Popping, poor running

[MarkCR750]

Just when I need the bike for the distinguished gentlemans charity ride it develops a problem!, it started popping a lot on rundown, tickover uneven, No3 downpipe is getting warm not hot, I've just swapped HT leads 2 and 3 over, no difference, new plugs, no difference, raising tickover to 4k No3 pipe does get hotter accompanied by backfires, I'm hoping it's something simple like a blocked primary but not at all sure it is, here's the old plugs, as you can see the No3 porcelain is white, any thoughts greatly appreciated

[hairygit]

I'd remove the tappet caps on the offending cylinder and check the valve clearances and the valves are not sticking or bent, easier than removing the carbs! If all is well there, turn the fuel off, then remove the drain plug from each carb in turn, and see if the offending cylinder has the same quantity of fuel as the others in it. If they are roughly equal, it's carbs off and check for crud in them, as you have eliminated points/condensors/coils as an issue by swapping leads and it making no difference.

[hairygit]

Also, try a new plug in the dodgy cylinder!

[MrDavo]

Something else you could check - one of my plug caps was going AWOL occasionally, giving me a misfire that came and went, with occasional spells of running on 3 pots. I found it by checking the resistance on each cap with a multimeter, after unscrewing them from their lead.

[K2-K6]

They were talking about the distinguished gentleman's ride on the wireless yesterday old chap I just caught a bit of it and thought it was for bicycles,  sounds more interesting to see if it's real proper bikes.

The plug from no 3 just seems to be saying lean compared to the others. As hairy says have a check of the valve clearance just to make sure your not missing anything.

Swop 2 and 3 plug leads to see if it changes the running on those two to cross check the caps and leads.

Without being in front of it,  looks like primary circuit on number 3 could be restricted. Maybe worth trying to see with a pipe into the vac check hole on that cylinder and dangling into a small pot of petrol to see if it'll tickover by drawing from an auxiliary supply and show if the problem is caused by that area.

[MarkCR750]

Good news, after spraying half a 500ml tin of carb cleaner up the primary balance tube, and using a syringe to suck the carb cleaner back and forth it is now running on all 4, with all 4 down pipes heating up at the same rate, bad news took it for a 2 mile ride and it's started baulking intermittently at about 5k , so it's carbs off and a thorough clean time, at least it's nothing more serious than crud in the fuel system, time to fit inline filters!, thanks for your suggestions all, I haven't got the inclination to do it today so I'll take the Duke out tomorrow on the charity run, (reliable bikes those Ducati's 😄)

[royhall]

Glad your Ducati is reliable, mine was a bag of spanners and it only had 1800 miles on it. I was glad to be rid of it.

[MarkCR750]

Yes Roy it seems OK so far!, I think I've done about 1800 miles (haven't checked mileage recently) with no issues other than the clutch slave cylinder needing a new seal and the front fairing subframe cracking, but it's a 25 year old bike so you have to expect a few repairs required, but as for starting/running it's spot on, which ducati did you have?.

[royhall]

It was a 750SS from 2000. Only had 1200 miles on it when it came to me sold it with 1813 the thing was horrible. Went a whole 35 miles on it in one go and damn near needed a crane to get me off the thing. In traffic all it wanted to do was pop back though the air box. Chopped it in for a brand new CB1300, what a good swap that was. Still own the 1300 nine years later. Ducati was a good buy though as Honda part exed it for way more than I paid for it.

[Greebo]

Good news, after spraying half a 500ml tin of carb cleaner up the primary balance tube, and using a syringe to suck the carb cleaner back and forth it is now running on all 4, with all 4 down pipes heating up at the same rate, bad news took it for a 2 mile ride and it's started baulking intermittently at about 5k , so it's carbs off and a thorough clean time, at least it's nothing more serious than crud in the fuel system, time to fit inline filters!, thanks for your suggestions all, I haven't got the inclination to do it today so I'll take the Duke out tomorrow on the charity run, (reliable bikes those Ducati's 😄)

Hi Mark

I think I mentioned using carb cleaner in my private post to you  ...
I have had the same issue with the PD carbs on mine & the carb cleaner did it for me...A inline filter a very good idea, I looked at putting one on mine but cant find the room or position, unless I lengthen the fuel pipe..

Regarding the Dukes, I think the newer models are now much improved...hopefully..

Good Luck
Greebo

[MarkCR750]

It was a 750SS from 2000. Only had 1200 miles on it when it came to me sold it with 1813 the thing was horrible. Went a whole 35 miles on it in one go and damn near needed a crane to get me off the thing. In traffic all it wanted to do was pop back though the air box. Chopped it in for a brand new CB1300, what a good swap that was. Still own the 1300 nine years later. Ducati was a good buy though as Honda part exed it for way more than I paid for it.

I found mine uncomfortable at first , usual place for me, wrists, but I dropped the rear 20mm and rotated the bars out a little and it's made a big difference , I still wouldn't want to do more than 50 or 60 miles without a coffee break though but that's the norm really with dropped bars, since selling my XJR1300 a few weeks ago I've been stuck with them on the honda and duke, gotta say I'm looking fwd to the arrival of the scrambler on Thursday so I get the high bar option back!.

[MarkCR750]

Good news, after spraying half a 500ml tin of carb cleaner up the primary balance tube, and using a syringe to suck the carb cleaner back and forth it is now running on all 4, with all 4 down pipes heating up at the same rate, bad news took it for a 2 mile ride and it's started baulking intermittently at about 5k , so it's carbs off and a thorough clean time, at least it's nothing more serious than crud in the fuel system, time to fit inline filters!, thanks for your suggestions all, I haven't got the inclination to do it today so I'll take the Duke out tomorrow on the charity run, (reliable bikes those Ducati's 😄)

Hi Mark

I think I mentioned using carb cleaner in my private post to you  ...
I have had the same issue with the PD carbs on mine & the carb cleaner did it for me...A inline filter a very good idea, I looked at putting one on mine but cant find the room or position, unless I lengthen the fuel pipe..

Regarding the Dukes, I think the newer models are now much improved...hopefully..

Good Luck
Greebo

Yes I should have fitted filters from the start but it was always one of those "I'll get that done soon" jobs!, regarding new dukes being better than old ones, I'm sure they are, but a new honda 750 is better than an old one!, I really can't fault my 25 year old SS, it hasn't missed a beat engine wise, starts first push of the button hot or cold, I think a lot of the negative attitude you get towards them isn't really warranted, the owner of racing lines (top mechanic, racer etc) said that his wife had one for 6 years never missed a beat, he had one for a couple of years with no issues, his comment was "it's not the bike it's the owner!"😄, anyway I certainly hope that the scrambler is better than the SS, if not it's going back! 😄