RM400N Oil in Crank...Help!!!

[LWC82PE]

LWC...When i had the cylinder rebored i was told by the Serco/Wieseco machinist that 20:1 is old school oil and with the advances in technology of oils 32:1 was fine. I have had this discussion with people before who say the same thing that you dont need 20:1 and others that say you do???.

Thanks guys

Tim

Well i strongly disagree with that, certainly not for old  air cooled engines. I will never understand why some people want to use or are told to use less oil.
'Its cheaper to use less oil' and 'my bike smokes less' are not valid reasons.

[Toolboy]

If i am running the bike so lean then why is the top of the piston black, also the plug???
When i havent changed my fuel mix or jetting in the 10 years i have owned the bike??

LWC..I am yet to sieze an engine but i am willing to try the 20:1 mix once i resolve this issue

Im guessing that with the barrel off and i refill the gear box oil i maybe i will able to see if the gearbox oil is seeping through to the crank when standing??? If not then it must be sucking it through???

Thanks all
Tim

[Graeme M]

I first heard of the 20:1 thing here on OzVMX, and also about how a certain amount of oil on the floor of the cases is a sign of a well tuned engine running the correct oil ratio. I later read much the same from Eric Gorr. I had been using 35 or 40:1 as a result of being led to believe modern oils allow that. Since I've gone to 20:1 on the RM125, I have found it to run cleaner and cooler and whenever I open it up everything looks just fine inside. I am a convert. I am no expert and won't say that I know what's best as it's a complicated subject, but 20:1 works for me.

[Doc]

Tim, what exactly is the issue? fouled plugs? the oil in the crankcase? You state on the last ride at Conondale it went well with no mention of fouling. If it's the oil in the cases that's bothering there isn't a thing to worry about. All my 2 smokers have the same thing and it is quite normal. I've owned my 400 since new in '78 and I too still run the original jetting, only time it has ever fouled a plug in 33 years was when I inadvertently mixed fuels, one synthetic premix and the other had a mineral based oil. The 2 simply don't mix and this combination will foul plugs everytime. If it was all going well, not fouling plugs and not pinging up top then I'd say leave well and good enough alone

[LWC82PE]

Yes thats right, you want to see oil in your crankcase. The big end and left main actually need lubrication so as Doc says its perfectly normal. Have you noticed a mysterious drop in gear box oil?

[GMC]

We could talk about oil ratios till the cows come home, and I once had a cow get out and it never came home.
20-1, 30-1, 40-1, people run all different ratios without problems
Any leaking into the crankcase has nothing to do with oil ratios.
And like has been said already, oil in the crank case is normal, it’s most likely from the oil you mix in your petrol, that’s why we put it there. If you want to fix a problem first you must make sure you have a problem,” if it ain’t broke don’t fix it”
If it was running fine then I would concentrate on the jetting, and if you increase the oil to 20-1 will make it run leaner.

I don’t know where I got the idea but I have been under the impression that the oil separates under pressure which is how small amount stays in the crankcase

[Lozza]

There is no real pressure in the crankcase. while running it is mixed , swirled and 'turbulated' (I pinched that one  ) by the spinning crank. Each cycle happens at a rapid rate, even though 1 fuel/oil particle takes 20 cycles to go through the engine, that at a moderate 6000 rpm is 1/5th of a second.

Tim a tell tale sign of a leaky crank seal is the presence of white(not blue) smoke and lots of it from the exhaust, and the disappearing gearbox oil.
With oil ratios I will defer to a brilliant tuner Jan Thiel who led the developement on the single most successful 2T racing engine, spanning 20 years. The Aprilia RSW/RSA  they have and always will use between 4-5% oil as Jan explained (20-25:1).

[LWC82PE]

Tim a tell tale sign of a leaky crank seal is the presence of white(not blue) smoke and lots of it from the exhaust, and the disappearing gearbox oil.

Yeah thats right, its all basic stuff, ive read that in many manuals 'troubleshooting sections' that most people just ignore. Sometimes it pays to just go back to basics. It should be obvious if your loosing gear oil. Going to 20 to 1 wont necessarily make it leaner or too lean with the standard sort of jetting which was set up for 20 to 1 front the factory. It depends on what jetting you have with the 32 to 1 currently. It will get things to about where they were originally. Suzuki was not in the habbit of shipping bikes jetted on the lean side in std trim. You need to work out if the plug is oil or fuel fouled.

One last thing are you sure you put the RHS seal in the right way?

[Mike52]

One last thing are you sure you put the RHS seal in the right way?

You are so right LW , the gearbox oil is on the right , I was looking at the photos and the black stuff is on the left side oiler/transfer area which is the flywheel side .

[Toolboy]

Ok,,,,more pics added. Looking more like the new crank seal i fitted.

Doc...I know you talk about residue in the crank from the fuel/oil mix but i think the pics show a bit much.











I am sure the B7ES plug burnt hotter stopping the bike from fouling up.

Tim

[Toolboy]

Pic taken of crankside of seal and o ring..

Is this oil bypassing seal/o"ring...or coming down breather tube into bearing?





Tim

[oldfart]

Drain some oil out of your gearbox and compare colours would be my first choice
How old is that crank seal pictured ( shows signs of rust  )  Might be a case of the rust mixing with your oil  giving it that brown colour.

A guess and a wild one at that.... is that the motor has got water in it at some stage creating scale on your crank webs and seals .If this is the case you need to replace  your main bearings ....get the webs pressed apart and bead blasted.

[Doc]

Tim, the amount doesn't bother me or appear out of the normal. My RM has always had much the same. It doesn't take much to pick up that amount of oil on the crank due to the close association between the crank and cases. The colour doesn't look pretty and there is some contamination but you have to remember the location of where it resides and how it gets there. It might seem like a lot on the crank but looking down the cases in the picture there doesn't appear to be much sitting on the bottom.

[pmc57]

The oil's pulling in from somewhere and it can only come from either the R/h seal area or the centre case gasket area.
Is the R/H seal and the O-ring genuine Suzuki parts? If not, go genuine if at all possible.
There appears to be an imperfection (at about 2 oclock) where the seal fits in the r/h case. Do you use a light smear of sealer on the OD of your seals? I do and don't have any problems with leakin seals on their OD.
The o-ring is there to stop oil from sucking through the clearence between the crank shaft and the primary drive pinion gear. If the o-ring is non-standard it may not be quite the right section diameter and not doing it's job by sealing the crank shaft and the bush that fits behind the primary drive pinion.

That plug looks ugly

[wmc83]

Interestingly the gear box side seal on my RMX250 goes the other way round to the seal shown and the manual showed a parts breakdown with the seal round the WRONG way but later in the manual a detail showed it correctly! Different model obviously but something to watch.