Oilways in crankshaft T35

[douglas1947]

I´working on a 90+ and MK4 and stationairy crankshaft.
There is the advise to make the oilways inside the 1. crankpin and the middle web clean from oil mud (see John Holmes T35 INFORMATIONS and Neville Heath SPANNERAMA).

When I had dismantled the 90+ crankshaft and looked to crankpins and they were in real good condition; also some oil in the rollers.
So I blow compressed air through the oilholes of the middle web and 1.crankpin.
The air passed through beautifull!

Today I wanted to put out the oil plugs in the pin. I tried in old manner to ore a hole in one and push the other one out trough that hole.
But I find an other kind of plug.

So I pressed out the "double plug" and was SHOCKED, when I saw the dirt in it.

It was complete closed with dirt, only the compressed air made a channel in the dirt!

Yes, it is very good, to clean the oilways when you have the engine dismanteled!

Is the "double plug" on the 90+ crankpin normal, or is it a modification of a pre owner of the bike?

Michael

(on IMG 1879 you see "double plug and normal plugs of MK4 crankpin)

 

[eddie]

Michael,
             Mr Douglas used 3 different arrangements for plugging the crankpins between 1946 and 1954. There was the single alloy dumbbell plug, 2 short alloy plugs (fitted from either end of the crankpin), and 2 short steel plugs (again fitted from either end). Each type seemed to be used as available, and were not matched to any particular model. The advantage with the single dumbbell was that it could be pushed out, complete with the solidified sediment, rather than forcing it into the oilways.
    When you come to dismantle the 'Plus' crank, if you find it still has the original stepped crankpins and 3/16" rollers, the pins will probably have oil holes that feed the oil direct to the big ends. If this is the case, make sure you rebuild it with the correct endfloat on the front conrod (it should be about .006"). When the endfloat becomes too large, most of the oil gets thrown out of the front big end, and starves the back one, causing it to fail prematurely.

  Regards,
                Eddie.

[douglas1947]

Eddie,

thanks for your reply.
This 90+ (you know it is a very early one) has a plain crank pin and 24 rollers 1/4" x 1/4" on each pin with oil coming on the side from mid web.

On the middle photo there are dumbell plug + 2 single plugs of a MK4 engine.

With single plugs, there is much more oil (and space) in the 1. crankpin. Is this better?

Michael

[eddie]

Michael,
             If your 'Plus' crank has plain pins and the oiling from either side of the centre web, it is basically a 'Mark' crank with the longer front web to accommodate the ballrace main bearing. With this configuration, the oil only goes as far as the centre web and then feeds each big end from the sides of the web. Obviously, the oil should not be allowed to become so dirty that it deposits sludge, but some sludge will be deposited by virtue of the spinning crank acting as a centrifuge - this will be aided by the sudden increase in cross section of the oilway through the crankpin allowing the oil to travel more slowly. Anything that partially fills that void will reduce the tendency to deposit sludge - I have even contemplated a trial with a 5/8" solid plug with just a 4mm slot along the side to feed the oil to the centre web without allowing it to slow down too much!

  Regards,
                Eddie.

[douglas1947]

Eddie,

I understand you, you would prefer a modification and use a special solid plug with a (f. ex. 4mm) small oilway in it, to have a higher speed in oil flow in the crankpin to reduce a deposit of sludge?

Michael