Topic: is the 26mm float height correct for 750k3?

[dakeddie]

Hey,  my carbs have always overflowed when the bike's been parked with the petcock open.  I rebuilt the carbs last year with brand new float valves and seats, and adjusted the height to what I thought was correct according to the Clymer manual.  Still they overflowed.  The floats show no signs of being leaky, they all float and don't make any sloshy noises.  I've just lived with making sure I've closed the petcock when parked, but I have the carbs off now and I figure I should give it another crack.

Now, the Clymer manual says that my bike should have the bottom edge of the float 26mm from the base of the carb when the float is just in contact with the valve and not compressing the spring.  What exactly do they mean by 'base of the carburator'?  Is it to the lip that surrounds the gasket, to the little notch that is located by the float bowl clip, or to the surface on the base of the carb that the gasket touches?  See picure.

I have mine adjusted to 27mm from the lip and they still overflow.  I didn't check recently, but last year I checked to make sure all the float valves were functioning by holding them in lightly with my finger.  So is the Clymer manual right?  Is it 26mm, or is it greater?

[Terry in Australia]

Yeah mate, 26mm is correct, as per my Honda factory manual. I use a vernier caliper and measure 25mm from the float bowl gasket (about 1mm thk) to the top of the float, with no drama's.

It's probably not your float height though, a lot of the float valves in the rebuild kits you see on Ebay are rubbish, and just don't seal well, particularly when your bike's parked on the side stand, so either use your centre stand, or just remember to turn your fuel off. Cheers, Terry. 

[cben750f0]

yep i agree with terry, just get in tha habit of turnin the fuel off, or go buy the honda ones.... you might only have to give up you first bor for them!!!!!...peace

[dusterdude]

did honda change the float design from the k1 to the k3,that float looks a bit funky

[cben750f0]

they are the same floats i run in the '77F... so might have some carbs off a different year?...peace

[dusterdude]

which could change the float height measurement

[dakeddie]

I did use honda float valves and seats... not aftermarket ones.  And it's true that when my bike's on centre stand it doesn't overflow.  But i'm really intrigued about my carbs being off a later bike.

I always thought I had a pretty stock bike, until I put in one of those APE 14% more friction clutch kits.  My clutch is supposed to have 7 identical friction discs, but it has one plate that is different (the outer one) that i had to leave in.  I think it's from an F or later bike.  Maybe my whole engine is from an F... i'm gonna check that out.  Even if it's from an F, the float is the same, right?

[DME]

did honda change the float design from the k1 to the k3,that float looks a bit funky

Honda went from using hollow brassfloats to these massive, "plastic" floats. The brassfloats were prone to leaking....
Not quite sure when they were replaced but I think it was as early as 1972...

Correct me if I´m wrong.

Cheers

Daniel

[dusterdude]

my late 71 k1 has the brass floats,who knows when that happened

[Terry in Australia]

The plastic floats are correct for a K3, and regardless, the float height is the same.

[HondaMan]

I saw brass floats as late as a few K4, but the plastic ones first appeared on the late K1. The K2 usually had plastic, and most later ones were plastic.

Like I just posted somewhere else: look closely at the edges of the little posts where the float pivots rotate around the rod. They often wore tiny rough grooves into the posts, which can make the floats stick down when the bike is sidestanded. A tiny file on those posts will re-smooth them, and round off the edges of the brass pivot bearing while you're at it.

Also, the plastic floats, if you ever used "gas saver" with formaldehyde (which is most of them), will have a heavy crust on them that makes them sink further than they should. If you have brass ones, they can condense water inside and also get coated with minerals from the fuels, resulting in the same problem. A little bit of scale makes them surprisingly heavy.

[Jonesy]

You probably have the correct carbs. The plastic is made from a fuel-resistant microcellular foam. The nice thing about this is if the exterior id damaged, only the cells in the surface are damaged and the inner ones will still be intact, allowing th efloat to still function. This is used in all kinds of float applications nowadays, including the floats in automotive gas tanks that send signals to the gas gauge. For many years soldered brass was the material of choice for carburetor floats, but they were more prone to damage and took skill to repair. An interesting note, in the outboard motor industry the carb floats were made from varnished cork!

My K3 will hold its fuel unless it sits for a couple days withthe petcock left on. Then it marks its territory.