RB30 Nikki carby float level problem

[dom14]

Hey guys,
I've been having performance issues with the carby lately.
I think the issue is it's running too lean.
Without me fiddling with anything, the carby decided to run the float level pretty low by the looks of it.
It is one quarter of the level as in the picture when I look at it from float bowl glass.
Is this float level ok for the RB30 Nikki carby or is it too low?
I thought it's better to confirm with some advice before I start fiddling with the float adjustment to get the float level to at least the middle of the float bowl.
Thanx in advance for any tips & advice.

P.S. the idling is also pretty low when cold start( around 400ish or even low at times). I haven't touched fast idle screw or the idle mixture screws yet. I thought it's better to deal with the possible float level issue first and then move onto the idle and mixture adjustments, if necessary.

[garett]

do these have a bucket (gauze thingy) before the needle? could need a clean. sticky seat ? low pressure?(blocking fuel filter/pump issue) bent/stuck arm on the float?
you got gas too so check cut off operation is smooth

[dom14]

do these have a bucket (gauze thingy) before the needle? could need a clean. sticky seat ? low pressure?(blocking fuel filter/pump issue) bent/stuck arm on the float?
you got gas too so check cut off operation is smooth

Yeah, cut off operation is manual atm. I had to put the selector switch in the middle and run the petrol out before switching to LPG, which is ok for me.
There's gauze filter, but it's outside the carby on the fuel line. I reckon it's not blocked, but yeah, it's worth checking it again.
The petrol gushes out pretty well after the filter and the fuel return unit and the fuel solenoid. But, the low idling rpm issue is there for both petrol and LPG. So, I think it does need fast idle and fuel mixture adjustment after all. I'm not too sure how the fuel mixture and idle setting in the Impco 300A mixer and the setting in the carby affect the end result as a whole.(I haven't touched LPG mixer settings).

Yeah, the seat could be sticky, but not too sure what caused it, 'cos it wasn't that long ago I opened and cleaned inside(late last year).
I'm also worried about whether it has blown a hole in the float, but that shouldn't cause the float to run low, should it? Should be the other way around with a blown float, shouldn't it?

[Patrol'n]

I thought a float worked by displacing area in relation to its (sealed) volume, hence it floats at a pre determined level. I would imagine a float with a hole would sit low, since it would not displace the same volume anymore, much like a tinny with a hole in its hull? Or is my slightly beer muddled brain totally wrong right now...

[dom14]

I thought a float worked by displacing area in relation to its (sealed) volume, hence it floats at a pre determined level. I would imagine a float with a hole would sit low, since it would not displace the same volume anymore, much like a tinny with a hole in its hull? Or is my slightly beer muddled brain totally wrong right now...

It's good food for thoughts mate. But, I'm no carby specialist. I have to wait for Garett to post bit more information on that.
Either way, the carby's possessed by my x-wife. :D
Sounds like it's gota come out and dismantled(not that I've done that with my x, but I wish I had :) )

[dom14]

This is what I've found so far. There's an obvious main body gasket leak.
This gasket is a gasket I crafted out of proper gasket paper.
I would've preferred wax coated gasket paper, but couldn't find any.
I didn't buy the gasket 'cos I had to buy the whole carby repair kit($78) for that.
I couldn't see the point of that, so ended up buying the paper and cutting the gasket myself.
That was last year. The gasket went fine, except it appears that it needed bit of tightening and I obviously failed to notice that. Gauze filter was fine.

I made the gasket by using acrylic paint on the main body and then printing that onto the gasket paper. To cut the gasket, I used a ute knife and then a hole puncher(with different sizes) to punch the holes. So, it came out pretty good.

[garett]

the idle screw should adjust both pet and gas idle speeds.
a hole in the float should make it over fill.
if you rev the engine does the level drop ? ( for more than 1 sec)
is the low level a recent happening or just noticed it ?maybe it was like this before ?

it still isn't leaking as bad as my carb.... i can smell the petrol leaking out of the pivots ... cant wait for my weber to get here :)

[dom14]

the idle screw should adjust both pet and gas idle speeds.
a hole in the float should make it over fill.
if you rev the engine does the level drop ? ( for more than 1 sec)
is the low level a recent happening or just noticed it ?maybe it was like this before ?

it still isn't leaking as bad as my carb.... i can smell the petrol leaking out of the pivots ... cant wait for my weber to get here :)

Low level is not a recent thing, but I kinda "knew" that it should be in the middle, rather than being closer to the bottom.
But, just recently(kinda coincided with the low idle rpm) it's started to go even closer to the bottom.
I haven't noticed whether the level even goes further down when I rev.
I reckon that test gonna have to be when I put it back together.
I opened it up and dismantled the main body from top. I'm just about to post few more pictures.
I don't think the gasket is that bad, the bolts were bit loose(not a lot), and the bit of leaking would've stopped if I tightened the bolts earlier.
Now, I'm wondering how to get the float level to get to the middle.
Only way I can think of is to bent the float tab that goes into the needle.
needle doesn't stick from the hand feeling, but I will polish the end of needle tip and the needle seat with tooth paste+cottton bud+drill combination.
So, bending the float tang is the only way to adjust the float?!!
What if I take off the needle seat and add a thinner aluminium washer or remove the existing washer?!!!

I'm wondering, is it that critical to have the float level at least in the middle?!!!
Can it be something else than the float level?
Can the quarter float level ok with these carbies??!!

[dom14]

These are the tear down pictures of the main body and top.

[garett]

in the manual it should give you a measurement to set the float level but yes bending the arm carefully is the way to adjust the level. close to the middle is ok but the closer the betterer. if you cant find the measurement bend it towards the top of the carby so the needle opens sooner

is this gasket the same thickness as tho old one ? try this but if your still having trouble you might have to put a kit through it.

[dom14]

in the manual it should give you a measurement to set the float level but yes bending the arm carefully is the way to adjust the level. close to the middle is ok but the closer the betterer. if you cant find the measurement bend it towards the top of the carby so the needle opens sooner

is this gasket the same thickness as tho old one ? try this but if your still having trouble you might have to put a kit through it.

The original gasket is still with me, but I didn't use it. I also have the gasket from the rebuild kit, which was used for about a year. Last year when I opened up the carby, I cut a new gasket myself(the ones you see in the picture), 'cos i thought the other older gaskets were worn out and leaking.
The new gasket is made from 1mm gasket paper. It does look like slightly thicker than the original one, but I thought it will settle after a while. After all, the carby has been going ok for a while, up until now.
I'll follow the measurements given on the patrol manual and see how it goes.
It has been through a kit not that long ago, plunger, boot, needle, seat, gaskets, all were changed.
Thanx mate.

You still got your Holley?
What is the Weber you are getting?

[dom14]

Gregory's manual says the float distance to be 4.5-5cm on RB30 Nikky carby. Mine's around 5.5cm. I'm adjusting it now.

[threedogs]

it is tuned to run on gas,,,, thats why on petrol it might feel a bit lacking
not much you can do with your set up

[dom14]

it is tuned to run on gas,,,, thats why on petrol it might feel a bit lacking
not much you can do with your set up

I doubt it. It's not going on either fuel atm. There's definitely an issue with the carby though.
Carby's that's been on LPG this long tend to develop problems from time to time(as I've seen and been told)

[dom14]

I adjusted the float level by bending the float tab(tang). Gregory's manual says the float height is 44-45mm.
Even after going all the way, I could see there's no way I could get the float height to be that. It's more like 50mm+
I had to bend it back again after bending too much to trying to match the above 44mm specification. I could never get it to be 44-45mm.
Even trying made it flood like crap. So, I reckon the 44.45mm can't be right. The needle and the seat are correct ones, 'cos the rebuild kit
and the old one matched.
Float level is "perfect" now, but it still idles too low.
Tomorrow, I'll start working on the idle issue. I'm not sure it drives ok yet, as I didn't get a chance to test drive today.

I replaced the two balls( plunger and the pump plug) from the carby rebuild kit last time, which I still have all the unused parts.
Last time I couldn't see or remove the balls 'cos
1) They were apparently stuck
2)I didn't have a more detailed carby manual for this RB30 Nikkii carby to locate where the balls are(Now I have Gregory's which has a bit more details about the carby)

[dom14]

I adjusted the idle speed and idle mixture screws, following the standard procedure(as in the patrol manual). It's going good at the moment. choke flaps aren't completely opening once the engine is warm. I'm not sure whether it's ok. I just turned the choke bimetal spring body adjustment clockwise to fully open the choke when warm. I would have to see whether that setting can upset the cold starting by choke flaps staying open too wide when cold start.
But, for warm riding, it's going good now. Perhaps it's not the choke bimetal spring that's causing it to not open fully when warm, it might be the vacuum advance mechanism attached to it not working properly. I'll find out tomorrow and post the outcome.
For the time being, it's going good.
Ideally I need and O2 sensor and gauge setup installed or have to take it to a dyno to get it tuned 100%


P.S. Petrol gauze filter banjo bolt has to be super tight onto the carby body, or else it leaks from the edge.
Since the aluminium washer is new, I think it's some other reason. Tightening it that tight to avoid leaking is a worry, 'cos the banjo bolt hasn't got enough thickness on the hex head to grab by a wrench. It can easily slip and get rounded, needing a small pipe wrench after that. I'm thinking using a petrol resistant sealant on the washer(or a rubber washer may be?)

[dom14]

Starting fine when cold with the current choke setting, which is moved towards the lean side.
I'll see how it goes for next few days. It hasn't been that cold in Melbourne lately. So, I'm hoping that I pretty much adjusted the mixture, idle and the choke for the current weather.

[dom14]

There's slight hesitation occasionally on accelerating on high revs.
That was yesterday. I'm yet to test drive it today and see how it goes.
But, I'm sure there's a lot to be done with the idle mixture setting.(no exhaust gas O2 sensor or gauge).
ATM, I'm trying to understand the purpose of the fast idle cam. It is a plastic half moon piece that has three "steps" cut to it, which sits on a tab sticking out of the throttle. It's used for tuning, but not sure it's purpose while driving or idling.(i couldn't see it engaging when idling or revving, unless I slide in manually into the position of the throttle tab).
I'm considering the possibility that the fast idle cam may not have properly positioned?!
I'm also having trouble with the idea of having to turn the choke bimetal align mark that much off the alignment mark.

I just started this morning to find out the choke setting(turned clockwise to open the flaps) does affect the revving(stalls when revving high). So, apparently the choke marks should align, but the choke flaps won't fully open when warm though(May be the auto choke is not in the best shape after all).

I added few photos of the cam setting.

[dom14]

I do have an old spare Nikki RB30 carby which has been having an issue of high idling revs(1500-2000), which I haven't been able to fix so far.
The cam setting of this spare carby is that it's second step always rests on the throttle tab.

[dom14]

This is a video of the choke breaker system of the RB30 Nikki carby, which I'm trying to understand function of it, as well as find any possible issues with it.
It's operated via a vacuum diaphragm and the a vacuum line(or air bleed) that connects to the carby body. That's all the vague information I know about it so far.
I'm hoping somebody will give me few tips about it and whether it can cause problems, how to test to see whether it works ok, etc etc.

https://www.youtube.com/watch?v=hHViQ46IgS8&feature=youtu.be

[dom14]

Checked the Choke Breaker System operation, following the guidelines of below, it appears to be working fine. When I remove the choke breaker vacuum line(the vacuum line attached to the diaphragm as in the above video), the choke flaps shut even further. So, it's working I guess.

http://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c1528004d5bb&CJPID=6148321&cmpid=cj