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Discussion in 'Airheads' started by alister102, Jan 19, 2011.
Doesn't look like a Viola to me.
The owner has reported that it works quite well and the cost was minimal. That makes it a very Airheady solution and I like it.
I agreed with Supershaft on his analysis of the need to have some sort of a catch tank and I followed this topic with interest as I have experienced oil coming out of the crankcase breather on my modified R90/6 at high RPMs.
I have been working on a crankcase breather box with a reed valve and oil return lines to the sump.The design is based on the concepts explained in the Eurospares crankcase sucker article (http://www.eurospares.com/sucker.htm) and on seeing the pictures of Udo Gietl and Todd Schuster racing BMW in The King of the Boomers article (<cite>www.omnilex.com/public/bmw78/kotb.pdf) and </cite>my own experiments, I made it with the help of a welder friend and it was installed and tested by Jim Cray, the English tuner, who judged it a complicated solution, but one that works.
The reed valve pumps the crankcase down, and any oil ejected out of the breather can return to the sump. I also fitted a separate reed valve, two variable/shut-off valves (the green and red knobs) and two lines to the exhaust headers to make an exhaust sucker. I haven't tested this system yet, but will do over the next couple of weeks. links to photos below.
That is one setup!
If I tuned a race engine from scratch I would set up a reed block too. Not like that but it's the same basic idea.
I think a fair crankcase pressure test would involve loading the engine. A lot of crankcase pressure doesn't come from the atmosphere, it comes from the combustion process. Even the best ring seals do not seal perfectly. Engine loads test the rings much more than no load. Our engines do run crankcase pressure. Tight top ends run less but they do run pressure. Something is blowing the oil out. It might just be a few ounces collected over many rides. Most any mechanic can tell you that just a few ounces can make a big mess. Oil leaks almost always look like a lot more than they are but a mess is a mess and just a few specks of oil on my back tire is too much. Plus, sustained high speeds that many a road going bike runs is very much more likely to throw oil out the breather. It seems that no one would argue against running their right (or left on the later models) airbox snorkel hose clamps with the screw on top versus the bottom at the carb to better hold in the oil that comes out of many a crankcase breather. I have seen tons of good and tight new beemers set up that way and it is for that reason. Oil out the crankcase breather makes a mess in and on and round your carb thusly. Why wouldn't it make a mess around a K+N filter.
I don't run a catch tank on my own bikes. I just run it out back.
Not sure if this belongs here but here it is:
Seen at AMA Vintage 2012 in the Cafe Racer tent. Owner said cover is being made in US but I forgot who/where.
Sam, that is a purposefully looking bike, just needs a front mudguard, you do like complicated solutions....chasbmw
I am glad that you like the solution to the oil problem. I would be interested to know how you would use the reed block and whether you would have a return line if you did that.
Thanks, I am glad that you like it, I do like complicated solutions! Howver I am really happy with it, no more oil spewing out of the breather at high RPMs and it goes and handles really well, plus Jim's engine is great,
I am still thinking on the front mudguard, the lugs (bosses?) on the K100RS forks are all at 90 degrees to the originals and I have been hoping to use the original mudguard. I am riding it in the meantime, but not in the rain if I can help it.
Are you going to either the Brighton speed trials or the ace cafe reunion? I'm trying to get to both this year.
I wouldn't use a return line. I would put a reed block on the case somewhere.
Same for me. I use a catch tank and live in a real humid climate. More water than oil and not much of either.
Mostly water comes out of mine too. Oily water. Both of my bikes leave a couple of drops on the floor after a ride. Both bikes will wick oil back up on the bike and rear tire up over around 80 or 90 mph unless the vent is just in the right spot. My last setup was running 1% leak down for a long time doing that.
Resurrecting an old topic no doubt. My 2 cents worth then. Been riding airheads for most of the time since 1985 and after 28 years of airhead skulldugery have come to the stage where oil dripping on my left boot is not cool anymore. My current ride is a R80 monolever roadbike (1985) with good compression and newish rings - total mileage 81K miles and she doesnt use much oil at all.
I decided to retain stock airbox and get rid of the breather crap inside the airbox so hopefully no more oily boots. Plugged the breather holes in the snorkels with some TipTop patches and the rest is WIP. The idea is to optimize the oem airbox without any breather crap inside it. Will probably run a separate pipe out back like I did on the '79 Honda which has worked fine for the last 15 years. Will post pics when done.....
What's wrong with just fixing the problem? Excessive blow by and leaking intake tract. I get oil weepage on the bottom of the intake tubes, at most...and that is on a very worn motor. But I do appreciate the bit of extra upper cylinder lubrication.
The clam shells favor the right carb and the square boxes favor the left. An engine in perfect shape can do what the OP is complaining about. Nothing to fix but the crank breathing system.
My advise is to resist the temptation to dump it into the box. It very shortly makes a mess. My setup works great with about 130,000 miles experience. 3/8ths auto fuel line fits perfectly into the vent hose at the airbox. Run that to a firewall coupler drilled out to maximum ID at the water drain and then another 3/8ths hose under the batt box and up the subframe and then back down the rear fender past my license plate. Real clean setup. Works perfectly.
Always test for oil getting sucked back onto your bike and tire at high speed. In my experience, it takes some 90 or 100 mph test runs to make sure the slipstream doesn't oil your tire. Apparently, it isn't a problem for many since I see crank vent setups all the time here that would very shortly make an oily mess out of the back half of my bike. That can be dangerous!
I took all the crap out of my R65 Mono airbox too, and this is my pretty crude system. I rode it with nothing, and seeing as very little oil came out just kept it short with this classic (out of my junk box) air filter. This is after about 2,000km, with lots of time at 7,000rpm and bursts to 8,000rpm - no sign of any oil mist, so it'll stay this way for now.
Oops, one snorkel has gone too, it was in the way. Test runs with it on and off, and with 2 different exhaust systems, running sweet as. Oh, and a K&N filter there too. This is an R65, it's about revs, and a 1,000cc airbox has no problems supplying the required air.