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Panic!

Submitted by mark_chapman2 on Thu, 26/09/2013
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Commando

Hi. I have just recieved my October copy of Roadholder (great as usual) and read with instilled panic the piece on 750 Commando woes being that on certain 750s with the small sump plug that a design flaw exists whereby at speed/high revs the oil does not return to the tank. Now as you can guess i have such a machine and wonder how on earth i can check this. I have considered riding at speed with the seat off and the oil tank cap off and ask my pillion (the wife) to look into the tank to check that oil is returning. I also have clear braided hose on the feed and return oil pipes and if learn to ride side saddle at speed i could watch to see if the oil is flowing, or i could ask some sensible likeminded owmers out there for their thoughts. The bike runs fine, is used regular and at revs that are often in excess of 4000.

Thanks Mark.

Submitted by simon_ratcliff on Thu, 26/09/2013

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Best place would be a rolling road, revved to max. and measure or observe oil return to tank. Other option would be to rev engine in neutral, bike on its wheels. Then again if you have no problems, don't worry about it and simply check/modify when engine is apart,

Simon.

Submitted by mark_chapman2 on Thu, 26/09/2013

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Previously simon_ratcliff wrote:

Best place would be a rolling road, revved to max. and measure or observe oil return to tank. Other option would be to rev engine in neutral, bike on its wheels. Then again if you have no problems, don't worry about it and simply check/modify when engine is apart,

Simon.

It would have been much more fun having my wife looking into the oil tank at 80mph. I have to agree to leaving it. i wont loose too much sleep and i refuse to keep the revs low. Ive covered a lot of miles on this engine without any oil problems to date. But i may, just to settle my mind right after a fast run switch her off and check the oil tank. So if you see an old boy at a set of traffic lights with the seat off his Norton dont worry it will be me. Mark.

Submitted by karl_nixon on Thu, 26/09/2013

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As it is the engine speed not the engine load that is the issue you do not need a rolling road to see if you have the problem just hold the engine at high enough revs. Of course this will mean holding the bike down as they do seem to like to walk around on their own also put as many fans as you can pointing at the engine to help cool it as heat builds up and even do all this on a cold (the colder the better winter is coming so should be lots of freezing days to come which is handy for this at least) day. Then you can watch oil level if the neighbourhood dont linch you or you dont bottle it out of fear or symphy for your motor.

Or remove drain plug from tank fitt a leght of clear tube with one end open to air above full level of tank and it will act as a sight glass then someone (may need to be on another flowing bike) can see it as you ride along with lots of revs on. Try going down motorway in third for a bit for example would be safest place for such a test.

But if its not been a problem so far then wait as Simon says till you have the engine in bits for some other reason before doing anything to modify it or just dont hold high revs for long periods drop the revs an let the oil return to the tank.

Karl

Submitted by keith_glassborow on Thu, 26/09/2013

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As Karl says, if it has not been a problem at normal road speeds it may never be unless regularly run at 5k + for several minutes at a time. Part of the reason is that the existing 'Combat' breather returns(ed) oil nearly as well as the pump. When it does go wrong is when the system (poor as it is) is messed with. Fopr example deleting the 'Combat' breather and improving it with an 850 style timing side mod. Mine had that done by the previous owner and at 4000 rpm or 70mph the tank emptied in minutes. I later did the case mod and it worked great until a pattern rod bolt from the West Midlands let go!

 


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