Thursday, November 7, 2013


I have spent so much time dreaming about the day when my Chief bottom end was finally put together for the final time.  Well, it's here!

This first picture shows the cams in and correctly timed:
This next picture shows the new pushrods, and also illustrates a problem.  I had too little clearance even with the adjusters bottomed.  I called a fellow Indian afficionado who has already saved my bacon once!  He asked me if I had the "thick" or the "thin" lock nuts...

Turns out I had the thick ones:

 So Duff saved me by sending a set of four thin lock nuts, as shown below.  Between these, and some home made .025" cylinder base gaskets, I got the clearance I needed.

I hope to be able to install the rings, and button up the cylinders this weekend.  Stay tuned for further developments!!

Monday, October 7, 2013

Relieving the cases for 80"

When I discovered I needed to replace the flywheels I decided to go from 74" to 80" displacement.  This involves several small operations, most notably buying flywheels with a 3/8" increase in stroke.

As mentioned in previous posts, the piston skirts needed to be shortened by about 0.250" and the heads had to be milled to clear the pistons at TDC.

The other modification involves relieving the cases to clear the rods at the front and back.  Bitmonkey helped me do this gingerly by hand with a file.  We checked it by assembling the pistons on the rods and crank, and then put the cylinders in place on just the right (pinion) side case half.  We ended up taking off about .125" from the front of the front cylinder opening, and the same amount off of the back of the rear cylinder opening.  I was worried about clearing the lip on the cylinder, but it was fine, and we didn't have to relieve between cylinders either:

Once we got the right case half relieved, we simply relieved the left case half to match.

This pic shows how far down the pistons are at B.D.C.   The skirt actually extends about 3/8" below the cylinder, and comes within about .100" of the case.

The final thing I checked was the clearance between the scraper and the flywheels, shown below.  It's supposed to run within about .025" , and I bent it up until I got the clearance right.  Apparently this scraper is a 1947 only feature, intended to make the scavenge pump work better.  In 48 and later, they cast a special channel in the case halves to accomplish the same thing, so I guess it worked!

Sunday, September 29, 2013

Crank be true!

Many aspects of the engine rebuild have been intimidating, but none so much as the equally black arts of balancing and truing the crank.

I hired out the balancing to Truett and Osborn.  They have been in business since 1974 or so.  I am confident they have figured it out by now.  The work looks very thorough.  Time will tell.

For the truing, I relied on the expertise of Fuzzy Jamison, owner of Classic Thunder, a fellow Seattle Cossack, and a good friend.  I also brought BitMonkey for moral support.  We used Fuzzy's  beautifully built ($$$) Rowe truing stand. 

Here's a little theory.  I read and re-read my Revised 2nd edition copy of trusty "Motorcycle Mechanics and Speed Tuning", circa 1939.  There are three distinct ways in which the crank may be out of true (probably more if any of the parts are damaged).  They are:
 A. This first kind of misalignment will result in peak readings when the crankpin is at the top or bottom (above or below the drive shaft and pinion shafts), or very nearly so.  The "fix" involves a well-placed "rap" (or multiple raps) with a lead or brass hammer on the outer surface of the trailing wheel, more or less 90 degrees from the crankpin.  DO NOT do this with the crank in the truing stand!!

Watching someone beat on your immaculate flywheels is like watching an orthopedic surgeon set your child's femur.  Not for the faint of heart.  Get it as close as you can in this direction before going on to "B" or "C"...

Both "B" and C" will result in peak readings when the crankpin is near the same level as the drive shaft and pinion shafts.

"Motorcycle Mechanics" suggests a wedge to correct the misalignment shown in "B".  Fuzzy has ground a 5/16" nut and bolt to exactly the right length to slip in between the wheels, and he spreads them with a pair of wrenches.  Very controlled and precise.

"C" illustrates the need to squeeze the wheels at the arrows.  "Motorcycle Mechanics" suggests a vise for this, but Fuzzy used a large C-clamp.  Again, very easy and precise.  

We were very careful to loosen the dead centers on the truing stand each time we squeezed or spread the flywheels.

Eventually Fuzzy figured that Bit-Monkey and I wouldn't hurt ourselves, and left us to our own devices.   With about 2 1/2 hours invested, we got the crank to .0005" (half a thousandth) on each side.  The Indian Overhaul Manual calls for a maximum runout of 0.001.  I am very pleased!!

Thanks very much to Fuzzy and BitMonkey for the help.  I can't wait to see how it runs.

Monday, June 24, 2013

Balance Factor

Blog readers will know I am working on understanding balancing crank assemblies.  This was stolen shamelessly from Jockey Journal.

Seems like a 60% balance factor keeps coming up.  S&S supposedly uses 60%, and Paul Osborn (from Truett and Osborn) told me he uses 60% unless the customer specifies otherwise.

Saturday, June 1, 2013

Barn Fresh

This one is just perfectly crusty. It sure makes me want to hear yours running again.

Wednesday, May 29, 2013

Stroked to 80"

Well, I have come to a momentous decision...  Because of my flywheel troubles (see previous post), it was recommended to me that I would be better off replacing the old flywheels with new ones.  Since the primary cost of upgrading from 74 cubic inches to 80 cubic inches is the flywheels, this caused some serious reflection...

The stock 74" has a bore and stroke of 3.25" x 4.4375".  The 80" (Indian's last ditch attempt to resurrect flagging Chief sales against the Panhead) came out in 1950.  Applying creativity in place of development $$$, Indian achieved the 80" by stroking the 74" by 3/8", to 4.8125".  This necessitated three (or maybe four) relatively simple changes:

1) Replace the flywheels
2) Shorten the piston skirts 1/4 inch to keep them from hitting the case at BDC

When I compared my new 74" pistons to the old pistons that came out, I was curious as to why the old skirts were shorter...  Turns out they were 80" pistons!  Just for the record, the old (80") pistons have a total height of just under 3" (2.995").  The new 74" pistons have a total height of just over 3.25" (3.255"). 

I'm not sure I have the guts to throw the new 74" pistons on the lathe with my remedial machinist skills.  I think I will try to exchange them for 80" instead.

3) Cut a recess into the heads to accomodate the piston at TDC, now sticking up 3/16"

This is my stock 74" head.  note the lower part of the combustion chamber is flush with the gasket surface.

This is an 80" head.  Note the cutout at the bottom, to accommodate the "pop-up" piston.

I may also need to relieve the cases at the cylinder bases to clear the rods a little bit, not sure yet.  I am told the stock cams and followers will work just fine in the 80", although  several different "hot" cams are available, with names like Bonneville, Shunk, and Ollie.

I took the plunge.  I ordered 80" Kiwi Flywheels (manufactured by Truett and Osborn) today, and also sent my heads off to be machined.  Hope I don't regret this!

Tuesday, May 21, 2013

Crank woes

I apologize in advance to the casual lurkers.  This post will be pretty esoteric.  I am trying to solve a couple of flywheel problems and want to share some pictures:

Problem 1: The crankpin does not pull through as much on the drive side as the pinion side, which appears to cause excessive side play at the rods when assembled with .067" thrust washers.

This picture below shows the pinion side of the crankpin, torqued.  Crankpin end is about .033" below the nut face, not too bad:

This picture shows the problem end, the drive side crankpin end.  Crankpin end is about .067" below the nut face, fully torqued.  Note exposed threads on nut...

By reversing the pin, I concluded that the problem seems to be in the drive side flywheel, and not asymmetry in the crankpin itself.  The taper (hole) in the drive side flywheel seems to be of too small diameter.  This would also explain why the wheels seem too far apart, and very thick thrust washers would be required to get the proper .020" side play on the rods.  Might also explain why I found that the last rebulder ground down the drive side case race on the inner surface with an angle grinder (to try to get proper crank end-play with a too-wide crank, I would guess).

Here is a photo of the outer surface of the drive-side wheel.  Note the "Z-metal" mark and that there is no stamped timing mark.

Below is the outer surface of the pinion side wheel.  This one has a problem too.  When I insert and torque the new pinion shaft, and then mount it in the lathe to check that the wheel is true to the pin, I get about .015" wobble at the outer diameter. 

Note the Z marking and the "84" casting tag.  Note also that the balancing hole at the top of the picture is the only hole on this wheel, and the other crank has no balance holes drilled anywhere.  The lack of drilled balance on one side makes me wonder if the wheeled are mismatched.

Close-up of the crooked pinion shaft taper.  I hope I can lap the new pinion shaft with a carefully indexed Bridgeport and straighten this taper...
Pinion side wheel, inner surface:

Drive side wheel, inner surface:

 Close-up of casting marks on pinion side wheel

Another close-up of the pinion shaft taper, Note wear on lower right, although the pinion shaft pulls in tight, just not quite true.