Z900A4 float levels

[sprint]

If your floats are in upside down the float tang will stop the floats rising sufficiently to fully close the valve. Are you 100% sure the stop tang is pointing down towards the float bowl and not up towards the carb body?

Yes the floats are the right way up, have checked and hoped that was the cause several times.

[sprint]

Here then.?
Where my less than straight line was meant to be.
P1020706.JPG-1.jpg

Yes

[warren3200gt]

This picture is the right way up. If they are like this then there's only two things that it can be.
1) your float valves are not sealing or the float valve springs are shot.
2) your floats are not as buoyant as they should be.

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[warren3200gt]

I see your in Eastbourne, I'm by Brands Hatch, if you want to bring them round we can sort out what's going on. If the missus would moan bribe her by dropping her at Bluewater shopping center (5 mins from me) just make sure she doesn't have your credit card

[sprint]

This picture is the right way up. If they are like this then there's only two things that it can be.
1) your float valves are not sealing or the float valve springs are shot.
2) your floats are not as buoyant as they should be.

Screenshot_20230709_153136_Samsung Internet.jpg

See attached photos re float, tang to bottom.

With regards to the valves. I have/had been using the rubber tipped ones, that came with the bike (not sure if they are original or aftermarket?) and not the Kester ones on which I have found that the sprung loaded plunger to be very sloppy with very weak springs. There is so much play in the plunger that it pushes over first rather than pushing up.

However, on looking at the side by side photo it can be seen that the rubber tipped ones are slightly longer but also the rubber tipped ones have a different angled profile than the all metal Kester ones. I am not sure if as a result the profiles mean that they are not interchangeable and can only be used with a paired seat?

Having said that I have tried both valves in the same seat and it has made no difference.

Can't see any obvious issues with the floats themselves, but how would I be able to establish if they have lost buoyancy?

[sprint]

I see your in Eastbourne, I'm by Brands Hatch, if you want to bring them round we can sort out what's going on. If the missus would moan bribe her by dropping her at Bluewater shopping center (5 mins from me) just make sure she doesn't have your credit card

That's a kind offer which I think I would like to take up. I would probably come over on a bike so no danger of the missus coming!

I should get the returned choke plungers in a day or two so I can fully rebuild the carbs as I have had to take everything apart to get them out.

Can you pm me your address details and what day's and times would be convenient to pop over and what bits apart from the carbs I need to bring?

[warren3200gt]

You have mail.

Valves, I've not ever used kyster valve or those rubber tipped ones.
Keyster are said to be good but looking at your picture the conical surface doesn't look very well machined to me. It looks to have grooves and scratches all over it. Don't think that would seal very well.
Regarding the rubber tipped ones as the are different length to the Keyster it means the static dry float heights you seem keen on are irrelevant. The dimensions Rob gave you are for genuine mikuni matched pairs.
Looking at your pictures the valve seat appears to be original mikuni so not sure either of those needle valves would work well.
I believe that mikuni did use the rubber tipped ones but not in 1977 so you could have a case of genuine mikuni seat, genuine mikuni rubber tipped valve, Keyster valve but none of them are matching pairs.

Your floats look very clean, so assume they are new?. Not aware of any aftermarket ones available so assume they are genuine mikuni and should be fine. Worth just checking they all float equally at the same height in a bowl of water and don't have any fluid sloshing around inside them from being perforated.

I think your issue lies with the mismatched valves and seats and if it were me I'd just bite the bullet and buy new matched seats and valve genuine mikuni sets from allensperformance. Co. Uk.
At least then you'd be working with a known quality and starting point.

If you want to come over I'd wait until you have Robs plungers and Allen's genuine valves sets.

[sprint]

The floats are original and not new replacements. Dropped them into some petrol, see attached. They all float to the same level so assume they are all OK? They are the sold type so nothing can get inside

I am not sure as to if the rubber tipped and no number/marking seats that came with the bike are original Mikuni, but I've have the same problem with either the original, Kester or mixed sets, so at a bit of a loss.

I will enquire to Allen's as to the availability of genuine Mikuni valve/seat sets but if they do not work not a lot gained?

[zed1015]

Those floats are sitting miles too low.
There should be approx half the float above the surface and that's why the static height measurment is way off.
Original float valves for the VM 22/24/26 and 28 are solid tipped but the viton ones should be better.

[warren3200gt]

I thought that too Rob so went and tested some spares that I have and free floating in fuel got very similar results.

[Barnett]

The wet method is the only sure fire way to get them set correctly in my opinion. Make a jig and or clamp the bank in a vice ensuring level, use spirit level. You can get variations due to tiny trapped air bubbles in the level indicator tube, try and have it pointing straight down when you turn on the temp fuel supply and then raise as the bowl fills. Give it a couple of min to stabilise and if course read from the bottom of the meniscus. Also tape it in place and wait a while, checking again for leakage past the needle valve, although it would need to be pretty obvious to affect the mixture when the engine is actually running. Its a faf but worth it in the end, use only fuel, bit iffy I know but using other liquids will give false readings due to differing density. Some after market needle valves are complete shite, I had a set in mine, fitted by previous owner which failed after a thousand miles due to the actual spring being made of what looked like nylon, fuel ate it, weakened springs and caused havoc. Fitted a set of genuine z650 ones I had in my spares and all was well.

[zed1015]

I thought that too Rob so went and tested some spares that I have and free floating in fuel got very similar results.

20230710_163145.jpg

The floats do degrade and get heavy over the years and if i get any that bad i replace them.
From new they should be close to half way.

[warren3200gt]

Disagree Rob. When mounted on the hinge pin and posts they are very much more buoyant than when free floating as a lot of their brass components weight is supported by the posts/pins.
The actual black float part of the floats I pictured sits about 50/50 above below fuel surface level when mounted and in the bowls.

[zed1015]

Disagree Rob. When mounted on the hinge pin and posts they are very much more buoyant than when free floating as a lot of their brass components weight is supported by the posts/pins.

True about the hinge weight but they should sit higher when new.

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[warren3200gt]

Interesting, never had to buy any new floats so didn't think it would make that much difference. Yours would be floating above the surface if the hinge were supported
Were and cost for new floats?