Sputter at 2500 rpm

Hobot · Jun 12, 2014

Ashley has the most charmed life in all regards of any one I've ever known about, so good there would be only great ride stories and what type tire to try next on almost silent forum. He did mention his backing up the boyah leads though. As for the rest of the world its not question of if boyah trigger leads will fray inside for mysterious intermittent mis fires till eventually easy to find on side of the road and glad you carry test light and electrical tape and these always on your mind where to look first.

Nater_Potater · Jun 13, 2014

ashman said:
33 years with my 850 motor in a Featherbed frame and a Boyar ignition and I have never had any problems with fractured pick up wires and poeple say Featherbed frame Nortons vibrate more than Commandos...

Ashley

Keep in mind that, for the most part, all of these engines will generate about the same amount of vibrational force. The Featherbed frame, being solidly mounted, will dampen a lot of engine vibrations into the frame, whereas the Commando lets the engine flail about much more which beats up anything that's bolted directly to it (ignition, wiring, carbs). Aircraft engines saw a noticable rise in carb and magneto failures and shortened life once the style of engine mounts was reconfigured. Granted, the pilot, instruments, and airframe all suffered much less, but it's the same effect.

jseng1 · Jun 15, 2014

I see this vibration problem with carb boots. Its much worse with the isolastics. The motor shakes so hard in the isolastics that the rubber boots fail in a couple years and so I had to offer expensive thick walled rubber boots with flatslide carb kits. For comparison my featherbed has the same boots 5 years now without cracks. The isolastics allow the motor to flail about and wear out the carbs and break the wires. In extreme cases with worn out isolastics the fuel can foam in the float bowls and cause loss of power or missing.

kerinorton · Jun 15, 2014

One of the things that caused my 850 to backfire when coasting at a little above idle was a minor leaks at the exhaust header. I t was hard to believe it was leaking and causing the problem, but a600 mile trip showed tell tale signs at one header that it was leaking. As soon as I resealed it, the backfiring stopped. Not sure if this is a possibility with your bike but something to think about.

Stillreel · Jun 23, 2014

Gotta hand it to you guys. I was told time and time again, if it sounds like a carb issue, its probably electrical. Despite being convinced it was the old Amal carbs, well, guess what ... you were right. I traced the problem right back tot he Boyer box. The zip tie I used to secure little black box beside the coils had migrated over to the B/Y wires and was pressing hard against them. Removed zip tie: no more problem.
Also installed new master cylinder from Madass this am. Again, night and day difference.

I can't really say enough about the helpful advise offered on the this forum.

Thanks again.

Bryn

JimC · Jun 23, 2014

Stillreel said:
Gotta hand it to you guys. I was told time and time again, if it sounds like a carb issue, its probably electrical. Despite being convinced it was the old Amal carbs, well, guess what ... you were right. I traced the problem right back tot he Boyer box. The zip tie I used to secure little black box beside the coils had migrated over to the B/Y wires and was pressing hard against them. Removed zip tie: no more problem.
Also installed new master cylinder from Madass this am. Again, night and day difference.

I can't really say enough about the helpful advise offered on the this forum.

Thanks again.

Bryn

The old saw, "95% of carburetor problems are electrical", is very true. Once this happens it will make a believer out of you.More than likely the spot where the zip tie migrated to has a worn spot in the insulation. If the wires on the Boyer pickup plate have not been changed from a solder connection to a post and ring terminal connection you still have a very likely problem lurking with exactly the same misfire.

Sputter at 2500 rpm

Hobot

Nater_Potater

jseng1

kerinorton

Stillreel

JimC

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