45" lifter block press fit, why?

[BigLakeBob]

Can someone tell me the reason the blocks are a press fit in the case? Wouldn't a .001 slip work just as well? BT OHV are slip, if I remember right Sportsters are a slip with an o-ring. Why are side valves a press fit?
Thanks.

[Rubone]

Just my guess but I believe it would be to prevent side to side deflection in the case since the valves do not operate at a true perpendicular position relative to the adjuster face.

[T. Cotten]

Can someone tell me the reason the blocks are a press fit in the case? Wouldn't a .001 slip work just as well? BT OHV are slip, if I remember right Sportsters are a slip with an o-ring. Why are side valves a press fit?
Thanks.

I was taught, Bob,..

Metal moves.

So motors survive longest, and produce the most power, when everything is as rigid as possible.

Have you measured the interference?
My thumbs are: A half-thou more or equal to the bore is a 'light press fit". A half-thou clearance can be a 'slip fit', and a full thou would be running clearance if it spun.

I'd hope for a thou and half of interference!
(They always slap-hammered in and out for me like a valve guide.)

....Cotten

[Paps]

The blocks are iron and expansion is very little. The cases are aluminum and expansion is massive.

[T. Cotten]

The blocks are iron and expansion is very little. The cases are aluminum and expansion is massive.

And didn't Sports have aluminum 'blocks', which wouldn't need any interference?

Good point, Paps!

....Cotten

[kitabel]

As a general (and sound) engineering practice, Harley-Davidson "clocks" (rotates) the tappet block in the 4-cam (D, R, W, G, X, V, U) right case half to align the tappet adjuster, cup, etc. with its destination.
Sportster pushrods are somewhat limited: the distance between the tappets (inherited from the 45) and the rocker arm sockets (in the XL box) are different, so exactly parallel is not possible.
In flathead engines (at least since 1929) the valve stems of each cylinder are parallel to each other, but "tilted" w/r/t the bore axis (each cylinder is inclined 22.5° from absolute vertical: the front angles forward, the rears angle back): the valves are inclined toward vertical (rears angle forward, fronts angle back). The tappet blocks are clocked to match this.
This has resulted in some interesting disappointments when amateurs attempt to make a Sportster right case from a K (written up in Easyriders? Iron Horse?), and discover that the K blocks inherit the flathead tappet clock angle, but the Sportster does not, resulting in very odd pushrod angles (and of course the cam event are all wrong). The fatal blow, of course, is the K tappet block inclination inward toward the center of the engine (to match the K tapered lobes) which causes the tappets to chew the Sportster cams to pieces.

[chuckthebeatertruck]

And didn't Sports have aluminum 'blocks', which wouldn't need any interference?

Good point, Paps!

....Cotten

Early sportsters had iron tappet blocks. They are a holy grail for speed freaks. Long lasting, easy to size, quiet in operation, and very consistent when HOT. I have a set on my 59 that I wouldn't consider replacing with alloy, ever.

That said, early sportsters, alloy or iron, do not have slip fit blocks. They are a light press fit and require a tool to pull. They have two grooves on the sides of the blocks for the tool's claws.

I will have to double check, but I recall the xr handbook stating clearly to polish to light press fit. I don't ever recall seeing slip fit specs.

That said, I remember working on my first btsv and thinking "wtf" when I went to pull the blocks. I had never experienced that fit, and it was an eye opener to a young, inexperienced mechanic.

[T. Cotten]

The pullers needed to push upon the cams, right, Chuck?

That's why I 'slapped' them out.

....Cotten
PS: Alloy tappet blocks, both Big Twin and Sports, tended to embed grit, that then wore the tappet quicker than the guide.

[chuckthebeatertruck]

The pullers needed to push upon the cams, right, Chuck?

That's why I 'slapped' them out.

....Cotten
PS: Alloy tappet blocks, both Big Twin and Sports, tended to embed grit, that then wore the tappet quicker than the guide.

Yes, that is correct. What sucks is that the ears of the alloy blocks occasionally break off when using the tool. That becomes frustrating. Solution is to knock them out from the inside with a wooden dowel :-)

To be clear, I don't own or work on 1000cc ironhead sportster models, so I'm not sure if there were additional changes, etc.

I strongly believe the excessive wear from embedded grit is caused more by poor servicing habits than anything else. Put simply, there is often a large amount of crap around the lower push rod covers that shadetrees and even many professionals overlook. Failure to clean all of that off before opening up the cover is the surest fire way I know of to introduce grit. Indeed, the iron guides can survive this with far less issue.

On early sportsters, the issue is compounded by the type of block and the type of lifter. There were several variations and most of the aftermarket offerings that are labeled as "performance" upgrades have differences from OE parts in alloy choice, tolerances, oil grooves, etc. Sadly, many people poo-poo 900 sportsters because they don't understand these quirks and blame the design when the failure is actually caused by someone "assuming" this or that "new" part is an "upgrade."

As my sportster mentor constantly reminds me . . . when in doubt, do it like the factory.

Just another one of those odd quirks that makes these motorbikes a life long learning experience. Just when you think you know something . . .there's another corner to peer around.

[chuckthebeatertruck]

And, I love the slide hammer. Here are two photos I snapped several years ago whilst stripping a sporty motor.

In photo one, I have the claws "held" in by a hose clamp -- and the second is that same tappet removed. Note it is a cast iron block :-)
DSCI1032.jpg

DSCI1033.jpg

It's almost as bad as my "tool" for pushing the crank out of the left case half . . .until I added a press to the home shop, the old scrounger plate worked just fine :-)

DSCI1055.jpg

[T. Cotten]

To be clear, I don't own or work on 1000cc ironhead sportster models, so I'm not sure if there were additional changes, etc.

I haven't touched a Sportster in nearly a quarter-century!

I strongly believe the excessive wear from embedded grit is caused more by poor servicing habits than anything else..

Its called "Sportster Disease", Chuck.

....Cotten
PS: Symptoms include a loose nut on the handlebars.

[BigLakeBob]

Thanks for all the replies. So what is the procedure to change a tappet gasket on a 45"? Remove the head and corresponding valve or does the cylinder need removed? And what is the best tool to remove the tappet block with the motor still in the frame? Thanks.

[tasturbo86]

tappet

You probably figured this out by now?
I don't remember if the cylinder has to be off, but thinking yes.

https://www.jpcycles.com/product/910...de-puller-tool