gs450 carb problem driving me nuts!

[Red]

Since completing my 1981 gs450s restoration two years ago there is one problem I haven't been able to resolve, the bike runs with one cylinder running lean and the other rich, the following is what I have to done to try to rectify this now protracted and irritating problem;

- Stripped & cleaned all channels, replaced jets, pipes you name it, it was done!
- Replaced air box & cylinder head rubber boots.
- Balanced carbs
- checked resistance on both coils
- Had igniter box tested
- Tripple checked valve clearance
- Tried various pilot & main jets
- Fitted new plugs & caps
Probably loads more that I can't think of at this moment in time!

So, after exhausting my options to fix this problem I decided to buy a 83 - 86 gs450 carb on e-bay and try my luck with a slightly newer/improved carb.
This newer carb was again stripped, cleaned, new needle jets etc.
Once fitted on the bike when I tried to start the bike the right cylinder just fired up with I think fuel starvation, the left cylinder would not fire up at all. On investigation there was no fuel getting to the left cylinder and a limited amount getting to the right cylinder. Both float bowls had fuel in them.
The 'attached' drawing is the newer carb I fitted with no fuel getting through.
Can anyone HELP!

[Maddevill]

Did you have the carb bodies ultrasonic cleaned? Because even if you pulled the jets, the passages inside the carb body may be plugged.

[Red]

gs450 carb problem

Not sure what u mean by 'ultrasonic' but after soaking for few hours I used compressed air to clear passage ways. What is the correct oprocedure for cleaning carbs?

[tkent02]

Do you have fairly even compression on both cylinders?

[Red]

gs450 carb problem

The carbs checkout as being balanced if that's what u m£ean.

[tkent02]

No, I mean does the engine have compression on both cylinders?
Did you ever check the compression?

[BassCliff]

Hi,

Just some background information for your reference:

Mikuni BS(CV) Carburetor Rebuild Tutorial
(Mr. Nessism)

CV Carburetor Rebuild Guide
(Courtesy of GSR and John Bloemer)
(Click here to see the CV Carb Notes)

GS450 Carb Rebuild Guide
(Mr. Flaming Chainsaws)

If you must replace any carb parts, use only genuine Suzuki OEM parts. They just work. Any aftermarket parts or kits will be of lesser quality and materials and not work as well.


Thank you for your indulgence,

BassCliff

[Red]

gs450 carb problem

To tell you the truth, no I never did because the cylinders were honed and new rings were fitted.

[snicrep5]

if you application has a fuel crossover tube, make sure your "new" carb doesnt have a blocked off passage. The reason Im saying this is because I replaced a messed-up carb on my 1100, and got a cold cylinder because the replacement carb I put in the #3 position, came from either the #1 or 4 so it had a blank hole. I carefully drilled it out and no probs. Just a shot in the dark.

[Red]

gs450 carb problem

Thanks for that Snicreps5, my carbs are an original pairing. I've ordered a compression tester on e-bay, my next move will depend on the results!

[pete]

You asked earlier about the correct procedure for cleaning carbs... the right way is to make sure they are absolutely thoroughly clean internally and that every single passage is completely clear of any fuel varnish. One little bit of varnish in the pilot circuit for example will definitely give you bad results.

The best way is an over night soak in proper carb cleaner. I chose to simmer mine in Yamalube carb cleaner but that is not the safest or most recommended method but it did let me get both done in a couple of hours rather than over night.

This was followed by a rinse in water after they had cooled down followed by compressed air through all passages, a spray through all passages with an aerosol carb cleaner, and finally one more go with compressed air through all passages.

I did this process for the carb bodies, float bowls, and all jets.

You should also replace all internal rubber O rings to be sure they're in good condition.

[Red]

gs450 carb problem

Thanks Pete, for some reason carb dips are difficult to buy in the u.k. But there is a solution were I work called Kem Safe, might use that.
Changing the subject slightly, can u do a compression test without the carbs fitted?

[tkent02]

Yes .

[pete]

Carb dip's getting hard to find here too, and Yamalube seems to be the only one I've found so far.

Testing compression requires holding the throttle wide open, so carbs off should be the same as that

[Red]

gs450 carb driving me nuts!

No, I mean does the engine have compression on both cylinders?
Did you ever check the compression?

Just checked the compression on both cylinders and both were 142-144 psi (tested with a cold engine). PHEW! Something less to think about I suppose.
Does anyone know if the compression readings go up or down with a warm engine?
Spark is good, so its back to the carbs I guess.