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Anyone know the dwell for 71 bonnie? #119217
07/04/07 3:23 pm
07/04/07 3:23 pm
Joined: Dec 2006
Posts: 3,895
Massachusetts, U.S.A.
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btour Offline OP
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btour  Offline OP
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Joined: Dec 2006
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Massachusetts, U.S.A.
I am not even sure what dwell is, but I need to know it, because friend with timing light thinks it is important.

I know manual lists static timing 14 degress and advance 38 degrees.

Is it one of these numbers? All I can remember is guys used dwell meter to set points gap more accurately, and more easily, I think. He has dwell on his timing light.

I never had one before. I happen to now. It is Sears engine anylsyer, but only goes down to 4 cylinders.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
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Re: Anyone know the dwell for 71 bonnie? #119218
07/05/07 12:24 pm
07/05/07 12:24 pm
Joined: Jan 2005
Posts: 1,662
East Bethany New York
Dick Harris Offline
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Dwell is the length of time the points are open,a moot point in regard to your Triumph. You should get yourself a good manual and study up on ignition timing.Set the points to the required gap and then after checking the auto-advance unit for proper operation,use the timing light to check the full advance setting,which is the aformentioned 38 degree.(maybe you want to use 36 degrees) and then go ride it. Dick beerchug

Re: Anyone know the dwell for 71 bonnie? #119219
07/05/07 12:26 pm
07/05/07 12:26 pm
Joined: Apr 2006
Posts: 1,708
Virginia, USA
SBoyd Offline
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SBoyd  Offline
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Virginia, USA
closed, expressed in degrees


Stop the insanity.
Re: Anyone know the dwell for 71 bonnie? #119220
07/05/07 1:57 pm
07/05/07 1:57 pm
Joined: Apr 2006
Posts: 1,708
Virginia, USA
SBoyd Offline
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Virginia, USA
PS
Dick is correct in his advice and procedure (except that dwell is time points are closed, [a typo]).

That figure is not published. You don't need to know it and it will not help in tuning your Triumph.
Dwell is determined by the shape of the breaker cam and the point gap. You can change the dwell by varying the point gap, but you will set the point gap to the manual spec.


Stop the insanity.
Re: Anyone know the dwell for 71 bonnie? #119221
07/05/07 2:51 pm
07/05/07 2:51 pm
Joined: Mar 2005
Posts: 10,157
Boston, Massachusetts
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John Healy Offline

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Boston, Massachusetts
If the manufacturer's recommendations are followed when setting the point gap you will have the proper dwell. Setting the dwell is just another way of adjusting the point gap. They are effectivley "one in the same!"

The dwell is ground into the points cam lobe. While it will be different when the points are set with a .012" clearance than when they are set at .015" clearance the dwell will fall within acceptable limits.

What is of more importance with these units is setting the auto advance unit into the camshaft's tapered hole properly. If the AA unit wobles it will effect the included dwell for any unit and also lead to the points opening twice. Once at the proper point, and another nearly opposite.

To check and see if the AA unit is set properly, one just has to watch the point gap as the point's rubbing block passes over the part of the cam that holds it open. If the gap varies while point lifter block holds the points open, the AA unit is not set properly. If the points actually close as the lifter block passes over the portion of the cam that holds the points open, you can have problems. You will get two sparks. THIS DOES HAPPEN!

So btour, don't fret about not knowing the dwell. If you want to know what it is set the point gap to .012" and then to .015." Measure the degrees the points are closed for each and you have the acceptable dwell ground into the AA unit you are using.


Re: Anyone know the dwell for 71 bonnie? #119222
07/05/07 3:08 pm
07/05/07 3:08 pm
Joined: Dec 2006
Posts: 3,895
Massachusetts, U.S.A.
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btour Offline OP
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btour  Offline OP
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Joined: Dec 2006
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Wow, thanks guys. I like the explanation.

Please do not think, I am getting weird wanting to know this. The guy who has the light keeps wanting to know this, and thinks it is essential. I want to have him use the light, so I asked. It is nice when everyone is happy, and no toes get stepped on, and you guys helped. But it still would be nice to have the figure, so I could say it is x

HI John,

Thanks specially to you. Wondering why I would use .012 and .015? Would it not be .014 and .016 which are the figures of acceptable range of gap in 71 manual? And why I usually try to gap it to .015.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Anyone know the dwell for 71 bonnie? #119223
07/05/07 4:16 pm
07/05/07 4:16 pm
Joined: Nov 2005
Posts: 706
Tennessee
Fisherman Offline
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Fisherman  Offline
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Posts: 706
Tennessee
Btour, I think John is trying to give you a reading at 'acceptable limits'. The optimal is .015, and as the points cam wears the points lifter block, it may decrease the gap to .012, likely without discernable problems.

The guy with the light has been working on cars, which have a distributor that allows him to adjust the points gap EXTERNALLY while the engine is running, through a window in the distributor cap. With this method, dwell angle is an easier way to set the points gap. No need to take the cap off and use a feeler gauge to adjust the points.

Set your points to .015, have him time the engine, then switch to the dwell setting on the light. It will be correct for your engine. Write it down and let us know what it is. The 'dwell angle' will be the amount of camshaft degrees that the points are closed when the points are set correctly at .015.

Bernie


'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
Re: Anyone know the dwell for 71 bonnie? #119224
07/05/07 4:23 pm
07/05/07 4:23 pm
Joined: Jun 2005
Posts: 626
Western Oregon
enigmaT120 Offline
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Western Oregon
A timing light won't help him to set the dwell anyway, he would need a dwell meter. I've heard of BMW guys using dwell meters to set their point gap, but they only have one set of points so maybe it's easier.

As far as I know only Chevy V8s (like the one in my '58 pickup) have the window in the distributor cap which allows you to adjust the dwell angle as the motor is running. That's sweet. My mom's 65 Imperial was not so nice. mad

Ed


Ed
1970 Bonneville
Re: Anyone know the dwell for 71 bonnie? #119225
07/05/07 4:30 pm
07/05/07 4:30 pm
Joined: Nov 2005
Posts: 706
Tennessee
Fisherman Offline
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Fisherman  Offline
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Tennessee
Ed, The guy has a light with a dwell meter built in. My experience with a distibutor with a window happened to be on a Buick....maybe all GM cars?...sure was easy though.


'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
Re: Anyone know the dwell for 71 bonnie? #119226
07/05/07 4:56 pm
07/05/07 4:56 pm
Joined: Dec 2006
Posts: 3,895
Massachusetts, U.S.A.
B
btour Offline OP
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Massachusetts, U.S.A.
Hi Bernie,

Thank you. I am trying. Guy rebuilds Triumphs to concourse condition. I have to be diplomatic. I can say once, or maybe twice, that I do not think it is necessary to know, but after that it is an insult. smile

I will make it a point now to find out and let everyone know.

First I have to solve coil problem. Did you see my thread on stuttering engine?

I am getting there, Bernie. I see light at the end of the tunnel. Hope it is not an oncoming train eek

Off to get crack in exhaust pipe welded. Hope I do not get caught in the coming T-storm. Three times this season, caught in the rain, and only ridden 5. frown


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Anyone know the dwell for 71 bonnie? #119227
07/05/07 6:33 pm
07/05/07 6:33 pm
Joined: Nov 2005
Posts: 706
Tennessee
Fisherman Offline
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Fisherman  Offline
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Posts: 706
Tennessee
Btour, Are you seeing Al Jr. again?

I think you have enough knowledge from this thread to explain the relationship of points gap to dwell angle to him.

Then maybe this 'concourse restorer' will condescend to shoot the stupid light at your rotor for a few seconds for you.

Of course you could always take him the shop manual and point out that the specs do not list 'dwell angle'.....and ask him what the angle was for his show bikes(and where he found the specs)...assuming they even run.

I'm sorry, I'm getting a little testy because of the apparent distain these guys seem to have for you. If I had to prove the direct relationship of dwell angle to points gap to some guy before he would lend me a stinking timing light, I'd save up the thirty bucks and go buy one at Advance.


'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
Re: Anyone know the dwell for 71 bonnie? #119228
07/05/07 6:58 pm
07/05/07 6:58 pm
Joined: Mar 2005
Posts: 10,157
Boston, Massachusetts
J
John Healy Offline

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Boston, Massachusetts
Well btour, Living up to my cranky old fart reputation, if this guy builds concourse Triumphs he already knows all this stuff... why is he asking us. Bring him a coffee, and some jelly doughnuts and then ask him to call me. That way you will be the good guy, and well, I will be the ...

As fisherman eluded to, all this dwell stuff harkens back to the days when the point adjustment screw was accessable from side of the distributor. You installed new points, roughly adjusted them to the clearance specified in teh manula and di the final point adjustment using the screw. Because you could not see the points the time they were closed, or dwell, was used to make the final adjustment.

Will bring to Fisermans attention that on the early points plate you would have to juggle the point gap to get the timing correct on each side. It wasn't uncommon to have one set of points at .012" and the other at .015" or more. The later points allowed you to rotate individually the plate the points themselves were mounted to. This gave you the luxuary of being able to use .015," or what have you, for the point gap for both cylinders.

No matter what you do, shy of changing the point gap outside of the Lucas recommendations, you will not change the dwell. To do that you will need to regrind the auto advance cam.
I still say it is far more important to get the alignment of the AA unit correct, than worrying what the dwell is at .015".


Re: Anyone know the dwell for 71 bonnie? #119229
07/05/07 7:09 pm
07/05/07 7:09 pm
Joined: Nov 2005
Posts: 706
Tennessee
Fisherman Offline
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Fisherman  Offline
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Posts: 706
Tennessee
John, thanks for the reminder, my running Triumph is a '72, but I recall the '66 I had did not provide for individual points plate adjustment.(Besides mine was within a degree or so at .015 so I never attempted to fine tune any closer.)

You may consider yourself a cranky old fart but this cat must beat you in spades if he won't let a fellow Brit owner use his precious light for a few minutes if he can't quote the freakin dwell angle....I'm about ready to ship mine to Btour.


'Never argue with an idiot, they'll bring you down to their level, and beat you with experience'

'72 TR6
'12 Hinckley Scrambler
'95 FLHTC Road Sofa
Re: Anyone know the dwell for 71 bonnie? #119230
07/05/07 7:31 pm
07/05/07 7:31 pm
Joined: Feb 2004
Posts: 1,956
Flint,Mich
norbsa48503 Offline
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Flint,Mich
Maybe the restorer has sent btour to the crib for a 10 minute weight.


norbsa
1960 TR6
1963 Super Rocket
1965 650 Star
1966 441
1968 Thunderbolt
1969 Twinkle 250
1972 Fastback
1974 Roadster
1970 S.S
Way too many BSA's not named
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Re: Anyone know the dwell for 71 bonnie? #119231
07/05/07 7:39 pm
07/05/07 7:39 pm
Joined: Jun 2005
Posts: 626
Western Oregon
enigmaT120 Offline
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Posts: 626
Western Oregon
I'm glad I don't have one of the early type like John mentioned. I recently checked my timing, and the left side was retarded a bit. I checked the points and that side had closed up some. I did an experiment to see if I could get the timing back right by adjusting the points, and after several failures I gave up, gapped the points, and used the proper method to then set the timing. Changing the point gap just was too big a change, at least for clumsy me.
Ed


Ed
1970 Bonneville
Re: Anyone know the dwell for 71 bonnie? #119232
07/06/07 1:35 am
07/06/07 1:35 am
Joined: Dec 2006
Posts: 3,895
Massachusetts, U.S.A.
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btour Offline OP
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Massachusetts, U.S.A.
Hi everyone,

I saw the my friend today, and mentioned that dwell info was not available. He said he usually uses 12.
He explained that with the light he has he must put in a dwell. If he does not he gets a false flash.

He gave me a few bits today too. The correct blinker stems for my bike. Right length. I got the wrong ones so many times, I am psyched.

I had another great experience today. I was driving by a bar, and saw a Triumph, so I stopped and met the guy. It is quite a bitsa bike! The guy is using a dual Harley coil so he gave me a couple of coils! I do not know how many saw my thread on stuttering, but remember projected plugs? Well part of the problem was the coil. For example when I started it today, there it was just running on one again. Man, I was depressed I got out the coil tester and no spark, and then a weak one once in awhile. I waited awhile, and started again. Running on two and I was off to get pipe welded. Never got there, because of the above, but the bike ran great all day.

Planets must have been aligned for the coil.

Anyone going to Sturbridge Ma this Sun?


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.

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