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tom banksSun May-13-07 06:34 PM

  
"74/75 noton commando wet sump issue???"


  

          

i recently bought a 74, but titled as a 75, 850cc commando. totally rebiult, with all usa or brit made racing parts. as good as it can be, dry clutch, norvil camshaft, etc. it's great, and has a few more than 1000 miles on the rebuild.
i was riding it the other day, and it suddenly regurgitated a large quantity of oil out of itself onto both my leg and the right side of the bike. it did this without making a single abnormal sound- no clunk, clank, rattle, not a peep. after wiping all the oil off of the bike, and searching carefully, it was not possible to determine just where the oil had come from- no obvious blown hoses, gaskets, not one single spot where the oil might have come from. everything is brand new, anyway.
i was told by a friend who also has old brit bikes that the nortons were known for this, and it has something to do with the "wet-sump", and that i should try to find an oil sump valve. i looked around on the internet,but came away with no real definitive info. i'm just wondering if anyone has had this happen, or has heard of such a thing as this happening before.
the guy who did the re-build (who sold it to the person i got it from) was a bit of a mechanical nut, who tweaked this bike out in all sorts of ways. apparently it was his 8th rebuild. one of the things he did to it was to install a shut-off to the oil sump, i guess. there is an inline shut off, just under the rear fender, and you can use it to keep the oil up in the motor after you have shut the bike off. at the time i bought the bike, the guy i got it from showed me this, and i couldn't see why i would ever want to go through all that, but maybe the incident i have described and the shut off valve have some connection. can anyone help me with this? p.s.- i am registering on the website to be able to post on the members-only page, but just thought i would post here also to see if i could get a quick answer from anyone. thanks in advance.

  

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johnmWed May-16-07 01:26 AM

  
#1. "RE: 74/75 noton commando wet sump issue???"
In response to Reply # 0


  

          

This is a bit of a long explanation but I hope it helps.

A Norton twin motor is a dry sump motor. ie It has a separate oil tank and the oil is circulated from the tank through the motor. While the motor is running perhaps 20 % of the oil volume is in the motor and 80 % in the tank. (This is a guess so don't hold me to the exact amount). Most cars and modern bikes are wet sump ie all the oil is in the sump or rest of the motor all the time.

When you turn off a Norton engine almost all the oil in the motor drains down into the sump. This is OK. But unfortunatly one bad habit that Nortons also have is that with time (say a week or two ) the oil in the OIL TANK can also drainsdown past the oil pump into the sump. Which means you can end up with 90 % of the oil in the sump. This is what peole generally mean when they say a Norton has wet sumped. It isnt supposed to happen but many many Nortons do it. There are ways to fix it which you could search on the web or consult a qualfied specialist.

So now when you start the bike several things can happen. The worse thing is that seals can blow and oil goes everywhere and you have to replace the seals. A better thing is that oil can come out the breather and pour on to the ground.

It possible for an owner to make this worse. It goes like this. You go to ride your bike for the first time in a month. You check the oil level in the tank. It is empty because the oil is all in the sump. You fill it up because you think you are out of oil. Now when you start the bike you have twice as much oil in the bike as you need and oil goes everywhere!

Im a bit confused by your post. You said the bike pumped oil out after you had been using it. If you have wet sumped as i describe above the oil comes out in the first one or two minutes. If your bike had been going for 10 minutes or more when it pumped the oil out then something else is wrong.

Lastly you described a valve or device a previous owner had put in the oil line to prevent wet sumping. This is definitly related but not something to be playing with if you dont have a VERY VERY good idea about how your engine lubrication system works.

I woud not touch this without consulting someone who is qualified and experienced on English bikes. It is not something to play with on the basis of internet advice and I would want to see it before I gave an opinion. You run the risk of shutting of the oil to your engine which will destroy it in a few seconds.

Goodluck

  

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ricochetriderMon May-21-07 03:11 PM
Member since Mar 18th 2009
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#3. "RE: 74/75 noton commando wet sump issue???"
In response to Reply # 1


  

          

hi, john and dynodave.
thanks for the repiles. so, to clear things up a bit, yes, the bike had been sitting a while. really, most of the winter, since it really just now is warming up, here in central pa. and yes, i had ridden the bike about 15-20 miles to a friend's house, it sat there for a while, and then i was riding home when the oil came out of the engine. and yes, by the way, there are a dry clutch, and a primary belt drive kit on the bike

i have found out that there are a couple of different fixes for this. one being send the timing cover and oil pump out for machining and installation of a new sump valve. or buy the cheapie in-line sump valve. what i have in the oil line now, that is under the rear fender, is a shut-off valve, and it appears now that it is there to maybe keep the oil from all travelling into the lower portion of the motor? that's what i was told it was for, by the guy who sold me the bike. someone else has told me that if i simply ride the bike more often, this won't be likely to happen, that it mostly happens, as john pointed out, after it sits for too long. what do you guys recommend? is there a third alternative here? i see this bike as my new regular rider. my other bikes-i also have a '79 bonneville, a "bobber"- '73,750 5 speed tiger motor in a 1969 hard tail frame, and a 1988 bmw k-100- have tolerated sitting for periods quite well.

i only got the norton this past september and just love it! i really want to ride it all the time, but i don't want to fire it back up and hurt it by doing so. it must be low on oil right now. how should i go about starting it? should i start it, and let it run a bit, shut it off and check the oil? will it be ok, or do i need to get the "fix"? my friends who have 60's bsa bikes say they have had to deal with this. one of them got the in line sump valve, and i don't know how the other guy dealt with it. thanks for the help. ricochetrider

  

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johnmTue May-22-07 04:16 PM

  
#4. "RE: 74/75 noton commando wet sump issue???"
In response to Reply # 3


  

          

Hi,

Dave has also replied to your question. Dave is working on these bikes all the time and has a great more experience than I have on a various modifications and therefore I would follow his advice.

My comments to your questions and possble solutions are as follows:

1 . Modification of the timing cover and oil pump. I have no experience with the timing cover mod. I have worked on an oil pump but only with an expert looking over my shoulder. So on this I would take Dave's advice or someone who really knows what they are doing. Finding someone is the biggest problem. There are 20 people with good stories for every one person who knows what they are doing. I could recomend someone in New Zealand but that is no real use to you. I would listen to Dave in the US.
2. Instalation of a "sump valve". I have no idea what this is and I have never heard of one before. Perhaps it is a different name than we use here but from my understanding of the problem nothing in the sump would make a difference. It could be that the term is confused with your 3rd suggestion

3 In line valve or toggle valve. This is a valve to shut off the oil draining down from the tank. It sounds like you have one installed already. There are various stories about these failing and shutting off oil to the motor. Again Dave would have more experience than me. A toggle valve should never fail but you must turn it on every single time. I have had friends wire them into the ignition or hook them into the kick start so it is impossible to start the machine without turning it on. I dont think I would trust this myself.

Finally there is the easy solution. Ride the bike every day or at least once every few days. This way you should never have enough time for too much oil to drain down (unless your oil pump is in really bad condition)

  

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ricochetriderFri May-25-07 11:15 AM
Member since Mar 18th 2009
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#6. "RE: 74/75 noton commando wet sump issue???"
In response to Reply # 4


  

          

hi guys.
well, it looks like the nortech timing cover mod + oil pump re-build is in my future, judging from what i am hearing. seems like the best way to play it. the real big question is this: can i ride it over the summer and send it out to nortech in the fall or should i just suck it up and send it out now? one thing i'm getting here is that with more frequent riding, it won't be as likely to wet-sump.

i'd like to start the bike to see if oil will leak from any seals, etc that may have been blown. i thought i would drain some of the oil out of the motor, pour it into the oil tank, and kick the bike through a few times to get oil back into the top end, then start the bike. but i absolutely do not want to do anything that will hurt the motor.

is there anything you would recommend in terms of getting the bike started? is it safe to start the bike? should i just take it apart, and send the timing cover and oil pump to nortech now and get it done? what is the bottom line, exactly? i am definitely in agreement about the shut-off switch below the oil tank- i know that it will eventually be the cause of a big problem, and haven't used it yet. peobably won't use it, except maybe over the winter. dave is right, it'll only be one time to forget, and that will be that.

  

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dynodaveTue May-22-07 08:47 PM
Member since Mar 18th 2009
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#5. "RE: 74/75 noton commando wet sump issue???"
In response to Reply # 3
Tue May-22-07 08:54 PM by dynodave

  

          

Hi RR
The basics are, that there are 4 paths for leakage.
when the pump wears it can pass oil from the oil tank through the pump into the sump by:
1. through the inlet of the feed side of the pump, in between the gears, then out to the crank for the final leak out the rod shell into the sump.
2. through the inlet of the feed side of the pump, between the ends of the gear teeth and the body of the pump, again then out to the crank for the final leak out the rod shell into the sump.
3. through the inlet of the feed side of the pump, between the SIDE of the pair of gears and the end plate of the pump. again then out to the crank for the final leak out the rod shell into the sump. Correcting this defect is so often refered to, as "rebuilding your pump". This is also an extreme exageration. It however can be done and can be helpful in reducing "wet sumping".
4. The oil comes into the feed side of the pump gets into the oil pump drive shaft and leaks through into the scavenge side of the pump and flows back the scavenge pick up into the sump.

The AMR/nortech mod puts the check valve AFTER the pump which eliminates symptoms 1 2 but does not actually correct the defect.
Also they "oring" the shaft that goes between the sides of the pump eliminating symptom 4.
However for the price they do fettle the pump defect 3 to reduce side clearance as it should be done anyway.

"before the oil pump" check valves have their risks, though small, I would not use one and would prefer to do the nortech mod. Bad pumps, if air bound, will not suck hard enough crack open the valve and pull oil and you will cook the motor...IMO fix the pump....forget the bandaid.

The manual oil shut off valve, works but you will only forget to open it once.....good luck.

With a good pump and tight rod bearings many can go a whole winter and not "wet sump". Some have dropped the whole load in a week.

  

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dynodaveWed May-16-07 08:19 PM
Member since Mar 18th 2009
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#2. "RE: 74/75 noton commando wet sump issue???"
In response to Reply # 0


  

          

I will add to John's comments about dry sump norton engines, that the malady know as wet sumping is all to common. It is the result of a wearing or worn out oil pump with excessive clearances. These clearances can be minimized by fettleing, but putting check valves or shut off valves is IMO a bandaid for expediancy and practicality.
You might have a belt drive, but might the oil be leaking out of the main crank seal?

  

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