Author Topic: Help needed with 600 ohv timing  (Read 3707 times)

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Offline alexd912

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Help needed with 600 ohv timing
« on: 21 Jul 2014 at 16:36 »
Hi there,

I have been trying to start my Dougie after the engine was stripped and had new valves and springs replaced.
The mag was reconditioning and now sparking in the correct rotation after points were changed.
All the cogs were put back to as original with the help of pictures I tool during the strip down.

I have set up the cam/ valve clearances which as far as I know I have done correctly.

Now need a real dummy guide (step by step) to setting up the engine as I have tried everything and still no life.

I cant see how to adjust the timing as everything is toothed or keyed.

Please I really need some help now how to time the ignition against the valve timing and pistons TDC.

Thanks from one very lost person.

Alex
Best regards
Alex
1930 Douglas G31

Offline Doug

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Re: Help needed with 600 ohv timing
« Reply #1 on: 21 Jul 2014 at 17:45 »
Alex,

The easiest thing to do is to fit a degree wheel to the end of the timing side of the crankshaft while setting up. However it sounds as if the engine is further along than that. You could stick the degree wheel to the face of the flywheel with double sided tape, or subdivide the circumference of the flywheel into degrees.

The era of your machine, I would expect it to have the "IN.OP.20" camshaft fitted. If so it is timed for the inlet to open 20 degrees BTDC. It is possible that you have a "10.50.63.20" cam fitted. That is timed for inlet opens 10 degrees BTDC. According to factory literature the valve lash on the later cam was 0.002" inlet and exhaust when hot. This setting always worried me as I would expect quite a bit of expansion in the cylinder and head, and I would be worried the valve clearance would be nil or slightly open when cold and first warming up. So I always set my '34 OHV Douglas for just being able to rotate the pushrods freely (about 0.002 inch) when cold and then if anything it would gain a little more clearance when hot. I do not recall seeing factory valve clearance figures for the "IN.OP.20" cam, but would expect the factory settings to be the same as the other cam mentioned. I have the "IN.OP.20" cam fitted to my '34.

You have the eight splines on the camshaft, which are not perfectly aligned with any one tooth. So playing about with that can alter the timing by a fraction of a whole tooth. Also the crankshaft pinion has three keyways to intentionally allow one third a tooth division for timing purposes. With that you should have no trouble getting it close. But it is not super critical, clearly from the above Douglas experimented with cams giving from ten to twenty degrees for the opening of the inlet valve. That alone will tell you that it is not the camshaft being out a degree or two that will prevent the engine from running.

The factory literature stated that there was no need to alter the cam timing regardless if one was running petrol-benzol or straight petrol, and indeed both cams were used in Dirt Track machines and road going models.

The factory literature also gives the ignition timing as 45 degrees full advance on DT motors. This is with the anti-fouling pockets still intact. If they have been drilled through and long reach plugs fitted, then the ignition timing is probably going to require a more conventional 35 degrees full advance to compensate for the faster ignition of the main charge. On the same '34 Dougie mentioned above, I ran with 42 degrees advance on straight petrol. Do not overlook the fact with the magneto that not only do you need to time the points to break at the optimum moment (moment of maximum flux), but that the brass segment of the slip ring is adjacent to the plug lead that you want to fire. In other words do not have the embarrassment of timing for the front cylinder only to have the spark occur in the rear cylinder! As far as the internal timing of the magneto (maximum flux), I think that as long as you are using original, unmodified point plates, that you really only have to worry about fitting CW or CCW assembles. The original key and keyway locations take care of the internal timing for you. However, and someone else can jump in here and comment, I believe there are CW and CCW slip rings? If the wrong one is fitted (during a rebuild) the brass contact may be too far away from the carbon brush to fire the plug.

-Doug


Offline alexd912

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Re: Help needed with 600 ohv timing
« Reply #2 on: 21 Jul 2014 at 18:34 »
HI there,
I have a 360 deg timing disc on the flywheel now. I think my problem is that im timing the wrong cylinder and the wrong stoke. I cant trust any of the original markings except for TDC on the crank are correct.
The cam issue we have discuss in depth and thanks for your help there. Im 90% sure that is correct now. to set up the cam i used old pictures which showed markings on the the cam shaft (not the cog).. I have pictures of this on the forum https://www.douglasmotorcycles.net/index.php?topic=3597.msg13050#msg13050

I have changed the advance retard ring from the last picture to the first picture.

https://www.douglasmotorcycles.net/index.php?topic=3597.msg13050#msg13050

Now im not sure which points I should be using. after some trial and error I used ones that sparked when spun in the CW direction (from points side)
Maybe I should go back to the original mag set up as shown in the last picture

Back to some stupid questions:
Which part is the brass segment of the slip ring do I use and where should it point to?
So I have to time the front cylinder at 40 deg BTDC with the brass segment of the slip ring pointing to that cylinder with the points just opening?  Do the valves have to be closed? If so to check this would I take the rocker cover off?

How do I now time the points so they are just opening at 40 deg BTDC? Do I manually turn the mag sprocket so the points just open then fit it the engine?
Do I have to take the cover of the carb side of the engine to make all the adjustments?

Sorry to ask all these questions I just think Im going round in circles and now I cant see the woods through the trees...

If anyone has time to give step by step guide with some pics then I would be very appreciated. A real idiots guide is what I need wrote now.

Not sure if this helps but I have attached one picture of the mag. I think I had to change the points to get it to spark in the CW direction.

Best regards and sincerely sorry for asking all this..

Alex


Best regards
Alex
1930 Douglas G31

Offline eddie

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Re: Help needed with 600 ohv timing
« Reply #3 on: 21 Jul 2014 at 20:24 »
Alex,
         The last photo you have posted shows the mag fitted with the wrong points plate. The correct points plate should have an 'L' cast on it's face, in which case, the heel of the points (the bit that rubs on the cam ring) will trail it's pivot when the mag is rotated in the correct direction (anti-clockwise from the drive end). If the mag was reconditioned with an 'R' points plate, then I would guess that the rest of the mag is built up to rotate anti clockwise from the drive end. When correctly set up, with the points at about 9 o'clock and just breaking, the front cylinder should be firing - and the rear cylinder firing with the points breaking around 3 o'clock.

   Hope this helps,
         Regards,
                      Eddie.

Offline eddie

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Re: Help needed with 600 ohv timing
« Reply #4 on: 21 Jul 2014 at 20:41 »
Alex,
        I've just had another look at your posting on 16th July - the 2nd photo shows the mag with the correct points fitted. With those points fitted, set the mag up so that the points are just opening, and at about 9 o'clock. Turn the engine to TDC with the valves rocking on the back cylinder, then turn the crank backwards about 36 - 40 degrees, then just pop the mag back into mesh on the timing gears. That should set the timing close enough to get the bike started - you can then play with the advance/retard to find the 'sweetest' setting.

  Regards,
               Eddie.

Offline alexd912

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Re: Help needed with 600 ohv timing
« Reply #5 on: 21 Jul 2014 at 21:33 »
HI there Eddie,

Cheers for this and Ill have another go tomorrow..

Im sure it is just me not seeing clearly after a few days trying, also im not used to mags or 4 strokes:)

I had to go and change the points on my messerschmitt right after trying to get the Dougie started and it took me 10 mins:)

Ill keep you posted.

Alex
Best regards
Alex
1930 Douglas G31

Offline eddie

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Re: Help needed with 600 ohv timing
« Reply #6 on: 22 Jul 2014 at 07:09 »
Hi Doug,
              With reference to your question about CW and CCW slip rings: Yes, they are different. The brass segment starts at a point 90 degrees to the poles of the armature, with the remainder of the segment trailing that point. Taking this into account, it is possible to get a magneto to generate a spark at full advance, irrespective of which slip ring is fitted, but, with the wrong slip ring, if the spark is then retarded, it will occur after the segment has passed the HT pickup, causing the spark to jump across the safety gap instead of going to the spark plug.

  Regards,
               Eddie.

Offline alexd912

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Re: Help needed with 600 ohv timing
« Reply #7 on: 22 Jul 2014 at 20:44 »
Hi there,

i got the engine started with a ot of pushing today.

checked valve timing at 20 deg btdc ok
checked that valve push rods had some rotation on both inlet and exhaust when at tdc.
checked that mag was firing on front cylinder at 40 deg btdc with advance cable slack. Done this by having mag out and rotating with front plug in and watching for spark. Then marked the mag points at just opening on front cyl.
placed mag back in with flywheel at 40 deg btdc.

after engine ran for 5 secs the furl ran out then inner sleeve came out of the clutch cable, do no more clutch.

so ill make new cable and try again.

thanks everyone.

alex
Best regards
Alex
1930 Douglas G31

 

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