XS650F misfire between 4000 and 5000 RPM. Boyer ignition.

[ebbaga]

Appreciate feedback from anyone who has fitted Boyer ignition and struggling to get their bike to run properly.
My 1979 XS650F is a UK model and has done 130 miles since a complete restoration. Boyer ignition was installed as part of that rebuild.
The bike starts and runs well except for a misfire between 4000 and 5000 RPM.
I have had some useful feedback on the Facebook page but the cause of the problem has not been identified.
The ignition system is new: plugs, leads coils (supplied with the Boyer kit) and the Boyer kit.
Ignition timing is correct as per strobe and advances to fully advanced mark at approx 3500.
The battery is a new fully charged AGM item.
The carbs have been professionally cleaned and rebuilt with stock components including the standard 135 main jets and standard needles.
Air filters are stock.
Exhausts are stock but do not have a balancing pipe.
Spark plug colour is perfect.
Thoughts appreciate!

 

[Raymond]

Hi Ebbaga, welcome to the forum. There's a lot of things that can cause a misfire and I'm sure a lot of people who know stuff will come along with helpful suggestions. But FWIW here's some of my first thoughts.

When I first had the bike, my XS had a terrible running problems which turned out to be caused a tiny perforation in the rubber diaphragm in one carb - you could only see the hole by holding the slide and diaphragm up to the light and stretching it slightly.

Later, the bike was misfiring at higher revs and that was due to a the battery earth being not fully tight. In fact, the battery earth - probably the original and therefore some 45 years old - was dodgy so I bought some heavy-duty cable and fitted ring terminals to make a new one. Whenever a bike has electrical issues, I would suggest at least checking & tightening the battery earth as a first suspect. Have you by any chance had the frame powder coated - that can cause havoc with earths?

I've run Boyer on a Z1, Norton Commando, Triumph TR6, the XS650 and have now fitted to my RE Bullet and not had any problems with it.

 

[ebbaga]

Hi Ebbaga, welcome to the forum. There's a lot of things that can cause a misfire and I'm sure a lot of people who know stuff will come along with helpful suggestions. But FWIW here's some of my first thoughts.

When I first had the bike, my XS had a terrible running problems which turned out to be caused a tiny perforation in the rubber diaphragm in one carb - you could only see the hole by holding the slide and diaphragm up to the light and stretching it slightly.

Later, the bike was misfiring at higher revs and that was due to a the battery earth being not fully tight. In fact, the battery earth - probably the original and therefore some 45 years old - was dodgy so I bought some heavy-duty cable and fitted ring terminals to make a new one. Whenever a bike has electrical issues, I would suggest at least checking & tightening the battery earth as a first suspect. Have you by any chance had the frame powder coated - that can cause havoc with earths?

I've run Boyer on a Z1, Norton Commando, Triumph TR6, the XS650 and have now fitted to my RE Bullet and not had any problems with it.

Thanks Raymond. Did either of the issues you had give a misfire in a limited RPM range and cleared once through that range?

 

[Raymond]

Thanks Raymond. Did either of the issues you had give a misfire in a limited RPM range and cleared once through that range?

No.

The loose/dodgy battery cable, the higher the revs, the worse it got. To be honest, I don't really run the bike past 5000 very much - mechanical sympathy, old geezer on old bike I s'pose?

There will be lots of help - but why not put up some pictures of the bike? We love pictures of bikes around here.