1935 R Model

[Tomz]

My 1935 R model is overheating and seizing I’ve replaced and tested intake seals replaced copper with peek, rebuilt engine, after it seized Seized again after putting back in bike. Has anyone seen this problem? Could something be bad in oil tank?

[Steve Slocombe]

Dear Tomz, the R models are like the VLs and run hotter than the later small twins. They were also not fitted with oil rings on the pistons until later. The 1934 T-slot pistons were given a factory clearance of one thousandth in the bores, which is way too tight if you use later style pistons. I would try again with say 5 thou clearance on the front piston, 4 on the rear, and no oil rings. The oil level is also important, and the pump needs to be adjusted so that you start and finish a run with say 6 ounces of oil in the crankcases.

[Tomz]

Thank you Steve, it seems like not too many people have experience with the R. I’m going to slowly investigate this before I put in new pistons. I appreciate any thoughts you might have

[T. Cotten]

So many folks get false-negative results bubble-testing, TomZ,..

That you must forgive me for asking, but you didn't use a tire pump, shop vac, or air mattress gadget for pressure, I hope?

Other common mistakes are a Schrader valve in the test plate, and failing to wait a minute for the tiniest leaks to present themselves. It is prudent to then turn the motor through to pressurize the combustion chamber, so the sparkplugs and headgaskets can be inspected.

If you do tear down, please measure your ring drag by slowly pressing the piston through the cylinder placed upon a scale:

ringdrag.jpg

As Steve infers, modern oil control rings produce significant friction.

....Cotten

[Tomz]

I used an air compressor the copper seals were leaking terribly. I’m going to have to tear down again this will be my 3rd set my clearance on first rebuild was 1000 now it’s 4000 front and back. How much pressure should it take to push the piston through?I used Hastings rings. It freed up after it cooled down. I have a heat measuring gun and don’t intend to let it get too hot because I want to see if the cylinders are oiling. I took it to get it repaired and evidently it was above their knowledge, cause they let it seize. Thanks for any advice

[Steve Slocombe]

Dear Tomz, I would hone another thousandth out of the bores and leave out at least the front oil rings this time. The flywheels turn clockwise seen from the right, so plenty of oil is flung into the rear cylinder, with the hotter-running front always struggling. Indian and Thor ran an oil line to the bottom of the front cylinder, but Harley relied on the crankcase baffles. The theory was that a more closed front baffle generated more suction to pull up oil mist. Many owners knocked out the VL and RL baffles after 1940 when they were removed on the recirculating oil models. When you're done you need to set the mechanical oil pump. For 1935 it is the same as the VL, so check the advice in my restoration book.

[T. Cotten]

I used an air compressor the copper seals were leaking terribly. I’m going to have to tear down again this will be my 3rd set my clearance on first rebuild was 1000 now it’s 4000 front and back. How much pressure should it take to push the piston through?I used Hastings rings. It freed up after it cooled down. I have a heat measuring gun and don’t intend to let it get too hot because I want to see if the cylinders are oiling. I took it to get it repaired and evidently it was above their knowledge, cause they let it seize. Thanks for any advice

Copper, Tomz?

Original manifold seals were brass; Any leakage will cause overheating of at least one cylinder, if it runs at all.

We should not blame the burnt rings if the fuse was lit elsewhere. Running with a leak should be avoided entirely.

Honestly, its been a couple of decades, and I do not remember any specs for ring drag, and worse yet, I cannot remember how we reduced it! So I must defer to today's motor builders.

....Cotten

[dukekleman]

Tomz,
I prefer to use a digital scale on the lines of what some refer as a fish scale. Install your piston assembly with the wrist pin in the piston. Use the hook on the scale to pull on the wrist pin. Note your drag rated in pounds over the stroke length. The poundage will vary based on the piston ring design you use. Refer to the piston ring manufacturer for the proper specification. Also ask them about the correct cross hatch angle, RA, RVk and RPk. Having these numbers correct allows the correct amount of oil lubrication and drainage. If your engine machinist doesn't understand the numbers provided by you from the piston ring manufacturer, please find another source. Hope this helps...
Duke

[T. Cotten]

I tried pulling on the pin, Duke!

Couldn't do it without clamping down the cylinder,...

Didn't have time for that. (Much less keeping the scale hook in the middle of the slippery pin.)

So how do you reduce oil ring drag? Thanks!

....Cotten

[dukekleman]

I know what you mean about the slippery pin. I install a piece of viton tubing over the hook. Works very well. One other method I've taught techs was to use the belt tension gauge (elevator tension gauge) and then you can push verse pull if preferred...
The typical method of ring drag reduction is to use a thinner piston ring. This is done when manufacturing and designing the entire piston and ring package. This is of course for performance orientated engines. Longevity has been increased on these types of designs over the years with cylinder finish methods. Typically on long service/mileage/EPA motors a higher pound of package is used.
Whether it's a low friction ring package or a higher friction ring package the Cross hatch angle and RVK and RPK will vary along with piston ring material. Most people are rebuilding these older engines with more modern materials and components, including modern engine oils as well. These older engines control combustion efficiencies quit well when equipped with modern materials and methods. Spark plugs stay clean which means a lot of other things are working better behind the scenes. Including fuel economy,
Duke

[T. Cotten]

... I know what you mean about the slippery pin. I install a piece of viton tubing over the hook. Works very well. One other method I've taught techs was to use the belt tension gauge (elevator tension gauge) and then you can push verse pull if preferred...

Yeah Duke, bathroom scales are probably all digital now anyway.

...The typical method of ring drag reduction is to use a thinner piston ring. This is done when manufacturing and designing the entire piston and ring package...

"Typical" doesn't exist in our world, Duke!
We can make the ring lands larger, but otherwise we must commission fresh pistons. T'aint practical if they make you buy four or more. (And forged offerings demand a rebalancing.)

Ever mess with the expanders? Sometimes you gotta.

...Spark plugs stay clean which means a lot of other things are working better behind the scenes.

Don't look now Duke,...

But that's the P4gas that keeps them clean!

....Cotten