[michaelwhays]

I started the investigation yesterday afternoon. Removed the seat and the battery. Unscrewed the catch can and pulled the breather lines off.  Sure enough inside the crankcase breather inlet was a big thick glob of mayo (at its seems to be affectionately named in this forum). It filled in the entire inlet up through the duckbill. Next i pulled the breather tube out of the crank case end. and peered inside. more of the same. wiped of the end and gave it a stern puff (outward) a little pressure delay and than splat, a huge gob of snot launched out. Leaned out the rest with compressed air, followed by a solvent bath and a rinsing of water to counteract any of the degrading affects on the rubber line, followed some more compressed air to dry it out. Gave the catch can a very through cleaning. pulled the timing case breather tube out and found it to be clean with some fresh oil residue dripping out. so i guess what happened is that the "mayo" blocked the crank breather line which caused enough positive pressure build up that the oil ejected out of the timing cover through the timing breather tube , filled up the can and flooded into the air-box. Any maybe, just maybe when i took the big leap off the curb the other day, the bump was enough to jolt all of the condensate "mayo" into a blockage. I wasn't very successful at finding a good way to re-route the breather tube to prevent a slight low point in the line without the threat of a crimp so for now i will just have to keep an eye and flush the line periodically (maybe every 1000K?)
I purchased a K & N filter cleaning kit but have decided that it is not worth trying to revive it as it is throughly soaked in oil. Last thing i want now is to have to be tinkering with the mixture to compensate for low airflow to the carb. I ordered a new OEM filter this morning and will have the kit for future use. My last concern is the bit of oil residue that made it to the carb. Does this seem problematic?

[t120rbullet]

K&N filters are soaked with oil when you buy em. The recharge kit contains a cleaner and more oil to soak the filter with. It's the oil that does the filtering on them.
All you need to do is clean it and re-oil it and you are good to go. A lot easier than going back to the stock filter and re-jetting your carb.   

IMHO that whole breather setup was doomed before it ever left the drawing board.

[Spitting Bull]

Michael, congratulations on such a thorough investigation.  I have a different theory on how the problem occurs.  I don't think the blockage causes oil to be forced into the can through the return pipe - the one from the can to the timing-cover.  I think the pipe from the crankcase to the catch-can gets blocked as you have discovered, but then pressure builds up until there is enough to overcome the blockage until there is a sudden massive splurge of mayo, oil-mist and oil through the pipe and ito the catch-can, filling it almost immediately and sending the overflow into the tool-box.

It used to happen to me on every long high-speed run (by which I mean around 45 mph or slightly more.  I was in the later stages of running-in at the time).

Following advice given on this forum, I removed the crankcase pipe, cleaned it, and fitted it the other way round, passing it over the frame cross-member instead of underneath it and with the right-angled bend at the can end, not at the crankcase end.  It then makes a continuous fall from the can to the crankcase.

I also began keeping the engine oil to just below halfway betwwen the maximum and minimum marks on the dipstick. 

*Touch Wood* My toolbox and air-filter have remained dry since that day.

Tom

[sopwithdriver]

I agree with Tom, same thing happend to me 3 times during the first 1000 miles and each time it was during a high(er) speed and longer run than the weeks before. The first time I heard the pop as the vent pipe shot the mayo-goo out and probably 1/3 of a quart of oil followed and filled the can then the air box. When I stopped it ran out like a faucet. I junked the whole crap can system for the old duckbill over the chain trick days later. No issues since. Keep it simple. Roger.

[michaelwhays]

Thanks for all the replies. The reason i suspect the oil coming from the timing vent is that A. no mayo was found anywhere in the can past the duckbill including the air-filter. B. there was a lot of mayo in the crank breather tube and not a trace of oil. C. the timing tube seemed to have a fresh trickle of oil when i removed it.
Had the oil come from the Crank tube, it seems it would have blown some mayo out of the duckbill, but it looked to me like there was a solid blockage prior to the outlet of the duckbill. if oil had passed through it seems like there would have been at least a small passage and i would expect to find mayo splattered all over the can and in/on the screen. I also would have expected to see some mayo draining back through the outlet to the timing compartment, but i didn't find a trace of mayo in the timing breather tube. What do you think? could it have passed through the crank? The other side of logic it seems lake there would have been a heck of a lot of pressure to blow oil from the timing tube, and with that much pressure it seems like it would have blown the mayo out of the crank tube. Maybe it did blow some mayo out but it all ended up on my exhaust pipe. didnt notice any while driving. didnt notice a swirl in the oil when it was pissing out on my driveway either.
After reading t120rbullet's reply i decided to give cleaning the old air-filter a shot. it is still very black and oily but ill hope for the best. its drying right now after the cleaning process and hopefully i can oil it this evening or tomorrow. added just over a half quart of oil in the tank. just above the halfway mark on the dipstick. hopefully all is well from then on. Thanks!

[Spitting Bull]

Michael, on the three occasions when my system blew its top, there was thin mayo running out of the toolbox along with oil, and when I cleaned out the pipes there was thicker mayo in both of them but mostly in the crankcase pipe.  I suppose that different bikes could show different severity in the symptoms, but inverting the crankcase pipe and avoiding overfilling has solved the problem for many owners.

Tom

[michaelwhays]

Well convinced that the tube reversal was worth my time i went out and gave it another shot. I tried to route the tube over the bar alongside the battery but its to high. i have to bend it back down to fit it to the inlet at the bottom of the can. now it has three bends plus a very tight squeeze behind the battery which could restrict airflow. i re-aranged the hose through every passage i could find but ran in to the same problem. the best routing still seems to be as it came which only leaves it with a bit of a dip right after the bend on the crank case end. do i have a uniquely low mounted catch can? i noticed on "scots bullet" picture it looks different. is this the more common model? guess i will just have to give the breather special attention and clean it out periodically.

[Spitting Bull]

Michael I have just had a thought.  My bike is a 350.  I wonder if the pipes are different on a 500?  If I have time tomorrow I'll take a couple of pictures of mine.

Tom

[Anon]

 I was just talking to Vince just yesterday about problems with my breather clogging with the dreaded mayo stuff.  I did shorten and reverse the tube from the crankcase to the can and it helped, but it still has a bit of a dip no matter what way I place it and it eventually clogs.  In my case, the way i know it is I start getting smoky starts or suddenly notice my oil getting low.  I'm guessing the crankcase pressure causes oil to push past the rings and then it burns off.

I think I'm going to try removing the current system and just route a duckbill to my chain.  For those who have done this, what did you use to stop up the return port on the timing case and the inlet port to the airbox?

Eamon

[t120rbullet]

For those who have done this, what did you use to stop up the return port on the timing case and the inlet port to the airbox?

A rubber vacuum cap, I think a 5/16 on the return to the timing chest and 3/8 on the air box.

[The Garbone]

I got some heavy pliers and crimped the air cleaner port closed being careful not to break the tube.

[Spitting Bull]

Michael I have just had a thought.  My bike is a 350.  I wonder if the pipes are different on a 500?  If I have time tomorrow I'll take a couple of pictures of mine.

Tom

Michael, our setups look different.  Here's what mine looks like. 

Tom

[sopwithdriver]

I was just talking to Vince just yesterday about problems with my breather clogging with the dreaded mayo stuff.  I did shorten and reverse the tube from the crankcase to the can and it helped, but it still has a bit of a dip no matter what way I place it and it eventually clogs.  In my case, the way i know it is I start getting smoky starts or suddenly notice my oil getting low.  I'm guessing the crankcase pressure causes oil to push past the rings and then it burns off.

I think I'm going to try removing the current system and just route a duckbill to my chain.  For those who have done this, what did you use to stop up the return port on the timing case and the inlet port to the airbox?

I cut the hose 1" away from the timing chest nipple and plugged it with a bolt and then put a hose clamp on the bolt. Works fine for me. Looks appropriately home-grown/field-expeidient on my military

Eamon

[michaelwhays]

K&N filters are soaked with oil when you buy em. The recharge kit contains a cleaner and more oil to soak the filter with. It's the oil that does the filtering on them.
All you need to do is clean it and re-oil it and you are good to go. A lot easier than going back to the stock filter and re-jetting your carb.   

IMHO that whole breather setup was doomed before it ever left the drawing board.

I am still using the OEM filter on my bullet. If i just put a new clean OEM filter in its place i wont have to re-jet will I? I cleaned the filter and am in the oiling process now but am still uncertain about wether or not its worth my tamie as it was very very saturated with 20W 50. the K&N oil is certainly much different than 20W 50 right?  Other question that is still to be answered is whether or not the oil that made it into the carb will be a problem, doesnt seem to be much but is evident around the 3 inlets located around the lower perimeter of the carb on the filter side of the venturi.

[t120rbullet]

I am still using the OEM filter on my bullet. If i just put a new clean OEM filter in its place i wont have to re-jet will I? I cleaned the filter and am in the oiling process now but am still uncertain about wether or not its worth my tamie as it was very very saturated with 20W 50. the K&N oil is certainly much different than 20W 50 right?  Other question that is still to be answered is whether or not the oil that made it into the carb will be a problem, doesnt seem to be much but is evident around the 3 inlets located around the lower perimeter of the carb on the filter side of the venturi.

Going from an OEM filter to a OEM filter won't require re-jetting.
Going from an OEM to a K&N or from a K&N back to a OEM filter will.
Any changes made to the intake or exhaust will require re-jeting the carb.
I wash K&N's with gas or kerosene and it will clean/disolve any kind of oil thats on there.
Don't use compressed air on a K&N filter.
The stock filters don't clean up very well. If they are oil soaked just toss em.
The oil won't hurt the carb, at worst it might foul a plug.