Bent valve- What did I do? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 18 (permalink) Old 08-08-2013, 04:42 PM Thread Starter
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Bent valve- What did I do?

Short version: Replaced blown head gaskets, bike was running good for about two weeks. Son called me out to garage yesterday. Bike would not stay running, and backfiring. Checked a number of things and knew it was a valve/timing issue so I got it torn down enough to pull head cover off back head. and the valve closest to the carb was bent. I need help pulling the motor but until then, What may have happened to cause this?
Thanks,
Ken
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post #2 of 18 (permalink) Old 08-08-2013, 05:29 PM
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Slipped cam chain?

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post #3 of 18 (permalink) Old 08-08-2013, 06:42 PM Thread Starter
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Once I get it apart I'll know more. Maybe the "rocker arm" slipped off somehow? Just wondered if anyone had seen this before.
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post #4 of 18 (permalink) Old 08-08-2013, 07:21 PM
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which head is it i have a good one here but i dont recall if it is the back or front

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post #5 of 18 (permalink) Old 08-08-2013, 08:13 PM
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Can't really make it out, but is it actually bent or the spring is just broken? Looks like the keepers may be about to fall off. I can see the spring is dropped down from the rotator.

If it's bent, I would say the valve stuck open, assuming the chain didn't jump or cause it some other way.

I'll be interested in following this if you can keep us posted. Mine has been doing an occasional tick, lurch, spit (out the intake for the front cylinder) at low rpm (below 2000), for a while. I put some additive in the oil in case a valve was sticking. Haven't found any posts about the problem.

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post #6 of 18 (permalink) Old 08-08-2013, 09:40 PM
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Never had a Vulcan 750 engine apart, but it looks like not only is the valve broken, but the cam is badly damaged as well. What is that just to the right of whatever that is with red paint on it? Is that the cam lobe just to the right of the valve spring?

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post #7 of 18 (permalink) Old 08-08-2013, 10:18 PM Thread Starter
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Got it apart. Yes Jerry that is the cam lobe and yes it's wiped. My best guess that I dropped something in the intake runner when I had it apart. One retainer is messed up, Cam is not useable, and valve was bent. There were also pieces of something stuck to the head and the piston and smaller pieces laying on piston.
Questions; the valve guide looks ok, can I check it? is it replaceable?
If so and I can reuse this head looks like I need a valve, retainers and a cam.
Can I reuse the almost new head gasket? I will post pictures.
Ken
1 bent valve
2 bent valve 2
3 Top of piston piece of metal about 11 o'clock
4 Piece of metal
5 cam lobe
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post #8 of 18 (permalink) Old 08-08-2013, 10:26 PM
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Turn the pic 90 deg to the left, and all becomes obvious....that lil bit of crud on the cam aint nuthin Jerry....stop scaring the guy....the piece with the red looks like the cap that goes over the valvestem/spring....fish that out....dont lose it down in the bowels...then remove the cam and keepers...that'll show you better as to whats going on. Youre gonna need to remove the head eventually though, Im sure....looks like just a bent stem...so, figure on 1 valve, valve seal (may as well do both at this point)....and a head gasket....



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post #9 of 18 (permalink) Old 08-09-2013, 12:37 AM
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How many miles and what year?

Looks like some pitting up high on the valve stem, but that should be behind the spring anyway, if that's what it is.

Is there much varnish built up on the lower end of the stem, like where it rides in the guide? Enough to scrape with a knife? Or barely enough to see?

I said it wrong too, it's the rear cylinder that sneezes out the intake on mine. Here's me hoping it clears up and doesn't kiss a valve.

Wonder why Kaw marked the valves like that.. IV and EV? Should be easy to tell them apart.

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post #10 of 18 (permalink) Old 08-09-2013, 07:02 AM Thread Starter
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Well the cam has rubbed against the spring I think and is rough on one side will have to see if it hits the rocker arm. Are you saying the guide can be replaced or is there a seal that goes over the guide (like a cars)? A new valve will have to be lapped in too. At this point I see I can get a whole rear head, cams and exhaust for $75, might be less work.
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