GSX 750 katana poor idle..... help

[Scott]

I need some help here. I have a 1982 GSX 750s1 katana that I have recently bought it has only done 23,000 killometres but I think it sat for a while before I bought it. From the outset it would not idle so I started out by doing the obvious and I striped and cleaned the carbs which where not too bad. I checked the boots for tears etc and then I reasembled and balanced the carbs. I adjusted the mixture screws to about 1 and 3/4 from the bottom and hey presto we have tick over.....well that's what I thought. when the bike heats up the bike wont tick over. There is a smell of unburnt fuel from the pipes and the plugs are still very sooty. All of this would indicate that it is running rich. but I am sure that I have covered all of the bases. Ive even stripped and cleaned the fuel tap...... help .... the summer has started and I cant get out of the shed!

[Billy Ricks]

Are you sure you got the needle components assembled in the right order?

[Scott]

yeh I'm sure. I did one carb at a time just to make sure I had a reference if I got lost.

Thaks for your input all the same.

[Billy Ricks]

How about float height? It's important.

[Scott]

I didn't check the float hight at all. I take it this is adjusted by flexing the sprung metal flap that the floats ar atached to. Do you know how it is measured?

[Billy Ricks]

If you have the carbs inverted you measure from the base of the carb where the bowl gasket sits to the bottom of the float. The bottom of the float is the actual bottom of it, not the bottom as inverted. The float should be resting on the float valve, not pushed down. Check the Letters to the Editors section of the forum. There is a post there that has carb specs posted by site users. You might find your specs there.

[Billy Ricks]

22.4mm +/- 1mm seems to be the magic number for most GS CV carbs.

[Scott]

thanks for the info. So it looks like I'm going to have to take the carbs off again. Is there anyway of checking and adjusting the hights by just dropping the bowls or do they have to be inverted?

[KEITH KRAUSE]

If the problem is carburetion, all your symptoms are rich related.
Difficult hot starts, raw fuel smell, sooty plugs.
The carbs have to be inverted as Billy says. Don't forget to remove the bowl gasket before measuring.
Since you inherited this problem, it could be a lot of things.
Check the float levels as suggested, and check for any bad o-rings or loose jets while you have them open. Verify you have the correct size main jet and pilot jet too.You never know what the PO could have done to these carbs.
Also, be sure your spark is good and the timing is correct and the air filter is clean.

[Scott]

Many thanks for your input. I'll post my progress once i've made the suggested changes.

[Scott]

Billy,

I am in your debt. I checked the float hights and low and behold it would seem the previous owner had set them measuring to the curved section of the float. I reset them measuring from the flat section at the back of the float and it seems to have done the trick nicely.


Thanks to a little rubber grease and my wife's hair dryer the carbs slipped back on with a minimum of fuss.

Many thanks to both you and Keith for responding.

Scott.