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How To: Make Timing Gear Bushings

August 27, 2010

I’ve had so much free time lately, I pulled the motor open in the Premier to check things over before the long ride.  There was a bit of aluminum swarf in the bottom of the timing chest, inspection showed that two of the timing gears had been rubbing on the inner timing case.  Then with the cover off, one bushing fell out of the hole that it was supposed to be pressed into.  So it was time to make some new bushings…

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Measuring the bushings.  Too large on the id.

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One bushing fell out of the case, but the others were still held tight.  So I used the old trick of popping them out by pushing in a dowel pin.  This works if the bushings have a through hole, and are mounted in a blind hole in the case.  Step 1. Fill the bushing bore with grease.

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Step 2.  place a dowel pin or drift into the bore.  This should be a sliding fit.

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Step 3.  Hit the end of the dowel.  The grease is an incompressible fluid, it has nowhere to go.  So it pushes up on the back of the bushing.  That pops the bushing up out of the housing.  For long bushings, you might have to stop and put in more grease, then hit the pin a second time to get the bushing all the way up and out.

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Lots of standard bushings are available from the typical sources  like MSC, McMaster Carr, Anchor Bronze, etc.  The dimensions on the Premier were not quite the same as the off the shelf bushings, so I made them from scratch.  This bar is SAE 841 oil impregnated sintered bronze, about $15 or $20 for 6” length from McMaster.  The material is porous, and filled with oil.  When the motor is running, the spinning shaft heats up, some of the oil comes out of the bronze to lubricate the bearing surface.  When it cools, it goes back in.  This material works very well for early motors that have minimal lubrication systems.  It is also easy to cut on the lathe, as it self-lubricates during cutting.

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Facing the bushing to the correct thickness.

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Milling the notch that clocks the bush in the cases.

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The bushings were lightly pressed into the outer timing case.  Small steel pins are in the case, they contact the notch cut in the bearing to stop it from rotating.  A small groove was cut into the face of each bushing flange to allow oil to run down onto the gear shaft.  When this timing cover is installed, each of the oil grooves is oriented vertically.

After the first bush was installed, the ID was checked against the gear shaft.  If it was tight due to the interference with the cases, the bush was popped back out for a very light cut on the ID.  Final sizing was about .0015” to .002” over the shaft diameter, with about .010” end float between the two bushings that support each gear (one on the inner case and one on the outer).  As the motor heats up, the aluminum will expand more than the steel gears, which will give slightly more clearance on both the diameter and end float.

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Gratuitous shot of the cast iron piston.  Wide rings, with bevel cuts.  Note that the top ring groove has two rings in it.  Also note that there are no oil rings (constant loss oil system).

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Here you can see the ball that rides on the cam lobe.  It is a very interesting design, I do not know of any other motor that uses balls for cam followers.

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So many parts in this valve train… From the top: 

Valve and guide

Adjuster and tappet

Tappet guide (on the left)

2 piece Lifter and compression spring

Ball cam follower

Cam, shaft and gear.

_________ZZZZZZZZZZZZZ 

assembled.

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16 Comments leave one →
  1. wagner peres permalink
    August 27, 2010 10:44 am

    very usefull and rare information! tks a lot

  2. Paul Louis Venne permalink
    August 27, 2010 7:05 pm

    Purring like a pussycat methinks. Nice.

  3. Richard McKenney permalink
    August 27, 2010 9:55 pm

    G’day Pete

    Now you tell me how!

    I just spent weeks making bushes for my old bike, I only needed 8 or 9, I made about 15 ; 6 fell throught the hole,” missed it bythat much”.

    How many did you have left over?

    I got $100 says you’ll finish the Cannonball, any takers?
    Cheers Richard

    • Pete Young permalink*
      August 27, 2010 11:31 pm

      hi Richard. I didn’t make any spare bushes, but I have several inches of raw material left to make up some more of them… 😉 messing with old bits is fun! Each bush was very slightly different on ID and OD to fit the various old aluminum bores and the slightly different shafts.

      I don’t know if I’d take that bet on the Cannonball! It is going to be tough for everybody. averaging 35-40 mph doesn’t look probable to me, but I plan to ride from sunrise until sunset and see how i get by.

  4. Richard McKenney permalink
    August 28, 2010 4:06 am

    G’day Pete

    I got tripped up with those spring loaded internal measuring tools, the radius on their ends give false readings in small bores. Don’t fit.

    Working with this 100 year old scrap of mine I’m humbled by how big were our for fathers………courage/coconuts/endeavour/ looking for translation without offence.

    Well mate I’m happy to put a ton on you, cos I’m such a big fan, I know you’ll give it your best, but it’s not worth ruining your health for, have fun. I’d be like a kid getting autographs. I’m excited about the Cannonball and I’m on the other side of the world.

    You probably know this, but you can ride huge distances like a man in your Levis and you’ll have so many blisters on your seat It’ll look like bubble wrap/blisters that get infected.

    Or you can do like cyclists, wear cycle shorts, under the bike gear and slide in a puddle of lanolin/chamois cream and complete the RAAM in good condition, just a hint.

    “Real Men Ride Belt Drive Singles”.

    Cheers Richard

    • Pete Young permalink*
      August 28, 2010 11:32 am

      Yeah, bore gauges can be tough to use. But I always try to remember to check the fit of the PARTS to each other, not just the fit of the parts to the measuring tools. With some practice, you’ll feel what a close or loose sliding fit feels like. Don’t fret. Everybody scraps some parts. Even the best machinists typically make an extra part or two for setup use, or just in case… 🙂 and I usually screw up a lot, but don’t always show the photos!

  5. Jim Abbott permalink
    August 28, 2010 10:01 am

    Pete: Very nice job! Missed you and Kim at the Rally this year. Maybe next year. Jim A. Tucson, AZ

    • Pete Young permalink*
      August 30, 2010 10:49 pm

      Hi Jim. We were very sorry to miss the Velocette Rally this year, but the Cannonball is taking all our time and money for 2010. We’ll be there next year in the Columbia River Gorge.

  6. August 28, 2010 11:28 am

    Pete,

    Thanks for reading a bit of my blog. I appreciate the comments but more importantly appreciate your generosity. Your articles have taught me a great deal while providing courage in tackling some mechanical projects that I never would have attempted otherwise.

    I wish you the very best on the Cannonball. It should be an amazing adventure.

    I am currently making a small forge to cast some little devils. You are definitely on the list to get one.

    Regards,
    Chris

  7. Richard McKenney permalink
    August 31, 2010 7:05 pm

    G’day Pete

    You know those bushes I just busted a gut making?

    I used LG2 Bronze leaded gunmetal standard, it was all I could get in a country town.
    I was hoping that would translate to SAE 841 but they’re different of course.
    What do you think? I’m not keen on making them again!!!!

    Any chance a balance factor “How to” for the piston and flywheels?

    I clicked on Chris Hutsons link, terrific stuff! You just got bookmarked Chris.

    You guys have a lot of talent over there, I’m only good at drinking beer, telling lies and ogling women, maybe I’ll try politics.

    Cheers Richard

  8. February 21, 2012 2:21 pm

    Hello Pete,

    Thank you for passing on so much information , there is always something interesting every time I visit your web site.

    I would like to ask a few questions relating to an old 1913’ish Veteran Sidevalve engine that I have. Whilst the engine has its Crankcases, Crankshaft, Con rod, piston and cylinder, the whole of the valvetrain is missing. I do however have the timing gears, which have their own cams, and these are 1 piece parts.

    Whilst I am only a Hobby machinist, still learing, I do have colleagues who may be able to assist in making the required parts. However, I do not know which material should be used for each part.. Looking at the engine, I would require some sort of Cam Follower/valve lifter, Cam follower guide, Cam follower adjuster, Valve, Valve spring, Valve spring cups and valve spring retaining pin. I believe that the original valves had an elongated retangular hole near to the base of the stem, into which a pin was placed in order to retain the valve spring and its cap. The original valve guide in the combined (Blind ?) cylinder/Head assembly is still in place , but may need replacing.

    I presume that if the valve seats are measures, a similar sized valve could be obtained and adapted as neccessary, but how is the hole for the spring retaining pin cut into the stem.

    I hope that I am not asking too much, but any advice om materials, parts etc would be greatly appreciated.

    On the positive side, I should again be watching and following the Pioneer Run in March. (But would love to actually ride a Veteran in the Run).

    All the Best,
    Cheers,

    Derek

    • February 21, 2012 4:25 pm

      Hello Derek. Choosing a material for a part is tough. There are very few resources for us to look at that describe what materials are suitable. I’ve searched online and through new and old books without getting very much information. Basically, nobody wants to stick their neck out and recommend a material that might break! But I don’t mind telling what materials that I like to use. For the cam follower, you’ll need a hard material where it slides on the cam. This might be a bit of stellite or other material that is deposited onto a mild steel arm. A chromemoly arm would be nice too. For the valve, you should buy new ones, and make your guides to fit them. The slot in the end of the valve can be cut by an EDM machine. I did that for my Excelsior valves a year or two ago. Another option is to turn grooves into the valves and use more modern types of valve keepers. The valve spring cups shouldn’t see any wear and don’t need to be hardened I think. mild steel or annealed chromemoly should be ok. For the valve retaining pin (this is the one that fits into the hole in the valve stem?) the material should be tough, and not too hard and brittle. Annealed chromemoly is again a decent choice, but I think that the originals might have just been mild steel. Is the cam follower guide a bushing? If so, I’d use SAE660 bronze (also known as Oilite) as it is impregnated with oil. The originals are often steel, but that has a lot more friction. Oilite may not last for 30,000 miles, but it is very easy to work with. Somewhere in your list of parts there must be a tappet that touches the bottom of the valve. You’ll want the face of it to be hardended or it will wear out quickly. A tool steel such as O1 or A2 would work, or something a bit more exotic like 8620 with case hardening.

      I’ll send you a private email, as I’d love to see your photos of the motor.

      Regards,
      Pete

  9. Bruce Williams permalink
    July 4, 2012 6:02 pm

    Pete, I have a 09 NSU 82×105 2 speed v-belt export deluxe. It came to me thru the Harry Buck estate. It has ball bearings riding on the cam lobes. My crank and cylinder were fine, but the cam and most of the intake parts were missing. It is standard bore, and the guides and valves are in fine shape. I have spent the past year making missing parts, and am making great progress. I plan to have it at Davenport again, but this time with wheels and all the stuff made so far. Hope to have it running next year. I need about half of the hub/clutch parts. Nsu sold clutches to several firms, notably Bradbury. I have part numbers, but need drawings and measurements to make the missing items.

    • July 5, 2012 10:00 am

      Hi Bruce. I’m glad to hear that you’ve been making some progress on the NSU. I recall reading on the AMCA site back when you were looking for wheel rims and things. I don’t recall knowing anybody with a NSU hub clutch. I’ll think about it and see. Their two speed that went on the end of the crankshaft was a very popular fitment on early bikes, but that was a different animal I think. If anybody reading this can help, please send in a comment.

  10. Anonymous permalink
    July 30, 2015 4:27 am

    Pete, finally all parts are made for the NSU. It has steel balls that ride on the cam also. I was able to borrow an original stamped brass headstock badge, make a silicon mold and reproduce it in plastic with excellent detail. I am going to try to pour it out of tin and hopefully nickel plate it. I have spares if anyone needs an early NSU badge. I am now getting ready to paint and stripe. Hopefully we will be riding in the spring.

    • August 3, 2015 9:28 am

      Excellent! I’d love to see photos of your headstock badge, mold and finished parts. Maybe we can post them here to show the world how they might replicate that process with other parts.

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