Wet Sumping into the Primary chaincase.

[Les Howard]

Well. I have had to leave my newly restored G12 for a couple of weeks unstarted.. Now I know it will wet sump, I expected this even though the pumps are in good condition. The double size gear pumps will inevitably drain back twice as much as the standard ones. I also use a 5W-40w multigrade oil in order to minimise excessively high oil pressure when cold (I know the pressure relief valve will lift but why loose oil volume circulation and pressurize the filter chamber so unnecessarily?). It will also ensure fast circulation on a cold start up. However, the thinner oil at cold temperatures will cause more oil to drain through the pumps somewhat too. Now today I noticed that after starting, quite a lot of oil had run through the crankshaft drive shaft seal (it is a spiral cut type) into the primary chain-case from the wet-sumping build up, causing some oil to blow out of the chaincase breather hole. Now here is my QUESTION please: Will the spiral cut oil-seal, pump back the extra oil from the chaincase into the sump? .... I reckon it should as the spiral constantly pulls back oil toward the inside of the engine, so will it clear the excess that has built up please? Much appreciate any views of this wet sumping into the chaincase phenomena. Many thanks

[les ward]

My experience is that you will need to remove some of the oil from the chaincase. A syringe with some fine tube makes this easier. The breather on the end of the crankcase also needs to be in good condition. A worn one will allow oil into the chaincase

[Les Howard]

Hi Les. Thanks for replying. Yes, I was thinking the same thing. I do have one of those large plastic oil filling syringes so I could suck out the surplus chaincase oil from the clutch centre hole if the pipe was wiggled down to the high oil level. So, from your experience, you are saying once the oil has run into the chaincase it stays high?. That is a pain...I really am considering fitting a tap on the feed pipe. It only needs to be turned off if leaving the bike for over a week. thanks Again

[robcurrie]

Les,

Rather just start the engine once every week or two. If you try riding it with a full primary case you are going to cover everything in oil including your rear tyre. When checking the oil level in the primary, you should use the lower access cover, not the clutch access cover, I run the oil level where it just touches the primary chain.

Rob C

[Les Howard]

Hi Rob, thanks for getting back on this. The reason I suggested the clutch cover cap is because if I open the correct lower cap, the surplus oil will gush out of it and all over the exhaust pipe, frame and centre stand, making collecting of it very difficult and wasteful. Using a syringe to suck out lots of oil from the clutch hole first, I can lower the oil level right down THEN remove the lower cap without it pouring out. If I've sucked out too much, it is easy to inject more back from the syringe to the correct level to just touch the chain. Yes, starting it up at least every week would be the answer...The reason it might have gaps in my riding of it is that I have 14 bikes with 5 insured that I also ride. It does make me appreciate my MZ two strokes, so little trouble

[Mollbhan]

Try to suck the oil out before you start the engine, it is a bigger pain having to strip down the clutch and wash the plates if they start slipping.

[bitza]

I think this is the reason owners fit the in Line tap, multi grade oils being a lighter viscosity than straight 40 or 50 grade even when cold.

[Ib-Denmark]

Well. I have had to leave my newly restored G12 for a couple of weeks unstarted.. Now I know it will wet sump, I expected this even though the pumps are in good condition. The double size gear pumps will inevitably drain back twice as much as the standard ones. I also use a 5W-40w multigrade oil in order to minimise excessively high oil pressure when cold (I know the pressure relief valve will lift but why loose oil volume circulation and pressurize the filter chamber so unnecessarily?). It will also ensure fast circulation on a cold start up. However, the thinner oil at cold temperatures will cause more oil to drain through the pumps somewhat too. Now today I noticed that after starting, quite a lot of oil had run through the crankshaft drive shaft seal (it is a spiral cut type) into the primary chain-case from the wet-sumping build up, causing some oil to blow out of the chaincase breather hole. Now here is my QUESTION please: Will the spiral cut oil-seal, pump back the extra oil from the chaincase into the sump? .... I reckon it should as the spiral constantly pulls back oil toward the inside of the engine, so will it clear the excess that has built up please? Much appreciate any views of this wet sumping into the chaincase phenomena. Many thanks

Hi Les
No the spiral will not take care of everything. In my G12 I have fit an oil seal by replacing the spiral bushing with a bushing of a smaller diameter.
The oil seal box (Is that the word?) is metric (I dont remember the measure, I can maybe find out if needed). This set up has worked fine for the last 25000 km which is needed because I got belt drive.
regards Ib Denmark

[Les Howard]

Thanks IB....having a rubber lip-type oil-seal will stop the leakage of oil if the crankcase has filled up due to "wet-sumping". Unless of course, it has filled up so much, the oil runs through the crankshaft breather hole. I think I will just have to make sure the engine is run if left longer than a week or fit a tap on the oil supply from the oil-tank. I have to say I cannot picture in my mind the way the spiral oil-seal operates in the chaincase and where there is an opening for the oil to leak out of it. Next time I remove the primary chain case cover, I will have a look. Thanks again...

[bitza]

Could be leaking it's way through the main bearing if they are open cage type