Thoughts on this carb wear appreciated
- Thread starter Ventodue
- Start date
Ta Paul. I fitted new slides (
. Rare things, these days ...) and yes, there is still some sideways movement. Which is what then led me to look at more closely the bores, of course ...So how much slop is permissible? (Or is that, 'How long is a piece of string?').
It doesn't pop. But it does like to be choked to start, even when warm (Which is why I checked and re-checked the float heights ...)
Does sleeving work, in your experience?
I have to say that this bike has never been great at maintaining an idle. Even Tony Brancato struggled. After he would set it, it would hold idle for maybe a couple of weeks and then lose it again. This time, I took it to Peter Clark, ex-Motodd Laverda, now chef d'atelier at Ducrappi here in Montpellier. A few years back, Peter had managed to get it to idle and then hold it for a reasonable period. But this time, same story. It's most frustrating ...
You're not wrong, of course. Towards the top of the list is valve closing/clearances, not least the closing rockers. I don't have the competence to check or set these - and which ideally should be done with the head off. Which means dropping the engine ....
You can see where I'm coming from with this, can't you?
You want to flog your Zane to finance a new pair of carbs and some pro head work? You won't get enough cash.You're not wrong, of course. Towards the top of the list is valve closing/clearances, not least the closing rockers. I don't have the competence to check or set these - and which ideally should be done with the head off. Which means dropping the engine ....
You can see where I'm coming from with this, can't you?
Paul
Can't help much with this, apart from try and find a known good set of carbs to try and see if things get better. I have no personnal experience with sleeving but as you know, it's current practice with Amals. I wouldn't know where to go for that. Piet mentioned someone in Germany some years back.Ta Paul. I fitted new slides (
So how much slop is permissible? (Or is that, 'How long is a piece of string?').
It doesn't pop. But it does like to be choked to start, even when warm (Which is why I checked and re-checked the float heights ...)
Does sleeving work, in your experience?
I have to say that this bike has never been great at maintaining an idle. Even Tony Brancato struggled. After he would set it, it would hold idle for maybe a couple of weeks and then lose it again. This time, I took it to Peter Clark, ex-Motodd Laverda, now chef d'atelier at Ducrappi here in Montpellier. A few years back, Peter had managed to get it to idle and then hold it for a reasonable period. But this time, same story. It's most frustrating ...
Yes, Peter Clarke, ex Motodd and also ex Simpson Mécanique. I should think he knows his Ducati.
Stick some Keihin or Mikuni on it.
Paul
Craig,
What have you got fitted, the stock 32 or the 40mm that are mostly retro-fitted? Dramahs came with 32mm and air filters here.
A new jet needle and needle jet often work wonders. In my experience, the Dellorto PHB/F/M tolerate quite a lot of slop at the slides, very much like the Amals of yore. How about those crappy rubber inlet stub gaskets? Most I have come across were rather shabby and wobbly, no chance in hell to attain a decent idle with those. Otherwise, check mixture screw tips for corrosion and the associated idle galleries and passages.
Of course, correct valve clearances are necessary, without, there's no point in even starting to set up the carbs. Setting the clearances is not witchcraft, the most difficult bit is having the correct sized shims to hand...
piet
What have you got fitted, the stock 32 or the 40mm that are mostly retro-fitted? Dramahs came with 32mm and air filters here.
A new jet needle and needle jet often work wonders. In my experience, the Dellorto PHB/F/M tolerate quite a lot of slop at the slides, very much like the Amals of yore. How about those crappy rubber inlet stub gaskets? Most I have come across were rather shabby and wobbly, no chance in hell to attain a decent idle with those. Otherwise, check mixture screw tips for corrosion and the associated idle galleries and passages.
Of course, correct valve clearances are necessary, without, there's no point in even starting to set up the carbs. Setting the clearances is not witchcraft, the most difficult bit is having the correct sized shims to hand...
piet
What ignition? What is the idle rpm? What is the characteristics of the "idle" does it high idle then drop, then stall, need to describe the actual idle moment to moment. Manometer is a great tool for judging the air pressure movement, rising ball type are ok, i use a proper inverted U tube mercury 4 station manometer, used moving gauge and rising ball, the mercury item is most revealing....HTH j ** worked on MHR and SSD motors, idle was surprisingly easy to set and maintain, though high hundreds to 1Krpm helped to keep the motor burbling..lumping along not good, its a 270 degree firing interval. Good hunting Craig...
Last edited:
. I hold my Zanè at zero book value ...
mauricejota7604
Hero member
- Location
- Victoria Australia
I assume its got Desmo heads?
Hi Piet,
Thanks for the thoughts. In reply:
32 PHF A type, i.e. not the later 'low emission' C type. Has always run with standard air filters these last 20+ years.
Needle valves are a couple years old, but I'll change 'em anyways. Ditto the manifold gaskets - as you say, they're not so 'confidence inspiring' even when new. Mixture screws are new, passages are clear.
As to the valves, apart from not having a stock of shims, the PITA is access to the back pot with the engine still in the frame. Which means more work, but I suspect I may have no choice ...
Apart from this idle issue, the bike is running remarkably well on the open road!
Dellortoman
Hero member
- Location
- Tasmania, Australia
You can still see the original machining marks in the carby slide bores, so they're probably not knackered.
I could never get my MHR Mille to idle. It was also a bugger to start sometimes, requiring a lot of cranking and tweaking the starter jet lever or accelerator pumps. It was always a hit and miss affair getting it started.
I went through the carbs many times, cleaning, adjusting, re-jetting, etc. It never got any better. Then one day I was out on a ride and one cylinder cut out. Fortunately, I was only a few km from home, so limped home on the remaining cylinder.
It turned out that one of the Bosch BTZ ignition boxes died, so I replaced the ignition system with an Ignitech. The first time I started the bike with the Ignitech was a revelation. It started instantly and settled to a nice idle. It's like a different bike now, starts easily and idles perfectly. All my carby fettling was a waste of time. What it needed was a decent spark.
I could never get my MHR Mille to idle. It was also a bugger to start sometimes, requiring a lot of cranking and tweaking the starter jet lever or accelerator pumps. It was always a hit and miss affair getting it started.
I went through the carbs many times, cleaning, adjusting, re-jetting, etc. It never got any better. Then one day I was out on a ride and one cylinder cut out. Fortunately, I was only a few km from home, so limped home on the remaining cylinder.
It turned out that one of the Bosch BTZ ignition boxes died, so I replaced the ignition system with an Ignitech. The first time I started the bike with the Ignitech was a revelation. It started instantly and settled to a nice idle. It's like a different bike now, starts easily and idles perfectly. All my carby fettling was a waste of time. What it needed was a decent spark.
Hello John,
Good to hear from you and thanks for your thoughts
Still running the standard Bosch ignition. However the insulation on the pickup wires has been replaced. (And I cleaned the inevitable iron sludge off them less than a thousand miles ago. So fingers crossed they're behaving themselves).
I try to set a fairly rapid tick over, around 1200. Experience has taught me that going lower is ok in the workshop, but can lead to unwelcome stalling at the lights!
I've got the idle screws set 1 turn out which would normally push the idle above this. Turn them in further, up go the revs, then falter and die. So I haven't been able to get the gauges on the blessed thing!
Both plugs however are clean with the nose a lovely shade of light grey. Twidling with the mixture screws produces the expected result - in and the engine stalls, out and the plugs soot up.
And the roll on is really nice and smooth ...
Thanks Cam.
Both your observations seem most pertinent ...
. Seeing those machining marks in the bore is what made me wonder, 'So is this thing knackered or not?'I fear the age old question is looming: "Change the carbs or change the ignition?"
Answer: "Try one and if that don't work, try the other. Just be prepared to have deep pockets ..."
Grrrrr ...
I haven't entirely dismissed that idea. From Planète Ducati, I know of a MHR owner ici en France qui a monté des Mikunis ...<snip>
Stick some Keihin or Mikuni on it.
Good man, the reporting is smooth, if not the idle. The BTZ, and the infamous anti start resistors ( if retained or fitted ) give rise to weak cold crank and idle spark, feeble really. As you richen up the mixture the engine and spark work better, the leaner you go the spark starts to have big problems. The BTZ at nominal battery volts/charging current, hovers around 15Kv (15,000V ) whereas a best spark will be in the 30-35Kv range.
Given the battery volts will sag at idle you may have two different parameters looking like one problem. Given the bikes history, and knowing what the duck twins respond like to better ignition ( did an iis for ducks ) then stand back from the bike and throw money at it, the bike will benefit from a decent ignition as Cam has indicated, in any course of remedy.
Then you can direct your attention to the carbs, knowing the spark is ok, provided battery volts are 12V or better at idle.... more free advice that will cost you money old bean... no need to thank me, what blokes are here for, free and easy with your money....grin....j
Probably wholly irrelevant but I will throw it in. My Pantah would idle well, slightly richer on screws than correct helps a lot but I spent a good year trying to find out why it had no guts just off idle. It needed clutch slip like a 2-stoke GP bike to pull away. So I kept at it doing the same thing over and over, that was setting the carb balance on vacum gauges, steel rod type as my mercury ones developed bubbles. After about a year with no improvement, I took to a bike shop who discovered that the slides set by me with those vacuum gauges were in reality 5mm out of sink, 2 minutes doing it with fingers in the carbs and that fixed it. To this day I still don't get it, but take care using these gauges when a finger will do. They work great on my 3c but not on that twin. BTW I disconnect one plug but add an earthed plug to that lead and adjust the mix screw to the strongest idle plus an 1/8 of a turn richer and repeat on the other carb.
Dellortoman
Hero member
- Location
- Tasmania, Australia
I just looked back through my Ducati records. I installed the Ignitech on my MHR in 2007. Blimey, that's 15 years ago, which was only a few years after Ignitech set up business. It was the very first Ignitech ignition I'd ever installed on any bike. I'd never heard of them before I found their website. I liked the specs of their system and the very competitive price, so I took a punt and ordered one. It's a very early version (version 54). The software doesn't even show a graphical representation of the advance curve. It just has a table of the advance degrees at different revs.
I used the existing VR pickups, so the only cost outlay was for the ignition box itself. I think it only cost around $100 at the time, which was less than the cost of a single Bosch BTZ box at the time. Back then I had to do all the wiring myself, but now you can buy them as a plug-and-play setup from Ducati suppliers like Belt and Bevel. They come with a wiring harness made up with the correct plugs. All you need to do is un-plug the Bosch boxes and plug in the Ignitech.
If Ignitech doesn't float your boat (some people find the programming confusing and tedious) there are other manufacturers. I think Sachse Elektronik does a system for bevel Ducatis that comes with Hall effect pickups, which might be a good choice if your original pickups are dodgy.
I'd recommend you spend a few bucks (around $300-$500 I'd guess) for a modern ignition system with sensible advance curve options. It'll transform your bike. Those old Bosch BTZ boxes were a crappy product back in the day when Ducati was installing them. They're rubbish compared to modern ignitions. I bought a new lawnmower the other day and it has a better ignition system than the Bosch BTZ.
I used the existing VR pickups, so the only cost outlay was for the ignition box itself. I think it only cost around $100 at the time, which was less than the cost of a single Bosch BTZ box at the time. Back then I had to do all the wiring myself, but now you can buy them as a plug-and-play setup from Ducati suppliers like Belt and Bevel. They come with a wiring harness made up with the correct plugs. All you need to do is un-plug the Bosch boxes and plug in the Ignitech.
If Ignitech doesn't float your boat (some people find the programming confusing and tedious) there are other manufacturers. I think Sachse Elektronik does a system for bevel Ducatis that comes with Hall effect pickups, which might be a good choice if your original pickups are dodgy.
I'd recommend you spend a few bucks (around $300-$500 I'd guess) for a modern ignition system with sensible advance curve options. It'll transform your bike. Those old Bosch BTZ boxes were a crappy product back in the day when Ducati was installing them. They're rubbish compared to modern ignitions. I bought a new lawnmower the other day and it has a better ignition system than the Bosch BTZ.
Dellortoman
Hero member
- Location
- Tasmania, Australia
Same here Vince. I balance the Ducati and Moto Guzzi carbs by hand (not vacuum gauges). I either do it by the finger method (looking at one slide while feeling the other with a finger), or by listening for a simultaneous click as they close. For some reason, vacuum gauges seem to be unreliable with twin Dellortos.