RM400N Oiling Plugs

[Toolboy]

Gday all,

This has been doing my head in now for the past 6 months.

My RM400N has been fouling plugs.

Its not compression as i have just fitted new Maico 440 piston

I have replaced Crankshaft seal, the bearing did not look oily.

I have replaced o ring on crankshaft.

I have changed jetting and needle clip position.

But the bike still fouls plugs and when i removed the barrel there was oil in crank area.

Now i am starting to think crank gasket that seals cases is leaking..

Any one else have this problem on 400N

Tim

[frostype400]

My pe400t is currently oiling plugs it has a faulty coil I'd check cdi coil and killswitch before you start pulling down the motor.

[Toolboy]

Just disasembled motor, crank full of oil..... not full full but crank coated, and on top of piston...

There is a hole on the top of the crankcases each side. Like a vent hole, is it possible that it could sucking the oil inside from the clutch???

Well its all cleaned and reassembled, i will go out for a test run..and i have decreased the oil level,,,,only 700 ml...

Dont want to kill the gearbox..

Tim

[bazza]

what fuel?   Type of 2/stroke oil? and what % oil/petrol?.  Electrics?

[oldfart]

Those 2 holes  are for oiling your crank bearings via 2T oil. 

[Mutch]

I had the same problems as you,and in the end i replaced the crank gasket and the bike run good
until Olfart busted up my gear box

[Davey Crocket]

He's like that.....will be thinking of you freezing next weekend and not having the time of your life at Conondale!!

[Toolboy]

I think i fixed the oil problem because the bike siezed today,,,damn,,,,,@#$#@@#$

[Mike52]

I think i fixed the oil problem because the bike siezed today,,,damn,,,,,@#$#@@#$

That doesnt sound good.
You say it.s fouling plugs ?
What do you mean ?
Are you getting a little bridge across the electrodes .
If so then it,s running too lean or you,re fuel is crap.
Nothing to do with oil unless you,re running too much oil , then it will run lean and seize.
Probably trying to teach you to suck eggs but the ratio should be 20/25 parts fuel to 1 part oil.
Please don,t get pissed with me if you have known this for the last 30 years but I,me still meeting people who don,t know the basics and think that the more oil the better when the reverse is true.
Mike

[Toolboy]

The fouling plug was due problem is gear oil getting into the crankcase.

I had replaced the stator thinking it was weak spark!!

Everytime i dismantle the bike the crank is coated in gear oil...

Today when riding the bike i had the same carby settings but difference was i was bored out 2mm for the 440 piston, so i should of known better.

The bike ran sluggish due to the oil baked exhaust but once cleared i pushed the bike too hard on a long stretch only on mid throttle and it siezed,,,my stupid fault.

I will disantle again tomorrow, the piston freed after cooling but lost compression so i know its not crank bearing.

I have been told that with the advances of 2 stroke that you dont have t run 20/25 mix...i was running 40/1 and still fouling plugs

Will advise tomorrow when the bike is dismantled..

[chrisdespo]

there are a few checks that you could have done to check if is sucking gearbox oil into crankcase check your oil level via level hole in clutch case with bike standing up straight after rideing at normal engine speeds again check level if it is down and there no other leeks it is sucking the oil into crankcase. i don't know how much you ride this bike but the bottom end on my big twostrokes was always rebuilt after about 30/50 hours. you could also check the main bearings for play as most of the time thats where the oil generaly gets in on the other hand if it has a bad bearing and it dosn't take much on the left even the smallest amount of play will let air come in through the seal and bingo a nip up or hole in the piston. with the clutch cover removed and flywheel cover off grasp crank and try and move up and down even the smallest amount of play means a bottom end rebuild. and this is the time that you can inspect the condition of the bigeng and the crank case gasket if fitted and make sure that the reassembely is done with threebond grey.

[Toolboy]

With the engine dismantled the problem looks to be crank gasket, there is not a drop of oil on the main bearings so its not a seal or O ring, with the cases spilt and a new gasket ordered its just a matter of cleaning up the gasket surface and wait for the part.

Interesting on reading the post about what sealant to use on gaskets....another thing to look into.

Tim