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#151981 - 09/22/06 4:42 pm Model G Timing  
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David Conway Offline
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David Conway  Offline
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Washington D.C.
Set the timing on my Ď48 Model G as per instructions (3/8 inches BTDC), on the compression stroke, and with the ignition in the fully advanced position. However, the engine will not run unless the ignition lever is fully retarded. The ignition lever seems to be functioning as far as I can tell (it appears to rotate the cam behind the points).

The engine seems to run fine with the lever in the full retard position, but immediately cuts out when the lever is advanced (yes, Iím moving it in the right direction.) What am I doing wrong here? Can I hurt the engine any by running it like this until I get my problem solved? It sounds and pulls well otherwise.

Appreciate any thoughts about whatís going on. Thanks

Dave

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#151982 - 09/22/06 5:00 pm Re: Model G Timing  
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dave jones Offline
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Emsworth, sunny south of Engla...
My friend had a model G and it has a magneto right? It is very easy to turn the magneto by mistake when you do the nut up after setting. Use a battery and bulb or cgarette paper for the points. Are you sure you found tdc accurately before you measured the 3/8" with the lever in the full advance position? It is easy to make a mistake and it is a good idea to use a dial gauge or a piston stop with a degree wheel. If it pulls well at full retard you must have set it too advanced. I will say also that my friends one went through a big end because he left the lever at full advance all the time, or so he said, so I would redo the timing if I were you.
Dave

#151983 - 09/22/06 7:50 pm Re: Model G Timing  
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David Conway Offline
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David Conway  Offline
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Washington D.C.
Dave, I set the timing as meticulously I as could. I used a top TDC tool with measurements, so I'm confident that this part of the procedure was done correctly. Put the timing cover back together and checked it again to make sure nothing moved. I'm baffled. And frustrated. It's tough being dumb.

#151984 - 09/22/06 8:16 pm Re: Model G Timing  
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triton thrasher Online content
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Could your magneto be a mixture of parts from several magnetos? It is possible to mis-match cam, cam housing and body so that the points open where there is little or no magnetic flux or whatever it's called.

If you rotate the armature of a mag with no points, you can feel the little pulses of magnetism twice per revolution. At full advance, the points should open very near the point of maximum pull from the magnets. This gives strongest spark at full advance. As you may have guessed, retarded spark is after maximum flux and so is weaker- that's a design flaw.

Ring cam type magnetos have a cam stop peg that can be adjusted eccentrically by a slot head hidden under a pressed-in button on the outside of the cam housing. This is for getting points opening and magnetic flux to coincide. I don't know about face cam magnetos, but they probaby have something similar.


Amateur Loctite enthusiast.
#151985 - 09/22/06 10:43 pm Re: Model G Timing  
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David Conway Offline
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I can't be 100% sure, but the magdyno appears to be all-original, as does the rest of the bike. I must admit that, when it comes to electrical problems, I am somewhat of a dolt. This is my first vintage bike and first experience with magdynos and dynamos. Both appear to be working well otherwise. The magdyno still sparks the plug well. The workshop manual doesn't address this issue. However, the more I think about it, it's probable that the ignition lever and cam may have somehow been reassembled, perhaps by a former owner. I may have to dive in there and see if that's a possibility

#151986 - 09/23/06 12:09 pm Re: Model G Timing  
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Dennis B Online content
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Hi Dave,
Sounds like your real close, I would try setting the points gap at 12 thou and try it, if that doesn't help, set the gap at 18 thou and see if that helps.(when you change the points gap, the timing will change a little bit)
Are you going to bring your bike to Leesburg on Oct.1 ? I'm going to bring my model S. If you are still having a problem, I would be happy to take a look.
Cheers
Dennis B


Member # 182
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#151987 - 09/23/06 12:52 pm Re: Model G Timing  
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David Conway Offline
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Hi Dennis,

I set the gap at 12 thou as per instructions. I also posted this problem on Hitchcock's website. I got a couple responses that indicated some magdynos ignition levers functioned in reverse - that is, the advance position is when the cable tightens. Iím beginning to wonder if this isn't the solution. I also noticed another notch on the cam where the cable can also be set, but am unsure if this is an option or not.

Yes, I'm definitely going to the Leesburg show! So I hope to see you and your S there.

Thanks to all for your replies.

Dave

#151988 - 09/23/06 1:13 pm Re: Model G Timing  
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triton thrasher Online content
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Rotating the points cam the in the same direction that the points rotate, retards the timing. Is that any help?


Amateur Loctite enthusiast.
#151989 - 09/23/06 3:36 pm Re: Model G Timing  
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David Conway Offline
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David Conway  Offline
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Thanks Triton, every little piece of info helps. I was very careful to rotate the engine back until 3/8í BTDC. The TDC tool was very helpful in doing this. I made sure the points opened right at this position using thin paper. And I made sure the ignition lever was fully advanced (pushed away from me) when I did it. According to your information, my lever, when pulled back (to full retard), appears to be functioning correctly, and turns the cam clockwise, in the same direction as the points. However, since mine seems to run fine on the full retard position, advancing the lever seems to over-advance the timing to the point of where it just wonít run. Donít understand why if I set the timing when it was on full advance. Something is out of synch here, and Iím not quite sure what that something isÖ..

Dave

#151990 - 09/23/06 5:57 pm Re: Model G Timing  
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With the plug out sitting on the head, is the spark obviously weaker at full advance than at retard, when you spin the engine with the kickstart?

That might give you a clue whether it's a timing problem or a mag problem.


Amateur Loctite enthusiast.
#151991 - 09/24/06 11:45 am Re: Model G Timing  
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cus Offline
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G'day David,
I have a '47 J model, pretty much the same bike.
When the lever is fuully retarded my bike idles
really well, but when I start riding & going thru
the gears I advance the lever to fully advanced,
& then I retard it again if I stop & want the
bike to idle. Forgive me if I'm wrong but I think thats fairly normal.

regards, Cus

#151992 - 09/24/06 3:26 pm Re: Model G Timing  
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james johnson Offline
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Cus,

Your J is much like my ariel 500 single.. The G should idle at full advance, a little better if retarded about 1/3 but nothing of consequence.

David-

Your symptoms are pretty vexing.... did you say that you in fact rode the G like this? The reason I ask is if you just give the bike throttle with no load and it is spitting and cutting you may have a problem in your carb ( worn slide, needle in wrong position, blocked pilot valves) The softer ignition from running at retard may mask these symptoms. If you are getting cutting out under load I would still check the carb but probably would put fault on the ignition.

If you wanted to check the point of mag flux do as triton suggested, that point on mine is in about the 9:30 position if I remember correctly. I can't remember how the cam is indexed on the magdyno and from my exploded diagrams it is not apparent, If you like I can scan and send you off a copy form "Modern Motorcycle Mechanics" by JB Nicholson ( which you should acquire a copy of as it is a wealth of information).

one last thought would be the condenser, It is buried pretty good on the magdyno and just maybe it has a leak which is made worse when advanced due to it shorting from the increased voltage, I can also send you the test procedure If you like.

just to satisfy my curiosity I would set the points to open 3/8 before TDC at full retard and see if I got the same symptoms.... I am not sure what that would prove though.

Hope you get your G sorted, they are really good little bikes with a VERY robust engine. I have put many thousand miles on mine and always have a smile on my face at the end of the day.

james

#151993 - 09/24/06 5:28 pm Re: Model G Timing  
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David Conway Offline
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Hi James,

When the bike runs with the lever at full retard, it seems to run great; no sputtering, coughing or hesitation. It pulls my lard *** with no problem and appears to have plenty of power. I previously had a modern 500 Bullet, and I think this bike is even more powerful (at least at the low end.) When I first got the bike, I completely dismantled and cleaned the carb and replaced the needle, which was worn. It idles well when at full retard and I donít think the carb is the problem. Itís actually nice and smooth and the engine has a nice note. If I advance the lever to advance, sheíll cut out on me as soon as I slow down or stop.

At first I thought the ignition lever might be faulty, but that does not explain the engine dying when it is advanced. I havenít done the spark test yet and may not be able to get to it today (too many errands!) So if advancing the lever is cutting out the engine, is it advancing it too far to hold, or too retarded to hold. I think the answer may be in something out of sync in the magdyno. Is it possible someone dismantled it and put the cam back the wrong way? My exploded diagram is not much help either. I noticed the cam has different notches on it and could possibly result in some confusion when reassembling. Iím not too keen on taking the magdyno apart just yet.

James Ė Iíll take anything you want to scan and send my way. It would be much appreciated. You can send to conwayde@yahoo.com. Thanks!

Dave

#151994 - 09/24/06 10:08 pm Re: Model G Timing  
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cus Offline
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Australia
David,
Does your bike run O.K. on full advance in top
gear?, if it does I wouldn't be too worried
about having to retard the lever slightly when
you are stationary & not under load, my bike will
idle at full advance but idles better when
retarded some, I wouldn't go pulling everything
apart just yet!

regards, Cus

#151995 - 09/25/06 4:12 am Re: Model G Timing  
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james johnson Offline
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David,

I would also change the needle jet in your carb, It may not be the problem but it stands to reason that if the needle was worn then the jet will also be worn out of spec... that bike should use a .106 jet... you can check the wear with a pin gauge but you should file two flats in the gauge to get an accurate reading as the needle jets tend to wear round ( larger ) and ovular ( egg shaped ) due to the fore and aft vibrations... yea even on a single.

about your mag, it is pretty hard to get something out of sink in there, it is all indexed pretty well, I was working on my G today ( re assembling after big end rebuild ) and also noticed the multiple notches on the cam ring.. I guess that was so that you could set it up at max flux... funny I never gave it much thought ... I have only had one cam ring out ever and I figure that I just put it in the same as the one I took out.

If you want to mess about in the end cover the cam is held in by a copper c clip.. they are pretty easy to remvoe but I would at least check that it is near the point of max fulx before mucking about with it further.

james

#151996 - 09/25/06 10:36 pm Re: Model G Timing  
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Rohan Online content
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I notice you say you were careful to rotate the engine back to 3/8" BTDC.
I think herein lies the problem ?

When setting the ignition timing, the engine should always be rotated FORWARDS.

Or all your backlashes will gather together....

opethiselps.
Rohan.

#151997 - 09/26/06 9:04 pm Re: Model G Timing  
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David Conway Offline
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Interesting. I posted this problem on Hitchcock's board and some else mentioned this problem about rotating the engine backward. Would the gear backlash be enough to effect the timing that much? Looking at the vintage after-market manual it does say the following: ďÖturn the engine in the normal direction of rotation until the piston is the appropriate amount before TDC on the compression strokeÖĒ Looks like I'll have to give it another try. Maybe this is the source of the problem.

Thanks to all for your help!
Dave

#151998 - 09/27/06 2:54 am Re: Model G Timing  
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james johnson Offline
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california
David,
Yes backlash is a problem with the timing set up, there are 6 straight cut gears in the timing chest and each has a little clearance so multiply that by 6 and you get a big swing by the time you get to the magneto gear. I must have missed the part where you were talking about rotating the engine backwards.

james

#151999 - 09/30/06 12:49 pm Re: Model G Timing  
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David Conway Offline
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David Conway  Offline
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Washington D.C.
Well, tried the timing again yesterday. After a false start (still not sure what went wrong) off came the timing cover again, set the timing like a I was working on a complicated Swiss watch, and lo and behold I had success! I was careful to take up all the backlash on the gears this time and it apparently made a big difference. She runs fine with the ignition lever fully advanced and you can hear the engine retard when the lever is pulled back. Took her out for a run and she did fine with absolutely no pinging under load. I think I am good to go for a while. Again, thanks to all for your suggestions and help. I will no doubt be back here with another problem in the future.

Regards,
Dave

#152000 - 10/01/06 10:32 am Re: Model G Timing  
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cus Offline
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G'day Guys,
I'm getting a few conflicting reports on the
rotation of the engine to set the timing, I'll quote a paragraph out of the Royal Enfield Instruction Book - June 1951.
"To time the ignition, turn the engine until the
piston is at the top of its compression stroke,
(both valves closed). Then turn the engine
backwards until the the piston has descended the
following amounts, which can be guaged by a piece of wire inserted thru the plug hole.
Model G -3/8 & Model J- 5/16. etc etc.

regards, Cus

#152001 - 10/01/06 11:40 pm Re: Model G Timing  
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David Conway Offline
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Cus, I believe you can turn the engine backward (I have 3 different manuals that give differing instruction), however, just make sure to turn it back far enough so that when you avance it again, it takes up all the slack of the gears. I think this was my problem. There's enough gears in the timing case that, if you only turn the engine back 3/8 of an inch, all the slack remains on the gears (and it adds up enought to throw off the timing.) It seemed to make sense after I did it - and it worked!.

Dave



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