Monday, November 25, 2013

Airhead top end rebuild

It's an '88 R100RS.  Problems are soggy performance and exhaust clearances tightening up very quickly.

Here is what the exhaust valves look like at 117 thousand miles.

I will be posting the entire rebuild along with some performance rework of the heads.

Sunday, November 10, 2013

T100R finished

It is ready to go back into the frame and after break-in will be returned to the owner. 
I want to take this opportunity to thank Mitch Klempf and Chris Stubbs at Klempf's British Parts in Minnesota.
These guys unquestionably are the benchmark of customer service and knowledge when it comes to parts for vintage British motorcycles, they really know their business and are an absolute pleasure to deal with.
They can be reached at:

Here are a couple photos.

And here are a few photos of what I found when tearing this engine down in preparation for the rebuild.

Incorrect clutch basket thrust washer
Worn valve guides
T100C pistons
The bigger Daytona valves made their own clearance.

The seller claimed that this engine had never been apart, if I had a dollar for every time I heard that one....

Thursday, November 7, 2013

T100R transmission

The trans was in pretty good shape except for the kickstarter pawl and the high-gear bushing where the seal rides on it.  But since it was apart I also replaced all of the bearings, bushings, seals and thrust washers along with the indicator plate which was worn completely bright.

The right-side trans support plate cleaned, refinished and the mainshaft bearing bearing installed.
Here is the mainshaft high-gear showing the groove that the seal has worn into the bronze bushing.
The old bushing removed and the new bushing.
The new bushing is installed and honed to fit the mainshaft.

T100R engine final assembly

New valve springs installed and the copper rockerbox gaskets are in place.  The reason I'm using solid copper gaskets is that the inner head bolts pass through the rockerboxes and a composite gasket would compress thereby altering the torque on the inner headbolts.

The rockerboxes are secured and the head bolts are torqued so now is a good time to adjust the valve clearance.  Since this is an early Daytona it lacks the access plugs in the sides of the rockerboxes that allow a feeler gauge to be inserted to measure the valve clearance.  There isn't really any room to use a feeler gauge accurately so I set up the dial indicator and used that to measure the valve lash.

Then the rockers are pre-lubed before placing the oil pipe bolts into their holes for safekeeping until the engine goes back into the frame.

The timing cover is installed with a new seal and it's time to move onto the transmission.

Tuesday, November 5, 2013

T100R top end assembly

The cams and timing gears are installed.  The Daytona cam timing specifications differ from the other T100 models which is why the cams are installed using the dashes rather than the dots.

  I lightly chamfered the backside if the cam gears in order to ease their installation.

 I also had to replace the intake cam due to some "mechanic" in the past using a hammer to install the gear and causing large chips on either side of the key slot.  Always use the proper tool for removal and installation of the timing gears.
The proper tool:

 The WRONG tool:

Pistons, tappets and cylinders are installed as are the timing gears.  Now I will install the degree wheel and pointer along with a dial indicator in order to precisely locate top-dead-center (TDC) in preparation for checking piston-to-valve clearance at TDC of the exhaust stroke, which is the overlap period where the exhaust valve and intake valve are both open.  During this period of crank rotation the exhaust valve has not fully closed, while the intake is starting to open.  It is at this point that the valves will be in closest proximity to the piston.

 To find TDC the degree wheel is mounted to the crank at roughly TDC and the dial indicator is mounted to the cylinder deck surface and set to zero while contacting the piston crown.
The pointer is adjusted until the degree wheel reads the same number of degrees on either side of the TDC mark with the piston .050" down in the bore.

 Now that TDC is accurately established, I install an intake and exhaust valve with lightweight checking-springs and temporarily assemble the head onto the engine with gaskets, pushrods and rockerboxes.  The valve adjusters are set to zero lash with the piston at TDC on the compression stroke and the dial indicator is set up on the head.

  Then the engine is rotated forward 360 degrees to TDC on the exhaust stroke and the dial indicator is set to zero while bearing on the valve adjustment screw.  Now the exhaust valve rocker is depressed until the exhaust valve makes contact with the piston while observing the amount of travel on the dial indicator.  The minimum piston-to-valve clearance is .040".  Since this engine was built with stock valvetrain components and pistons the clearance was not an issue, but it always pays to be sure, especially when dealing with a head that needed to be straightened and trued.
 Then the process is repeated for the intake side.

Now the actual valve springs can be installed and final assembly of the top end can commence.

You might have noticed the intake "manifolds", they are the stock pieces machined for spigot-mounted carbs.  No, the owner doesn't want Amals.