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'66 A65 Running on One Cylinder-Help! #462872
11/12/12 2:53 am
11/12/12 2:53 am
Joined: Jan 2003
Posts: 523
San Diego, CA
Will S. Offline OP
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Hope you guys can help me fix my Beezer!
'66 BSA A65, single carb 928 Concentric, Boyer. Bike ran fine, then sat for 6+ months (battery on trickle charger). Tried starting it after sitting and it only runs on the right cylinder with the left side occasionally sputtering in. Tried the following: Swapped plugs, swapped plug leads, new plugs, and fresh gas. No change, bike still only runs on right side. Did compression test, got 150 on left side, 160 on right side.
Before I start tearing into the top end, any thoughts on what could cause this or what I should look for?
Thanks!


Will S.
BSAs: '66 & '69 Lightning
Triumphs: '68 TR6R, '68 Bonneville, '73 TR7, '55 6T
'71 Norton Commando

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Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #462874
11/12/12 2:58 am
11/12/12 2:58 am
Joined: Jul 2001
Posts: 12,962
Central Virginia
Lannis Offline

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Central Virginia
Well single carb so it can't be ethanol-varnish clogging up your jets.

Compression test was the right thing to do first. Ignition next - you've eliminated plug leads, plugs, and gas.

I know it's a bit of trouble, but can you swap coils? Do you still have two coils (6 or 12 v?) or are you using a dual DynaCoil? The stock connectors that connect the Boyer trigger plate to the coil wires are notorious for breaking INSIDE the insulation where you can't see it, and where the broken ends will make momentary contact and it will sputter and fire a little bit.

Just sitting for 6 months wouldn't have made them break, however. Maybe someone else here can get us on the right track .....

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #462876
11/12/12 3:14 am
11/12/12 3:14 am
Joined: Jan 2008
Posts: 1,114
Noblesville, IN
Jack Adams Offline
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Noblesville, IN
Check for any nests plugging up the exhaust on one side.

Re: '66 A65 Running on One Cylinder-Help! [Re: Lannis] #462877
11/12/12 3:23 am
11/12/12 3:23 am
Joined: Feb 2003
Posts: 2,951
Ohio
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Rickman Offline
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Ohio
Have you checked all the wire connections, and continuity?

Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #462891
11/12/12 5:22 am
11/12/12 5:22 am
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Vic. Australia
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If you've got a coil problem,it would be on the high-tension side or in the lead.Have you tried connecting the coil leads to the opposite plugs?

If that changes nothing,look for a sticky valve.They're more likely to stick when they heat up.At cranking speed when the engine is cold,the compression could still be good.

It might only take some WD-40 to clean the crud off the valve-stem.

Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #462896
11/12/12 7:08 am
11/12/12 7:08 am
Joined: Feb 2012
Posts: 77
TX
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TX
I would think my next step would be to make sure your getting fire to the spark plug as that would seem the next simplest step. If no fire then atleast you know its an ignition issue.
But thats just me.


1967 BSA A65 Lightning powered by a 71 A65 Firebird

AKA phsyco4u

Technology is not the cure for stupidity!
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #462903
11/12/12 10:46 am
11/12/12 10:46 am
Joined: Mar 2011
Posts: 836
derby england
wak Offline
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derby england
Push rod jumped out of its seat?


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Re: '66 A65 Running on One Cylinder-Help! [Re: ] #462925
11/12/12 2:30 pm
11/12/12 2:30 pm
Joined: Mar 2007
Posts: 51
Dimmitt, Texas
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David_S Offline
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Dimmitt, Texas
In my opinion, which may not be worth much since I dont know a lot about these engines, I think it is ignition related. I dont think it would be a carb issue since it is a single carb and will run on the one cylinder. With your compression numbers like they are, I dont think it would be a valve or push rod issue. If it was mine, I would check or swap the points, coil, plug and check the wiring for the dead cylinder before I ripped the top end down.

Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #462956
11/12/12 5:41 pm
11/12/12 5:41 pm
Joined: Oct 2012
Posts: 296
lancashire united kingdom
run990 Offline
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lancashire united kingdom
just had a similar problem with my single carb a65 ,it was a sticky inlet valve,got compression at kickstart speed but would not run just occasionally chimed in for a second every so often,you can check it easily ,start bike with rocker cover off & you can see the pushrod trying to escape.mine was only very slightly tight in the guide but it overpowered the valve spring.if you dont want to remove the head try some penetrating oil on the guides up the port it may work if its only a bit of carbon or rust on the valve stem.if the bike was fine before being laid up it can only be something simple.

Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #462979
11/12/12 8:34 pm
11/12/12 8:34 pm
Joined: Mar 2011
Posts: 215
netherlands
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lemans Offline
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netherlands
as the bike has been standing for quite some time maybe the contactbreaker of the offending cylinder has corroded a bit. this will prevent a proper spark.
clean the contactbreaker with a little piece of emery-paper .

with the points closed, putt the paper between the point and then pull to remove. twice will clean both sides of the contactbreaker. repeat with the other set.

succes.

Re: '66 A65 Running on One Cylinder-Help! [Re: wak] #462988
11/12/12 9:11 pm
11/12/12 9:11 pm
Joined: Jul 2001
Posts: 12,962
Central Virginia
Lannis Offline

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Central Virginia
Originally Posted By: wak
Push rod jumped out of its seat?


It wouldn't occasionally "sputter in" on that side if the valve never opened ....

I'm liking either the mouse nest in the exhaust, or bad points/coil on one side.

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
Re: '66 A65 Running on One Cylinder-Help! [Re: Lannis] #462998
11/12/12 9:54 pm
11/12/12 9:54 pm
Joined: Jan 2003
Posts: 523
San Diego, CA
Will S. Offline OP
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Thanks for all the input! I have a Boyer ignition and 2 6 volt coils. I've swapped the coils, plug wires, plugs, no change.
I'm thinking the Boyer ignition plate in the points cavity is my next place to look. If I'm thinking about this correctly, a short in the pick up would stay with the left side despite switching coils, wires, etc. I have a spare so I'll try swapping it out.
If that doesn't do it the next thing will be to take off the valve cover...Oh and check in the exhaust pipe for a nest!


Will S.
BSAs: '66 & '69 Lightning
Triumphs: '68 TR6R, '68 Bonneville, '73 TR7, '55 6T
'71 Norton Commando

www.britironsd.com
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #463046
11/13/12 2:00 am
11/13/12 2:00 am
Joined: Aug 2001
Posts: 4,550
Owego, NY, USA
Mark Z Offline
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Owego, NY, USA
Ok, Boyer ignition, one carb. No breaker points. Pickup coils are wired in series and both come into play with every cycle. Both coils are powered simultaneously on every cycle. The only difference from one side to the other is the coil, the HT lead, and the spark plug, and you've swapped all those, right? If so, I think it's time to rule out ignition and look for an engine problem. Start by checking your valve clearances.

Compression testing sometimes doesn't tell the whole story. A leak-down test would be better, if you can do that.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #463205
11/14/12 3:20 am
11/14/12 3:20 am
Joined: Jul 2001
Posts: 12,962
Central Virginia
Lannis Offline

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Central Virginia
Can't wait to hear how this one comes out. Sounds like something that's happened to me before ... !

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #463931
11/19/12 1:18 am
11/19/12 1:18 am
Joined: Jan 2003
Posts: 523
San Diego, CA
Will S. Offline OP
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Finally had some time to work on the BSA today, changed out the Boyer for a new one and.... no change, still not running on the left side. Measured the valve clearances and they looked ok, kicked it through a few times and watched the valve train do it's thing, nothing looked wrong.
I kicked it through a few times with the plugs out and grounded, saw spark on both plugs.
I also ran a broomstick up the muffler all the way to the bend and didn't find any nests.
So in summary it's not running on the left side and I have swapped coils, wires, new plugs, fresh gas, replaced Boyer, checked compression and checked valve clearances. Single carb. I'm stumped!


Will S.
BSAs: '66 & '69 Lightning
Triumphs: '68 TR6R, '68 Bonneville, '73 TR7, '55 6T
'71 Norton Commando

www.britironsd.com
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #463936
11/19/12 1:43 am
11/19/12 1:43 am
Joined: Feb 2012
Posts: 151
tasmania australia
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razor Offline
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tasmania australia
Are the gaskets between the manifold and the head intact .

Last edited by razor; 11/19/12 1:44 am.
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #463937
11/19/12 1:44 am
11/19/12 1:44 am
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Vic. Australia
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Pete R - R.I.P. Offline
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I'm still suspecting a sticking valve.You might see something if you run it without the rocker cover.
If that gets you nowhere,try running it without exhaust pipes.The exhaust valve is the one most likely to stick.

Re: '66 A65 Running on One Cylinder-Help! [Re: Lannis] #464089
11/19/12 10:30 pm
11/19/12 10:30 pm
Joined: Feb 2012
Posts: 77
TX
RustySled Offline
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TX
Im with Lannis on this one. Once the problem is found I will be making note of as this is deff something that would happen to me!!


1967 BSA A65 Lightning powered by a 71 A65 Firebird

AKA phsyco4u

Technology is not the cure for stupidity!
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #464126
11/20/12 4:10 am
11/20/12 4:10 am
Joined: Aug 2001
Posts: 4,106
argyll. scotland, uk
gavin eisler Offline
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argyll. scotland, uk
Plug leads are not in your list of swapped items,


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: '66 A65 Running on One Cylinder-Help! [Re: gavin eisler] #464178
11/20/12 12:54 pm
11/20/12 12:54 pm
Joined: Jul 2001
Posts: 12,962
Central Virginia
Lannis Offline

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Originally Posted By: gavin eisler
Plug leads are not in your list of swapped items,


They were, though. First post.

"Tried the following: Swapped plugs, swapped plug leads, new plugs, and fresh gas....."

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #464190
11/20/12 3:17 pm
11/20/12 3:17 pm
Joined: Aug 2001
Posts: 4,106
argyll. scotland, uk
gavin eisler Offline
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Sorry, memory failure.
I feel for you,
It could be a touch of induction bias, with the air filter off and the motor running try blanking the carb intake with your hand to forcibly enrich it, then see if the other pot will chime in. Worth a try.

Last edited by gavin eisler; 11/20/12 3:27 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #464221
11/20/12 6:52 pm
11/20/12 6:52 pm
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Posts: 523
San Diego, CA
Will S. Offline OP
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Thanks Guys, I should have some time on Thu to try some of the tests mentioned.

Gavin/Pod - Don't know if you remember this, but long ago I traded you a Hendrix guitar book for some A65 headlight brackets that are on the bike in question :-)


Will S.
BSAs: '66 & '69 Lightning
Triumphs: '68 TR6R, '68 Bonneville, '73 TR7, '55 6T
'71 Norton Commando

www.britironsd.com
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #464522
11/22/12 11:17 pm
11/22/12 11:17 pm
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San Diego, CA
Will S. Offline OP
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Good News!
Took the air filter off to follow Gavin's suggestion and it fired right up and is running on both cylinders! The filter was very dirty!
With only one carb I don't know how it would only run on one side with a dirty filter. The side that wasn't running was down 10lbs of compression compared to the good side, 160 vs 150.
Thanks all for the help and Happy Thanksgiving everybody!


Will S.
BSAs: '66 & '69 Lightning
Triumphs: '68 TR6R, '68 Bonneville, '73 TR7, '55 6T
'71 Norton Commando

www.britironsd.com
Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #464524
11/22/12 11:25 pm
11/22/12 11:25 pm
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Vic. Australia
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Pete R - R.I.P. Offline
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You never get exactly equal mixtures with only one carb.A lot of things can affect it,even the angle of the carb.

Re: '66 A65 Running on One Cylinder-Help! [Re: Will S.] #464535
11/23/12 3:18 am
11/23/12 3:18 am
Joined: Jul 2001
Posts: 12,962
Central Virginia
Lannis Offline

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Originally Posted By: Will S.
Good News!
Took the air filter off to follow Gavin's suggestion and it fired right up and is running on both cylinders! The filter was very dirty!
With only one carb I don't know how it would only run on one side with a dirty filter. The side that wasn't running was down 10lbs of compression compared to the good side, 160 vs 150.
Thanks all for the help and Happy Thanksgiving everybody!


They actually make an angled spacer for that carb that tilts it preferentially toward one cylinder. If you can figure out which way it needs to be tilted to make your particular bike run optimally, it might be something to try ....

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
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