78 GL-1000 769A carbie piston springs ???

[Pedrotq]

G'day to All,
i am having trouble getting my GL-1000 to run smoothly under 2500 to 3000 rpm, i have had the carbs out and in a dozen times, she runs good and plenty of grunt above 3000 rpm, but under that she seems to be running out of fuel as you just amble along at say 70Km/Hr.

Over the years i have had many carbs to bits and i am just wondering if i have mixed the piston springs up and have a set of 75-77 springs in there instead of the 78-79 ones?

Maybe someone could enlighten me

I have the spring on the Left fitted into my 1978 769A carbies.

Thaks in advance, Peter

[Whiskerfish]

https://www.ngwclub.com/forum/viewtopic ... 43#p334243

[redglbx]

One other thing I would check is the idle circuit as it is the main fuel supplier up to about 2200rpm. If you pull the carbs, then sand the red plastic tube from your gumout can down to a taper, then put the taper into the idle jet and spray (protect your eye’s & face) you should have gumout come out of the idle mixture screw hole with the screw removed and the idle discharge hole in the throttle bore with the screws installed. If no fluid comes out & I’d bet it won’t, you have a plugged idle mixture circuit.

Now while whiskerfish’s excellent photo in his attachment shows the spring differences in the various year carbs and you have the wrong springs in your 78, these really shouldn’t come into play until around 2200-2400rpm.

And without knowing the spring rates when the main slide/needles start to move/open and add fuel you should have a bog from the slides not opening (springs to stiff) or from the slides banging open to quickly (springs to light) . The slide movement is created by the air rushing through the bore and under the slides where the communication holes on the slide bottoms create a vacuum on the top that lifts the slides. The 78/79’s have slightly smaller bores than the 75-77’s which increase the slide vacuum signal so I’m thinking the 78/79 springs are stiffer than the 75-77 springs you have installed. So your slides are opening to quickly (my opinion).

Anyway put the right springs in so the slides work right but I’d also make sure the idle circuit is clear with some carb cleaner. My.02

[ericheath]

The 78-79 springs which were in one set of 764A (77) carbs were much weaker than the longer 75-77 springs. (I must have four sets of 764A carbs) Weaker springs will lift with less vacuum and fuel will come on faster.

I can’t say whether the springs were different rates. I believe the number of coils are the same. I use Octane’s suggestion for comparing springs and slides which is in Shoptalk in his carb rebuild tutorial. You can at least confirm that they are close. Using Octane’s method of inverting the cap and measuring how far the slide’s weight compresses the spring, the 78-79 springs in mine, pushed the slide all the way down in the inverted cap.

If you have one of the four springs different from the others, it’ll probably run like crap.

[gltriker]

quote-" i have had the carbs out and in a dozen times,"

Risking sounding ridiculous, are all of the fuel bowl retaining screws and their complementing carburetor body screw threads in very good condition after so many carburetor disassemble/reassemble sessions?
Securely clamping the fuel bowl gasket onto the carburetor body where it covers the aluminum puck and seals the idle circuit passages is my concern.

[Pedrotq]

Thanks so much for the help guys

I did have all the piston springs wrong, had the longer 75 ~ 77 springs installed. I have many spares and the correct ones are now fitted.

The carbs have been cleaned a few times, all passageways clear, new OEM Honda needle and seats, all OEM jets and needles, Randakk's "O" ring kits fitted and all bowl threads have been Helicoiled.

I am sure she will run better now

Happy and Safe Riding to All, Peter