M8 trans fluid leaking in primary

[HV]

The only questions I would have is.....where does the end of the hose go ? up high ? is there a filter of any kind on it to keep dirt or rain water out ?

[PoorUB]

I don't know if I would get too excited about dirt or water entering the vent. I suppose you could put a vent on the end of the hose like they do for cars.

[02roadcling]

     If I knew this would fix my bike I would have done it the first time it transferred. I would put a smaller vent tube on it, May do that later but it's fixed.   

Remember our motto: Keep fixing it until it breaks again.

   cling

[hd06]

It goes up the frame then turn down about 2" to keep crap out. You could put a small inline gas filter on it but I left mine open.

[Maddo Snr]

For the life of me I can't see how making it easier for fluid to enter the primary can solve the issue. This venting gig doesn't make sense to me. If anyone can offer a sound engineering/physics based opinion on how venting might work I'm all ears...

[hd06]

 I was a bigger skeptic than you are now the rep. said this would fix it. It's fixed I put 860 miles on my 17 RGS and there's been no transfer. Now give me a engineering/physics based opinion why some bikes will transfer and some will not. Look man all I can say is this fix my bike. I have not found any one that put vent on and didn't work except a guy on another forum said a guy in Germany but I don't peek german. 

[Maddo Snr]

...Now give me a engineering/physics based opinion why some bikes will transfer and some will not...

Riding style, gearbox fill level, gearbox oil type, primary oil level, hyd/cable clutch, RPMs, gear selection, road speed, cornering angle, gearbox temp, clutch actuation depth, slave cylinder diaphragm sealing, carrier bearing oil deflector seal.

Enough variables?

The ONLY way a primary vent can be a cure is if the primary void is going into vacuum. Easy enough to check. Not saying it doesn't work and vacuum isn't the reason though, but...any engineer (well maybe not the MoCo's) will attest that oil turbidity and conducted heat will both create positive pressure in a void, not vacuum.

I'm stoked it worked for you HD06, but the Engineer in me wants an answer.

It's TOTALLY possible that the heat and oil turbidity in the Primary makes the air void heat and expand, venting through the gear shaft, then as RPMs drop and the primary cools, the shrinking void creates a vacuum and sucks gearbox oil into the primary.

That theory would explain why transfer commonly occurs during dyno pulls...

I cured mine with a air-bleed hole in the gear shaft and a tight-fitting bullet cap on the S/C side of the actuator rod. I know 'where' the oil is flowing, 'why' is the issue.

[hd06]

 Maddo Snr,  Do you have a transfer problem?

[hd06]

  Maddo Snr,   I didn't catch that bottom part of your reply how you fixed your problem, Sorry my bad. There something different about this new setup that has everybody scratching heads. This was done by a Harley rep. so will not hit my extended warranty if there is a problem with my trans. later down the road.

[Maddo Snr]

Maddo Snr,  Do you have a transfer problem?

Not on the road 06, only on the dyno. It raised the primary oil level by 1.5mm over 20 or so pulls. Last session (after mods) it didn't budge.

I'm starting to think that the primary IS going into temporary vacuum and sucking trans oil. Keen observers will note the 20% reduction in trans oil volume between TwinCams and M8s. My hunch is the MoCo were well aware of the issue during testing and dropped the oil level to get it under the shaft centres.

Thing is, filter-venting the primary can do no harm IMO, it's cheap and simple, I'm going to run one.

[hd06]

  It must be a vacuum problem. My bike been in shop 13 times for this problem. Harley MoCo thought it was a crank seat, which was replaced and no change.     
  I think there is more M8's out there with this problem. I asked a lot HD dealers about it and there is a pause then they say, oh we had a few.  My local service department told me I was the only one that has this problem. I talked to a salesman one time he said this is a problem we are having with M8's, he's a pretty cool guy. This the problem I had with my bike.                                                                       
  When I talk to Harley rep. at a bike rally and he saw how many times it's been in 5 different shops. He had the solution and put the vent tube on. I haven't had any transfer problems since. This will not ding my extended warranty later down the road. It's a cheap fix. 

[hd06]

 Typing problem, That's crankshaft seal left side.

[Maddo Snr]

Also 06, the primary void was drastically reduced for the M8, increasing the chance of pressure gain (and subsequently going into vacuum after the pressure event). The primary oil-fill was dropped by 10%...(1124ml to 1000ml) but the air volume decreased dramatically.

Also, filling the primary with the MoCo's prescribed fill-volume (1000ml) creates an oil level WAY above (4mm- 3/16") the MoCo's own specified fill height (bottom of pressure plate)

Next dyno pull I do I'll stick a recording Vac/Pressure sensor on the primary and see what's going on.

One last thing 06, do you think the MoCo know darn-well what the problem is but don't want to lose face fixing $40K bikes with a $2 mod? There's something fishy going on here when the Tech Rep knows exactly the right cure off the top of his head...

[hd06]

 Yes,I don't know why I had to go through so much crap to get my bike fix. If I knew this would fix my bike I would have done it a long time ago myself no questions asked. I would like to know the results.    Thanks

[lonegoosehonking]

Is that an 1/8" NPT fitting into the primary? What size hose / barb ?

[borno]

Why not use a breather vent plug, like on a gearbox?

[hd06]

   Yes  1/8 NPT
     I don't know about the breather plug, The Harley rep. put it on he ran the hose up the side of the frame across the top and down the other side about 3". I don't think it has to be that long but I know it works.   Good luck

[hd06]

 Hose is 1/4 it fits snug on the fitting

[lonegoosehonking]

Thanks for the information.

[hd06]

     

[Hilly13]

Also 06, the primary void was drastically reduced for the M8, increasing the chance of pressure gain (and subsequently going into vacuum after the pressure event). The primary oil-fill was dropped by 10%...(1124ml to 1000ml) but the air volume decreased dramatically.

Also, filling the primary with the MoCo's prescribed fill-volume (1000ml) creates an oil level WAY above (4mm- 3/16") the MoCo's own specified fill height (bottom of pressure plate)

Next dyno pull I do I'll stick a recording Vac/Pressure sensor on the primary and see what's going on.

One last thing 06, do you think the MoCo know darn-well what the problem is but don't want to lose face fixing $40K bikes with a $2 mod? There's something fishy going on here when the Tech Rep knows exactly the right cure off the top of his head...

Maddo I'd be interested to hear what you find out re vacuum. The fat rod might be a band-aid in this.

[Maddo Snr]

Maddo I'd be interested to hear what you find out re vacuum. The fat rod might be a band-aid in this.

I'm tuning a pretty warm 114 next week which has transferred since it was new.

I've made a primary vent using all KTM genuine parts (crank-vent spigot and fuel breather hose with one-way valve).

I'll do the pulls with and without the mod. The mod will force the primary to vent through the cross-shaft but breathe in through the vent hose.

The pressure/vac gauge will tell the story in two seconds...I'll drop a couple of O'rings onto the cross-shaft to seal the primary first.

I'm not a fan of the fat-rod idea, it's (partially?) sealing a void that is designed to be vented. It is obviously placing greater stress on the sealing gaskets...

[hd06]

 Looks like you have your ducks lined up.   

[rudi_ufg]

air vent filters work bi-directionally

https://skarke.de/en/products/air-vent-filters/air-vent-filter-series-bef-bed

[Maddo Snr]

air vent filters work bi-directionally

https://skarke.de/en/products/air-vent-filters/air-vent-filter-series-bef-bed

MX bike vent valves certainly do not.

I used a YZ250 vent hose and valve attached to a KTM250SX flange.

To test we used a new primary gasket with Hylomar coating both sides and sealed the cross-shaft vent with 2x O'rings

On the dyno we saw the primary air pressure get to 5/6 psi and after bleeding it developed 8-9" of vac.

We've fitted the mod to the problem bike and it's done 500 miles now with the primary level sitting constant at 1/2" below the derby hole notch.

One bike proves very little but it was a bad transferer.

As an aside...I did a viscosity test on a new container of Formula+ and it tested 75W at 77 degrees F. I thought it was 50W?