crankcase breather on turbo engine

[marcovandevelde]

Hi Guys,
After running my turbo GS1100S katana engine with wiseco 1168cc kit through the summer, I'm constantly having oil-leaks from the strangest places. Like the camchain-tunnel to front of the engine, seal of the clutch-arm, and the seal behind the ignition rotor. It has the standard breather on top of the engine + an extra 19mm dia. (.75") hose on the filler cap to a K&N breather-filter. I run 7-12 psi of boost. Is this kind of blowby normal, and can it be fixed with extra large breathers? It doesn't use any oil.

Greetz, Marco.

[Kaptain Ketchup]

I had, almost, the same problem with my turbo. I did not see any leaks in the gasket surfaces of the motor, rather the pressure vented out of the turbo return oil line and pressurized the inner workings of the turbo causing oil to leak into both the compressor wheel and turbine wheel cavities. I also had the stock breather routed to a PVC valve attached to the frame above the motor.

My solutions... along with a long deserving turbo rebuild.

I removed my oil drain line from the oil fill hole. Then installed a breather, of large diameter, where the oil fill cap was. I modified an oil cap (cheap part at the wreckers) so that the breather still threads into the fill hole. A small baffle on the underside of the breather cap prevents most of the oil from splashing into the breather element (it still gets oil soaked a little bit). The turbo oil return line, which should ALWAYS run on a natural downward slope, was relocated to the rear of the clutch housing casting. You can see the hole if you look closely at the lower left part of the pic.

http://i17.photobucket.com/albums/b83/Kaptain1100/13854fce.jpg

This is a pic of the drain off the turbo.

http://i17.photobucket.com/albums/b83/Kaptain1100/c0b88ea8.jpg

I would also check the age, history, condition of the cylinder head. If the valve guides are leaking then pressure may be getting into your cam valley. A naturally aspirated motor relies on ring seal and valve seating to hold back combustion pressures. The intake runners are normally under vacuum from the downward piston movement. On a turbo bike the intake runners are under pressure (7-12 psi in your case). If this pressure were getting by any of your 8 intake valve guides (16 valve head I assume) then it would cause a bit of pressure to build up in the cases. I imagine if you leak tested a used, aged cylinder head with valves in it under water at 7-12psi you would see tiny bubbles coming from around the valve stems on the top of the head. It would help if you could run your crank vent into your air box (if used) or tap them right into the filter pod heads.

Hope this helps,

[LW_Icarus]

this may be a solution: http://www.fastbygast.com/catagories...n/vacuumii.asp

I was perusing their site a while ago and saw this, thought if you needed positive crank ventilation that may be the ticket.

but Id do a leakdown test on the bikes engine I think, just to establish that you don't have an issue there. compression tests are ok, but ive seen a cylinder pass a compression test and fail a leakdown test miserably. if youve been to the dragstrip you probably know people that own the tool for it, or you can improvise a little and use a regulator and your ears (not as accurate)

[lecroy]

Gas ported pistons

http://i17.photobucket.com/albums/b83/Kaptain1100/c0b88ea8.jpg

This is a nice setup!! I had to make a new one and copied the original one from Mr Turbo. It is very easy to over tighten the drain and warp the block. Then things leak.

[marcovandevelde]

Thanks for your fast response, guys.

This is how it is fitted now. Don't mind the cheap hoses; these will be rerouted with new hose to a 90 degr. elbow which will fit into the clutch spacer rather than the cluth cover.

I've been thinking to reroute the breather from the filler cap to the intake tract (where will be vaccuum) instead of the breather-filter, with an oil separator in between. But do we want this waste-gasses and slight oilmist into the intake? It will probably create problems. Is a vent to the exhaust an idea?
The vaccuum pump is also a good idea but IMHO when you need this kind of kit it's better to find what's causing it first.

Pardon me but how is a leaktest performed?

Grtz, Marco.

[Kaptain Ketchup]

Leak testing explained (hopefully):

At a casting plant I used to work at we leak tested cylinder heads and blocks at various stages of machining to locate holes, casting flaws (core fins, dropped cores, large porosity), and machine cutter depth flaws. To leak test a part we would block off an internal passage of the block or head (water jackets, MOGs ? main oil galleries, cylinder liner interfaces, and intake and exhaust runners) and apply a regulated air pressure to the passage. If the leak was large or highly visible it was possible to hear the air leaking and use soapy water to find the location of the leak and determine root causes. If no leak was seen, or heard, then the part was lowered into a large tub of water, pressure still applied. Once the part settled and the water calmed down it was possible to see air bubble rising to the surface like little champagne bubbles. We just tracked down the leak and made sure it wasn?t a fixture-sealing problem and then measured the amount of rising bubbles in one minute with a submerged graduated cylinder. I have used this process many a time in the kitchen sink to check and double check welds and to determine where leaks are. I know that they use this process for new gas tanks before they are put on cars and is very similar to finding a hole in an inner tube.

Hope that clears things up,

Mark

[marcovandevelde]

OK.
But do I need to whip the engine out (80kg) and dip it in a bucket?
Sorry! What I did to analysers when I worked in a Plastics-plant was use soapy sprays to determine leaks. So I guess I can put some air-pressure on the engine to find the leak with this soapy spray then.

And compression test it.

Grtz, Marco.

[Kaptain Ketchup]

HA! or you could just drive into a lake, or large body of water (pool, ocean, etc.)

The leak test I am talking about is strictly component based. You'd have to take the head off (not much work really) and prep it for submersion and build some sort of fixture to cover the intake runner you want to test (would be nice and easy to do one runner at a time). Then just supply air to it and watch for bubbles. It would be a very BAD idea to pressurize your engine as it sits just to see where it leaks. You would run the risk of blowing out gaskets and seals all over the place.

What type of oil are you running in that thing?


Mark

[marcovandevelde]

I'm running Castrol GPS 10W40 semi-synthetic it it. The business!

Marco.

[Anonymous]

Not to hijack your thread, but you guys seem to know a thing or two about turbos.

Recently I found out a guy who does contract work for our company has access to a Whitaker(?) turbo that was previously installed on a 79 Yamaha. Seems his father owned a Yamaha dealer in the 70s and early 80s.
Anyway, if I go ahead with a complete teardown on the 750, I thought the turbo might be a little fun addition. Anyone hear of the brand?

[LW_Icarus]

for the automotive world, snap on makes a nifty regulated leakdown detector, it uses a hose similar to a compression tester. either rotate the engine till both valves close and hold the crank (it will wanna rotate with air pressure!) or even better remove the cams, so all valves are closed, then the tool regulates air down to about 12-18 psi I believe. it also has a gauge measuring volume of air escaping from cylinder.

so you may see a number like 20 % leakdown on #3 at 15 psi.

some leakage is normal and unavoidable, and my experience is not with turbod GSs, but with the automotive end. we would use it to diagnose cracked rings, burnt/bent valves and the like. if any of the cylinders show abnormal leakage, you can usually listen and see if its blowing into the crank case, out the exhaust or whatever.

a friend of mine had a supercharged subaru, it ended up busting the ring lands, and that broke rings. it eventually blew its oil out every hole. compression test was a lil down but not what youd think was "bad" but it had alot of leakage.

other solutions may work for you, and you may not have any abnormal leakage. and I would believe that yes, you can use exhaust for crankcase scavenging without a problem. I think that should be done carefully to make sure it goes somewhere that it will get suction is all.

[lecroy]

Recently I found out a guy who does contract work for our company has access to a Whitaker(?) turbo that was previously installed on a 79 Yamaha. ... Anyone hear of the brand?

I never have. It may have been a repackaged unit. There are a lot of companies that were buying the Rajay's and putting their own labels on them back then. Can you post a few pictures of it?

[Anonymous]

I haven't commited to buying it, and have not seen it (yet!) , maybe this weekend.

Concerns range from plumbing, streetabilty, my lack of turbo knowledge and the 750 is the absolute most reliable machine I ever had, really don't know if I want to mess the bike up. Still it is tempting....

[Kaptain Ketchup]

Never heard of them either. Pics would really help. If I were you I would pass on the whole set up. There are days I wish I had my original '78 750 back... long before I tore it up by putting a turbo on it. Once I got the turbo it was a never-ending list of upgrades and sacrifices. Its a great bike and I have lots of fun with it, but its much higher maintenance now and miss the days of throwing a leg over my gs750 and taking off for the day. I intend on finding another plain gs750 to use as a daily driver soon. Just too much fun to pass up the reliable 750 IMHO.

But if the deal is right (and when is a deal never right!!!) Then pick it up with intentions to sell parts to board members or on the all mighty Ebay.

Keep the 750 as the dependable 750 it is now. Us turbo guys envy the guys with the low maintenance, drive anywhere, anytime bikes. I know I do... sometimes.... that is until I fire my beast up and get into the boost.

If I were to do it all over again, I would have kept my 750 the way it was and bought a junk/basketcase 750 frame and engine and started on a turbo bike from there. The gremlins buried deep in your 20-25-30 year old bike will come to the surface with a vengeance when you try to hold +200hp in the frame rails. Stock frames turn to wet noodles under power and the suspension seems to disregard the laws of physics and jump ship when counted on the most.

Regards,

Mark

[Anonymous]

Thanks for insight, IF I pick up the turbo unit, it will be shelved for another bike, another day .

As they say, Back to your regular scheduled programming.....


Thanks, greg