Jet Kits

[PatM]

Hi All

Been a few weeks weeks since Ive looked/posted. I question- looking at the photograph-(if it attatches..) in the Panels opinion- which groove- say from the top down, counting- should the circlip be in for the needle? I'm sure I put mine in 2 down...

One of the problems with carbs etc over the years is people sodding around with them, re-jet kits from the '70's, K+N upgrades... its difficult to know whats Right and whats wrong when rebuilding!

Ive alway thought my 400 a bit hesitant until it gets going- say over 2.5k- and a remark Yoshi made has had me thinking ever since we met at The Gamecock on the 2/9
Rgds

PatM

[K2-K6]

On all the bike carbs I've seen the needle has 5 grooves and ordinarily comes with the circlip in the center position (2 clear grooves above and below clip).

Adjustment is provided to cope in a small way with variance in local conditions against design spec (altitude, temp, humidity etc) and as we have similar local conditions to Japan then developed spec should be quite accurate for general use assuming engine is in good order.

[exvalvesetdabbler]

I have just removed one from one of my spare carbs which I am sure is original and not been messed with.  The circlip in in the middle or third groove and is marked with the number 18234. 

These carbs came from a ex courier hack with 72k on the clock that i bought for spares in the late 80's. You can see a slight narrowing of the needle where it would contact the top of the emulsion tube at idle. What killed this bike was a small washer embedded in the side of the piston and deep scores in the barrel.  The top of the combustion chamber looked like someone had taken a chisel to it.

The Haynes manual also says the third groove.

The way that I noticed my problem was to insert the needle into the emulsion tube and try to wiggle it side to side, it was clear that one tube had much more clearance than the others. Closer examination revealed that the chamfer just inside the top of the tube had been eaten away and the inner diameter was enlarged.

From what I have read up on these bikes is that they always ran a little on the rich side at idle to workaround the drop in vacuum when you open up the throttle at low revs, and as I found out with my bike, wear in the needle/emulsion tubes can make it too rich when rolling on the throttle at low revs.

Problem is that the needles are a sod to get at so I'm leaving mine as it is for now and sort it out over winter,  It's not too bad with a matched set of worn tubes and 10x better than it was with one completely duff tube. It does stumble a bit at 3000 if I'm very gently on the throttle in 6th, This could be carb balance because they have only been done statically,  I put my vacuum guage adapters in a safe place a few years back and memory aint what it used to be!.  I'll machine up a set when I get time.


Regards
Dave

[florence]

.....talking of things going into the engine, it is worth keeping an eye on carbs as metal fatigue can cause problems on old Hondas.  On my CB350 there is a small metal flap on the choke which came off one day and went through the carburettor and into the cylinder.  As I started the engine there was suddenly a terrible clattering noise.  I stopped the engine straight away and took the cylinder head off to examine.  Luckily, not too much damage done and after taking the offending article out and smoothing the worst of the dents in the combustion chamber it was completely fine.  When I examined the other carb I noticed that a small piece of the choke flap on that side had detached itself and, presumably, had been through the engine without anyone noticing.  It is worth stopping the engine if a strange noise develops so that one might find the cause before too much damage is done.