crank seal failure?

dirk · Post by **dirk** » Wed May 20, 2009 3:42 pm

hi folks,

my crank is ~ 4500 miles old.
now RHS exhaust smoke much more than LHS.
it smokes with cold engine much more then LHS and smoke very much especially i accelerate fast the first time after the engine is warm or after a longer time with lower revs.
rev up the (warm) engine in idle it smokes too. not much but you can see it.
i feel no power loss but the engine splutter a bit at ~4500-5500.
RHS spark plug is a bit darker then the LHS.
i can’t say 100 percent whether i loose gear box oil or not because i have a leak in the clutch cover and loose some millilitre at every tour but the symptoms are the same as my old crank.
the only different is my old crank leak only with warm engine and the exhaust was not smoke more when the engine was cold.

i don`t understand this....4500 miles is not a long time for a crank seal and the bike is only a road bike.

what is the cause of crank seal failure?

cheers
Dirk

garye345 · Post by **garye345** » Wed May 20, 2009 3:59 pm

When my crank seals went(twice),it bloo the oil out every ride,did 30 mile to the gallon-oil that was,hope that helps.

the-elf · Post by **the-elf** » Wed May 20, 2009 6:40 pm

Is the RHS smoking more than usual or the LHS less?

It does sound like it might be a crank seal on its way out.

dirk · Post by **dirk** » Wed May 20, 2009 8:09 pm

the-elf wrote:Is the RHS smoking more than usual or the LHS less?

......

hi

thats a very good question =D>

yes the LHS smokes only a few after start the engine (cold) and if i play with the throttle the RHS smokes normal.
the LHS end can is uncommon dry. perhaps only one oil drip .
normaly both endcans are wet if the bike run on road.
Only after few miles on "Autobahn" both end cans are dry
spark plug is between dark gray and light brown.
RHS all in all darker but it don't look to rich.

ok what have i done the last weeks

the LHS carb was flooding and i have changed the needlevalve and checked the float hight on both carbs.
and yes after this work i have for the first time noticed that the RHS exhaust smoke more than LHS.

so far so good but what can happen with the carbs?
i am very sure that the float hight on both carbs ok (19mm)

garye345 wrote:When my crank seals went(twice),it bloo the oil out every ride,did 30 mile to the gallon-oil

one gallon gear oil??:shock:

Dirk

garye345 · Post by **garye345** » Wed May 20, 2009 8:32 pm

That was meant to be a little joke dirk

it did'nt blow a gallon out

but you had to tilt the bike right over to see the oil level in the inspection window

the-elf · Post by **the-elf** » Thu May 21, 2009 1:13 pm

K if the LHS is smoking less it sounds like its running lean. Check for air leaks or a crankcase air leak first. Try swapping the carbs over from Left to right hand side and see if the problem follows.

The LHS outer crank seal is to air (Stator) and not to the gearbox so that could also be sucking in air, it is also the easist seal to change.

KwakOn · Post by **KwakOn** » Thu May 21, 2009 4:26 pm

worn centre pin/seals can lead to plug fouling (i.e. wet plugs and hard to start) and fuel mix building up in crankcases.

dirk · Post by **dirk** » Thu May 21, 2009 8:01 pm

hi

thanks for you help.

i hope that is only a problem with the carbs or the manifolds.

sometimes i think it is better to sell this bike.
you can believe me i am a bullet proof 2stroke fan but the KR is till today only a maintenance nightmare

Dirk

the-elf · Post by **the-elf** » Fri May 22, 2009 8:53 am

dirk wrote:hi

thanks for you help.

i hope that is only a problem with the carbs or the manifolds.

sometimes i think it is better to sell this bike.
you can believe me i am a bullet proof 2stroke fan but the KR is till today only a maintenance nightmare

Dirk

Dirk, We have all had a few problems, but look at it as a challenge. The trouble is with any 20 year bike is that things will always fail, but its worth it when they go well. I had a simular problem last year and it turned out to be a crankcase air leak on the LHS.

dirk · Post by **dirk** » Fri May 22, 2009 1:08 pm

What a bad day.

first i found some gear oil under the crankcase.
left side under the shift mechanism cover........

and then i saw a very long crack (more or less from side to side) in the RHS
bottom engine mount.

last year there was no crack.

Words fail me.

the-elf · Post by **the-elf** » Fri May 22, 2009 4:52 pm

dirk wrote:What a bad day.

first i found some gear oil under the crankcase.
left side under the shift mechanism cover........

On the outside of the motor? If so that might be just a leaking seal/gasket and not a major problem.

and then i saw a very long crack (more or less from side to side) in the RHS
bottom engine mount.
last year there was no crack.

Words fail me.

Thats a very normal crack in any frame of the early 90's. It's due to sloppy tolerences from the factory. Measure the width of the engine and frame mount and get a shim made to remove the slop between them.

Two choices, if the weld is only partally cracked then drill the tip (down to the un-fused land), or get it dressed out with a drimmel and rewelded. If its not too far gone and the mount is still attached to the frame

you can just shim it and keep an eye on it for crack growth. Chances are that onced shimmed the stress will have been removed and the crack will just stop growing. I raced an entire season with a simular crack and once it was shimmed the crack didn't grow a single mm.

mgtkr1 · Post by **mgtkr1** » Fri May 22, 2009 10:06 pm

mine has no cracks but its a bloody wonder!! bottom mount must of ha .25 mm of slop!!!!!! even when torqued up the spacer was able to spin round easily. dirk, has your bike had diffrent cases at some stage in recent yrs! seems odd that a crack has developed in the last year when its been ok for 18-19yrs? maybe the alloy fatigues ect with age. i found that an old shim from the gearbox works perfectly for shimming the bottom mount. hth. i feel for you dirk, not nice when you have problem after problem with your pride n joy. look at it like this, only so many things to go wrong on a kr. before long it will be 100% reliable with mostly new parts!! id change suppliers/crank builder ect just to try and improve your run of luck. your supplier may have a batch of friday night special spares (bad batch/poor qc)?? who knows.

dirk · Post by **dirk** » Sat May 23, 2009 11:26 pm

hi

the crack is to long and the gap to thick for a repair with a shim.

i hope i found an aluminium welder.
that is not easy and i think very expensive.
and then i hope i found what´s wrong wit the engine.
with my luck a crack in the crankcase and the crank seal.....perhaps barrels and pistons, gearbox

it's all ok

but the engine mount... nightmare.
during my first full rebuild i had changed the crank and the crankcase.
perhaps the "new" crankcase was a bit to small.

thanks for the tip with the shim.

KwakOn · Post by **KwakOn** » Sun May 24, 2009 11:06 am

Mine had the same crack, as Elf said, you can run with it.

A friend is an experienced welder and he assured me there was still plenty of strength left as the mountings are welded in enough places.

the shim doesn't repair it - just takes the stress off it.

I ran mine for a couple years like that (not clever but safe enough), repaired it month or so ago and found that the bolt (engine) hole also had cracked.

Fix engine first, probably air leak or something, welding should be cheap - half an hours work.

the-elf · Post by **the-elf** » Mon May 25, 2009 12:18 pm

The only thing about welding Alloy is that the set needs to be DC, while for any other material its welded using AC (or is it the other way round). Anyway if your getting it welded, do the prep work yourselve by Veeing out the crack first as that'll save the welder time. The welding it-self shouldn't cost much at all.