Carby primary and secondary throttle valve operation

[dom14]

Hi Guys,

Below are the photos & videos of RB30 Nikki carby throttle valve operation, taken from the bottom
of the carby while it's outside.

Does the primary throttle valve look ok?
It looks like it doesn't shut completely & sort of leaves a gap in the bore where the air can sort of leak through.

The valve moves freely and doesn't sort of "stick", but I wonder what we see in below pictures and videos can be thought as a slightly sticking valve?!

Larger valve with vacuum diaphragm attached to it is the secondary.
Smaller one is the primary.

Primary valve operation video.

https://www.youtube.com/watch?v=S3kQ...ature=youtu.be

Secondary(& primary) valve operation video.

https://www.youtube.com/watch?v=RAXw...ature=youtu.be

I'm sort of happy with the secondary valve operation(mechanical movement and closing), but I can't say the same thing about the primary one though.

I would appreciate few opinions/advice from guys who know about this better.

Thanx in advance guys.

P.S. I posted the pictures on below posts. My issue is the above carby's running too rich on idling(cold or warm).

[dom14]

Primary valve

[dom14]

Secondary valve

[Throbbinhood]

My primary doesn't shut completely either. If you closed it completely though, there'd be no air at idle, no?

[dom14]

My primary doesn't shut completely either. If you closed it completely though, there'd be no air at idle, no?

Yes, of course mate.
I was wondering whether it's allowing bit too much 'cos during the cold start, the choke doesn't shut completely but stays open a bit via choke brake(vacuum assisted).
I thought, it's good to post and seek few opinions.
Mine's running rich all the time on idling(the carby in above pictures and videos).
I'm trying to figure out why.
Thanx

[Throbbinhood]

Oh haha, can't help with that. I wound my choke all the way off :P

[mudnut]

Are you dead sure the carby running rich is for an RB30 and not a TB42?

[dom14]

Oh haha, can't help with that. I wound my choke all the way off :P

That should be fine as long as it doesn't cause any cold starting issues, back fires, etc.
It will run bit lean during a cold start, but I guess it should be fine as long as the engine's running without backfires during take off.
Cheers
Dom

[dom14]

Are you dead sure the carby running rich is for an RB30 and not a TB42?

That's the carby the troll came with.
I'm pretty sure it's an RB30 carby 'cos of the way it's setup, but who knows!
Most of the TB42 carbies came with a slightly different looking choke(same thing but minor differences in the casing).
I've gota a dirty looking TB42 carby with me which I haven't even touched yet, but it looks different. Mainly the choke casing.

It has been running good for a good length of time after I rebuilt it back in 2013 with a rebuild kit.
I think(I mean I guess) the problem started after I increased the float level from quarter to half 'cos I was told at the time
(last year) the float level should be half full all the time, as I see from the sight glass.
So, I bent the float "neck"to increase the float level to half bowl.
I had immediate performance improvements after that.
Now, I'm thinking may be it has turned into a perpetual rich running problem for the idle circuit.
I'm about the reduce the float level a bit & see how it goes.
I don't have a AFR gauge yet, but a Gunson Colortune plug.
According to the sight glass view of the Gunson plug, it's running badly rich on idling and improves when the throttle is applied.
So, my main aim at this stage to get the idle circuit to function properly.
If there're any half and full throttle AFR mixture issues, I can start dealing with that once I receive the AFR gauge kit and install it.

For the time being, I have to get this carby issue sorted out.
It builds up soot within seconds, so it's running pretty rich, and can't be a jetting issue since it's the idle circuit( if I get it correctly).

Basically my issue right now is..

1)Original carby the troll came with is running way way too rich on idling and I still haven't found a way to fix it.

2)The spare carby is running way way too lean on idling and I still haven't found a way to fix that either. And it idles too high
which to me indicates it's actually not idling, but jetting has partially kicked in via slightly open primary throttle.


But, for a start, I must get the original rich running carby issues sorted.
I'm just about the reduce the float and fit it back and see how it goes.

Let me know your thoughts, and tips etc.
Any speculations, wild thoughts, etc are welcome at this stage, 'cos I ain't buying another carby.
I'm fixing at least one of the carby to run the way it's suppose to run.

[dom14]

Are you dead sure the carby running rich is for an RB30 and not a TB42?

I know, it looks like I'm asking too much when I wanna run both carbies "perfectly" for the same ignition timing & fuel pressure.
So, I've downgraded my expectations to get one carby to run properly for the set fuel pressure & ignition timing.
I'll worry about the other one later.

I prefer the original carby(the one's running rich), 'cos it's the one I put a brand new rebuild kit through and gave lot of TLC through my cleaning and rebuilding and maintenance of it.
If I can get that one running good, then that's enough for me.