Misbehaving Monza

c13pep

Member
UKGSer Subscriber
Joined
Oct 11, 2019
Messages
25
Reaction score
0
Location
Doncaster
I`m posting this across several forums in the hope that someone may have experienced the same symptoms
My Monza fires up as normal and for the first 5 miles runs extremely well but then just like a switch one cylinder goes AWOL, not even a cough and a fart, however once the revs have risen to 4000rpm then the offending cylinder kicks in again (just like flicking a switch) and the bike behaves as normal. This is my third V50/3 bike so I have some experience but this is doing my head in, to date I have checked/changed the following
points and advance mechanism checked
condenser changed on offending cylinder
carburettor stripped and cleaned three times
coils changed including HT leads etc.
new plugs fitted
tappets checked
fuel taps removed and cleaned
fuel tank vents checked
While it is running on one cylinder there is absolutely nothing from the dead side but it does sound nice for a 250 single :okay
This is driving me bonkers not least because I have to ride the bike for 5 miles or so just to see if my latest solution has worked
This bike is a recent rebuild and has done less than 100 miles since so 4000rpm would be my optimal for running in

HELP :comfort

CHRIS
 
Presumably copper cored plug leads. What about the caps? ..... or was that the etc.

What is the plug colour like on the offending cylinder after she drops into annoying mode - black & sooty, maybe wet suggests ignition related; reasonable/pale colour suggests fuelling.
 
does it drop out below 4k rpm once it is going ? or runs normal ?

fuel level on that side ?

fuel supply ? l+r or joined ?

nearest good man , Jason Sutcliffe , 07977 504 215 Shipley.
 
Yes sorry about the etc. plugs and caps are new and from Green Sparkplug Co., ht leads are copper cored and bonded into coils which are motoplat however swapping to Nippon Denso made no difference.
The bike is fitted with a new fuel crossover system so both sides linked
The bike, when warm, switches between 1 and 2 cylinders when revs are on or around 4000 rpm, ie above 4000 the bike performs extremely well but I am still running in, but below 4000 it`s a 250 single with not a murmur from the dead side. Dropping down a gear helps but because of the `running in` I am loathe to rev it excessively.

CHRIS
 
swop condensers l to r , yes i know they are new. do this with plugs and caps . 1 thing at a time , ride it after each change you make. this double checks everything you do and only costs time. it narrows down what is left.
 
This all sounds temperature related , is something heating up then earthing shorting out the offending cylinder. Can you remove the points cover and observe what happens at 4000 rpm. Is it like an electrical storm in there or is the advance and retard doing something odd eg hitting one of the points. daft questions I know but you have already tried the sensible options.

lastly when the bike has not been running on one cylinder , and under 4000 rpm if you do a plug chop is the plug wet? eg can you definitely rule out fuel.

Steve
 
The quality of condensers are crap, so try swapping,I think gutsibits do an electronic version, I have had the problem on my LM, and it was the new ones, replaced with an old one, but then replaced with electronic ignition.
 
Resting at the minute due to a dose of the shits now that toilet rolls are in short supply so giving it a miss for a few days while I regain control of my arse.
I am at an age where the opening bit of Bonanza comes to mind ie. `ring of fire`:tears

CHRIS
 
Undoubtedly the best next step is to do what baldrick said...after all when was the last time you got free expert advice
 
I had a spada like this many years ago. Turned out to be a problem with one of the advance/ retard weights jamming. Never really did work out how it had the effect it did?? When I was messing with it I spoke to motorworks who at the time we're doing guzzi's. He said "we had one that did that" I asked him what the fault was. His reply, " never did find it so we broke it for spares":D
 
Finally managed to get out on the Monza to try out the `cures` I had done and following a short 10 mile ride all appears to be well. As advised by the `oneandonly` I swapped out the plugs, caps, coils and condensers in logical order only to realise that my two new sets of condensers were the problem (both sets from reputable Guzzi suppliers) and having reverted to a second hand set from a previous project the bike goes like a goodun. The condensers that are in at the moment have manufacturers stampings on them and were only swapped originally as part of a rebuild. I assume the faulty ones are `Chinese` as there are no markings on them at all. For the future I will source some Fiat parts and look to fit two remote condensers under the tank, this will at least stop me having to keep removing the `brittle` alternator cover.
As ever I am grateful for the input but especially `Baldrick` for plugging my brain back into `logic` mode instead of `random`.
I shall refrain from celebrating too much until I can get out on a proper longer ride but not yet as it was bloody freezing out there:D

CHRIS
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
You must log in or register to reply here.

Similar threads

Jem Wilton
Binding Brembos
Replies
7
Views
316
cookie
cookie
nicholsonj2252
First Guzzi
Replies
14
Views
655
DrFarkoff
DrFarkoff
Motormed
Sportster poor running at low RPM
Replies
19
Views
430
The Other PaulG
The Other PaulG
Morety
LHS header's gone blue
Replies
3
Views
409
wessie
wessie
Russgas
No power to fuel pump?
Replies
0
Views
40
Russgas
Russgas


Back
Top Bottom