Z900 A4 fuel leak any ideas please?

[warren3200gt]

Good spot. Another issue. All four should be as top one. They are the choke fuel pick ups.

20240328_180431.jpg (211.73 KiB) Viewed 405 times

[Gray17]

Thanks Guys, yes did notice that myself, its the same on the other pair too.
I have today ordered the Keyster full kits from Nigel ( Aire Valley) upon arrival plan to fit all the jets needles everything as no idea whats worn, whats original and whats not. That way all carbs are the same as each other.
Moving onto the brass vents whats best way to tackle this, just leave it? Or solder up end and re drill with 1mm drill?
Any suggestions?

[warren3200gt]

You can solder it and re drill. If the choke plungers seals are good then they are only operational when the choke is on. Alternatively if you have a parts set, with a bit of heat they just pull out and replacements push in.

[Gray17]

Thanks Warren, when say a parts set do you mean they will come in the keyster sets ive ordered? Why on earth would anyone drill out the brass tubes like that? Or more bizarely only do 2 and not all 4, makes no sense to me, same with the main jets i can understand changing jet sizes due to 4 into 1 which usually requires a richer mixture and/ or it originally in USA had a different air flter, but why on earth only do 2 not all 4, and if as Warren pointed out its usually the inner 2 that require the larger sizes so mine were in the wrong place anyway.
Considering how bad it runs im very concerned theres further issues with the carbs, thats not yet been discovered.

[warren3200gt]

Parts set = parts bank of carbs. 90% of the bits are common between all the vm carb sizes. It's always handy to have a cheap junk bank of carbs to "borrow" the odd bit from. Those choke pick up tubes are common to all sizes but are not included as a replacement part in any kit.
Heat the carb body with a paint stripper hot air gun pull out the duff tube and push in the borrowed one.
Remember those carbs have been around 40+ years that's plenty of time for po's to have had "bright" ideas.

[Gray17]

Ah ok thanks Warren, yes i can see that would be an option and long term benefit, problem being theres not many around and when they do crop up command high prices, however i will keep my eyes open.
As i want bike on road as quickly as possible think thats maybe something to look for in future, if i leave as is what are the implications of the 2 tubes having slightly larger openings, i guess when on choke 2 carbs receive more fuel, but surely thats governed by the choke opening ie how much the choke is actually on? And as you only use choke at cold start shouldnt effect running once off choke? Or am i getting it wrong?
I am going to remove choke plungers tomorrow as out today and re check them but assume the seats will be worn so its off to Rob for repair, think he turns them over fairly quickly these days with his new tooling, depending on queue. I note you only need to send brass part so will have to dismantle plunger assembly, hopefully be easy enough, will take photos for re assembly.

[warren3200gt]

Fully open 2 will have rich mixture and 2 will have very rich mixture. Partially open 2 will have rich mixture and two will have lean mixture. Solder and re drill em as small as you can at least they'll be similar if not identicle.
Any vm carbs would do for those parts. There's parts or full sets on ebay for £40. That's a lot of spares for £40.

[zed9]

On the lower carb in photo with red circle on it looks like tip of float valve is pushed to the side but float tab, it should sit central and not flop about in valve float body but you will get new ones in kit anyway.

[Gray17]

Ok thanks Guys been out stripping choke plungers ready for shipping to Rob, first off i measured the larger holes in choke tubes they are 2mm, however the other 2 that look like smaller holes are solid def no opening, its just indented, so question how the hell have tbese been working if the rich mixture flows up these tubes and 2 of them are blocked, more bizarely surely if 2 are blocked only 2 culinders should be sooty, not all 4? However i also tried a very fine copper wire down holes neither would go through all the way even with choke plungers removed?
Finally Zed 9 had a look at lower photo and actual float on carb cant see what you meant, but i will be replacing everything that comes in the kits, so hopefully it will resolve it.
Thanks

[Peteypops23]

Hi Graham.....I can see what Zed9 means...the float needle isn't sitting central in the housing..it looks like it's sitting to one side and not seating properly. As he says you will get new assemblies in the kits.
Never give up, never surrender!
Pete

[Gray17]

Ah yes i can see that now, ill def check that out once the new ones are fitted to ensure all are central.
Thanks

[gray]

At the bottom of the choke pickup pipe, there seems to be a small length of brass pipe with the tiny hole in the centre - probably a push fit into the pickup pipe. I guess it restricts flow. Over time it may have corroded/ loosened/ fallen out (as opposed to previous owners drilling them out.) So refitting similar restriction - of any type- would suffice. Even a tiny dod of Araldite with a little nylon bristle up the centre- remove the nylon bristle before the Araldite sets and that might do you fine.
As regards the off- centre float valve - I'm unsure but could the float valve be the wrong diameter? ie too small . ? I'm unsure if they come in various sizes or not.

[Grog]

Hi Gray;

Good to hear you're making progress on the choke plungers. The small sections of brass pipe you've found are essentially the starter jets - they work in the same way as the pilot and main jets, but are usually fixed (as you say) to the bottom of the pickup pipes - it never occured to me they might not be all one piece. The two 'intact' pipes should have tiny holes like the loose bits you've found, they should not be solid but may be properly gummed up with crud. I have a vague idea these pickup pipes also have a couple of tiny holes up near the carb body to draw in air to help with atomisation - it's possible they've also been drawing in fuel.

The float needle has a small amount of play between the actual body and the little 'tail' that the float tab acts on - it's probably just been dragged across a bit and needs a reseat, although if you're fitting new then not a problem.

Warren's idea of a set of spare carbs to scavenge for bits like this seems a good one - in fact I think I'm off to have a gander at some ads myself!

TTFN Grog

[Gray17]

Thanks for all the replies, i have now completely stripped carbs, re cleaned and blown through every orifice with air, everything is clear.
The 4 tubes 2 with blocked holes have been removed from carbs
(exactly as Warren predicted) just warmed body with hair dryer
removed cleaned and holes opened up with piece of stiff wire, then blown through they are both now clear too, the 2 others have been soldered upside down so solder ran downwards then re drilled using 0.5mm drill, smallest i had again blown through and now clear. ( see photo) What i cant understand is why it was rich on all 4 when 2 were ? other jets well worn and not

correct sizes.
I have also stripped choke plungers and packaged ready for tues post to Rob. The Keyster full gasket sets ordered will also be shipped Tues so perhaps those and the choke plungers will arrive back together.

[warren3200gt]

Getting there. Think your next start attempt will prove more successful. Correct jets, needles, float heights, fuel level, plunger seals, airscrews 1.5 out and things should be different from last time! Just ensure no carb to head rubber leaks.