I have a 1980 Darmah which would just about tick-over a couple of weeks ago, but which needed new throttle cables. I fitted new cables and also (regretfully) decided to clean the carbs as they were looking a bit grim inside. I gave them 30mins in the electrostatic bath and rebuilt them using new gaskets etc. I have replaced the mixture screws as they were past their best and I swapped the slides as the idle adjustment wasn't working on one at all due to the ramp being worn. I have also replaced the inlet gaskets with VeeTwo upgraded items. I now cannot get the bike to idle. The idle screws are lifting the slides, but even fully in the bike fades and dies. The mixture screws have to be at least three and a half turns out to get it to run at all. (the idle jets are .60s) The only way I can get it to keep running is if I use the top cable adjuster to lift both slides and it will run at about 1500rpm + The bike runs well once it gets going and pulls like a train but no amount of adjustment will get it to idle again. I'm at my wits end!
You have a blockage in the pilot circuit. take the pilot jet out, spray some carb cleaner up the hole from a pressurised can and you should see it come out of the pin hole on the engine side of the slide about an inch forward from where the needle goes into the needle jet
I have done this and all the air/fuel ways seem to be clear. I've also checked the float height using a gauge.
OK next spray some carb cleaner around the inlet rubber insulator with the engine running and see if the revs pick up.
I'll give it a bash tomorrow, thanks. I've kinda lost the will to live with it today! I wasn't sure whether to apply any sealant with the new VeeTwo gaskets or not but opted for not. I'll let you know.
Even with balanced & tuned carbs on my Darmah with 40mm it will take a few miles & getting it up to running temperature before it will idle strong & consistent. You can't just fire him up from cold and expect it to idle. Flooding with the ticklers is a pre-requisite. So when I do balance the carbs I'll always run him on the throttle for a minute or two to get him warm and even then usually have to set the idle stop screws quite high to get it to idle without dying. Once it's doing that you can then faff about with the mixture screws and balance cables/throttle stops to get the desired even idle. Plus I always like to tune the carbs outside rather than in an enclosed, possibly hot & stuffy, garage. And when you do go out of that first ride and are amazed at the smoothness of it all make sure you take a screw driver because it'll then get up to proper running temperature and no doubt the idle will be too high and the throttle stops can each be wound out by the same amount.
Well I sealed the inlet manifolds and re-cleaned the idle circuits of the carbs. Refitted everything and it's no better at all. The bike fires up at the first touch and revs cleanly but it won't idle or anything like it, even when it's had a good run and is up to temp. No amount of adjusting will get it to tick-over properly, even though it was a few weeks ago. I'm going to try .65 idle jets and see if that helps at all. Not convinced though....
Worth reading Ducati Paddie on differences in slides, I don’t know if it’s the same issue with changes in old and new slides on 40mm the same as with 32s. I was fortunate that Ducati Paddie was able to sort me out with a good condition SH 32mm slide.
Sorry but going up on the pilots to mask a problem elsewhere is a waste of time. You have a blockage in the idle circuit as thats the only thing likely to have changed since it last ran. There is a drilling from the inlet side to the mixture screw and from the mixture screw to the pilot circuit which is basically the air feed for the mixture. Check that first.
I'm sorry, I should have added my reasoning: I'm beginning to think that the only reason the bike was ticking over is because it was hanging on the throttle cables. I'm now certain that the idle circuits are clear - i've blasted carb cleaner down them and they're fine as are the air-correction valves and anything else with a hole in it. The closest I can get to an idle is to let the slides hang on the cables, but the mixture screws need to be 3.5 turns out. I'm thinking that there just isn't enough fuel getting through until the needle starts to lift.
65 is std for an 82 Darmah, i can put a pair in the post if you dont have them. Just seems odd that it ran on 60's before. The usual problem with pilots is they are too big because the ethanol fuels run rich so i usually recommend people go down but it depends on a lot of other factors like float height and needles etc. worn slides will give you an erratic tickover but not no tickover
It's a 1980 bike but, as I understand it, it's basically a 900ss engine without a kick-start. Certainly in has 58mm studs and larger valves etc. Not sure about the cams. From what I could see online .65 seemed to be right. I'm not convinced it will sort the issue, but it's worth a try if only to see what happens and it just might. Thanks for the offer but I have some .65s on the way from Doug at Mdina. I actually ordered them when I got the VeeTwo gaskets but he sent .75s by accident. They should be here tomorrow. The carbs are certainly worn and I think the slides have seen better days. To be honest, if this doesn't work I'll probably look to either buy a new set ot have these fully refurbed. Could you help with either option if so?
40's are not worth refurbing as its cheaper to buy new if you need slides. its different with 32's as you cant buy them new anymore. List on PHM40 AS/AD is £662.00 inc vat I could do them for £540.00 + shipping, save you about £120.00 P
Writing from memory here. I recall that the carb slides have the slants adjustment section on both sides so that the same slide can be used in front and rear carbs. If one of the slants is so badly worn from the slide being dropped onto the adjuster screw, that you are unable to adjust properly, just swap the slides from the two carbs and you will be starting with a new slant surface on both.
You’re quite right and I already did that in this case. The slides now rise on adjustment, but it has no real effect on tickover until the screws are fully in. In short, the idle circuit isn’t working as it should at all. Ive now tried bigger jets with no success and am of the opinion that the carbs are simply worn too much to regulate the fuel/air mixture properly. I could fit new slides /needles/emulsion tubes etc. but they would still be old carbs. I was about to take up Paddy on his very reasonable offer when I came across someone with a set of brand new PHMs for sale for £400. Hopefully, this will allow me to get the bike running something like and I can concentrate on getting it to stop safely and find out why it feels like the forks are full of concrete. They certainly keep you out of mischief these Ducati bevels……
If you want to send the old ones to me i will check them over just out of interest FOC, just the return postage.
I've never been entirely sure if there is a correct routing for the fuel lines i.e. over or under the bellmouth/carb and whether that can have an effect on the (idle) supply. Could it be as simple as that I wonder?
