent level. The seal in the link is FKM, so same as viton as far as I know. I’m thinking the the V-ring or part of the V-ring could be installed in the seat of the Type 14 float bowl. It would be more difficult to get a piece of viton attached to the Type 14 needle. I’m just guessing at this because I’m not able to get to the shop at the moment to have a look at the seat.
The first photo is litnman’s comparison between large type 14 needle and the smaller (I’m assuming) 302 type.
Second photo is my type 14 needle showing the area where it seals ( more or less) Those viton needles and seats aren’t of any use on the type 14 style. The needle could be used to modify something like a type 302 top feed.