Desperate for help GS450 wet fuel height

[rekidiw]

I have rebuilt my carbs, replaced all o-rings including the ones attaching to the cylinder head. i’m having issues with hanging idle and stumble on full throttle which leads me to believe i’m lean. I have a workshop manual but i don’t really trust if it’s giving me the right fuel height because it lists the wrong float height for my bike. I have a 1981 gs450 with bs34ss carbs. this is the style that does not have a plug on top of the pilot jet in the bowl. so my question is does anyone know the correct WET FUEL height? my manual says 6.5mm. if you don’t know the manual recommendation can anyone with a good running 450 tell me what there’s is at? i’m desperate lol. i’ve been through these carbs at least 5 times.

so according to my manual..
float height 22.4mm(my model after research requires 26.3)
fuel height 6.5mm(since my float height is different i am wondering if my fuel height needs to be too)

another funny thing is my tamper proof caps over the mixture screws were still in tact when i bought the bike. i personally removed them and recorded the screws at 3.25 turns out. it seems to me that everyone else in this worlds are something like 1.5-2.5.

another note is the idle is very smooth and nice sometimes then very rough if i have it set low at like 1000-1100 sometimes. sounds like it’s almost gonna die between revolutions. almost like a huge lopping cam. seems like it idles down and gets rough the longer it sits at idle too. and i hear very random (pops/clicks)? coming from the carbs. this is very random and tends to happen more often if i open the mixture screws and give it a richer mixture.

of course these issues are all on top of the god forsaken mother fu***** air box. the thing is impossible to mount and seal evenly.

 

[LAB3]

Mine are set at 21mm dry, never did get around to setting them wet. The screws under the caps on mine where at two turns out but two and back half is where it likes to run best. Had to take out the air box mounting screws and remove the battery to get everything sealed up properly then reinstall afterward. Have you checked your valve shim clearances? Also, replacing the petcock made a world of difference on mine.

 

[LAB3]

Clarify: two and a half turns out!

 

[rekidiw]

appreciate the reply. yours being set at 21 makes me think we have the different models. you must have the newer style carbs because 21 would be overflowing my carbs. yep i?ve re-shimmed the valves, new petcock, new o-rings everywhere, new air box seals, full motor rebuild...haha everything. i?m convinced it has to be a small adjustment somewhere.

does anyone one know if low compression could these symptoms? even after rebuild the compression isn?t great. don?t think the rings seated well. gonna rebuild again this winter

 

[LAB3]

Hmm, mine is an 82 GS450 with the bs34ss carbs. Have a hard copy of the Haynes manual, that's where I'm getting my info.

 

[rekidiw]

hmm ok well i appreciate the reply. is yours the style that has the rubber plug over the pilot jet?

any one else have their fuel height/float height setttings?

 

[Gorminrider]

OK...well I have THIS for you. Can't remember where I got it but it might help confirm things for you.


but, indeed, check the petcock very carefully. They are often are a source of problems. You seem to have quite a lot going on there with poor airbox seal etc...are the rubberseals wrecked? it's maybe only my experience that the airbox seal is seldom a problem otherwise, on twins...you can make a simple fuel level gauge (simpler than I can describe it!)with a piece of 1/4 clear hose by heating it just enough(not charring!) and pulling the ends until it stretches, then cut the tube at the "neck" the stretching created. This can now be turned tightly into the drain screw hole threads...take it out and trim it so it doesn't hit the floats inside- and hold up the rest of the hose alongside the carb bowl to test the fuel level...which should be just below the bowl gasket...yes, it's primitive but doesn't drip if it's done right. (I still use the first one I made)

I've never noticed that fuel height to the mm is crucial and resetting the float height from the manual is to be avoided , because if they are not working, the needle and seat are more likely the problem...or I'm looking in entirely the wrong place for a running issue...

 

[Gorminrider]

I have rebuilt my carbs

sure but did that include cleaning? Especially the tiny holes in the jets? they must be removed to know... (a very common source of trouble! trying to compensate for dirty jets by turning out the idle mix is a thought I'm formulating... ) and all passages in the carbs?

....I'm curious about this-

this is the style that does not have a plug on top of the pilot jet in the bowl

. I thought they all did.

 

[rekidiw]

hey man thanks for the reply. yep i have cleaned them twice so it is definitely not that. i got new air box rubbers, but the box itself seems warped so it’s impossible to get on perfectly flush. i ordered a used box on ebay yesterday so i’ll give that one a try too when it comes in. i removed all jets and everything to make sure they were the right size and lucky that i did cause i can now match which bike on that chart is mine. it’s is definitely the one that the fuel height says 6.5mm. i already have a wet fuel tube gauge so i’m all set with that. the main issue i’m having is in order to achieve a 6.5mm fuel height, the float height is no where near 22.4mm. for me to achieve that fuel height my float height is set to 27.6 mm which strangely is much closer to the specs of the gs400. i guess what i should try is ignore all float height measurements and just set the fuel height once for 5mm run it, then once for 6.5mm and see which runs better.

starting to to wonder if someone put different (wrong) floats in it and that’s why the measurements are off. just ordered new floats to try out.

that chart is awesome but after tons of research i have found there has been some contradicting info on the very early gs450 carbs. i have seen 3 different float heights(everything from 22.4-26.6) and also some models have pilot plug caps and some don’t.

is there a correct place for the height of the fuel to be relative to the parts in the carb bowl? say maybe sitting at a certain level relative to the position of the jets? maybe i could ignore specs and set it to that physical location? you mentioned it being just below the bowl gasket. anyway you could show me on a picture where you believe is the correct spot? like just a generic photo and mark a line on it?

one mor5 thing out of curiousity...how is it that the same bike and pretty much same carb can have such a big difference in jetting? one has a 17.5 pilot and one has a 45? how does that work? is there any way to identify the model id number on the carbs? almost wondering if someone mixed up the jet sizes combining specs from different carbs


i think i’ll go out in the garage today and go through them again to make sure the the pilot air jet is the size it’s supposed to be to match the other jetting. i don’t remember identifying that one..

 

[Guest]

I think the question is how you cleaned them. Anything less than a 24hr soak in carburetor dip is pretty useless. I have dipped carburetors that looked clean enough for food service that boil out crud within minutes of dipping. It takes a while to melt years of baked on crud in the tiny passages you can't see.

 

[rekidiw]

really? i dipped them for like 2 hours because the chemical directions said it would damage them if done longer. what do you mean boil out?

 

[Gorminrider]

but the box itself seems warped so it?s impossible to get on perfectly flush

You might try a heatgun to warm it enough to straighten it. or,maybe a hairdryer would work and is safer being not as hot with danger of really melting... OR without any of that try wrapping in a towel and soak with really hot water..might work. Lastly you could resort to the oven or blowtorch but I didn't tell you to do it!!

one has a 17.5 pilot and one has a 45? how does that work?

not sure! Like I said, this is just something from my collection...you might just look around the web with a search on the Mikuni 34SS etc... It might just be a part "superseding" to please the EPA...You could search for posts by Mekanix. He was really into it and had a thread cataloguing such details with lots on twins. Also look up pete who squeezes as much as possible from a 450.

is there any way to identify the model id number on the carbs?

Um, that's hard too. Only place I've had to know was an oddball Honda with Keihins and I was able to find it in the REAL ACTUAL Honda shop manual....Suzuki goes some distance to identifying real specifics to certain changes in there REAL ACTUAL shop manuals but I don't know where to find yours ...my bike is slightly different-an '81 GSX400 from that list above-and carbs are a wee bit different too.
not helpful but still...enginewise, 1980-'81 were sooo similar but the wheels,sprockets and style are the MOST different on the E..little things got changed up to...85? but a lot of it was fancier ways to set the choke or different clusters, different rims ...stylish things.

anyway you could show me on a picture where you believe is the correct spot?

I used to have such a picture...Haven't found it yet... just on or below the bowl's flange a bit below the gasket is what I recall last time I bothered to check . I couldn't see it as being super crucial in mm unless it's obviously not near that...don't forget the carbs are not exactly level on the centrestand or really, when riding around either, so I take fuel level to be "always enough gas" riding uphill but never spilling out the overflow hose... which the above pretty much satisfies....again,I don't think fuel-level is going to be something that needs much setting IF the floats and needle and seat are doing their job and set as the manual says. Shake the floats to test for leaks in them is about all that I would want to do unless someone else has been bending the tab...

 

[Gorminrider]

Found it! But now you have to trust that this is THE BEST OF POSSIBLE FLOAT LEVELS which I wouldn't know beyond saying the bike runs pretty well ...and is my interpretation of what the manuals say per float levels because these carbs came apart several times being really badly varnished and me replacing parts from donors as they came available

 

[Gorminrider]

here's something I didn't know until I got into mine...might help!

 

[rekidiw]

ok i’ll give heating up the box a try today. other than that i’ll put all my new parts on and try everything mentioned and let you guys know what happens and officially post the best height i find. i appreciate your guys`s input!


thanks for the pic but it’s a little hard to tell where the fuel actually is relative to the bowl. is it to the blue or green line?

 

[Gorminrider]

I can't see your pic with blue and green lines very well-it's too small - but I think the green line is the one you want if it's lower than the bowl gasket...my picture is a bit tilted but judging by the gas in the pipe, the carbs are pretty level when I took this.

 

[Gorminrider]

I'm trying to use the level of fuel to straighten the picture but I think it's pretty close to showing the tilt of carbs when on the center-stand...

 

[rekidiw]

aright guys, i have appreciated all the help but i am still at this. i have one question that i?m dwelling on and it?s frustrating because it isnt talked about in the shop manual. when setting the wet fuel height the manual states to measure from the surface of the float bowl that contacts the carb body when mounted. my question is do i take into account that when mounted with the float bowl gasket, the bowl is actually 1mm lower than it would be without the gasket. just in case i?m not explaining this clearly, i have attached 2 photos. 1 without a float bowl gasket and one including the float bowl gasket. can you tell me which measurement is correct when trying to set a wet fuel height of 6.5mm? thanks again..bikes running pretty good but i?m trying to get this thing running perfect

 

[LAB3]

If I where reading the instructions and no pictures where used to show how it was done my impression would be to measure from where the bowl meets the gasket. Keep in mind that the tolerance for setting the hieght is + or - 1mm. I've gotten myself caught up in splitting hairs many times before without getting much in the way of results for my efforts.

 

[Gorminrider]

A wet level is taken below the bowl's "mating surface" or another way that Haynes has it: "below the carb body-to float-chamber-mating surface"

Yes of course this surface mates to a gasket which mates to the carb body...you can't practically do a wet test without the gasket...
and Anyways, the gasket isn't going to affect the bowl's fuel level that you are testing However, gasket thickness would affect the jets .... So being finicky, use the oem gasket .