Crass

I'm posting this up in case it helps others in future. As most will know there isn't much room under the tank of oil cooled bikes leading to issues with trapped and kinked fuel hoses. This is made worse when things are not laid out as standard. I've found my bike to be a PITA as the fuel hoses were so short it was a real struggle getting them on and off the fuel tap with the tank not lifting enough to get in. As I was rebuilding the carbs and replacing the hard hoses here's what I've done. First thing to note which is probably part of the problem is that routing on the L model is different and the change came with the RK model. Originally the hose feeding carbs 1 & 2 connected to the fuel tap outlet which points backwards and the hose feeding carbs 3 & 4 connected to the tap outlet which points across the engine. This was reversed with the RK and the hose from 1 & 2 now went straight forward to connect with the tap outlet pointing across the engine with the hose from 3 & 4 running parallel with the rear of the carbs before turning 90 degrees to connect with the tap outlet pointing backwards. Owing to the extra plumbing under the tank if the hoses are not routed correctly you stand the risk of them becoming trapped. On my bike as it came to me the hoses were routed wrongly as per earlier models and were too short to be routed as per the service manual routing diagram. The associated anti-kink protection springs were also only long enough for these truncated hoses. Did it come like this from the factory, who knows? So, the picture below should be self explanatory and show the correct revised arrangements which I have installed. For reference I have used 11mm OD hose and the one connecting carbs 1 & 2 is 38cm long, the one to carbs 3 & 4 is 35cm long. I bought another length of OEM anti-kink spring (still available) and snipped it into two 12 & 15cm lengths and added it to the extended hoses with the original springs. It fits just right to 11mm hose providing support against kinking and the combined lengths compress the springs slightly adding protection. Be aware that you will probably get a sharp burr when you snip the spring so smooth that off and to be extra safe position the cut spring so the snipped end is at the fuel tap end, so the smoothest as-supplied end is in the middle of the hose. Spring clips for 11mm OD hose will fit over the hose at the fuel tap outlets ok (not the case if you use bigger OD hose as there is limited clearance for a clip to slip on). I find that with this arrangement the tank can be tilted plenty far enough up for easy access to the hoses, they fit in the space available without being trapped and they curve without kinking. The springs also provide protection against contact with hot surfaces, although as set out above they do not contact the engine (although it will still be a bit toasty under there).

If you've got camchain wear it will be longer than new. The tensioner will maintain correct tension, however. Provided you have the exhaust mark lined up and the correct number of pins counted then any slight discrepancy in positioning is probably down to wear. Doesn't mean the chain is worn out but obviously as it wears the mark will slowly drift out of the ideal position. Provided the chain isn't worn beyond serviceable limit everything is fine.

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!

Thanks. Was led up the garden path by some online videos showing the float left unsupported on the valve with the carbs upside down and chaps measuring like that. BST38s as well. Can't beat OSS know how.

The float valves on the BST38s ( and I presume others) have a sort of spring loaded plunger where the tang on the float actuates. When the manual says to measure float height with the float tang just contacting the valve am I correct in thinking that you need to support the float so that you can measure the height when it just touches this plunger? If you don't support the float it compresses the plunger and you're going to get another reading. Seems like a job for an octopus.

I'm pretty sure I've got exactly the same problem you had. Rebuild kit from Wemoto, not branded but the float valves look identical to the wrong ones you were supplied with and yep, fuel pissing out. Thankfully I saw on here to benchtest first. The floats definitely sit at a significantly different height to the OEM valves with these. The OEM ones weren't actually causing a problem so they're going back in. I only wanted the kit for the gaskets etc but decided to use the new valves as well.

1990 750 also has 5.5" rear wheel

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.

You're not, you've just saved me a load of grief. Information is only obvious if you already know it.

No, it's not that one it's too small and there's another o-ring supplied which fits the float bowl mounting stem. I'm wondering whether perhaps this kit fits more than one bike / carb and as supplied for a GSXR750L there is an o-ring that is not used?

Nope, it's neither of those. You get the pilot mixture screw o-ring in the pack, this isn't it. It's too thin to work as the o-ring on the carb cap sealing the carb balancing vacuum takeoff. The latter don't come with the set, I had to buy those separately. See photo - the mystery o-ring at the top. Bottom left is a mixture screw o-ring (smaller) and bottom right is the o-ring for the cap.

There is a small o-ring with the Wemoto carb gasket kit for the BST38s that I can't match up to anything existing on the carbs. The only thing I can think it fits (which it does) is the float bowl drain screw but mine don't have any, nor does the parts fiche show one. Should an o-ring be present?

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.

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.

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.