RM400N Oil in Crank...Help!!!

[vmx42]

I think a proper pressure test is the best way to determine if there is a leak from the crankcase into the gearbox or ignition.

Filling everything with oil or petrol might work, but the viscosity of the liquid, by its very nature, will probably just hide a small leak - which may well be the problem.

Pressure testing is much easier, cleaner and more definitive. It can be simply done at home with some scrap materials, a schrader valve, a bicycle pump and a spray bottle of soapy liquid. It take minutes and will give you an answer one way or the other.

If you don't want to go down that path then most bikes shops will do it for you for a nominal sum.



P.S. don't overpressurise with the pump. A few psi is all that is needed.

[DOK]

Hi Tim
Yeah you could do that but its a little difficult to see where the fuel would leak in from (crank in the rode and you would just see a puddle in the middle.
The other way around you would see the fluid around the seal and if its the gasket it would flow from the gearbox to the clutch housing.
Another thing to consider is a compression test when its assembled it was mentioned earlier in this thread I think. If you have low compression the fuel combustion is not complete the volitile fuel will burn and leave the oil to pools in the crankcase.
Check your ring gap should be equal to .05mm/25mm of bore ( the old Tech days .002th/in ) also use a feeler gauge between the skirt of the piston and the bore.
put the feeler gauge into the bore and slide the piston in start with .05mm and increase in size by .05 until the piston can be held in place by its own wheight this should tell you piston to bore clearance check with w/s manual that its within spec.
David

[wmc83]

Again I know this is a different model but just be careful how you interpert shop manuals I got caught out buy this when doing a rebuild



note the orientation of the transmission side seal

and two pages later


The first image is wrong I found this out by the puffs of white smoke wafting out the exaust,     I'm not saying your seal is in wrong but I'd get some one who knows his suff to check it out first.

[LWC82PE]

The vent holes are clear, so is the seal fitted the wrong way???

You say the vent holes are clear. What i was meaning is that you need to check the vent hole to the gear box housing. Some where there will be a vent from atmosphere to the gear box. If that is blocked with mud or something you will have problems of gear oil getting pressurized and be forced out of areas its not ment to. This can particularly a issue on race bikes and bikes with poor gear box venting such as many english bikes and to fix this additional gearbox venting may be required if the std vent is too restrictive.

I have thought about this all day and nothing is making sense. If what PMC says is correct then all bikes with the cavity towards the crank would leak. I have always done it like that and never had leaks .

I am looking in my RM400 manual right now and it shows a photo, not a drawing, showing the oil seal fitted in the case with the cavity towards the crank like Toolboy has it. I also checked with a RM400 owner and he agrees thats the right way.

[Toolboy]

LWC...Yep i understand what you saying now, I will check the breather tube. Yes i too am confused about the seal fitment.

WMC.. I will recheck my manual...its confusing.

DOK.. Brand new rings and rebore, everything is well within spec. I though is was compression at one point, when it first happened.

DOC... Yes Doc that was me and my RM's first outing on the track, i do remember chatting to you and having a good discussion about engine vibration..hahaha,,,,i had so many people came to me to talk about my shiny new lookin RM400N,,all them said "damn i had one of these and should never have sold it". I never realised how popular they were. This is how it looked on the day:



Tim

[monaro308]

With all the confusion going on for you Tim.
This is a pic out of the RM400N manual (compliments to Luke)


Then you put the RM250N into it and get this

cheers...Mario


Great to have Doc back too

[LWC82PE]

I have a photo of the RM400 similar to that top one Mario and you can see its a RM400 case with the seal that way. It actually says its RM400 too.

[lukeb1961]

and here's a PE400 being pulled apart shot, (Dan on the PE list), just to sorta help confirm.

[Toolboy]

Monaro...yes it is all confusing, there are so many conflicting pic's in the manual and parts list.

I will try to pressurise the crank and check the seal fitted both ways???

Tim

[crs-and-rms]

leak down test is the best way to go  remove carbi and pipe  and seal mannnifold and inlet manifold pressurise to 6 psi spray with soppy water  ,a loss of 1 psi per minute is acceptable

[pmc57]

I have thought about this all day and nothing is making sense. If what PMC says is correct then all bikes with the cavity towards the crank would leak. I have always done it like that and never had leaks .

LWC82PE, I'm sure you're right in the true sence about he direction of the seal, but i think it has more to do with the length of the sleeve behind the primary drive gear that fits inside this seal.  When the seal's installed cavity side out and the seal is installed only as far in as flush with the r/h housing, this should allow the inner lip to be just short of the bearing inner race. If installed the other way around (cavity in) there is a risk the seal is installed too far in (so it matches the sleeve) and runs the risk of blocking or partially blocking off the r/h lube transfer hole with the outer cage of the seal.
I haven't done this model for a while now, but I'm sure when I did one last, i had a think about this and took a few length measurements to confirm where the seal sat in relation to the sleeve. Also my Clymer manual shows a few pics of 400 N or T cases with the seal cavity side out.
I still think there's a leak from somewhere else with this one, maybe when the screws got jammed in the rotor it gave the crank shaft a big shunt and disturbed the centre case gasket or maybe cracked a case.  Needs further investigating I think.

[oldfart]

Pete on the T  the flat sides face out and are flush with casings( no more than 9mm in)   end of story.
I will explain why.
Next time you have your cases apart, pay particular attention to the mag side inner case as it has a 9mm area to take your seal and  a 1mm step on the bearing housing. This  is there to allow some oil to feed the bearing via the crank oiler hole.
Now if you where to put the seal around the other way ( flat side in ) and it was  pressed in too far and rest against the bearing your liable to have bearing failure.

check it out next time 

[pmc57]

Stewy,
Yes your mention of the mag side seal position is correct, but I still think the r/h side has more to do with the dimensional position of the seal in relation to the sleeve hense the way it faces. If you read my thread again, I say the inner lip (I say inner because I'm presuming the flat side of seal is facing in) of the seal fixed with cavity side facing transmission, should just clear the bearing inner race if the seal is pressed in so it's flush with the casing, no contact of the inner lip on bearing and no chance of bearing failure because of seal contact.
I still think it's a dimensional thing that dictates the way this seal faces as well as the sealing quality, check the lengths of the sleeve and how the seal positions itself with it. The seal will do it's job either way around, but what we don't want is the r/h lube hole being obstructed.
There's still a problem with this 400, whether the oil's coming through the seal or somewhere else, it's still coming in and the challenge is to find out where from.

[pmc57]

Toolboy,
Any update on the oil leak in the 400? What did you find or do to fix the problem?

[Toolboy]

Gday PMC,

I have been busy at work so not much to tell you at this time, i tried the leak down test without much success (no oil in the crank no matter what i did) so i have resorted to flipping the seal around and test run the bike... i also had issues with engine vibration/cracking the pipe so i have drilled the frame to engine bolt holes and welded the cracked pipe. So on my days off work this week i will be able to get the bike finished and out for a run... ohhh and I will also try the 20:1 fuel mix.

Cheers

Tim