Keihin CVK34 carb set up

[moizeau]

Cheers Al, Getting hold of my mates colortune and just ordered the 10mm adaptor on Prime. I've got about 4cm of clearance under the carbs because of the alternator and the screw is about 5mm up the hole. I've been searching various offset tools for doing the adjustment on the centre 2 pots. A lot of the carb tools like the Laser one doesn't seem to be able to get up the hole.
Any advice regarding this?
Thanks
Oh, and I cleaned the plugs with a wire brush..........

[Al]

I started out with the inch snapped off the end of a screwdriver with a square shaft but not enough grip or sensitivity.
Tried these but not enough arc to rotate properly.
https://www.ebay.co.uk/itm/313181830173 ... Sw-rxcG5fv
I settled in the end for the 'bits' from one of those sets you always get in socket sets but have no use for.
https://www.ebay.co.uk/itm/192834129014 ... SwURNdg4FI
You just need to thumb them into the slot.
Never had the micro ratchet as above but discovered you can get longer extended versions of these which you can combine with a 10mm spanner.
Something like on the RHS of this item.
https://www.ebay.co.uk/itm/373548859047 ... %3A2334524
They also do angled versions of the micro ratchet.
https://www.ebay.co.uk/itm/114450178382 ... Sw~2FffZgB

AL

[moizeau]

Colortune and adaptor arrived. These carbs are doing my head. Can't get a yellow (rich) flame. Almost took the screws out on 1 and 4 and still blue, it does change the revs but...Not bothered trying to burn my fingers off on the centre 2 at the moment. Looks like carbs off again. Inlet rubbers are brand new genuine but the o rings are not genuine but viton and measured. I'll stick some grease round the rubbers to take them out of the equation though.
More fun tomorrow. It does say in the Colortune bumf that if all carbs show blue only it may be crank case breather but right now I can't get that round my head either. Need beer

[Al]

I dont know if these are suited to you carbs but would be a great solution if they were.
https://www.amazon.co.uk/dp/B00F3XBX46/ ... tsfixit-21

No yellow flame suggests blocked pilot fuel feed on at least those two.
For reference; fully blue on mine to fully yellow is about 1/2 of a turn!!

AL

[Big Fluff]

CVK34's are a bloody nightmare to set up. I've been having fun with mine too (GPZ1000RX).
I've had repeated issues getting the carbs to stop taking in fuel (resulting in an extremely rich running on the pilot circuit, and also dumping the contents of the tank into the engine, twice now!).

Some tips from other owners and carb restorers regarding these carbs:
* Float height (not fuel service level) should be set with the carbs on their side and not inverted.
* Early type had press in fuel valve seats - I polish the walls and seating area of these with T-cut to ensure the fuel valve slides freely.
* Use genuine fuel valves
* Test the fuel valve sealing with the float bowls off and the carbs inverted whilst hooked up to a remote fuel cell at a good height.

Be interested to see whether you get to sorting these.
Never used to have this amount of crap to deal with before ethanol fuel came along!

[moizeau]

Thanks Al and Big Fluff for the responses. I have taken a while to reply because I wanted to update at the same time as saying thanks.

So, took the carbs off, removed the float bowls and set up a tank with about 3 litres of fuel in it at approx. 40 - 50cm above the carbs. No leaking whatsoever so this proves the seats are good as are the viton tipped valves.
While I was in there I re-checked all the jets including the two front ports. I also removed the pilot jet, spring, washer and o ring. I then used a small set of jet files to ensure the pilot hole in the carb venturi was clear. I then noticed 4 small holes in a diamond shape where the butterfly closes. Again got a very fine jet file down these. I hadn't noticed then before.
One thing I haven't done is to remove the choke plungers, ever, is it worth doing this?
Next thing was to reassemble and reconnect the fuel tank.
No. 2 leaked out of the front port. Bent the tang, re-checked, all OK.
Then I decided to simulate the bike on it's side stand by wedging a bung under No. 4 carb.
No. 2 leaked again. Bent the tang a little more, repeated the test, all OK.
Then I put the carbs back into the centre stand position (all the time with the fuel on).
'kin No. 4 leaked!!!!!!! Bent the tang, all OK.
Put it back into the side stand position and No.2 leaked again.
I've come to the conclusion I need another 2 fuel valves as 1 and 3 were replaced and have behaved themselves, 2 and 4 are being a pain in the arse. I haven't checked but would guess the float heights are now out of spec due to the springs being tired.
When I removed the float bowls I did notice that 1 and 2 had the valve ears the other way round to 3 and 4. Although the ears didn't sit correctly (at a slight angle) it obviously didn't make any difference but I did turn them round so they are closest to the centre of the carb body.
I'm about to swap 1 and 2 valves and floats over just to confirm the problem stays with valve. If I can get them not to leak in the centre stand position I will remove the airbox rubbers, refit the carbs without throttle cables and see if I can get a yellow burn on colortune.
If I can't do either, I have a box of wine and 1/2 a crate of beer!!!
I realise it's a long post but want to include every step in case I'm missing something or doing it wrong.
Cheers

[Al]

Pete ive not seen the float valve needles before that have the wee wire clips round them. If the internal tapered seat on the float valves is worn, is it possible for the wire clip to contact the brass seat rim before the viton tips of the needles make a perfect seal?
Did you test the spring plungers in the float valve needles against the new ones when they arrived? Any significant difference there?
Will made some good points in his post. The one about testing the shut off point with the float bowls removed was my favourite. Is there any possibility that the float itself can 'top out' (hit its stops) before the float valve can shut off the fuel flow? That might include the hollow centre part of the float coming into contact with the body of the main jet post which runs through the middle of it!!

AL

[moizeau]

Just had them back on. A new tool arrived today that allows me to set the pilots without burning my hands off. It needed a mod to be able to control the head (note the screwdriver jube clipped) and I needed to take 2mm off the screwdriver bit to get it in to No. 2 but it works. They sell the same thing with a handle but I was concerned the handle would argue with the alternator.

Got all pilots to 2 1/2 turns and seems better but still not right. I can't get a yellow burn on any cylinder. I realise I don't actually want one but should be able to get one to prove the adjustments.
How does the choke system work on these carbs?
With the engine hot I can raise the revs on the choke!! Surely confirming the lean mix?
I think I need to separate the carbs again and remove the plungers to make sure everything is clean.
I haven't got access to an ultra sonic so looking at other possibilities to dip the carbs overnight. Apparently carb dips are nothing like they used to be due to enviromentalists. I have read that a variety of fluids can be used to simmer the carbs in (having removed all rubber / plastic bits ). These range from laquer thinners to lemon water. I've also read white vinegar but not to be used if there are steel parts because they will rust.
I did check that the valves shut off with the float bowls removed and the carbs inverted.
The 2 older valve springs aren't as strong as the new ones.

I did a dynamic fuel height check on No.4 ( I'd tweaked the tang to stop it flooding) and it was 5mm too low.
So I think I may as well get 2 more valves. Although they are probably the most expensive part on the bike / gramme should sort the flooding so I can concentrate on the cleaning....

The bike has a 'clean air' system to help with emissions, would this have any impact? I can't see why it should but I need to ask.
Cheers again

[Al]

How does the choke system work on these carbs?

If the seals on the choke plungers were 'passing' i would anticipate a rich condition right through the range. Perhaps more so lower down because of the tiny fuel flow implied by pilot jet running on low throttle openings.

The bike has a 'clean air' system to help with emissions, would this have any impact?

I would disconnect it an plug it for the purposes of any testing. Its the same 'clean' air system fitted to some zed models by the looks of it. Even if its leaks actual 'clean' air (not how it works) it looks like it feeds into the airbox so shouldn't matter but just be be sure!

I ultra sonic cleaned the new RS flatslides when i bought them. Horrified to see teeny weeny brass swarf coming out of the corrector jets!
The thing with US is the high frequency vibration not just the scrubbing action of molecules of cleaning fluid in small drillings and passageways. The vibration can move larger objects and with the assistance of gravity will drop them out. Dont use anything that contains salt!

My question about the wire ears on the float needles contacting the rim of the brass seat was a loaded question. Say it isnt so. It will save me banging on about specific gravity where we both end up going down the rabbit hole.

AL

[moizeau]

Not a choke issue then if it richens the mixture.
Just been out and photoed the float, the ears don't touch, not even close with my eyes...

There is a chap with a lawn mower shop who has an US so it looks like I need to pay a visit. I'd like to buy one, we had one years ago for my wife's jewellery business but it died quite quickly, I don't think I can justify the expense for a decent one for this job.
Thanks Al, your time is very appreciated.

[moizeau]

Carbs have been cleaned in the US at 60 degrees. The chap gave them 4 sessions of 15 mins. I've also bitten the bullet and 2 more valves are arriving tomorrow.
I'm going to polish the seats as Big Fluff mentioned. I haven't got any T Cut and it's no easily available here.
I've read that toothpaste on a cotton bud or baking soda on a damp cotton bud also works.
Could someone confirm that this won't do any damage please?
Cheers

[Al]

I cant see that it can do any harm if approached gently. Brass is relatively inert unlike the parent metal of the carb bodies so if it does go wonky you can always buy a new seat
How do the new seats look with a magnifying glass? Is the tapered sealing surface consistent and round etc? Any scores in the parallel part?
AL

[moizeau]

Update: With the carbs not in a bank I checked each one individually. All have new float valves and a toothpaste clean.I'd set the float tang level to start. Fuel level was spot on on 1 carb, 2 carbs were slightly high (3mm ish) and 1 carb couldn't be adjusted on the tang!
The 2 that were slightly high were brought into spec with a slight tweak on the tang, the other....
Then I noticed the 2 1/2s of the float weren't parallel on the dodgy carb, carefully bent the metal that carries the tang to bring them into line and retested, all is good.
All 4 now have a good fuel height and hold the level, no flooding.
Rebuilt the bank and after much swearing got them back on the bike. I can see why people fit pods, bloody nightmare to stop an airbox rubber getting stuck inside the venturi, but now done.
I've set all the balancing screws and tickover screw to halfway.
Will have a look tomorrow to see if they want to work, hissing down outside........

The seats look nice and clean now Al, they're not new as they're press fit and I read not to try and replace them.
Will see if it behaves tomorrow.......

[moizeau]

Well finally got to have a play (put my back out changing a clutch on the wife's car...on the drive). All pipes back on, fired her up...nice. Stuck the mercury gauges on and set those to within a cm. Tickover is spot on, stable, picks up on the throttle from idle nicely and returns the same. No coughing at all. Haven't had chance to put the colortune on yet but all seems good. 20 euros well spent at the local lawnmower place. US bath and he had a very good screwdriver to take the pilot jets out. I didn't want to attempt it in case I buggered the heads.
Colortune next to to do a final confirmation but it sounds and responds like a different bike.
Thanks very much Al for your advice and patience and also Big Fluff.

[moizeau]

OK, so still not there.....but much closer. Can't get a full yellow burn still but can get little coughs of yellow. I've now got the pilots set to 2 3/4 turns, idle seems more or less stable but it still wants to stall after a straight, needs a blip to bring the revs back up around 1000 from 500. Once it's back to 1000 it stays there. So I've still got a blockage albeit a smaller one.
Just wondering whether a bit of injector cleaner or something similar chucked in might help over time?
Any suggestions gratefully received. I really don't want to have to pull the carbs again but I fear I might.
It starts from cold on the button.
One thing I haven't tried, out of curiosity more than anything else, is if I can get a full yellow burn by giving it some choke?