Rough running low down and high idle when warm

[FrankenDesmo]

Minor progress - front cyl carb is mostly stripped bar the butterfly (not quite sure how to tackle that yet) and the idle screw (only screws out to a point). Emulsion tube appears to be round (as opposed to oval) which is almost disappointing. Haven't seen any obvious sign of blockage or residue anywhere yet. Still, I do have another whole carb to strip, and that's the one that appears to be running lean (although the front cyl seemed to be the one doing all the hesitating, if exhaust pulses from the can were anything to go by).

I think I am going to go with buying an ultrasonic cleaner rather than sending them off, seems like it'll be fairly cost effective given I've got at least 3 other carbs to do for another bike.

Can't seem to find any markings on the main jet so far (assuming the push-in jet is the main and the screw is just a retainer, although it looks like a jet too), and have pulled out 3 other tiny jets. Absolutely no idea what they are for, nor the small spring-loaded diaphragm on the side under the plastic cover.

Off on holiday on Sunday so wont be making much more progress, but I'll come back ready to tackle the clean & rebuild as well as checking the valve adjustments.

[utopia]

Don't take this as a definite but, from my fairly recent work on the carb from my honda dominator, which is a similar diaphragm carb, I think the small, spring-loaded diaphragm on the side is a "coast enrichener", whose purpose is to reduce any tendency to pop and bang on the overrun.

And while I'm posting .. are you aware of Allen's Performance as a source of carburettor spares ?
I've had decent service from them, as have other forum members.
They seem to keep a good stock of jets and other carb consumables.

[FrankenDesmo]

Aye, I have seen reference to them, but thanks for the reminder. Unsure if anything needs to be replaced as yet, but I'll see when I get the other carb open, and work out what jets I've got vs what I probably need to baseline it.

[FrankenDesmo]

Bah.

Stripping down the other carb tonight (French ski resorts all closed so no going away for me), and I got to the point of getting this wee jet out of the top, had the screwdriver set in there nice and square, taking care and all, and as soon as I turn it CRACK



I'm guessing I'll need to get this to a specialist of some kind for extraction, or will any old engineering shop do? Also can anyone tell me the name of that jet...

[the lodger]

Try forcing in an allen key and using that to undo it

[FrankenDesmo]

1.5mm fits in but can't seem to force it to get any purchase. 2mm is too big. Cheers for the suggestion though, and I'll take any others!

[Mr Gazza]

That's unlucky! and a very bad start.
It's exactly why I would always try everything in the book before doing a carb strip as it nearly always opens an unknown can of worms, but hey ho, you had no choice really.

I would try an easi-out on that sometimes called a stud extractor. You might have to drill the hole out a bit bigger perhaps to get one in, but they do go down to some very small sizes.
Get the carb body held carefully in a vice or get some thick gloves and then pour boiling water on the body when you're ready to apply the easi-out. You could also soak the body in penetrating fluid while the tools are coming in the post or whatever.

Good luck, you will start to move forwards with this soon I hope.

[manwithredbike]

Originally Posted by FrankenDesmo

Bah.

Stripping down the other carb tonight (French ski resorts all closed so no going away for me), and I got to the point of getting this wee jet out of the top, had the screwdriver set in there nice and square, taking care and all, and as soon as I turn it CRACK



I'm guessing I'll need to get this to a specialist of some kind for extraction, or will any old engineering shop do? Also can anyone tell me the name of that jet...

Not to derail the thread but i was in France over the weekend skiing and they closed the resorts on Saturday night - after assuring us that they were to remain open. Big dash home, booking new flights etc. Mad times.

[FrankenDesmo]

I was supposed to fly out on the Sunday morning, so I'm glad I found out when I did, but since they didn't cancel flights or shutdown the chalet operators I'm not sure how much luck I'm going to have with the insurance claim. Worth a crack, though.

[FrankenDesmo]

Further to my post about the main jets - I haven't seen a mikuni symbol on them, so I suspect it has a dynojet kit in it and it's a dynojet 175, which is somewhere between a mikuni 162.5 and 165. I'm not getting too bothered about it though as the main jet doesn't really matter a whole lot for me at the moment - I rarely full throttle it.

Having thought about it, the needle jets are ~£17 each from Allens, so I might as well replace them. I'll keep those pilot air jets to 1.3.

The aim is to cure the issue with high idle/really rough running at lower revs, so if I find it's not 'perfect', I can come back with a factory pro kit at a later date (don't really have the £££s for it at the moment given that I'm buying tools more than anything for this).

Also probably going to get the bevel head 90deg screwdriver from Morgan Carbtune to make the sync & idle adjustments easier (possible, even!).

[manwithredbike]

Originally Posted by FrankenDesmo

I was supposed to fly out on the Sunday morning, so I'm glad I found out when I did, but since they didn't cancel flights or shutdown the chalet operators I'm not sure how much luck I'm going to have with the insurance claim. Worth a crack, though.

They pulled the plug on Saturday night so you shoud be on the right side of it if you were planned for Sunday - and you have travel disruption on your policy.

[FrankenDesmo]

Took the carb to dynotech ecosse to get the jet removed - was told it likely can't be done without damaging the carb, so leave it in as it's fine otherwise (which was my own first thought), especially for an ultrasonic clean. So that sorts that.

I've ordered replacement needle jets, so now I'm just waiting for those and the ultrasonic cleaner.

In the meantime, valve clearance checking and mounting a new headlight.

[FrankenDesmo]

Aye, it definitely seemed to be a sudden issue that had developed while sitting over the winter (rather than incorrect jetting). The battery was new on the bike when I got it, but it hasn't been replaced since the RR was replaced (it holds a strong charge though, and was off the bike and kept topped-up with a trickle charge over the winter). I'm hoping it was old fuel gumming up the works, but I'll see when I go to start it again.

However, I've just done the valve clearance checks...

Vertical Inlet Open: 0.04mm (0.05 required a tiny amount of force)
Vertical Inlet Close: 0.14mm
Vertical Exhaust Open: 0.04mm
Vertical Exhaust Close: 0.09mm
Horizontal Inlet Open: <0.04mm (didn't have a feeler gauge smaller, 0.04 required a tiny amount of force)
Horizontal Inlet Close: <0.09mm
Horizontal Exhaust Open: <0.04mm (same as Inlet)
Horizontal Exhaust Close: <0.09mm

I used the 'loaded gap' method from Chris Kelly to measure the Closer gaps, so the <0.09mm on the horizontal Closers means 0.13-<0.04, so probably 0.10 assuming the Openers are 0.03mm.

I triple-checked these measurements, going up and down feelers (where possible) to ensure I had the one that slid in without force. Where I need to apply a tiny amount of force, it was really minute and more aligning the gauge with the gap by using a finger at each end of the gauge, but I assume that counts as the gauge being just too thick.

My Closers seem to be within spec (0.03-0.20 according to Haynes), however it looks like all four openers are out of spec as Haynes has the lower bound at 0.05mm.

I gather that this means that the Opener shims need to be ground down by 0.01-0.02mm, in order to open the gap a bit.

Bugger, I was hoping to not have to go that far just yet. Still - could be worse. Off to machine mart to get a micrometer, some 400 & 600 grit, and a flat surface.

[Dukedesmo]

Originally Posted by FrankenDesmo

However, I've just done the valve clearance checks...

Vertical Inlet Open: 0.04mm (0.05 required a tiny amount of force)
Vertical Inlet Close: 0.14mm
Vertical Exhaust Open: 0.04mm
Vertical Exhaust Close: 0.09mm
Horizontal Inlet Open: <0.04mm (didn't have a feeler gauge smaller, 0.04 required a tiny amount of force)
Horizontal Inlet Close: <0.09mm
Horizontal Exhaust Open: <0.04mm (same as Inlet)
Horizontal Exhaust Close: <0.09mm

Unfortunately your readings are essentially 'inverted' as in you want the closers tighter and the openers looser, but that's what happens as they wear - the openers close up and the closers open up due to wear and you basically need to move the clearances by adding whatever you remove from one to the other.

I aim for 0.1 - 0.12 openers and for the closers to be as tight as possible without binding but definitely under 0.1, 0.05 is good IMO.

My advice is fit MBP retainers rather than the half-rings as much of the wear/variation comes from the rings, just re-fitting them upside-down can change the readings significantly.

I was checking the clearances on my 916 this week and I only needed to change one opener shim on all 8 valves (I didn't really 'need' to change it either as it was only at 0.14mm!) and that is the first one I've changed in probably 5 years. This is a huge benefit on a 916 as the exhaust clearances are tricky to check due to access, especially the rear cylinder as the rear suspension/subframe is in the way, plus there are twice as many valves/shims as a 2v and changing them is trickier.

I reset the Monster clearances last year as I had the heads off and they were unchanged this time round.

General rule of feel is that you can't 'feel' a clearance of 0.05 or less by hand so you can get get an idea even without gauges.

BTW, I don't know where Haynes get their clearances from? - at least for the 4v...

[FrankenDesmo]

Thanks for the input everyone. I'm going to leave the valves and aim to shim them all back into "assembly" tolerance next winter - I'll aim to get myself a kit from EMS duc (incl the MBP retainers). Or maybe just individual shims since a kit w/ MBP retainers will set me back around £430 once shipping and customs is factored in

The kit is probably the better investment in the long run given I don't intend to get rid of this bike (and may end up with more 2v 900 powered Ducatis in the future).

Anyway I've started the reassembly - carbs are seated with cables & hoses re-attached. Unfortunately the throttle is not snapping back, so I must have messed up the routing and/or adjustment of the cables - but that's tomorrow mornings first job.

I've got the oil cooler off and laying on the front tyre, I'll leave the heater disconnected and attempt to rig the bike up in a running state without the airbox on (though that might not be possible given I need to get the battery box w/ igniters & coils back on - maybe I can sit it on the bike backwards?), so that I have a chance in hell of getting a screwdriver at the sync screw (my regular philips will do it if I can see what I'm doing, the long one that I purchased is too long ). Really hoping that the sync/adjustment part of this process isn't going to be too much of a saga!