How my bike stopped wet sumping!

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Sep 15, 2005
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Hi I,ve been meaning to post this for a while but never got to it.
This will get some brain matter up & running trying to figure out why it stopped wet sumping!
This winter I put Total Seal piston rings in my 74, 850, and put the recommended valve seals on both the intake& exhaust valves as recommended by Total Seal.
I did not hone the cylinders as they looked perfect, instead I installed the rings dry, no oil except on the piston skirts.
I did a normal start up & break in. Later I noticed that even when the bike sat for a month that there is no evidence of the wet sumping that I used to have. I have not had to drain any oil from the crank case since, and there is zero oil consumption and the sparkplugs are always a light grey color.
I'm running a Lectron 40mm carb on a Drouin supercharger, Bike runs
great. So why did the wet sumping stop??
Bruce MacGregor
Wakefield RI :roll:
Fresh oil seems to result in lower consumption and if it is retaining its viscosity, it will drain less quickly. Could it be that the new rings are keeping the oil freer of contamination which is extending the interval before it degrades ?

Or is it so much fun that you're riding it more often than you think ? :)
79x100 said:
Or is it so much fun that you're riding it more often than you think ? :)

Indeed, I've been riding my 750 at least twice a week this summer and wetsumping has not been a problem! :D

Did you remove the oil pump at any time? Sometimes the face joint between the pump and crankcase can cause excessive wet sumping. Rings and valve seals cannot have any effect on this problem.

A Drouin? Can you give us your experiences with it? How long have you had it? Problems?
Ron L said:
Did you remove the oil pump at any time? Sometimes the face joint between the pump and crankcase can cause excessive wet sumping.

Also a timing cover gasket that is damaged around the crankcase relief drilling would allow oil to drain directly from the tank to the sump (even on an 850 Mk3 with no corresponding drilling in the timing cover) replacing the damaged gasket with a new one when refitting the cover could suddenly halt a drain down problem?

An oil pressure relief valve stuck open would also allow the oil to bypass the pump, causing a rapid oil drain down, but not on a Mk3 this time, (or any other model fitted with a Mk3 timing cover) the problem would miraculously disappear if the valve started working properly again?
Incidently, I was at Norman White's the other week to get a few things sorted on the MK111 and he noticed it was fitted with an anti wet sump valve, like this one on the ES2 (bottom left of pic) ... C05772.jpg

he said he's rebuilt around 30 engines because of these valves. I told him that I was intending to replace the black oil lines on the Commando with clear plastic ones like the ES2 as I can then see the oil circulating instantly on start up. He more or less nodded approval at this.

On second thoughts, it may have been a resigned shrug :oops:

Be careful clear pipes have been known to pop due to hot oil. But then again there might be some heat reststant pipe available.
The typical "clear" tubing is polyvinyl chloride. This material requires a plasticizer for flexibility. Unfortunately, this plasticizer is soluble in hydrocarbon solvents (gasoline and oil) and it is leached out of the tubing over time. This is why your fuel lines become hard and dark after a few months of usage. Once hard, they split fairly easily.

I have been using polyurethane tubing to make fuel lines. This tubing generally has a blue cast to it, but doesn't seem to darken like the PVC and stays flexible.
I have an anti sump valve and use a pressure gauge mounted front and center on my top yoke to make sure the valve is not sticking, which from this site appears to be a common approach. I have been castigated by other Norton owners for even having an anti sump valve on my bike, but I have never seen first hand an engine being damaged from a stuck valve, nor have I nor anyone I know of had this happen to them. I appreciate the potential danger, but I've also seen engine damage due to clogged internal oil passages, lost sump plugs, metal debris due to broken internal parts, broke oil lines, etc. Wet sumping is a pain in the ass and I would rather deal with it with an anti sump valve and a gauge, than leave these off and have to deal with the sumping....I second Ron on the polyurethane fuel line, I now use it on all my bikes (Parts Unlimited - sold in 5' rolls on Dennis Kirk). It will yellows somewhat after several months, but never clouds over like almost all other fuel lines I have used, and remains pliable for much longer.
I've only ever came across two motor failures due to fitting anti drain valves and in both cases the valve had been installed the wrong way round.
For me it goes against the grain to suck a valve open, however Vello's don't have a problem.
FWIW, CNW is now fitting anti-drain valves on their builds. Doug McCadam told me he feels the valves are safe IF properly installed - pump, valve, and oil line below the valve all primed with oil. His opinion is that the failures are caused by incorrect installation.

I have an RGM anti-drain valve that's been sitting on the shelf for a couple of years. I've been afraid to install it because of all the horror stories, but I do have an oil pressure gauge and dealing with the wetsumping is pretty annoying. I'm tempted to give it a try. I might wait until I have that spare engine put together though! :lol:

As for fuel lines - I'm also using the blue polyurethane line from Dennis Kirk. Works great for me! No more ugly, thick, black inflexible automotive fuel line for my bike :mrgreen:

Now, back to our regular topic, whatever it was...

I made my own anti-sump valve starting with an airline check valve, the strength of the spring is important, too strong and the pump can't pull it open, too weak and the seal is not made properly when stationary. Once I had the spring rating correct I could blow it open with my own lungs.
Well, back to fuel lines for the moment..

You can also get silicone based fuel lines at hobby stores. (for the guys with the 1/8th scale B-17).
I believe it would work well with gas and alcohol, also I use it for my brake bleeder as it doesn't ever seem to harden and break so it fits well on the bleeder nipples.
It may well be the type of material found in small engines like chainsaws.
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