Blew the crankcase breather hose off.... - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 12 (permalink) Old 11-14-2011, 08:07 PM Thread Starter
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Blew the crankcase breather hose off....

Ok, so long story short today I had a VERY close call on the bike. I had the return throttle cable break and stick open on me, forcing me to pull the clutch in and shut down the bike/coast to a stop. Unfortunately the bike bounced off 11k rpm rev limit for a couple seconds before I could get it shut down while I had the clutch pulled in.

As I pulled to a stop I heard a pop from what I thought was an exhaust backfire, and as I was looking over the bike I saw a fairly substantial oil leak coming off the front cylinder. Long story short the only place I can see that the oil came from is the crank case breather tube next to the exhaust manifold on the front cylinder. I'm pretty sure it blew the line clean off because it wasn't even attached to the bike NOR the airbox.

So, what all should I be checking to see if I did further damage? I'm thinking compression test at a minimum. I pulled the plugs and they looked a little lean on the front cylinder. I have a spare throttle cable I can swap on.

All in all it happened in the best place it could have, literally on a flat straight street right next to my house so I was able to push the bike to my garage. I'm just glad it didn't stick/break when I was coming out of the turn immediately prior to it. I had noticed the throttle acting funny/sticky for about a mile before this happened on my way home. Just glad to be all in one piece!

-Steve
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post #2 of 12 (permalink) Old 11-14-2011, 08:31 PM
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Sounds like a spooky event, glad you (and the bike) made it without any real incident. Good luck with the repairs.

The one thing I would check for is metal shavings in the oil / screen, if none are present I would take that as a good sign. Rev limiters are there to prevent (er, minimize) damage from occuring, and a couple seconds on one is most likely not going to harm the engine especially when fully warmed.

That said, it isnt hard to spin a bearing in a car (I-4, V8) by over/dry revving, I'm not sure about a V-twin.

Take this with a grain of salt as I am new to the world of bikes, and not entirely sure *everything* carries over mechanically speaking.

Last edited by DevinWolfe; 11-14-2011 at 08:34 PM.
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post #3 of 12 (permalink) Old 11-14-2011, 09:50 PM
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To my knowledge, the Vulcan has no rev limiter.

You should replace the breather hose, start the bike and see how she sounds.

High revs on this bike might sound bad, but if the bike starts and runs fine I doubt any damage was done.

Next time try hitting the kill switch..... That's what it's for.

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post #4 of 12 (permalink) Old 11-14-2011, 11:37 PM
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I doubt there is any damage caused by that. I would have hit the kill switch and the brakes, and left the clutch out.

Which cable are you talking about? The one that pulls the throttle open against spring tension, or the other one? The one that actually opens the throttle is attached close to the front of the throttle housing, the other one is attached behind it. The throttle is closed by the carb mounted spring. I read about such an incident on another forum, looked the situation over on my Vulcan and Rebel, and removed the "push" cables from both. Now if the cable that actually operates the throttle breaks, the spring will close the throttle. If the spring breaks (never heard of that happening) you still have the kill switch right under your thumb. Both throttles now work better, with less drag (caused by the other cable, when opened and released, they snap closed easier. Many bikes were made with only one throttle cable, so there is no need for two.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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post #5 of 12 (permalink) Old 11-15-2011, 10:01 AM
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Jerry, you really need to stop telling folks here they don't need the other throttle cable. The bike was designed to have two, and if you don't want both on your bike, take it off for all I care, but don't rationalize your actions as safe simply because you haven't had a problem yet.

We have been over this subject before, everyone knows "your opinion" on this so it does not need to be gone over again.

You are suggesting removing a safety feature of the bike, and although you present some logic for it, it is still what I view as "possibly unsafe" and should not be presented in any other way.

If any one else wants to know why the 2nd cable is useful, you should try timing shifts..........

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post #6 of 12 (permalink) Old 11-15-2011, 11:32 AM
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Oh, and before I forget:


"Blew the crankcase breather hose off...."


You spit or swallow?

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post #7 of 12 (permalink) Old 11-15-2011, 05:37 PM Thread Starter
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Thanks for the replies guys, I did hit the kill switch with the clutch disengaged. When the throttle stuck open I tried to flick it a couple times first before I pulled the clutch in but it ended up just opening the throttle more. I was more concerned with stopping the bike from taking off down the street than killing the motor at that point in time so it took me a second to slow down/pull off to the side of the road quickly before I hit the kill switch. At any rate I shut it down quickly and no one got hurt so that's all that matters to me. I'm going to replace that breather hose, change out the throttle cable and try to crank it back up and see what happens. I will definitely be going through and greasing all the cables on the bike after this!

I will report back after I have time to dive into the bike more and find out what happened and why the throttle stuck open, in theory it should have closed like everyone has said even if the cable broke seeing as that's what the return spring at the butterflies is for....

Edit: And I forgot there is no rev-limiter on the bike....it did however spin the tach as far up as it would go and was bouncing around the 11k mark.

-Steve
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post #8 of 12 (permalink) Old 11-15-2011, 05:56 PM
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"so there is no need for two" This is the only part that is opinion, and should have been left out. I have been riding the bike for several thousand miles now, with no problems. I have a good grasp of mechanical things, it is my profession. IN MY OPINION, the other cable serves no purpose, and could actually be dangerous if it were to bind, not allowing the throttle to close. Yes, the other cable could bind as well, but the throttle won't work without it. I just keep mine well lubed, and check it's condition frequently. I AM NOT SUGGESTING ANYONE ELSE REMOVE THEIR'S. If they choose to do so, it is their choice, and they accept any and all responsibility for it.

Just like I have proven the right front brake is not necessary for ME to ride safely, and removing it actually makes modulating the brake easier, I still don't recommend anyone else doing it. Just because it works for ME doesn't mean it works for everyone else.

However, I do have to take exception to the way you put it. Many members here are running K&N filters, removing the "goats belly", punching out the baffles in their pipes, and even running car tires on their bikes, all of which I recommend against. But recommend is all I can do, it's their bike, and if they want to do it, they are going to do it. With two different bikes, I have proven that the stock Vulcan 750 can be very reliable, and rack up a lot of mostly trouble free miles, with only a couple of exceptions which almost everyone here knows about (I'm talking about the splines and the accts) Absolutely nothing else has caused me any problems on my bikes, including all of the modifications I have made.


Anyway, as far as the throttle cables, it is up to each individual owner what they want to do. I did what works for me. I have never had a throttle failure on this bike.


EDIT: "I will report back after I have time to dive into the bike more and find out what happened and why the throttle stuck open, in theory it should have closed like everyone has said even if the cable broke seeing as that's what the return spring at the butterflies is for...."

The problem with a dual cable throttle setup, and this is my opinion based on my mechanical knowledge, is that if the second cable breaks, frays at break point, and gets stuck in the housing, or gets stuck in the housing for any other reason, like corrosion or lack of lubrication, it will prevent the spring from closing the throttle. Now, it is also true this could happen to the primary cable as well, the one that actually pulls the throttle open against spring tension. But it seems to me that having two cables doubles the chances of this happening. I only have the "pull" cable on my bike, and keep it well lubed and adjusted. Theoretically, if it breaks, the spring will close the throttle. The exception is if it gets stuck with the throttle open. Not likely, but possible. I have had the throttle stick open on a couple of different bikes during the past few decades, just like with Toyotas. Both were due to worn or broken parts which should have been checked. I've gotten more picky about that.

As I said above, I won't get into the one cable vs two thing, but either way, if the throttle stuck, my immediate response would have been to hit the kill switch while applying both brakes while steering the bike off the road if possible, all while not touching the clutch lever. Under the circumstances, I probably wouldn't have even thought about the clutch. Yes, I would have come to a bumpy stop with the clutch out and the bike in gear, but that is what the MSF recommends, and what I have conditioned myself to do, and have done successfully a couple of times before. Ideally, with the kill switch and engine off, you should pull the clutch in just before stopping, to avoid an abrupt stop, but if you are otherwise occupied with the situation, that is not critical.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike

Last edited by VN750Rider/Jerry; 11-15-2011 at 06:15 PM.
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post #9 of 12 (permalink) Old 11-15-2011, 09:45 PM
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Quote:
Originally Posted by VN750Rider/Jerry;
..................... Many members here are running K&N filters, removing the "goats belly", punching out the baffles in their pipes, and even running car tires on their bikes, all of which I recommend against. But recommend is all I can do, it's their bike, and if they want to do it, they are going to do it. With two different bikes, I have proven that the stock Vulcan 750 can be very reliable, and rack up a lot of mostly trouble free miles, with only a couple of exceptions which almost everyone here knows about (I'm talking about the splines and the accts) Absolutely nothing else has caused me any problems on my bikes, including all of the modifications I have made.
The problem with your logic here is there are hundreds of riders that have gone to the "dark side" by putting car tires on their bikes, hundreds of thousands of folks running K+N filters, and yanking the goats belly or switching to an aftermarket exhaust is almost an everyday thing here...and on other bike forums. Drilling out baffles kinda universal too.

But in the ten years I have been a member of the Vulcan 750 forums online... I have only read about two people who removed one of the front brakes off their bike... And you are one of them. And, in all that time .....you have been the only one I can remember that removed the 2nd cable off the throttle and wrote that it "is not needed".

You have dissed ABS, EFI and have actually written that the stock seat on the 750 is the most comfortable bike seat you have encountered.


So it's pretty clear you don't think like anyone else here. I'm not sure what that means. I'm not here to judge, I just don't want some new rider tearing out safety switches, brake parts, or cables because "Jerry said it was OK". That's all..............

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post #10 of 12 (permalink) Old 11-16-2011, 03:39 PM
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Yep, that's true, I've never been a crowd follower. I go my own way, and do things my own way. But all modifications I have made to motorcycles have been for a reason, I have put considerable thought into them, and they have been well tested. Remember, the OP had a throttle lock up, and he had 2 cables. And, while I did state my opinions on these modifications, I have never suggested anyone else do it. I would hope that anyone capable of riding and working on a motorcycle has the ability to decide for themselves whether to do something, and as I always say, "if in doubt, don't"


While car tires work fine in a straight line, there is some evidence that they do n ot corner well.

And while running a K&N air filter (or any other "high flow" filter) and punching the baffles out do not present a safety hazard, there is ample evidence that doing so will shorten the life of the engine. How much is unknown. Again, it's up to the owner to decide if what ever they gain is worth that.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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