Carb rebuild recommendation

[gazza49]

ive used keyster kit from webike for gsxr 400 gk76a,nice comprehensive kit ,didnt get charged any import duties,would recommend if you can find the right kit for your bike

[gazza49]

tthese are the parts supplied

[Crass]

20 hours ago, gazza49 said:

tthese are the parts supplied

You can buy a Keyster kit for a GSXR750L from NRP in the UK, no need to risk any import duty issues. But as you can see from your parts list in the images, if all you want is some o rings and gaskets that's a very expensive way to go about it because you are also paying for OEM-spec jets, needles and emulsion tubes which in some cases (like my case where the carbs are Dynojetted) you don't need or want.

[Crass]

So just a confirmation about the slide o-rings. As @Upshotknotholemmentioned if you look at the applications for the part number listed you get all sorts of random shit relating to dirt bikes etc. The parts having arrived I can confirm that part number is correct, these are just some generic o-ring used by Suzuki for all sorts, don't be put off. 

[Crass]

Next problem is the replacement slide guides from NRP. These grip the slides so that they do not move freely and I'm expecting that as they only move by spring / vacuum pressure this is not going to work. The issue seems to be the moulding which houses the rounded stem of the slide which has a taper to it, rather than being parallel. It's about 0.2mm narrower at the top of the channel. The worn guides show no sign of a taper. I'll have to smooth a bit off with some fine emery.

Edit - so you will also need to take some material off the outer edge of the guide where the blade of the slide rubs against. The guides are too tight towards the top. 

What I did was first turn the slide over so you can get the blade part of the guide right first. Once you know that is running freely then you can sort the part of the guide where the slide stem runs. I ended up using some coarse paper to make progress as there's a fair bit needs to be removed then finish off with fine.

The guides themselves are well made and are a very good match for OEM but clearly some of the tolerances are a bit out and hence some Oldskool modding is needed, which really shouldn't be the case. Had these been fitted by someone ignorant the result would almost certainly have been unsatisfactory, if not dangerous. I'll see what NRP have to say and report back, this may be a bad batch.

Edited November 23, 2024 by Crass

[Crass]

So here we are now, everything rebuilt thanks to a lot of info and help from this excellent community- thanks all. A few curve balls along the way but to be expected when working on bikes of this age.

I checked all the float heights as part of the rebuild and all were within spec anyway, so no fiddling needed there.

It wouldn't be OSS without a bit of anal attention to detail and even though the power jet circuits are isolated for cosmetic reasons I repaired the broken float bowl nipple with a fuel tee end Plastexed into the broken stub and replaced the missing hoses. Does bugger all but makes me feel better.

So now, learning from the bitter experiences of others, next step is a 24 hour bench test.

Edited November 25, 2024 by Crass

[Crass]

Today was bench test day. So glad I read on here to do this, I would have been so pissed off if I'd struggled to refit them to the bike with how it turned out.

So, carbs in an old bowl and connected up to a dummy fuel tank just above them and....fuel pissing out of the air jets in the bellmouth. Mainly 1 & 2 but I didn't leave them long enough to see if 3 & 4 would have followed. So drain the rest out and back onto the bench. The issue is clearly the replacement float valves in the Wemoto kit. Whilst they look similar to the OEM ones removed a detailed examination shows they are not quite right, so others beware. They are slightly longer and the rubber sealing tip is a slightly wider diameter but the same height so it is not as pointy. I didn't actually need these out of the kit, the ones in the carbs looked fine so now to put those back in.

This has done me a favour as it happens as I now see from the way the floats sit lower with these in that the way the service manual shows you to measure float height is misleading. Having the carbs inverted as you measure leads to the spring loaded nipple on the valve being depressed giving a false height. Another trap for the unwary. @Swiss Toniputs me right with a better way to do it. With the original valves back in a couple of heights are slightly off so I put them right. Rather than filling the whole lot up at once I sorted 1 & 2 then bench tested, then did 3& 4. Then filled the lot and bloody 1 started leaking. However, that appears to have been a badly seated valve as a quick drain, couple of taps on the float bowl and refill seems to have sorted it.

So, currently they've been stood hooked up to fuel for 4 hours and no leaks. I'll give them 24 hours to be sure.

What a palaver!

[Upshotknothole]

Congrats, hopefully a ride will be in store soon. Think of it this way, the next time you need to rebuild them, you'll have a lot more experience going into it and it'll be easier.

[gazza49]

the keyster kit is called ,keyster tornade it is a tuning kit that includes,

KIT INCLUDES： - CHAMBER GASKET - NEEDLE (VALVE) - JET,MAIN (6 sizes:#95 #97 #100 103# 107# 112#) - JET,PILOT (3 sizes:#15 #17.5 #20) - JET NEEDLE (4 sizes:#S #L #R #RR) - NEEDLE JET - HOLDER - SCREW,PILOT - SPRING - WASHER - O-RING - SCREW,DRAIN - VALVE,STARTER - GASKET,JET BLOCK - PLUG -allowing you to experiment with exhaust and inlet mods.