Leaky Carbs ............... again.

[GavD]

Flipping carbs aren't shutting off properly again. Switched fuel on to run the engine and within a couple of minutes had fuel dripping off the airbox, thought I'd cured that after stripping them down and doing the fuel levels a few weeks ago.

I'm starting to think that maybe the tip of the float needle has gone a bit hard and brittle over the years.

Has anyone else had this with the keihins?

Sprint manufacturing charge £23 for one float needle, NRP carbs do a float bowl refurb kit for £19 which includes a seal and pilot screw set up.

Has anyone used NRP?

Cheers
Gav

[nickjtc]

I'm starting to think that maybe the tip of the float needle has gone a bit hard and brittle over the years.

Apparently that is a common issue with 'maturer', well used, bikes. I read somewhere that we should be thinking of float needles as a consumable item that should be changed as a matter of routine every few years, just like tyres.

[GavD]

I had 'em out over the weekend checking float height. The haynes manual says 14mm but the general internet consensus for the keihins is 17mm.  2 of em were at 17mm, one was at approx 14mm. Set the one that was out to 17mm then checked fuel level using the clear tube up the side method. All the levels were ok, and I left it for an hour with the fuel switched on with no leaks.  Just need to get out on it to see if it happens again with the engine vibrations. If so I reckon I'll be changing all the float needles.

[GavD]

Got out for 10 miles or so this afternoon with no leaks or rough running, in fact the throttle response felt the best ever. It sounds really crisp and pulls up the rev range quicker than i've been used to.

On a slightly different note, I've got the 17" rear in now with a new tyre and the handling feels good after the sprint front end transplant. It's now ready for the sunny days, so fingers crossed the weather will improve soon.

[Sin_Tiger]

  hope someone's listening.

[GavD]

Been a bit busy with work/family commitments recently, and the bikes not really been out of the garage much. Started it over the weekend and even managed to do 30 odd miles, but 5 miles from home got the old rough running feeling again, pulled over and stuck it on the sidestand, got off and saw fuel running off the bottom of the airbox again.

Got home, carbs out in about 20mins (I've got quite good at it now). Set fuel tank and carbs up on the bench turned fuel on and all was good. left it for half an hour, still ok. I don't really wanna stick em back in without doing something meaningful, so I've ordered some new float needles.

It's definitely not gunk getting through as I've got 3 filters,
1 on fuel tap, 1 in line and 1 where the fuel line attaches to the carbs, so I'm hoping its just that the float needles have got old and maybe a bit hard and so don't seat properly.
All 3 floats appear intact and move freely.

Let ya know how i get on.

[Sin_Tiger]

Fingers crossed 

3 filters  how many pairs of underpants do you use at once 

[GavD]

I haven't quite got to the stage of life where I need multiple pants yet!!!

[GavD]

Well,

Got my new float needles through, installed them and adjusted the floats for the correct float height. Set fuel tank up on bench with carbs on shelf underneath, connected them up and switched fuel on. Left for 5 mins and no sign of them not shutting off, so I thought I'd leave them for a lot longer to see what happens. Went out to look at them every 15/20 mins, and after about an hour there was fuel starting to emerge from the small right hand hole at the bottom of the main air inlet (i.e where the air filter attaches) on the right hand carb.

After alot of draining/swapping bits around/resetting float height/putting back together and trying again I could not stop this. Got a small wooden dowel to try to clean out any gunk that may have got stuck where the fuel enters the bowl but still no change.

After lots of fannying around, couldn't be bothered to mess about any more so slung 'em back in and went for a 30 mile blast. No sign of them not shutting off, but then again before i changed the float valves I could do 3 or 4 rides with no probs then all of a sudden it would start again.

Suppose I'm just gonna have to be aware of it and if I feel it running rough when I'm out, keep going but shut the fuel off for a bit then turn it back on again.

Don't ya just love these steamers.
I'm starting to think I may need to get a bike with some of that new fangled fuel injection stuff!!!!

[ram33]

do the keihins have an oring around the float valve like mikunis? if so maybe its the cause of the leak?

[Sin_Tiger]

Don't ya just love these steamers.
I'm starting to think I may need to get a bike with some of that new fangled fuel injection stuff!!!!

Yup, once they got more complicated than an Amal Concentric they sort of lost their appeal. I love carbs so much I have a set of throttle bodies that look just like carbs on me Thruxton 

[GavD]

do the keihins have an oring around the float valve like mikunis? if so maybe its the cause of the leak?

No they don't, the keihins appear to be a bit simpler than the Mikuni's (to me anyway), and I suppose in theory less troublesome.