Author Topic: Pushrod question - problems starting new engine  (Read 9036 times)

Online bsa-bill

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Re: Pushrod question - problems starting new engine
« Reply #30 on: 15.02. 2011 17:22 »
Hi - here is the pic of camring in position
The Photo is not good. colours off and not as sharp as I wanted but you should be able to make out the camring and it position in relation to the screw I spoke of on the top of the maggie, also you might be able to see the camring is inboard of the end of the maggie a little.
Hope this helps.
I see SRM are selling camrings described as universal (pic included if it copies), think maybe yours is similar
All the best - Bill
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Offline Duncan R

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Re: Pushrod question - problems starting new engine
« Reply #31 on: 15.02. 2011 17:46 »
Hi Groily,

Thank you - Mine has a third cut out on it, I think that is the correct one to locate it in the points open just as the copper section of the slipring comes into view. I can twist it in the housing by about 1mm -1.5 mm and it is a loose fit in the mag housing,I can hook it out just by putting a small screwdriver in the whole. Is that too much rotation?

Thanks Bill, I think I have a universal one as shown in the SRM photo, the cut looks like its been done by hand.
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Online groily

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Re: Pushrod question - problems starting new engine
« Reply #32 on: 15.02. 2011 18:41 »
Well, I'd be unhappy with 1. any unchecked movement of a rotary sort, and 2. with any discernible sloppiness in the end housing which allowed discernible up and down or side to side movement.
If the ring isn't central, and/or if it can turn 40 to 60 thou at will, you can kiss accurate timing goodbye.

If you can't really move it up and down or side to side in the housing, then it may be possible to locate it well enough by that third notch with the peg (or an oversize version) and eliminate the rotation problem. The thing is, if there's any fretting, it'll only get worse. I doubt you can rely on the end cap to hold things tight - and anyway, you can't tell what's what when it's on.

I didn't know there was such a thing as a universal cam ring, and I am having a rare cynical moment believing it might be a cheapskate pattern part rotten bad idea. If I had a spare fixed cam ring of the original sort I'd willingly give it to you.

If forced to use it . . .  I'd either make a bigger locating peg to get rid of the rotational movement, or contrive an additional locating grub screw. I'd put the ring in and then check the points gap was close to the same on both cylinders (which it will only be if the ring is in the middle of the housing), and maybe use something like low strength loctite to help keep the thing where it's meant to be.
I dunno, I donta kinda like it, but maybe I'm being too picky and it will all be OK. Other better counsel may be at hand!
Bill

Offline Alan @Ncl

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Re: Pushrod question - problems starting new engine
« Reply #33 on: 15.02. 2011 18:53 »
Groily echos my concerns.  I also noted Duncan said the slipring conductor is just coming into sight when the points open.  I would have thought it needs to be well in place under the pickup by then as this is when it fires.  Also noted mine has two oil holes at 180 degrees apart and these line up vertically when the mag is fitted (the bottom one supplies oil to be held in the felt pad underneath).  This is a good location marker.  The locating peg is then at 1 o'clock (there is only 1 slot in the camring). This looks rather different to the camrings in the pictures though.

Alan

Online groily

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Re: Pushrod question - problems starting new engine
« Reply #34 on: 15.02. 2011 19:04 »
FWIW here's a version of the cam ring locator with larger eccentric mentioned light years ago. With thanks to my unsung mate who designed and drew it and made one, and to Alan@ncl for getting the file to a usable size.
Not necessarily a good thing on a magneto per se, but excellent for elec ign conversions, and could fill the gap in Duncan's ring!
Good point Alan about the slip ring position . . . sounds a bit off.
Bill

Offline Duncan R

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Re: Pushrod question - problems starting new engine
« Reply #35 on: 15.02. 2011 19:34 »
Hi All,

Just checked when the points break with my trusty fag paper - the conductor strip is well into the pick whole when they break, so assume that is ok.

Noticed a post a few days ago on a search regarding the mag cover, my old one had a crack in the terminal where the kill button  wire goes so I bought a new one, the rim on the new one is set a lot deeper than the old one. Maybe the old one holds the camring in place better, so will try again with old cap. Never had any spark problems before.
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Offline wilko

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Re: Pushrod question - problems starting new engine
« Reply #36 on: 15.02. 2011 20:10 »
Just to add confusion there are clockwise and anti clockwise point sets and camrings too!

Offline Duncan R

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Re: Pushrod question - problems starting new engine
« Reply #37 on: 15.02. 2011 20:13 »
Hi Wilko,

Sure this is the right camring, as I had no spark problems before rebuild. Easy starter , idled well and no misfires. The mag has not been touched except for timing.

Cheers

Duncan
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Offline Alan @Ncl

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Re: Pushrod question - problems starting new engine
« Reply #38 on: 15.02. 2011 21:05 »
It is very hard to see why it should not work now, when it used to before (I know the feeling).  Did you ever get round to trying the timing on both sides and the points gap on both, just to ensure that if the ring is a bit sloppy, it is not affecting the firing and timing?  Did you also check there was no unwanted resistance in plug caps etc.

Another tenuous thought is induction bias.  Was there a taper washer or gasket in there and if so, has it gone back the same way?

Alan

Offline trevinoz

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Re: Pushrod question - problems starting new engine
« Reply #39 on: 15.02. 2011 21:49 »
Duncan.
              The cut-out on the cam ring should be a snug fit on the locating peg which stops all rotation.
 Trev.

Offline Duncan R

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Re: Pushrod question - problems starting new engine
« Reply #40 on: 15.02. 2011 21:54 »
Hi Alan,

I just tried both mag caps - with the new one fitted and shaking the mag you can really hear the cam ring hitting the cover, with the old one there is much less rattle. I have just made up some cardboard gaskets to take up the slack with the old cover (bit of a bodge) now there is no rattle. You only have to push down the ring very lightly to stop any rotation.

Points gap is the same both sides, does not appear to be any resistance in the caps or lead 0 ohms on the meter.

No bias washer was fitted, the engine always idled lovely even with its dodgy internals and no more than 4 kicks to start from cold.


When I had it running on one it responded to throttle ok, but not a backfire or anything from the other.

I will stick the mag back on in the morning and see if that makes any differnce.

Cheers
Duncan
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Offline Duncan R

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Re: Pushrod question - problems starting new engine
« Reply #41 on: 15.02. 2011 22:08 »
Duncan.
              The cut-out on the cam ring should be a snug fit on the locating peg which stops all rotation.
 Trev.

Hi Trev,

I am hoping my bodge of the cardboard shims and the old cap will hold the camring tight. The new cap has its rim set quite deep so it looks like it puts no pressure on the camring at all and you can hear it rattle quite a lot when you shake it. I noticed that you only have to lift the ringout slightly and you get rotation, with light downward pressure on the ring it barely moves at all. I might put a drop of bearing lock as well

Cheers

Duncan
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Offline trevinoz

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Re: Pushrod question - problems starting new engine
« Reply #42 on: 15.02. 2011 22:19 »
Duncan,
              For a really sweet running engine, you need to ensure that the magneto fires at the same degree of advance on both cylinders.
These cam rings can be many degrees different between cylinders.
It is a fiddly job to do, I always do mine while the head is off and grind the cam ring until both sides are equal.
Trev.

Offline Alan @Ncl

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Re: Pushrod question - problems starting new engine
« Reply #43 on: 16.02. 2011 12:00 »
What do the plugs look like Duncan?  Is the non running side plug damp at all and can you smell any unburned petrol in the exhaust on the non running side? Is it worth trying to temporarily richen up the mixture a bit?  Just stabs in the dark as I expect you have done all this already.

Alan

Offline Duncan R

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Re: Pushrod question - problems starting new engine
« Reply #44 on: 16.02. 2011 12:19 »
Hi Alan,

I don't think there is any problem with fueling - when I could not get anything out of the engine the plugs were equally wet. I have managed to lock the camring with some loctite and am just about to set the timing again.

Cheers

Duncan
Anglo - Indian A7SS (Actually is a 650)
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