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1981 gs450 fuel level in float bowl. too high?

  • Thread starter Thread starter matt_gs450
  • Start date Start date
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matt_gs450

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Hey All. I had set my float height to the Suzuki Svc Manual setting of 26 mm, instead of the Clymer setting of 22 mm. Below are pictures of the left and right fuel level with the carbs on the bike. Does the level look too high?

I suspect the fuel level is causing the bike to bog down and stall if I try to give it too much gas too quickly from idle. All other carb adjustments have been done. The manuals don't specify how to read this measurement so your expert analysis is appreciated :)

Thanks,
Matt

Left fuel height:
fuel-height-left.jpg


Right fuel height:
fuel-height-right.jpg
 
Hey all. Just giving this a bump, and adding a cutaway picture with the fuel level shown in red. It looks like the level is right up to the needle valve. Question: if the needle valve isn't seating properly, is this where the level would be? Or would the level keep rising until gas spilled through the main bore?

And of course the original question: is this too high?

Thanks,
Matt

carb-cutaway-fuel-height.gif
 
The level looks about right to me. If the needle valve leaking the carb would overflow into the engine and/or air intake.

Strange how suzuki and clymer differ in opinion.
 
Rats. I was hoping the level was high and causing the bogging problem. I briefly discussed the issue with a mechanic on Friday, while helping a friend drop off a bike. His first response was, "why the hell are you messing around with that piece of sh*t?" After he realized I was pretty heavily invested in these 450s, he thought about it and was thinking that it might just be parts wear. E.g. the slide bore is a bit loosened up from years of service and the diaphragm vacuum doesn't hold. Or maybe the fit between the needle jet and the needle. So who knows, maybe this is the best these bikes can run after 30 years without doing something drastic like fitting aftermarket carbs. It's not running terribly, it just needs to be coaxed from a stop. Idles great. Runs great at speed.

Anyone else with a 450 able to throttle up, drop the clutch and NOT stall out?

-Matt
 
The problem is with your mixture. The bike can run great if you can get the fuel to air mixture right on all circuits. I don't know what carbs you have an wouldn't be able to help even if you told me. I am fairly certain that you just need to adjust them though.
 
If anything, setting the floats to 26mm instead of the stock 22.4mm would drop the fuel level, not raise it. When you set the floats, the carbs are upside-down, so a larger number makes the float farther away from the carb body. When you turn them back over, that greater distance makes them lower.

According to the pictures, they actually look pretty good. I believe the stock spec for fuel level is 5mm, and that is measured from the top of the float bowl, where it meets the carb body. If you don't have a metric scale, 5mm is about 3/16", right about where the pictures show your fuel level to be.

Not sure it it's what you were meaning to say, but worn slide bores will not cause any kind of vacuum leak. You may have just been mentioning that both conditions exist, but not that one caused the other. How are you measuring a vacuum leak? There is no good way to measure the vacuum above the diaphragm. If you suspect low vacuum up there, look for pinholes in the diaphragms. If you have holes, you need to replace the diaphragms. However, the symptoms of holey diaphragms would be poor top end, not a stumble off idle.

Have you checked for other vacuum leaks, like your intake boots or o-rings? Even incorrectly-tightened clamps can cause an intake leak that is bad enough to cause stumbles. Have you ever cleaned the carbs? Are you sure the idle mixture adjust screw is set properly? Should be set somewhere between 2 and 3 turns out from lightly seated.

.
 
Hey Steve,

Thanks for hanging with me on this issue.

I did clean the carbs. I'll double check for any sort of vacuum leak. I've heard that a squirt of wd-40 around the boots would help indicate any leaks. I'll try that.

You mentioned having the air screws out between 2 and 3 turns. I used the highest idle method and have them at about 1 turn out each right now. But I'll put them out an additional turn and see what that gets me.

Thanks again,
Matt
 
What model 450 (I see you have several)? The float height specs do vary between models.
 
I've only got two GS450T's (that run). I've got two L's for parts. In any case, they all use identical carbs. I just looked at a service record for one of the bikes from when I brought it in a couple years ago. My mechanic was nice enough to record the mixture screw settings (2 turns). So my guess is that is the issue. 1 turn is probably not enough. I'll be able to give it a try later today when I'm not glued to the computer.
 
Woohoo! Success! 2 turns out for the mixture screws and I've got the low end power again. Now I notice the petcock is giving up on me :( Well at least that's an easy ($40) fix!
 
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