Wet sumping cure - oil flow rate query

I have a newly acquired Fastback with nice provenance and fully rebuilt but inevitably wet sumps. I have read with great interest the various ways of overcoming the problem and was going towards the in-line spring loaded valve until I read about the problems some have experienced with them, including someone local to me who had his engine seize using one.
So, I sourced a nice looking brass ball valve on / off tap to put in line, sold suitable for the 5/16" oil line. However, on receipt I find the orifice in the ball valve is only 4mm, so I bore it out as far as possible to 1/4". So, for ease of calcs let's say oil flows from 8mm bore down to 6mm and then back to 8mm, a 25% reduction in diameter. Hold on a moment though, perhaps it is not that simple? The area of the 8mm bore is pie x radius squared = 50mm2. The 6mm is pie x radius squared = 28mm2 i.e. a whopping 44% reduction!

Whilst I think it likely a 25% reduction wouldn't matter, if it is indeed 44% that probably would. I am neither a mathmatician nor an engineer so would be grateful for opinions before I use this. I think if I managed to find one with a 5/16" actual bore it would be too big and look a mess.

A tap in the oil line?

Don't be a bloody fool.

I though the whole point of a tap in the oil feed line was to reduce flow :?

I'm with Triton Thrasher on this, it can only end in tears!

Another way to deal with wet sumping is to let it happen.

Then if you still have to worry, worry yourself about the oil getting back to the tank more efficiently on start up. Consider a sump level reed valve, a la Jim Comstock/CNW.

Even my MKIII will wet sump. Generally not too fast but over time it certainly will. Occasionally it will wet sump quite quickly; perhaps a piece of carbon holding the timing cover valve open. The spring is verrryyy light.

Anyway, I just let it do it! If most of the oil is gone from the tank I'll drain the sump and pour it back in.

It seems that many supply side anti sump valves, whether automatic or manual, have been a disaster.

There is a mod that both blocks the outlet like the MKIII AND seals the oil pump. It's not all that expensive and seems fool proof.

+10 on what tritonthrasher said. Put something in your feed line? thats just plain crazy. Is there a need to? a big fuckin NO.

madass140 said:

+10 on what tritonthrasher said. Put something in your feed line? thats just plain crazy. Is there a need to? a big fuckin NO.

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How do you really feel?

All the fatalistic warnings aside, there are a couple of ways to put a valve in the line without any threat to the motor.
I've been running one for a couple of years now and that setup will still be working when all of us old guys are done and gone. It's 3/8 right thru, so there is no added restriction.
The only ignition key stays stuck in the closed valve until the rider opens the valve. The bike won't run without oil on.

I would try the AMR mod first, apparently it works, or works well enough about half of the time.


Glen

Certainly everyone has a right to their opinion,... IMO, commando's have more than one design problem than just wet sumping. The good thing is that using a Comstock sump breather solves the oil leak down problem AND the crankcase pressure problem at the same time. The reason that parallel twins have a history of being leaky bikes is related to trying to seal a crankcase that develops a lot of internal air pressure. The comstock breather relieves this pressure... It couldn't be any simpler to cure the crankcase pressure issue and pump the sumped oil straight back to the oil tank when you start the bike...

*I actually don't have a comstock breather because it doesn't fit early framed bikes because of a crossmember on the frame, but if it fits your bike you should get one and forget about blocking the oil lines with some mechanism.

worntorn said:

snipped The only ignition key stays stuck in the closed valve until the rider opens the valve. The bike won't run without oil on. snipped
Glen

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Could you post of photo of this "key with the valve" setup?

On a Vincent special.

This works. I had it done to my bike several years ago. It was a bad wet sumper. Would drain the tank in a couple of days. You may still get some leak down with this. If I let the bike sit for a month it will be to the bottom of the dip stick, but still safe to start. I once let it sit for 6 months and had to drain the sump. Not perfect but a huge improvement for very little cost and work. Unlike a check ball on the inlet side this places it on the output side so you have full pump pressure opening it instead of relying on suction. Similar to a BSA internal check ball.
http://www.amr-of-tucson.com/nortech.html

fastbackboy said:

Whilst I think it likely a 25% reduction wouldn't matter, if it is indeed 44% that probably would. I am neither a mathmatician nor an engineer so would be grateful for opinions before I use this. I think if I managed to find one with a 5/16" actual bore it would be too big and look a mess.

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A slight reduction (say up to 20%) in bore results in only a very slight (about 5% or less) reduction in flow if the length of the reduced section is less than 10 times the full bore diameter. This a well known fluid mechanics principle to fluid engineers. Moreover, the internal diameter of the oil junction block and the ports in the 750 engine is 3/16" diameter ..... since this causes no problem, your 1/4 inch valve will not be a problem either.

If you use a shut off tap in the oil line, be sure to include a fail safe method to ensure the valve is open before starting. It is inevitable you will forget to open the valve and vindicate all those recommending you do not use one.The AMR mod is is a better alternative and at $70 US plus 2 way shipping, it is cheap.

Slick

htown16 said:

This works. I had it done to my bike several years ago. It was a bad wet sumper. Would drain the tank in a couple of days. You may still get some leak down with this. If I let the bike sit for a month it will be to the bottom of the dip stick, but still safe to start. I once let it sit for 6 months and had to drain the sump. Not perfect but a huge improvement for very little cost and work. Unlike a check ball on the inlet side this places it on the output side so you have full pump pressure opening it instead of relying on suction. Similar to a BSA internal check ball.
http://www.amr-of-tucson.com/nortech.html

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Yes.

This.

After having solved my Commando wet-sumping problem for good, with zero measurable leakage, and NO danger of cutting off oil flow, the only answer I have to the "how can I stop wet-sumping?" is .... "Fix your (put expletive here) MOTORCYCLE!"

Taking time grubbing around on the floor draining oil out of a dirty sump hole (unless you cleaned it) into a possibly dirty container (unless you cleaned it) and pouring it back into the motor and replacing the sump plug seal is just dumb. Putting a check valve in the input line to a suction pump is dumb too. Putting a manual or electrically operated or sensed on/off valve in the inlet line is just dumb. Starting up a dry-sump motorcycle with two and a half quarts of oil in the sump is maybe not dumb, but even if you've been doing it and "It Seems To Be OK" .... why do it?

Just fix your motorcycle. It's easy, and it's cheap, and the problem goes away. If the only objection is rumors that "well I had it done and it didn't work", AMR-Tuscon is a quality operation, and if the work you paid for isn't satisfactory, they will make it right.

Maybe it's just something people like to talk about, and that's why they don't just Fix Their Motorcycle.

Lannis

+1 Lannis

fastbackboy said:

I have a newly acquired Fastback with nice provenance and fully rebuilt but inevitably wet sumps. I have read with great interest the various ways of overcoming the problem and was going towards the in-line spring loaded valve until I read about the problems some have experienced with them, including someone local to me who had his engine seize using one.
So, I sourced a nice looking brass ball valve on / off tap to put in line, sold suitable for the 5/16" oil line. However, on receipt I find the orifice in the ball valve is only 4mm, so I bore it out as far as possible to 1/4". So, for ease of calcs let's say oil flows from 8mm bore down to 6mm and then back to 8mm, a 25% reduction in diameter. Hold on a moment though, perhaps it is not that simple? The area of the 8mm bore is pie x radius squared = 50mm2. The 6mm is pie x radius squared = 28mm2 i.e. a whopping 44% reduction!

Whilst I think it likely a 25% reduction wouldn't matter, if it is indeed 44% that probably would. I am neither a mathmatician nor an engineer so would be grateful for opinions before I use this. I think if I managed to find one with a 5/16" actual bore it would be too big and look a mess.

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It's your bike to do with as you please and obviously you ( after reading with great interest) think a ball valve is the way you want to proceed then fire ahead . I personally think that this post is a wynd up , as you know that this subject is controversial . Good luck and how's your bike running Phil!

auldblue said:

I personally think that this post is a wynd up , as you know that this subject is controversial . Good luck and how's your bike running Phil!

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If it is a wind up, it worked. We have Lannis shouting in Capitals and labelling those with differing views as dummies.
This dummy will keep the valve, it did fix the motorcycle.

This is deja view already, a local motorcycle mechanic fell into hate with my valve some time ago. He took great pleasure in telling me what a stupid idea this was. He then demonstrated how he refaces Norton oil pumps bringing them back to tolerance so that wet sumping is stopped. Only thing is, the pump he was demonstrating with went on my Buddies 99, which after total resto turned out to be one of the worst wet sumpers I've ever seen. It's leakier than Nana's Depends after three pots of Sanka!
Shame of all shames it now wears a large catch bottle to pick up all of the oil it pukes out after a two day sit

The AMR mod is next for it and it that doesn't work-it gets a key valve, which does work 100% and is no big deal really, not worth getting worked up over.

Glen

No, my post is not a wind up - just a newbie stepping into a minefield! The AMR mod looks good but I am in England so means shipping the bits over to the US and back.

Thanks to all for your posts and to Slick for answering the question posed (putting my mind at rest about the flow rate).

Sorry about raising so many blood pressures on this one!
Cheers,
Chris.

fastbackboy said:

I am in England

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It's a good idea to update your profile to show your location.
That way people can proffer solutions more tailored to your particular situation.

Chris, I don't know why people get so worked up over the oil in sump topic. There definitely are a couple of valve types to be avoided, but there are also safe types.
As far as the AMR mod goes, Colorado Norton Works used it years ago then gave up on it as it was a hit and miss solution.

Glen

I am working on an updated AMR, it uses X ring seals in the oil pump to double up on sealing surfaces and a 1/4" EPDM ball instead of steel ball, just waiting on the balls which are now promised for July. Previous work on using an airline non return shows that if either the seat or the ball are rubber the seal is more reliable than steel to steel (one small piece of dirt gives a leak), that leaves final decision is on what to do with the pump outlet, leave as flat ended tube or machine it with a ball cutter to match the ball shape.