VN750 Engine Knocking - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 07-20-2016, 01:29 AM Thread Starter
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VN750 Engine Knocking

Gents and Ladies too,

This is my first post after lurking here for two years since acquiring my 2001 vn 750, it now has 33,000 miles. I have developed a noise in the crankcase which now has developed several other symptoms in short order.

First, developed a slight tapping coming home the other night and the oil light came on.

Changed the oil, before riding anymore, with a new K&N filter and 10w-40 Motorcycle grade oil. Found what appeared to be some brass in the pump screen. Put it all back together and still had a slight tapping. Oil light went off and has stayed off. Strange thing is the fresh oil I put in is almost completely black, as I was filling it to full in the sight glass I noticed it was kinda dark in the sight glass. So I drained little bit into a clear container, it just appears to be really dark gray.

Started this morning, still had a light tapping, the farther from the house I went, the louder the tapping became and less power I had. I pulled over just as it stalled while idling. Bike wouldn't restart and had to have it towed the 2 miles back to the house. I noticed a small pooling of coolant on the right side of the front cylinder. Appeared to be coming from the bottom gasket of the cylinder. Coolant level is still full. There doesn't appear to be any coolant in the oil when I drained a little out to check tonight, still black.

Now tonight it will start but it has a pretty loud tapping noise.

Not real sure how all this is connected or if it is. I attached a picture of the oil but won't be able to share the link to my video of the noise until I'm at 5 posts, you know to prove I'm human and not selling stuff Any help or insight with this would be greatly appreciated. This bike saves me $6 a day on my commute and is just a blast to ride. Help me get back out there!! Thank you in advance!!!!!!!!!

maybe this will work if you copy and paste? youtu.be/IMlF9PD8fvE
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Last edited by John Cunningham; 07-20-2016 at 01:30 AM. Reason: attempt at getting video of the sound on my post
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post #2 of 9 (permalink) Old 07-20-2016, 01:32 AM Thread Starter
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Oh, and there are no mods done to the bike, except for new tires. As best as I know everything else is stock. THANKS!!!
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post #3 of 9 (permalink) Old 07-20-2016, 05:01 AM
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Oh my, not the best sound. Conventional oil will turn pretty black fast I've noticed so that may be unrelated.

I'm sure someone that has experienced a similar issue first hand will post, but my initial thought is some sort of bearing failure.

...unless a spark plug has worked it's way out. Simple stuff first I guess (sounds unlikely, but hey... thinking positive)

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Last edited by thtanner; 07-20-2016 at 05:18 AM.
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post #4 of 9 (permalink) Old 07-20-2016, 10:43 AM
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yea, to me the 'uneven' cranking sounds like a spark plug, or other issue where one cylinder is way low on compression.

as mentioned, check the simple/cheap stuff first.

the 'knock' sounds more upper end than lower, if its not one of the simple things.. I have had a spark plug wire shorting out on one of the throttle cables (the metal sheath) and it made a sharp tic like that, but wasnt nearly as loud. also had a slightly loose plug make a similar sound, a sharp tick/tap.

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post #5 of 9 (permalink) Old 07-20-2016, 03:17 PM Thread Starter
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Thanks for the ideas. I'll look into this tonight and tomorrow when I'm off work. Hopefully it's something simple. The most concerning thing is the start of the coolant leak from the front cylinder. Anyone have any insight there?

I'll update the thread once I run down some of these simpler ideas.
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post #6 of 9 (permalink) Old 07-20-2016, 11:04 PM
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If the coolant isn't running down from the top of the front head (o-ring on the steel coolant pipe), then it's probably the base gasket.

Couldn't get to the video, but if you post a couple more times, you should be able to post links after that.

Signs read like it's going to be rod bearings, to me. Gold flakes in the screen, knocking more, losing power. Was it a considerable amount of material in the screen or just a couple of minute flakes? A close look at the oil in sunlight might show gold sparkles, dab some with your finger and look.

Clutch material is usually darker, brown or black, with tiny shards or flakes of gold here and there. Bearing material is all gold flakes.

One trick is to remove spark from each cylinder, one at a time. If the knock stops or lessens considerably, it's a rod bearing on that cylinder 99.9% of the time. On the VN750, you have to pull two plug wires instead of one. A top end tick or timing chain would keep on ticking, regardless of spark.

It's dangerous to ride with an engine that may be ready to throw a rod. If the engine locks up and you can't pull the clutch due to internal damage, the back tire slides like you jammed on the brake. Oil drops onto the tire(s) if the rod comes out of the case. Ice isn't nearly as slick.

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post #7 of 9 (permalink) Old 07-21-2016, 09:08 AM
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Well it's actually probably good that the oil is getting dark, that means it's cleaning out the junk. The viscosity will not break down that fast. Have you tried adjusting the cam chain tensioners.

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post #8 of 9 (permalink) Old 07-21-2016, 09:23 PM
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Is it smoking? I had this noise with a stuck wrist pin making the piston scrape the walls and causing compression issues, but the obvious elephant in the room was the smoke when oil went past the rings as the piston was tilted. Huge increase in oil consumption when the wrist pin started sticking.


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post #9 of 9 (permalink) Old 07-21-2016, 10:20 PM
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Quote:
Originally Posted by John Cunningham View Post
Gents and Ladies too,

This is my first post after lurking here for two years since acquiring my 2001 vn 750, it now has 33,000 miles. I have developed a noise in the crankcase which now has developed several other symptoms in short order.

First, developed a slight tapping coming home the other night and the oil light came on.

Changed the oil, before riding anymore, with a new K&N filter and 10w-40 Motorcycle grade oil. Found what appeared to be some brass in the pump screen. Put it all back together and still had a slight tapping. Oil light went off and has stayed off. Strange thing is the fresh oil I put in is almost completely black, as I was filling it to full in the sight glass I noticed it was kinda dark in the sight glass. So I drained little bit into a clear container, it just appears to be really dark gray.

Started this morning, still had a light tapping, the farther from the house I went, the louder the tapping became and less power I had. I pulled over just as it stalled while idling. Bike wouldn't restart and had to have it towed the 2 miles back to the house. I noticed a small pooling of coolant on the right side of the front cylinder. Appeared to be coming from the bottom gasket of the cylinder. Coolant level is still full. There doesn't appear to be any coolant in the oil when I drained a little out to check tonight, still black.

Now tonight it will start but it has a pretty loud tapping noise.

Not real sure how all this is connected or if it is. I attached a picture of the oil but won't be able to share the link to my video of the noise until I'm at 5 posts, you know to prove I'm human and not selling stuff Any help or insight with this would be greatly appreciated. This bike saves me $6 a day on my commute and is just a blast to ride. Help me get back out there!! Thank you in advance!!!!!!!!!

maybe this will work if you copy and paste? youtu.be/IMlF9PD8fvE
Since you have been lurking here for at least the last two years and now are getting direct information for your bike how about doing an introduction under the Newbie Check-In heading and tell us a bit about your riding/wrenching experience and where you are located. It can be as short or in depth as you want. You would be amazed at the number of Newbies that fail to do this simple forum request and yet want every bit of information for their specific problem. That will come anyway so I am not sure why there is a fear factor with this.

and always remember, "Ride until you rot!"
**Really not sure if the Big "C" is back right now
but having to face the fact that this is a lifetime routine
going forward. Five operations done and it still continues.

Tom
Vulcan 2000
New ride: 2009 Victory Vision Arlen Ness Signature Series
4507 miles
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