Can anyone help - cylinder cutting out when hot

Maestro, SEI-V
Post Reply
RodB
Posts: 6
Joined: 24 Feb 2022 19:00
Location: Kinross UK

Can anyone help - cylinder cutting out when hot

Post by RodB »

I have a 500 - I've changed to digital ignition, cleaned and balanced the carbs - but no matter what 2 highly respected mechanics do ,the bike rides perfectly for 15-20 miles then one cylinder starts to cut out then cut in - the plug on the cylinder that is the problem is black but when changed the fault just recurs.
Can anyone help - what are we missing?
MickeyMoto
Posts: 2240
Joined: 22 Nov 2008 17:41
Location: Even further oop North

Re: Can anyone help - cylinder cutting out when hot

Post by MickeyMoto »

Is it the same cylinder? If so, do you have a faulty coil?

You could try swapping the coils around and see if the fault moves.

Which ignition system do you have?

Mike

PS - Kinross is a nice part of the world. :)
RodB
Posts: 6
Joined: 24 Feb 2022 19:00
Location: Kinross UK

Re: Can anyone help - cylinder cutting out when hot

Post by RodB »

Hi Mike
Thanks for the reply - I fitted a brand new digital system to cure the problem all it did was extend fault to occur from approx 1.5 to 15 miles running...
Yes it is the same cylinder - the rear one. For the first 10+ miles it runs like a dream then the cylinder starts cutting in and out getting progressively worse. 2 really good mechanics have looked at it and cannot understand what is going on
mbmm350s
Posts: 573
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Can anyone help - cylinder cutting out when hot

Post by mbmm350s »

Hi,

Can you tell us which ignition system you have installed please.

Does it recover if you let it cool down?

Thanks
Mark
RodB
Posts: 6
Joined: 24 Feb 2022 19:00
Location: Kinross UK

Re: Can anyone help - cylinder cutting out when hot

Post by RodB »

Hi I'll get the name of the system it's the one recommended by the guys who advertise in the magazine and yes leave it to cool down and everything seems fine....
Really appreciate the help
Steve Brown
Posts: 1285
Joined: 12 Nov 2007 23:44
Location: Leicestershire

Re: Can anyone help - cylinder cutting out when hot

Post by Steve Brown »

Plug black wet or black sooty?
If the whole ignition has been changed and your resident rocket scientists are flummoxed another regular culprit is choke plunger seal degradation. Or knackered rubber seals on the choke plungers. Does the fault swap cylinders if you swap carbs? Or swap coils?
I'm guessing you mean the Sachse ignition system? A stronger spark would likely cope with over-fuelling for longer than a traditional 40 year old system.
Also the float height if a long way out could make it over rich. On another bike that fooled me for a while, the main jet was loose in its thread so excess fuel was leaking past that.
Another clue-when left to cool down a wetted plug can dry out!
All donations to the rest home for old Camels, Leicestershire.
RodB
Posts: 6
Joined: 24 Feb 2022 19:00
Location: Kinross UK

Re: Can anyone help - cylinder cutting out when hot

Post by RodB »

I'm checking but I do believe when the carbs were swapped the system seemed to correct itself however the ignition was changed at the same time. The plug is I believe black and sooty not wet (but I need to check I am correct on this. I think it is a carb problem but they've been cleaned any worn parts replaced etc and the problem persists.
Steve Brown
Posts: 1285
Joined: 12 Nov 2007 23:44
Location: Leicestershire

Re: Can anyone help - cylinder cutting out when hot

Post by Steve Brown »

and the choke plunger seals? If they leak your bike will never be right.
All donations to the rest home for old Camels, Leicestershire.
3potjohn
Posts: 1109
Joined: 02 Jun 2007 13:58
Location: Devon

Re: Can anyone help - cylinder cutting out when hot

Post by 3potjohn »

You can quickly swap the choke mechanisms and see what happens, and have a look at the end seals whilst at it. Will it start without choke?
John
RodB
Posts: 6
Joined: 24 Feb 2022 19:00
Location: Kinross UK

Re: Can anyone help - cylinder cutting out when hot

Post by RodB »

It won't start without the choke - once again thank you for the help
Rod
User avatar
Daddy Dom
Posts: 486
Joined: 16 Nov 2006 19:48
Location: Auckland, New Zealand

Re: Can anyone help - cylinder cutting out when hot

Post by Daddy Dom »

Bummer!
I was also going to suggest swapping carbs - in fact, I believe you can swap the entire top ends piece by piece if you want as they're the same.
(Correct me if I'm wrong, someone.)

Have you checked the inlet manifolds aren't split?
DD
MRC 3082½
dunk 1
Posts: 204
Joined: 25 Oct 2007 18:16
Location: cumbria

Re: Can anyone help - cylinder cutting out when hot

Post by dunk 1 »

When I first got my 3.5 it would cut out on the front after exactly 7 miles then recover when cooled and do exactly the same thing again. It was uncanny how precise the distance was for it to recur. It turned out to be the stator coil breaking down when hot, or at least getting it rewound solved the problem.
thanks - Duncan
dunk
norbert
Posts: 672
Joined: 15 May 2007 15:15
Location: Lübeck/Germany

Re: Can anyone help - cylinder cutting out when hot

Post by norbert »

To me as well that sounds like some lectronic part cannot deal with heat.
RodB
Posts: 6
Joined: 24 Feb 2022 19:00
Location: Kinross UK

Re: Can anyone help - cylinder cutting out when hot

Post by RodB »

One of the mechanics did swap the carbs this changed the cylinder that was cutting out - rebuilt that carb and the problem seemed to go away - actually the distance before the problem increased the road test wasn;t long enough...
Really appreciate everyone's help. it's going in to a really good mechanic on Monday - its a beautiful bike just hope I can find the problem and fix it - will try everything suggested until we find an answer
Post Reply