Dodgy pilot screw????

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Dodgy pilot screw????

Post  R056rx on Mon May 05, 2014 7:20 pm

I'm trying hard to set up my carb properly for the first time. I'm confident I've got it really, really clean, new float valve, new O rings and gaskets all round, new 68s pilot, 175 main, B53e on 3rd notch, float height adjusted to 16mm, K&N air filter cleaned and re-oiled, FMF Q4 system. Valves all correctly adjusted.  Bananatool 

Before I cleaned and serviced it, it would start first or second kick on choke, but idle was all over the place and hung badly. It also popped badly on decel. It also had a 65s pilot jet. At the time I tried adjusting the pilot screw but it hardly made any difference whether turned all the way in, or all the way out.  Frustrated 

So now I've worked on it it's not quite so easy to start. I have to start it by priming, kicking on full choke. It'll nearly start. Then flick the choke to half, a small turn of the throttle stop screw and it'll start everytime. Sounds a bit rich??

However the idle is smooth and constant.  No popping on decel. Everything is great all through rev range. No hanging idle.

Maybe I should leave well alone, but I'm still getting no reaction to turning the pilot screw all the way in. I've given it plenty of time to react, but it does not kill the engine or even decrease the idle. This suggests I need an even smaller pilot jet  beat head 

I've put the 65s back in and still the same, but starting is a little more difficult.

It points to bring too rich but I haven't read anywhere of anyone going down to a 62 pilot. I 'm at sea level so a 68s should be fine.

The only thing I can think of is that the pilot screw is damaged, but it doesn't look too bad to me. Some very slight pitting and it may be bent a very, very tiny bit. I've got nothing to compare it with so for all I know it may be missing a few mm off the end, but I doubt it.

Thinking of buying a new pilot screw before a 62 pilot jet.

Picture of the screw below. Let me know if there's anything obviously a miss, or if I haven't thought of something.  asking for it 

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Re: Dodgy pilot screw????

Post  BuRP on Tue May 06, 2014 10:12 am

Sounds to me you need to give the cables (push-pull) a bit more play, too tight at the moment?
Then, during idling wave a gas-torch (OFF!!!, NO flame!!) over the intake boot..... do the revs pick up? If so you've found a leak ie renew the rubber boot.
Failing this, did you plug the tiny hole in the small cover (behind which a small diaphragm lives) with a little epoxy/silicone? You should...  Wink 
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Re: Dodgy pilot screw????

Post  R056rx on Tue May 06, 2014 6:39 pm

Thanks BuRP. Probably my unclear, long winded explanation, (blah blah  ) but I'm no longer having a problem with hanging idle, popping on the decel, or even starting her up. It starts off the choke which to my simple mind says too rich, and turning the pilot screw all the way in doesn't kill the engine or even decrease revs, which again to me says too rich. I don't really think I should be needing a 62 pilot jet so I was just exploring other possibilities, like a slightly damaged/ worn pilot screw  Question   Question 

My understanding is that a leaking rubber boot would cause the mixture to be too lean which I don't think is the problem?? shrug 

I've just had a brainwave and think maybe I've over oiled the K&N filter. doh doh The instructions weren't very detailed so I put plenty on both sides. I've noticed excess coming from the drain on the air filter cover, so I'll clean it all off and start again. That could surely make it run rich Question Question   scratch scratch scratch
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Re: Dodgy pilot screw????

Post  AURORA on Tue May 06, 2014 10:27 pm

Are you using real Keihin parts?
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Re: Dodgy pilot screw????

Post  R056rx on Tue May 06, 2014 10:37 pm

All OEM parts from a honda specialist  2 thumbs 
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Re: Dodgy pilot screw????

Post  BuRP on Thu May 08, 2014 11:39 am

K&N filter.....
is a cotton gauze filter......
allows fine dirt in the engine.....
will bugger it up if you ride offroad!
Foam filters bru, OEM or UNI or TwinAir or whatever, but foam, not cotton gauze!
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Re: Dodgy pilot screw????

Post  R056rx on Thu May 08, 2014 12:44 pm

I hear you BuRP and I've read all the arguments about the K&N. The bike came with a K&N with only 2hrs muddy green lane use. I've got a trip with mates next Month to the Pyrenees which is going to be on the road, so I'm not going to ditch it just yet. When I get back and use it a bit more off road I'll change it for a foam filter.  nice 
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Re: Dodgy pilot screw????

Post  BuRP on Thu May 08, 2014 3:04 pm

Hey, no problem,
it's your valves
and seats
and guides
and rings
and crucial costly nikasil liner.
LOL  Bump  no sweat, for on-road it ain't too bad.
Don't clean it though, they start filtering better (and let less air through then too) when they foul up a bit, it is what you want.
Enjoy your trip, sounds good!
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Re: Dodgy pilot screw????

Post  Zoro on Sun May 11, 2014 10:48 am

I had a hanging/ erratic idle.
I changed the 65S to 68S, running a 168 main, needle on 3rd clip and mixture screw set to 2.25 out.
Backed off the cables and lowered the float height.
Fixed the hanging idle, runs smoother at lower speeds and limited popping on decel.
Much happier now.

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