I've searched this subject, and seen a variety of ideas. Has anyone tried running a hose from the PCV exit holes to the barb on the intake on the carb holders? I hooked it up, and didn't see any issues, although it did raise the idle slightly, cured by turning idle screw. Any ideas whether this would be a good or bad idea? Thanks for any input.
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Gordon
XS650 Junkie
First off, these engines were designed without a "pcv" system, & relie on crankcase pressure to 'relieve' the gas. The most successfull method of relieving the pressure from the gas is by installing a common auto brake booster check valve , so the gas only travels out & not back in. The stock system does not do this, but uses a series of baffles to keep dirt & debris out of the engine. The stock system also used the air filter 'box' to keep out the debris. It also did use the incoming air for the carbs to 'recycle' some of the fumes. By running a "PCV" system will create a 'lean' condition & burn up your engine. Thats why the idle speed went up. I run the stock system with a small conicle filter on the end, to catch any oil, prevent debris from entering the system. Thats because I have 'pod' filters & no air filter 'box'. Works well for me, & I clean the filter at every oil change. Same with the air filters.
Thanks for the response. So the original set-up would be better described just as Crankcase Ventilation, minus the positive? My original thoughts were as this was piped into the airbox, the suction from the carbs pulling air from the box would create a bit of a vacuum on the crank vent, but maybe the air box is big enough of a space that the draw would be negligible. While jetting, I've spent some time revving the engine quickly to check engine response to jet changes. I get a small amount of oil spurting out of the crank vent. Do you have trouble with the oil seeping out of your pod filters? I have read about a recall that these dipsticks were marked incorrectly, and ended up with too much oil in the base, causing this spurting issue. Just wondering what your experience was with that. I just don't want oil everywhere. Thanks again.
I use a one way breather in the down tube on my 80 and still use the stock air box although modified with another vent tube.....3 each works great...I still find some oil collecting on the left side when the bike is on the sidestand........I just loosen the right vent tube to the air box and pour out the little bit every time I change oil............I wouldn't lower my oil from the 2 guarts.........I just notice where it is on the stick after the oil change and keep it there...........
I have seen posts in the past where people have glued a small tube into the pod filter near the bell to get what little oil might collect in the tube.....thought that was pretty clever.........once the engine is running and the valve is working properly there isn't much air coming out the vent due to the negative pressure created by the valve in the crankcase......and thinking if the tube wasn't going down then up to the filter there would be no place for the oil to collect....
Forgot........for those that don't use the crankcase vent and use the stock air box it might be a good idea to drain that tube once in a while.......before installing the vent mod I noticed a lot of oil would collect in the vent tube at the bottom and eventually the bike would smoke on the left for a mile or 2 on cold startups.........doesn't do that now that the vent is installed and less air is moving back and forth but if left long enough it might......did find a 1/3" of a shot glass or so of oil in mine after a year so now I check it at oil changes........don't want to polute left .......
xsjohn
I have seen posts in the past where people have glued a small tube into the pod filter near the bell to get what little oil might collect in the tube.....thought that was pretty clever.........once the engine is running and the valve is working properly there isn't much air coming out the vent due to the negative pressure created by the valve in the crankcase......and thinking if the tube wasn't going down then up to the filter there would be no place for the oil to collect....
Forgot........for those that don't use the crankcase vent and use the stock air box it might be a good idea to drain that tube once in a while.......before installing the vent mod I noticed a lot of oil would collect in the vent tube at the bottom and eventually the bike would smoke on the left for a mile or 2 on cold startups.........doesn't do that now that the vent is installed and less air is moving back and forth but if left long enough it might......did find a 1/3" of a shot glass or so of oil in mine after a year so now I check it at oil changes........don't want to polute left .......
xsjohn
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Thanks John. I had thought about piping it into the pod, but didn't want oil to soak the pod too much, and make a big mess, guess some type of container in there might do the trick. Sounds like the brake booster valve is common, and haven't read of any negative effects. I have the vent with the two pipes exiting, but have a spare engine with the single exit point. Are those interchangeable, and would that be acceptable? Sounds like vent to pipe with brake booster valve, then down into pod, with some type of catch tube, does that sound reasonable? I have fresh oil, but didn't so much measure it, just kept adding until I hit the full mark on the dipstick. Maybe I will drain, and use two quarts, and mark the dipstick accordingly, then with valve in place perhaps oil exiting will be minimized.
Definately less oil leaving the engine with the valve...........yea the smaller single spigot is good and you don't have to bore it out or anything....just leave it at (.220 thou)......there is so much less air coming and going I can hadly feel any thing happening at the end of the hose after the valve was installed............
just thinking .......maybe a loop down then up with a drain valve in the tube at the bottom of the loop for the little bit that collects in there that could be drained at oil changes....I never see any oil on my filter now ....I always considered the stock box to be better than any pod arrangement foa a multiple of reasons.....not sure what bike you have but this is what I did to my 80 box to make it breathe better............and maybe the older metal air boxes breathe better than the new (80-84) ones........I just put my valve in the single oil down tube that comes on the single spigot later ones................I make my own filters for mine using the existing wires with all that fuzzy filter stuff removed.........
xsjohn
just thinking .......maybe a loop down then up with a drain valve in the tube at the bottom of the loop for the little bit that collects in there that could be drained at oil changes....I never see any oil on my filter now ....I always considered the stock box to be better than any pod arrangement foa a multiple of reasons.....not sure what bike you have but this is what I did to my 80 box to make it breathe better............and maybe the older metal air boxes breathe better than the new (80-84) ones........I just put my valve in the single oil down tube that comes on the single spigot later ones................I make my own filters for mine using the existing wires with all that fuzzy filter stuff removed.........
xsjohn
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Gordon
XS650 Junkie
Iron will, there is some of a vacuum from the carbs, but that vacuum is directly related to throttle plate position. It occurs after the carbs, not before, like the vacuum barbs do. The only pod that gets a little oil in it is the one on the end of the vent hose. And that is a very small amount.
i think the crankcase vent system on these engines is horrible. seems like every year yamaha changed the design or function of it. I've had my 75 for 2 yrs now and I still can't get a straight answer on how it was factory.
I know with my head breather design I will lose a quart of oil every 250 miles if I don't put restrictors in.. when I bought the bike there was just 2 vent tubes to the ground with no restrictors in the head breather... the bike was spitting out oil. I have to add oil all the time. I then plugged one side and inserted a piece of vacuum line in the other side to smaller the ID. I vent this line right to the ground... now I have an oil leak due to the increased pressure. I can't win with the breather design...
I know with my head breather design I will lose a quart of oil every 250 miles if I don't put restrictors in.. when I bought the bike there was just 2 vent tubes to the ground with no restrictors in the head breather... the bike was spitting out oil. I have to add oil all the time. I then plugged one side and inserted a piece of vacuum line in the other side to smaller the ID. I vent this line right to the ground... now I have an oil leak due to the increased pressure. I can't win with the breather design...
Sounds good. I unhooked it today from the barb. Had a feeling the barb might be a bad idea, and figured better to ask than destroy the poor thing. Also, wasn't sure about the valve, but it sounds like alot of people have done it, and run there engines long term this way with no problems. A little amount of oil is fine, I was just afraid the little pod would end up soaked, and dripping everywhere. Thanks for the input.
John...thanks for the picture...neat arrangement. My bike was built in late '78, making it a '79, I think, though I've never checked the numbers, but could easilt enough. It had pods on it when I bought it, and the vent lines were just hanging down. I don't have the original airbox. So would you bother piping it into the pod, or maybe switch to the single port vent, then tubing to the valve, then maybe a T in the line to connect the small pod like Gordon has, then another inch or two of tubing with a plug in the bottom, to catch any oil, that comes out.
If I did pipe it into the carb pod, would it be acceptable to vent it into one, or should I stick with the double vent port, and pipe it into both carb pods?
Sounds like the first option might be best, single port, line, valve, mini-pod, and drain plug. What do you guys think?
If I did pipe it into the carb pod, would it be acceptable to vent it into one, or should I stick with the double vent port, and pipe it into both carb pods?
Sounds like the first option might be best, single port, line, valve, mini-pod, and drain plug. What do you guys think?
Gordon
XS650 Junkie
Most people have written that they join the 2 lines with a 'T' like you said, then run a line with the little pod filter on the end. Some, with the 2 spigots, have used 2 booster check valves, one on each nipple. OOOOHH, I said nipple. Like 'em, love 'em gotta have them. Sorry, poor attempt at humor.
Then they 'T' them as described.
Malloym, sounds like you got a blow-by problem. Either that, or the baffles are missing in the breather assy. on the head. T- Cat had a similar situation, and I believe his cleared up after doing the mod I just mentioned, with the 2 check valves. I am not positive on his fix, but you could PM him for the info. Also, the oil level could be too high.
Then they 'T' them as described.
Malloym, sounds like you got a blow-by problem. Either that, or the baffles are missing in the breather assy. on the head. T- Cat had a similar situation, and I believe his cleared up after doing the mod I just mentioned, with the 2 check valves. I am not positive on his fix, but you could PM him for the info. Also, the oil level could be too high.
.....in some cases nipples are better in pairs...
Yuh....I wasn't sure why they switched to a single vent port, maybe the double was overkill.
Gordon
XS650 Junkie
I do believe thats right. As i wrote, the single one on my '80 G works fine with out any trouble. As with ALL engines, there is some blow-by, & those gas's are harmfull & need to be vented. Not to say nothing about blowing out seals & oil contamination. When I started fixing engines, there were no PCV systems at all, just a tube that ran down the side of the engine to the bottom of the oil pan. Had a slash cut so a 'draft' was created while driving down the road. Boy, how things have changed. My new Harley's have a PCV system, along with a closed loop fuel injection system. Waiting for them to be fitted with cats soon. And vapor recovery systems. Kinda got that now, but no charcoal canister, just a closed fuel system that vents to the intake during warm-up. They may even have a cat, haven't read the whole damn manual yet. It's as barge as one for the new truck we got. Like 300 pages.
Designs certainly have changed, you pop the hood on some of these newer vehicles, and your like HUH, so full of electronics. I like the simplicity of the older stuff, but I'm cheap, and like to do my own work......300 pages...YOUCH!!!
TeeCat
One-Mik Wonder
Sorry I'm late on this, guys:
What I ended up doing on my '73 was blocking off the left spigot of my Y with a vacuum plug, and running some fresh Mike's breather hose to the front of the battery box, where I mounted a Mike's reed valve, and then continued down to the swingarm with more hose, capping the outlet with a small conical breather. After making sure I had no more than the recommended two quarts of oil (for my '73 after the oil capacity service bulletin) and some test miles, I'm cautiously optimistic that my oil leak (which appeared to be coming from the left forward case joint behind the alternator) is largely mitigated. The Mike's valve is a pretty substantial unit that does not let air back in. I also think it's important not to mount the valve any lower than the battery box, as I have heard it may impair formation and maintenance of vacuum in the crankcase.
Worth a try!
Thanks for the response TeeCat. I actually ran it up the road for the first time today, to check jetting etc. Didn't do anything with the crank vent yet, tomorrow hopefully. Kids on VAC this week so spending most of my time with them.
yamaman
xs650 addict
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G'day mate, yep from the factory they spat oil out of the breather! The fix was put out in a service bulliten to drop the oil level to around halfway on the stick! A copy of the service bulliten & the required measurements for the new mark is on this site somewhere! I shall endevour to find it for you.
Gordon
XS650 Junkie
Glad you found a difference there. On the rider site, and the garage site, too, they were talking about a mod to the valves which involved drilling out the valves. Forgot why, but it didn't make sense to me. Yea,you want it to be sort of free flowing, but they gotta have some kind of oil baffle, & then some way to drain off that oil back into the engine instead of to the air.
There isn't a whole lot of oil pressure on these engine's, but enough to make the oil 'mist' on the top end. All of which is good, not just for lubrication but cooling as well.
So you might want to do what Tee Cat did.
There isn't a whole lot of oil pressure on these engine's, but enough to make the oil 'mist' on the top end. All of which is good, not just for lubrication but cooling as well.
So you might want to do what Tee Cat did.
... Boy, how things have changed. My new Harley's have a PCV system, along with a closed loop fuel injection system. Waiting for them to be fitted with cats soon. And vapor recovery systems. Kinda got that now, but no charcoal canister, just a closed fuel system that vents to the intake during warm-up. They may even have a cat, haven't read the whole damn manual yet. It's as barge as one for the new truck we got. Like 300 pages.
Gordon, lots of bikes have cats. My FZ1 has two of them. And the California versions of all the sport bikes have charcoal canisters.
