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BSA Rocket 3 won't start after top end job... #331039
09/01/10 3:00 am
09/01/10 3:00 am
Joined: Jun 2008
Posts: 197
portland, oregon, USA
Paul Burdette Offline OP
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Paul Burdette  Offline OP
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Joined: Jun 2008
Posts: 197
portland, oregon, USA
Yeah, I know... cliche start to a thread, huh?

Anyway, I'm pretty stumped. I wouldn't be here asking unless I was at my wit's end, but here I am. I was changing the top end gaskets to fix a leak at the head and found really worn valve stems and guides. I replaced all of them and had the seats reground. Put everything back together with new gaskets and pushrod seals, but now I can't get the engine to do a thing.

Compression is even between the three. Not ideal, but neither is my test gauge. Firing order is correct, as per the manual. All three plugs fire. With starting fluid, I'll get a bit of a bang back through the carbs, but having not touched the cam timing or ignition timing, and the firing order appears to be correct I'm not sure why I'm getting the backfire.

confused


1972 Norton Commando Combat
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Re: BSA Rocket 3 won't start after top end job... [Re: Paul Burdette] #331052
09/01/10 4:37 am
09/01/10 4:37 am
Joined: Jan 2004
Posts: 3,903
ca, us
D
DMadigan Offline
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DMadigan  Offline
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Joined: Jan 2004
Posts: 3,903
ca, us
I would take the plugs out, put your thumb over the timing side plug hole and turn it over until you feel compression. Turn on the ignition with the plug laying on the head and kick through. See if that plug fires. Check the other two plugs the same way.
Look at the rockers as you turn it over, they should open left, centre, right. Pretty hard to mess up the pushrods though. Recheck your valve clearances.

Re: BSA Rocket 3 won't start after top end job... [Re: Paul Burdette] #331147
09/01/10 7:29 pm
09/01/10 7:29 pm
Joined: Sep 2007
Posts: 223
Vermont
7
750 Tracker Offline
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If all you did was rebuild the top end and did not disturb the points, and the compression is over 100 psi, then it "should" start. That it pops through the carbs would indicate that the plug wires have been mixed-up. Double check that the wires inside the points housing match with the correct coils and that the high tension leads from the coils are connected to the correct cylinder.

Re: BSA Rocket 3 won't start after top end job... [Re: 750 Tracker] #331162
09/01/10 9:20 pm
09/01/10 9:20 pm
Joined: Jun 2008
Posts: 197
portland, oregon, USA
Paul Burdette Offline OP
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Paul Burdette  Offline OP
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Joined: Jun 2008
Posts: 197
portland, oregon, USA
Originally Posted by 750 Tracker
If all you did was rebuild the top end and did not disturb the points, and the compression is over 100 psi, then it "should" start. That it pops through the carbs would indicate that the plug wires have been mixed-up. Double check that the wires inside the points housing match with the correct coils and that the high tension leads from the coils are connected to the correct cylinder.


that really seems like the answer, right? that is what's driving me crazy, is that the colors and order match what the manual says: I have (black and...) yellow going to the top coil and primary cyl, red to the middle, and white to the timing side.

By the way, after posting last night it backfired and caught the airbox on fire... luckily no damage!

Last edited by Paul Burdette; 09/01/10 9:21 pm.

1972 Norton Commando Combat
Re: BSA Rocket 3 won't start after top end job... [Re: Paul Burdette] #331163
09/01/10 9:29 pm
09/01/10 9:29 pm
Joined: Aug 2010
Posts: 25
San Mateo, CA
C
Cookie Offline
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Cookie  Offline
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Joined: Aug 2010
Posts: 25
San Mateo, CA
I'm just going on general knowledge, I haven't worked on my triple much yet. Bring it up to the timing mark on one cylinder. Check that both valves will be cosed for that cylinder. With the plugs out and the one for that cylinder on a good ground slowly roll the engine past the firing mark. If it fires at the right time you are good on that one, check the next and the next. If it fires at the wrong time you are on to something.
Even if the wires appear to be the right colors somebody may have mixed them up at another connector.

Re: BSA Rocket 3 won't start after top end job... [Re: Cookie] #331217
09/02/10 3:02 am
09/02/10 3:02 am
Joined: Jun 2008
Posts: 197
portland, oregon, USA
Paul Burdette Offline OP
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Paul Burdette  Offline OP
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Joined: Jun 2008
Posts: 197
portland, oregon, USA
yeah, i don't know why it didn't occur to me to check it this way. thanks guys, i'll report back soon...


1972 Norton Commando Combat
Re: BSA Rocket 3 won't start after top end job... [Re: Paul Burdette] #331228
09/02/10 6:45 am
09/02/10 6:45 am
Joined: Oct 2008
Posts: 5,286
Gnashville
DavidP Offline

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DavidP  Offline

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Gnashville
It is all too easy on triples to time to the hole in the crank without checking valves.
You can get the engine timed off by one revolution.
Don't ask how I know.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: BSA Rocket 3 won't start after top end job... [Re: DavidP] #331310
09/02/10 5:49 pm
09/02/10 5:49 pm
Joined: Aug 2010
Posts: 25
San Mateo, CA
C
Cookie Offline
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Cookie  Offline
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Joined: Aug 2010
Posts: 25
San Mateo, CA
That would make perfect sense David. I used to see that on cars the owner swapped the distributor on and would not start.

Re: BSA Rocket 3 won't start after top end job... [Re: Cookie] #331315
09/02/10 6:11 pm
09/02/10 6:11 pm
Joined: Mar 2005
Posts: 10,251
Boston, Massachusetts
J
John Healy Offline
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John Healy  Offline
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Joined: Mar 2005
Posts: 10,251
Boston, Massachusetts
Quote
By the way, after posting last night it backfired and caught the airbox on fire... luckily no damage!


The trident is not a motorcycle you want to just kick and kick if it doesn't start. As you experienced it is very easy to light three cylinder air filter on fire. Some of these came with petcocks with a plastic center. If you own a three cylinder that still has the original petcocks with the plastic centers change them before you start your motorcycle again!!!!!

With very little heat from a small fire in the air cleaner they melt. If you ever seen one of these melt you will understand fully the meaning of conflagration. The heat from the fire expands the fuel in the tank and when they melt the pressure produces two flame throwers. Typically you are standing directly in the path of the flame and get covered with burning fuel.

Don't ask me why I know...

Last edited by John Healy; 09/02/10 6:12 pm.

Re: BSA Rocket 3 won't start after top end job... [Re: Paul Burdette] #331354
09/02/10 9:56 pm
09/02/10 9:56 pm
Joined: May 2005
Posts: 3,857
ohio
shel Offline
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shel  Offline
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Joined: May 2005
Posts: 3,857
ohio
I've seen pictures of a couple that have burned to the ground.


When given the choice between two evils I picked the one I haven't tried before
Re: BSA Rocket 3 won't start after top end job... [Re: Paul Burdette] #331374
09/03/10 12:03 am
09/03/10 12:03 am
Joined: Aug 2005
Posts: 1,552
melbourne florida
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bodine031 Offline
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Posts: 1,552
melbourne florida
i would re check the push rods are in the proper rocker arms,that the valve adjustment is correct. and you have a battery the cks out with aload on it.



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