Z1A float height

[MrDavo]

I’ve just wasted a weekend failing to set the float levels on my Z1A project, I have the early 28mm carbs, as fitted to the Z1.

I set up a remote fuel supply using the chain oiler bottle and a length of fuel hose, and used the KHI clear pipe attached to a drain plug tool to measure the fuel height. I treated the carbs in pairs using the T piece fuel feed, and took the carbs off together for adjustment. Try as I might all measurements gave me too low a fuel level. I tried setting the height to 24mm static, using a homemade cardboard template, I tried bending the tang on the float, as far as possible in the end, but never got a high enough level.

A post I read by an engineer suggested removing every avoidable variable when problem chasing, so I’m looking at the new but possibly knock off float valves. After my experience with my CL450 barn find I have a low opinion of cheap carb repair kits. I bought two for that bike, had a nightmare setting the carbs, and resorted to cleaning up as many of the 50 year old original parts as I could and using them. Plus brand new OEM brass floats, only because idiot here used heat to get stuck float spindle pins out, melted the solder and the floats fell to pieces! I could only get the bike to run right using the genuine original float needles and air screws, with the pattern parts it was hopeless. The bike now has a solid reliable tickover at 1000 rpm and starts first kick if the battery is low, so it was worth the effort.

The Z1 float valves have 20 stamped on, as do the genuine ones, but I’ve also seen photos of replicas stamped. The carbs have been rebuilt with all new parts by the previous owner, and I don’t have any of the original parts to try instead. However if I had to guess, I may have pattern float valves which I’ve seen as cheap as £20 a set, as opposed to the real thing at £180 (for four) give or take a bit for discount and postage. It’s a lot of dosh to throw at a problem to see if it works, but reading posts I can find dealing with similar issues you can chase dodgy fuel levels forever if you are using non genuine floats or valves, plus there’s not many things it can be, this would cross off a big unnecessary variable.

I’ve bought a few ‘cheapest on eBay’ parts such as a rev counter cable, only to send them back because they didn’t even try to fit properly, and bought OEM instead. The reason one valve is £5, and another £45, may be more than just corporate greed, and reflect the accuracy to which it is made.

[zed1015]

Are you sure you have the floats i the right way up.
If they are upside down they will shut the fuel off early.

[MrDavo]

I reckon so, as there are cutaways which face upwards, and correspond to lumps and bumps on the carb body.

[Ultim8pc]

A common issue with some of the repro float valves is that the little sprung nib isn't as long and/or as wide as the original. This means you have to bend the float tang far more acutely that expected. This cause issues with getting correct fuel heights.
as mentioned make sure you have the floats the right way up. There is a tang that acts as a stop onto the float pin pillar, this tang needs to be facing towards the end of the float pin pillar.
I've got an assortment of 2.0mm float valves I can send you to try out if that helps.
I use and recommend Keyster carb rebuild kits.

[MrDavo]

Thanks for the offer, but it’s got me thinking - According to the listing on Z Power’s website, the float valve I need is 2.6mm that matches the part number at ZPower and in John Brookes’ book 16035-25. the ones I’m looking at in the carbs are stamped 20. What are we measuring here, the size of the hole or something to do with the valve’s length?

Maybe that’s my problem, later float valves in my early carbs. The stop tang on the float seems to be the right way round, as it hits the pillar and stops it from dropping too far.

[Ultim8pc]

Thanks for the offer, but it’s got me thinking - According to the listing on Z Power’s website, the float valve I need is 2.6mm that matches the part number at ZPower and in John Brookes’ book 16035-25. the ones I’m looking at in the carbs are stamped 20. What are we measuring here, the size of the hole or something to do with the valve’s length?

Maybe that’s my problem, later float valves in my early carbs. The stop tang on the float seems to be the right way round, as it hits the pillar and stops it from dropping too far.

Oh yes, for sure the wrong float valves - I should have realised. The size relates to the diameter of the hole at the bottom of the brass valve.

If you think about it a narrower diameter hole will not allow the valve to travel in as far and this give a lower fuel height.

[MrDavo]

I've ordered a set of genuine 2.6 float valves. Sod the expense (not something I often say) I want this to be right.

Looking on eBay it is astonishing how many listings there are for incorrect pattern 2.0 valves that claim to be right for my bike, when they are not. No doubt this is how the PO ordered the wrong parts. I need to check the jets are the right ones while I'm at it.

I didn't find any 2.6 pattern ones. People who happily list stuff as suitable for all Z1 - Z900 models are starting to really get my goat. I've realised that this is how I have brake pads that are too thick - as they had twin discs I bought a set of 4 that fit a Z900 that allegedly also fit the Z1, of course now I know that early bikes had thicker discs (the 6 bolt ones). I'm going to try and shave the pads down a bit, at the moment they are dragging.

[ogre]

i had quite a bit of trouble with my z1a but with overflowing set them up on bench with a bottle etc original valves etc.sorted it eventually kept getting irratic results then put a filter on the remote bottle cured it.when the bike was finished at work been left a while come to ride it home pissed fuel out of overflow be crap from tank you only need a bit so another clean out then filters in pipelines been ok since.as for the hole dia 2.6-2.8 is ok i think its to make sure the float bowls fill up quick enough when on full chat.when i have come to do my z1 new filter on remote bottle and new valves from allens performance saved hours of scratching yer head.

[MrDavo]

Thanks. There is a filter in the chain oil tank, so dirt shouldn’t be an issue.

I’ve been checking over my carbs today, I needed to check the jets were right (they were) after the episode with the float valves.

It turns out my carbs are older than the bike - they are 147 3 carbs, made in May 73, the rest of the bike is coded March 1974. Whether they were using old stock, or for some reason they aren’t the set the bike started life with, we’ll never know for sure. Anyway it probably explains how the wrong float valves came to be in there.

[MrDavo]

The 2.6 float valves arrived, and the good news is that I can now set my float levels properly.

The bad news is that, on the two carbs I’d been trying to set the level, the float tangs which I had bent down as far as practicable, didn’t like being bent back level again - I felt them ‘go’ as I bent them back. They haven’t fallen off, and I’ve set the levels, but I don’t trust them. The tangs seem much easier to move now, and I’m worried that if they give by a fraction as they close, or maybe bounce around as I go down a bumpy road, I’m going to have flooding carbs all of a sudden.

Of course floats for early 147 carbs are NLA, and I don’t see replicas of the the type I want, the asymmetric ones with moulded (not straight) cutaways. They all have a nickel finish on the metal parts, rather than brass.

If anyone can point me at a source, or has a couple in a drawer somewhere, I would be most grateful.

[steve452]

Would it be worth dropping a bit of solder onto the tangs to act a a reinforcement?

[MrDavo]

Not a bad idea if I don’t find another pair. I’d wondered about using epoxy to do the same job, but solder would be better.

I’d have to be careful I didn’t get everything too hot and melt the float or something, but at least I’m not dealing with brass soldered floats - on my CL450 I had to use heat to free stuck float pins, and the floats fell apart as the solder turned liquid!

[MrDavo]

Well that went well! Not.

I nearly got the adjustment right, one last tiny tweak at about 5mm fuel height below the carb body, and.... the blasted tang broke off. That said I knew they were delicate, and I was doubtful about trusting them, even with a blob of solder as reinforcement.

Despite being as widely available as unicorn poo, until I can source two floats (for the 147 carbs only, see my ‘wanted’ post, my Z1A is nothing but an expensive paperweight, so please keep your eyes open. The part number is 16031-24, the floats have a complex curved cutaway not a straight one, and the metalwork is silver, not brass. All the usual sources have drawn a blank so far, although Z Power gave me a number to try tomorrow.

[MrDavo]

I may have found a workround for the broken tangs, the idea was mine, the execution by my mate Mark, he's an ex classic racing buddy of mine, who's into pre war bikes, and therefore making stuff rather than buying it! He has previously got a loose baffle piece out of my CL450 exhaust (also made of unobtanium) using keyhole surgery, and defecked all kinds of crash damage and blowups for me over the years.

Basically, take a strip of thin brass, wrap it around the float 'pipe', then the double thickness where the tang is was soldered together and the strip sweated onto the float This is the result, at the very least worth a try, and if these floats are as elusive as it seems, my best shot! A picture is worth 100 words etc...



I need to polish the marks out of the tangs if I can, otherwise we are ready to have another go.

[kev edwards]

No reason why it should not work, unobtainium parts calls for outside the box thinking