Plastic Floats

[Linus]

Ok so I've been troubleshooting with my 260 Z it has hs6 su carbs rather than the standard ones but I'm having trouble getting it to fire up from cold and keep running without starter fluid etc. What I just noticed is if I screwed the jet down as far as I could it would just start but I can't adjust to anymore so I figure the float level must be wrong when I had a look both the floats are a plastic type and I can't see any way of adjusting the float level has anyone else had this issue. Because when I topped up both the float bowls a bit higher it's started so I'm pretty sure the float level is my problem

[PB260Z]

Hi Linus

 

The adjustment for float level is in inside the float chamber.

Take the lid off and make sure that the float actually floats before changing anything else.

In regard to setting the level, hit up Google for the specs.

 

Cheers

 

PB

[Linus]

Sorry its hs8 and google says non adjustable? When I fill floats it runs. And I have to adjust jets right down

[PB260Z]

Hi

 

So are you saying the float chamber is empty, or just low ?

Is the float gap within spec ?

 

Cheers

 

PB

[RAP260]

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Edited May 19, 2018 by RAP260

[1600dave]

HS6 plastic floats are adjusted by adding or removing aluminium shims / washers under the needle valve, you take the valve out of the float chamber lid, adjust the number of washers between valve and  lid the re-assemble. Not sure about HS8, can't imagine they would be any different though.

 

Or get yourself a set of adjustable floats to make life easier.

 

http://www.sumidel.com/shop/item/su-carb-hs-hs2-hs4-hs6-hs8-stayup-float

 

I assume your choke is hooked up and working properly ? When you pull the choke on, it should pull the jets down, you shouldn't need to pull the jets down yourself to get it to start ?

Edited May 19, 2018 by 1600dave

[Linus]

Chokes work but need to be full on to run. Float has fuel but I think its too low. New fuel pump etc.

When I remove float and top up fuel a little it starts easy. Chole is already on too far and jet is too low...but it's only way it will run...so I think float is too low. Cant find float level specs for my model hs8

[Linus]

[Linus]

[Linus]

[1600dave]

Chokes work but need to be full on to run. .... Chole is already on too far and jet is too low...but it's only way it will run........... Cant find float level specs for my model hs8

 

Float level specs are :

 

HS carbs with the later all nylon float and delrin type needle. The gap between the float and the lid face should be between 0.062" and 0.187" with the float resting on the needle but not depressing it. This type is non adjustable.

 

The float itself is non-adjustable in that with the earlier floats you could adjust them directly by bending a tab on the float. On yours, no tab so you can't adjust that way. To adjust float level in your carbs, you remove the whole needle valve (#5 in your exploded diagram) and add or remove aluminium shims / washers between it and the float chamber lid to alter float level. Personally, I don't like messing around with this, if you don't have a stock of the correct washers, rather than buying washers, put that money to buying adjustable floats I put a link to above somewhere. However !! Check your float level first. If its in spec, that's not your problem. Don't set the float height  so the car will start, fix whatever the real issue is.

 

Having said that, could you clarify the bit about the choke ? You say it "needs to be full on to run" - is this they need to be full on to get it to start and run for the first few minutes while its cold, or choke needs to be on all the time ? If the former, that's how they work - pulling the choke on pulls the jets down (so adding more fuel for when its cold) and also engages a little "cam" in the throttle linkage that gets it to idle at a higher RPM. If its the latter, something is wrong. Not sure what you mean by "choke is already on too far and jet is too low" ? The choke can't really be on "too far", it can only go to the limit that the carb allows. 

 

Have the carbs been tuned on your engine ? What needle are you running ? The taper on the main needle is what determines mixture, if not correct, get the right needle and a good tune ! Needles are easy to find and only a few bucks, good tuners with SU knowledge aren't as easy to find or as cheap........

Edited May 20, 2018 by 1600dave

[Linus]

thanks, I got it sorted enough for now, without getting them rebuilt (I had triple SU's on a ford 6 I built, and never ran right till the carb guy rebuilt all 3, then it ran sweet). 

I am just trying to get it running enough to have the car mobile as still got to sell it off as moving. 

I have researched more on the carb float and apparently many people use shims on the the needle and seat to adjust level. So I followed their guide and got it in spec as it was sitting way to high originally. Now car will start and run. 

I also changed plugs, and ignition parts to ensure good spark...that helped.

 

I am pretty sure the carbs need a rebuild as car sat 14 years, but it runs OK enough to sell as a project. It doesn't need the choke on to run, just start so thats sweet. 

 

thanks again, and shame I have to sell it but I have several cars to unload due to moving, including a mint 80K original klms R31 Skyline.

[gav240z]

The throttle shaft bushings can wear and cause a vacuum leak, making them impossible to tune or sync between each other.

 

I've never heard of using shims with the nozzle and needles... I'd say probably a case of wrong / needle / seat set up more than anything else, if shims fixes it.

 

PS: I saw on your video you mentioned that for some reason people don't like the flat top SU's on 260z's. My take on this is that they are mostly misunderstood, Gordon Dobbie also mentioned this once before, problem with them is rebuild kits are not easy to come across and you need to understand how they work to properly tune them.

 

They also have a separate idle circuit which actually makes them superior to the early ones in some respects as you can have a lean idle, but richer mixture in general without fouling at the plugs at idle.

 

Anyway you have what you have on the car now.

[1600dave]

I've never heard of using shims with the nozzle and needles... I'd say probably a case of wrong / needle / seat set up more than anything else, if shims fixes it.

 

That's standard practice for adjusting float height on HS-series SU's that are fitted with non-adjustable floats.There's no other way to adjust float height. See latter half of this vid

 

https://www.youtube.com/watch?v=Z6Le_HkrkKQ