Crankcase breather, filter or airbox

[thumperjsa]

When I hooked up the hose going from the Crankcase to the airbox, it started to choke out my engine and made it run rough. It seems there is a lot of air being pushed out of the crankcase and the engine don't like it.

I disconnected the hose again and my ride runs fine again. DO most people have the hoses hooked up or did anyone opt for a putting a filter on the hose and running it to another location towards the rear of the bike.

When hot I get some of what looks like vey light smoke or steam coming from the crankcase out the hose. Is this normal?

I have only had this bike for about a month now and I am still getting used to its little quirks.

[John]

One thing to check is compression in the cylinders. It should be around 150 psi for a strong motor, but 130 would be acceptable, anything lower than that and I'd be worried about the rings. The important thing is that they be within 10% of each other. The hose in question is a crankcase vent hose and it should connect to the airbox between # 2&3 carbs. It is the large hose, about 1/2 inch, right? When you have it off the airbox, can you feel the air pulsating from it? Kinda like a 'puff, puff, puff...
It may be that the piston rings are not sealing properly, and the compression is blowing by them and into the case. Try removing the oil fill plug, and checking for the puffing there. If you have it there, then I'm afraid you have a problem with the rings. I suppose you could leave it detached from the air box, and put a filter on the end, just to keep varmits out, but don't forget to plug the nipple on the airbox also. How long has it been running? Did it sit for a long time? If so, try squirting some Marvel Mystery Oil in the spark plug holes, put the plugs back in and let it set for a few days. Could possibly be a stuck ring and the MMO might free it up.

[thumperjsa]

I did not think about compression loss. Maybe cause the bike still has so much power.

It feels like quite a bit of puffing from the tube at the top of the crankcase.

I hope not to have to do a ring job on this bike.

The guy I bought it from only had it for about 8 months and he said he would use it a couple of times a week. I have no history before that. I will check on the compression as well as try the oil.

[thumperjsa]

update

John, I popped of the oil filler plug and there is puffing there.

Well I got a compression tester and the news is not what I consider real good.

I am not sure if headers in bad shape might reflect on the compression but one header has a small hole in it near the head and another is half crushed. One is on cylinder 2 and the other is on cylinder 3.

From left leg to right leg:
115/112/100/120

There was a trick in the Yamaha Service Manual I have that said put a few drops of oil in the cylinder and retest compression. If compression goes up, most likely bypass of the rings, and if not, could be valves or rings.

After oil, I got the following,
From left leg to right leg:
125/110/110/155

Yea, 120 to 155.

Well, it looks like an eventual ring job on this bike and I have never gotten this far into engine teardown nor do I have all the tools to do it. I do have a clymer manual and an original yamaha XS1100 service manual which does have the procedure in detail. Not having all the tools to do it deters me from attempting it.

So here is a question. What do you think I am going to have to plunk down at the shop to do the iing job and possibly the valves to since it might need that as well?

One other thing, I put brand new plugs in the bike about 2 weeks ago. 3 look perfect however the one in cylinder 3 looks fouled.

Is there anyone on this forum from South Florida that can give me a recomendation of where to go.


Thanks for the advice.

-Jonathan

[MartyA]

Did you do the compression test with the throttle wide open?

Rings are gonna be tough to find. Valves and seats can usually be repaired, and you can still buy stem seals.

Holes in the exhaust won't affect the compression readings, nor should a partially crushed pipe. However, that partially crushed pipe 'might' be causing the fouling on #3 plug.

Might also be #3 float is too high or sticking.

[skids]

Holes in the exhaust may not affect compression readings on a gage, but they can really affect exhaust scavenging. When this happens, you will have dead torque spots at certain rpms. The cylinder can not draw all of the intake that it needs because it can not exhaust the gases completely. I think this causes the cylinder to operate at a higher average pressure than normal and cause some presuring in the crank case. This is my own unproven theory, but when I took off the harley mufflers (dead spot between 2500 and 2800 rpms) and installed the Jardine
4-1's the breather quit puffing so much and the torque was more even.

[ratbyk]

Excess Crankcase Pressure

Jonathan, do not be in a hurry to open up the engine. Try the marvell oil trick. Then ride the bike for a month. Even change the oil (if you have not so far). Go with something like 20-50 GTX Castrol. Many times when an engine has sat around much of it's life things get gummed up and stuck in an engine. Simply running for a few hours will get things freed up and functioning properly again.
While doing the compression test, make sure that the engine is warmed up, remove all spark plugs, hold throttle wide open while completing test, crank over at least 5-6 times on each cylinder.
Compression guages are notorious for being inaccurate.(a bit off)try and borrow another guage and repeat the test. Then compare differences. The main thing on compression testing is that each cylinder is within 10-15% of each other. A bit low or a bit high may just be variables in the guages.
There will "AWAYS" be some blow by past the rings/piston/cylinders. Even a brand new engine suffers from some blow by.
Having a M/C engine rebuilt commercially can be very expensive and many times heartbreaking. There are so many steps that must be performed properly at the right time to get a successful job. And no matter how good or bad the job turns out getting any warranty for problems (particularly major ones) is "DIFFICULT"!
Run it for awhile if at all possible before opening it up.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[thumperjsa]

Well, I did the test with the throttle wide open and all plugs removed with the engine warmed up. I cranked until I got the highest reading for a few cranks. I am not blowing out any noticeable white or blue smoke from the exhaust either.

Since the bike still has lots of power, I am in no hurry to rebuild the engine. If I lose the power, then I will consider it. In the meanwhile I will try some engine restorer for a week or so and test it again to see if there is any change.

I just wanted to get an idea of how much it may set me beck to do a rebuild.

I bought a new Mac 4-1 exhaust and gonna put that on and see if stops the fouling on the number 3 cylinder.

My plans is to make this into my hobby bike and restore it. I had opportunites to do this witho old cars when I was younger but neither had the time nor money (mostly money) so now I want to start small and work my way up.

Thanks for the advice.

[TopCatGr58]

Hey there Jon/Thumper,

As has been said, 1st oversized pistons and rings are next to impossible to find now, Yamaha doesn't support the main engine parts anymore. Being in Fla. does have a benefit, there is a place that sells the Big Bore kits(can't remember the link right now, it's posted in a message here somewhere), and aside from a low scale 0-75ft/lbs(non-click) torque wrench, a few torx bits, and metric wrench/socket set and allen set, you can make a valve compression tool from a large "C" clamp and piece of pipe, you don't really need any "Special" tools for the engine tear down and rebuild.

The Big Bore kits are around $400 bucks, do a search on this site and you'll find lots of info and talk about them. It comes complete with pistons, rings, wristpins, keepers, head gasket. You'll have to pay a machine shop to bore the jugs to match the pistons($150-250), and you can get the rings and pistons back in without a fancy ring compressor!

But like the others said, some MM in there and run it for a good while at proper temps can free up carbon stuck rings, and blow out old carbon, and with your exhaust and carb work, the engine should come back pretty strong!! I also agree with running the thicker grade of oil afterwards, can help those rings to seal better, especially as the Fla. Temps rise!! I've got my crank vented to air behind the engine, JCW and DK sells nice little chrome filters for them if you want to get fancy, I've even seen some at local auto stores! Congrats and good luck!

[TopCatGr58]

Found the link:

Pro Flo in Pensacola, Fla.

T.C.

[thumperjsa]

As to ring sets for the pistons, it looks like Bikebandit.com has them.

Although I don't know what is meant by std (standard) versus 1st (alternate parts) and 2nd (alternate parts). About $41 for the set according to the website.

Since the valve cover is leaking, I am planning on pulling it off and replacing the gasket. While I am there, is there anything in particular I can look at as far as valves and guides that might indicate excessive wear?

[ratbyk]

Cam Cover Off

Re-torque the head bolts and check valve clearances.
Ken/Sooke

[TopCatGr58]

Hey Thumper/Jon,

The stock bore is 71.5mm, and then it increases in 0.25mm increments for each oversize, 71.75; 72.00; 72.25; and 72.50 as being listed as the last factory recommended size. The smallest Big Bore is 74.00mm diam!!!

The Standard sized rings would be good if your wear limit after pulling the jugs and having the cylinders micrometered was less than 0.1mm, then you could HONE the cylinders and go back with the new OEM sized rings, however that's doubtful!?

As Ken said, check the valve clearances, otherwise all you can do is visually inspect the cam lobes for signs of uneven wear, and you could measure the lobe heights. Without pulling the head and valve springs, you can't really check the guides and such! You can look at the cam chain sprockets and teeth for signs of wear there also. As you turn the engine over by hand/wrench while doing the clearance checks, you can inspect the lifter cylinder walls for signs of scratches/scoring.

You may want to pull the rubber half moons and inspect them for leaking, and put a thin bead of RTV around them if they appear to have shrunken a bit, you can find a thread/tech tip on this. HTH.
T.C.

[chevy45412001]

breather hose

i too run my crankcase breather open,for about three years now,no ill side effects other than a LITE coating of engine gook.It wipes right of w/rag.I actualy went out tonight and bought one of those cute chrome breather elements ,at auto zone $9.99.Have to figure out a nice way to put it on though.It needs a 90 deg. fitting to keep it upright.

[chevy45412001]

breather

theese might work
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well i want to small but you get the picture...lol