Poor Fuel Economy, Even After New Emulsion Tubes

[TDMberlin]

So the carbs have arrived, so that i have it right:



1: Fuel In

2: Float bowl drain/overflow

3: Diaphragm Breathers as on the 3VD Carbs

4: Fuel Overflow / Breather

5: ????



Cant figure out how to post an image so :

https://www.flickr.com/photos/chris900ss...ed-public/

https://www.flickr.com/photos/chris900ss...ed-public/



Thanks All!

[TDMberlin]

Had the carbs apart yesterday and cant see how to remove the Needle Jet/Emulsion Tube. Unlike the 3VD carbs there inst a plastic insert in the carb body and from below there is a jet in the body next to the emulsion tube and i cant remove that either? It appers to thread in but it looks like there is a C clip in there or something.



HELP!

[dapleb]

If ewe is talking about late mk2 carbs, I think they are press fit in / not easily removed. Though i think kedo list replacement toobs so guess it's possible.



Too modern for me. One of the few 850 parts I have never owned/examined.



Studley and some udders will know... hopefully along soon with useful info.

[TDMberlin]

Ok, found a similar question on a German Forum. They are pressed in and basically you cut a thread into them, insert a bolt and pull them out. Obviously they are scrap after this.

 

So for now i'll leave them in.

 

My 3VD carbs had a 140 main jet, these have a 155. So...... fit the 140s to this carb or is the carb construct such that there is no coralation between BDST and BDSR carbs?



Thanks as always.



Chris

[Studley Ramrod]

Factory Pro needles, there stepped iirc and are really more suitable to a lightly tuned engine. Try stock needles.

[bjorge]

Ok, found a similar question on a German Forum. They are pressed in and basically you cut a thread into them, insert a bolt and pull them out. Obviously they are scrap after this.

 

So for now i'll leave them in.

 

My 3VD carbs had a 140 main jet, these have a 155. So...... fit the 140s to this carb or is the carb construct such that there is no coralation between BDST and BDSR carbs?



Thanks as always.



Chris

When I swapped the 3VD carbs for the Mk2a ones it was because reports suggested the later ones rarely required servicing. Are you sure they need fettling?

[TDMberlin]

Thanks all!!!



the carbs on the bike are OK, work well enough, but do have issues related to fuel consumption. Despite new Needles, Tubes and Choke plungers - which are metal not plastic on the MK2a carbs.



Having read here that the MK2a carbs are superior and so cheap to buy that they'll pay for themselves in saved fuel .... is my motivation. The carbs i bought for 50 Euro are extremley clean inside. They are split and broken down into as many components as is possible without breaking anything so will get "ultrasounded" as a matter of course.



I'll compare and measure all 3 needle sets, 3VD / FP / MK2a and hopefully have a little more insight. I'll start with the 140 Main too.