Clip position, either too rich or too lean

[Raveydavey]

PHBH30
Pilot 53
Slide 45
Tried Needle AV264 + X13 2nd clip from top = tad lean, 3rd clip from top too rich at half throttle
Tried needle AV266+ X7 it's less noticeable but same symptoms , 2nd clip lean, 3rd clip rich

I have the little washer on or off makes no difference.

Do you think a bigger pilot, e.g. 55 or richer slide, e.g. 40, would solve this?

[MickYork]

or try it a tad lean and fit a filter ?

Maybe a dyno would be an easier option ?

[Raveydavey]

or try it a tad lean and fit a filter ?

Maybe a dyno would be an easier option ?

Cheers for the reply Mick. I have a ram remote filter on already. Although I think you might be right about the Dyno. It's got me beat.

[MickYork]

Thinking outside the box:

What's your timing set at ? might be worth checking to see if you're too far retarded/advanced, this will alter the colour of your plug.

Also, have you checked for air leaks ? again this will alter the characteristics of a plug chop.....might be worth checking.

[Donnie]

What little washer is it you are talking about?

[Raveydavey]

I did have an air leak which Must have been there since I built this engine but I'd jetted to compensate ; it ran sweet across the range. Only issue was poor top speed. I wanted to fix that which led me to finding and fixing the leak. That's where the fun started. If I could put that leak back I'd be sorted

Varitronic ignition, which I did change from 23 @fast idle to 21 @fast idle. Difficult to say what the timing will be at; not looking at speed or revs, just throttle position

Donnie- the little washer, which seems to act like a spacer under the clip. The slide has a small recess where this sits so might just be irellivent here (and a necessary must have)

[Warkton Tornado No.1]

The washer fitted between the slide & the needle clip effectively gives ‘half positions’ between grooves so does make a difference.

As do new needless & atomisers that have no wear.

Of course, that is what you have, isn’t it?

[Raveydavey]

Cheers for the reply Warkton tornado. I've heard that a spacer exists which gives a half clip position but I've always thought that was something different to the washer here. The washer sits flush in a recess in the slide the top of which seems level with the surface the clip sits on. happy to be wrong

Atomiser and needle are about 1000 miles old so wouldn't have expected any noticeable wear?

[Warkton Tornado No.1]

The washer sits flush in a recess in the slide the top of which seems level with the surface the clip sits on.

I’m certain I am right but should explain a little better. I dragged out my spares to check.

Regardless of the recess in the slide which the washer (really a shim) fits into, it still spaces the needle clip up by the thickness of the shim.

BTW, when not ‘in use’ the shim can be ‘parked’ on top of the clip to be held in situ by the needle plate that the slide return spring bears down onto.

Atomiser and needle are about 1000 miles old so wouldn't have expected any noticeable wear?

Any wear to the needle & atomiser will be dependent upon the amount of vibration they are subject to, of course, as you will surely know. 1000 miles seems very little for a road going scooter. However, the slide has a little sprung plunger to keep the needle concentric to the atomiser & if that is ineffective, or missing, the wear will accelerate.

I doubt you have worn components in your case!

[Raveydavey]

I wish I could say I knew what you meant by a plunger to keep the needle in line. There is nothing like that in this carb.
I am still a bit sceptical that this washer is a spacer. It is almost like its there to keep the needle in position. It sits snug on the needle and had a smaller diameter than the hole on the slide. If I fit it on the needle against the clip when not in the carb I can see if DOES make a half clip difference, so logic says when it's sitting in the recess in the slide that difference is cancelled out. It would need to be thicker to do any spacing....I might be totally wrong here, but when I've tried running with or without I've noticed zero difference in performance or plug colour. Change the actual clip position and straight away you feel it.

This is why I was suspecting something else, e.g. Pilot jet. I know this is for idling which it seems to be ok on, it does have a marginal effect across the range. I'm thinking make it a bit richer so it's happier on 2nd clip...clutching at straws really. Dyno looks inevitable

[MickYork]

posting.php?mode=reply&f=6&t=5943


Might help with spring ?

[Donnie]

Im in a similar position with my jetting currently, in fact nipping out for an hour or two today to try and narrow it down a bit more, a little lean on one clip, too rich on another so will be trying a different atomiser and needle.

as for the spacer for under the needle clip, are these not simply a thin washer?

[Warkton Tornado No.1]

I wish I could say I knew what you meant by a plunger to keep the needle in line. There is nothing like that in this carb.

So, you don’t have a plunger, eh?

Nothing in your slide that looks like this image I acknowledge Scooter-Center for? No likelihood of a little plugged hole shown here on the round face of the slide vertically above the number 35? That connects through to the central round hole. Have a really good look.

As for comments about the function of the needle & atomiser, their choice is influential from ¼ to ¾ throttle. That is termed the HIGH SPEED range.

If you cannot understand the concept of shimming the needle, yet understand clip positions & I can’t convince you, perhaps you could borrow a vernier or digital caliper to measure the amount the needle sticks through the slide in various positions.

That way, the penny might drop…..

as for the spacer for under the needle clip, are these not simply a thin washer?

Ever get a sense of Deja-vu?

Regardless of the recess in the slide which the washer (really a shim) fits into, it still spaces the needle clip up by the thickness of the shim.

[Raveydavey]

Apologies for the late response. I finally got the chance to have a good look at the washer/ spacer thingy, and I can now see that if its not there the clip sits in the recess in the slide; the recess the washer sits in...so it is a spacer you were totally correct. I did say I'm happy to be wrong

If the weather is less pants tomorrow I'll have a spin and see if that does give me that bit more. I'm sure I've tried it before without success. Maybe I got that wrong too. Fingers crossed.

Regarding the plunger thing. I can see the brass item sunken in the hole in the slide; how does it work? There doesn't seem any means of moving it.

[Warkton Tornado No.1]

Regarding the plunger thing. I can see the brass item sunken in the hole in the slide; how does it work? There doesn't seem any means of moving it.

You don’t need to move it, just check it is there, which I am pleased about. Occasionally they come out, but I’ve only known it happen to Adam on this Forum.

Now that you’ve located the plunger, what you see is a blanking plug on the outside radius of the sleeve. Now, look on the inside bore of the slide & you should see a little bit of the plunger poking through. That is sprung to push against the needle when in place.

If it is there, as I suspect it will be, you can now imagine that it will be merely a way of taking up any clearance between the needle & the hole in the slide by pushing the needle to one side.

It is simple, often overlooked but important within the scheme of trying to cut down the effect of vibration.