WD Oil Pump Problem

Dougie · Post by **Dougie** » Tue Jan 29, 2008 6:01 pm

Dick H, I was very, very careful when rebuilding the engine. I don't think I have made any errors with gaskets etc. but, you can never rule anything out completely!

As for the time spent waiting to see oil circulation, I guess that it was no longer than 2 minutes at most but tried about 5 times. When the engine is virtually dry after a complete rebuild I didn't have the balls to risk it running any longer. Call me fussy but...

I will try the old trick of back-filling through the return side to get some oil in the sump. Once I am reasonably happy that we have circulation (however weak) I will feel bold enough to run the engine.

Crawsue, Dougie is our late father's name. It is used as an ID tag for the forum as we have joint membership. He also rode a WD Matchless in service in 1945/46!

woster · Post by **woster** » Wed Jan 30, 2008 4:16 am

As Don says these pumps are slow. If you do the math, at 1000RPM (fast tick over) the maximum (100% efficent) the high pressure side can pump is 3.876 cubic inches/minute=12.8864 tea spoons/min, or 4.295 table spoons/minute or 1 table spoon every 14 seconds.

At high speed, 6000RPM, max flow is 23.25 cubic inches/minute=75 tea spoons/minute or 25 table spoons/ minute, or 2.4 seconds/table spoon. You can dip the oil by hand that fast.
This is about .8 pints/minute

You can see why it takes so long at idle to pump enough to have oil to pump back to the tank, and fill that big old oil return hose.

paul knapp · Post by **paul knapp** » Wed Jan 30, 2008 7:14 am

Hell's Bell's!!
I think it would be easier just having ITMA's worry beads to play with.

crawsue · Post by **crawsue** » Wed Jan 30, 2008 7:21 pm

So,a quick go at the "math"(s)! on the back of a "fag "packet would suggest that if you change your oil every 4,516 miles...it will have been round the engine .....once! Hardly worth fitting an external filter then

woster · Post by **woster** » Wed Jan 30, 2008 8:21 pm

Actually I did the math to determine if 1/4 inch tubing is large enough for the oil return flow to and from a external oil filter. No problem!

Mounted oil filter between front down tubes, under magnito. Added benfits, added cooling, eaey change with no oil mess.

Sorry but I think if you don't have the best oil filter you can get you are missing one of the major reasons rubbing parts wear. Even on the oil return any dirt only gets one chance, then it's removed.

chris kelly · Post by **chris kelly** » Wed Jan 30, 2008 10:57 pm

"This is about . 8 pints/ minute"

Is this English pint or American pint?

Chris

woster · Post by **woster** » Wed Jan 30, 2008 11:28 pm

Didn't know there was a difference between English and American pints, its Imperial Measure. 28.875 cubic inches, or 16 fluid ounces.
Even if there is a differance would it change the conclusion that with a dry engine you need to run it for more than 5 mim to see oil return?

bjork · Post by **bjork** » Wed Jan 30, 2008 11:58 pm

No, the pints are the same, it's the gallons that got mucked about.

Back to the topic, 5 minutes would worry me too, but then I would have dropped about a 3rd of a pint into the crankcase and filled the return filter and pipe, just as Itma said before.
I read and re-read the original post and couldn't add anything that Itma and Biscuit had not already covered. So kept quiet before. It did seem to describe that the pump was not moving oil? The only thing that I could think to add didn't really fit what I thought I'd read.
But here goes anyway-
I wondered if the felt filter could be the fault? This happened to my bike when I bought a new felt element. The turned over felt at the top was blocking the outlet to the tank so hardly anything got through and the crankcase filled up. I just bought another new filter and the same thing seems to be happening there too and I even trimmed it back before I fitted it! Maybe I will just wash the original for the 1000th time and bung it back in!

Dougie · Post by **Dougie** » Thu Jan 31, 2008 6:25 am

Hi Bjork,

Good suggestion but I was already onto that.

I intially didn't even put the filter in so that I could look down the filter chamber and watch for oil returning.

I have also trimmed the top "collar" of the filter just in case.

Going back off the subject again, if English pints are the same as US pints, and there are 8 pints to the gallon for both English and US gallons, how is there now a difference between the two gallons?

I think you'll find that an English pint is 20 fluid ounces.

That equates to more beer!

But it don't make no difference to the oil "conundrum"!

crawsue · Post by **crawsue** » Thu Jan 31, 2008 12:57 pm

Winton,would it be possible to post pictures of your oil filter modification? There have been numerous threads in the forum over the past couple of years,with different answers to the problem.