85 Honda VF500C Sudden Engine Noise and Power Loss

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Shonky · #1 Unread post by **Shonky** » Wed Jul 09, 2008 6:28 pm

Hi. I purchased a used 85 Honda V30 Magna, 4 cylinder. I've been riding it for a few months, now has over 20,000 miles. This is my first bike and I'm fairly new to motorcycle and small engine repair.

I was riding last night and I had a sudden noise from the engine. It wasn't immediate, but came in bursts, then about 3 mins later it was constant. I guess the best way to describe it is it started to sound like a lawn mower. Noise is in line with the RPMs. I was thinking that I had just blown a gasket on the exhaust, but I'm also getting a major performance decrease.

I have a 11.5 red line, when I get to about 6-7 the power would cut and it would bog down. It would not idle either, I had to give it some throttle. I was able to get it home, but didn't have enough light to look at it. The noise was also not as loud now as before.

I checked around this morning for a min or two before work, looking for anything obvious. I was looking for the noise and feeling around. I got to my Front Left cylinder and I could feel the piston hitting the spark plug.

Could this be the sole issue? I haven't pulled the plug yet, but could I have blown it out or damaged it in some way that I'm losing compression on this cylinder and this is causing the noise and lack of performance?

I'll be doing more trouble shooting tomorrow, as well as replacing the plugs, cause I'm sure they all need it. So any advise would be great as to what to check for!

MrShake · #2 Unread post by **MrShake** » Thu Jul 10, 2008 7:04 am

How can you tell its hitting the spark plug? That would be a pretty catastrophic problem.

Shonky · #3 Unread post by **Shonky** » Thu Jul 10, 2008 10:43 am

When I hold the spark plug I can feel it "tapping" it. The plug is also loose and turns easily by hand.

Going to check it out now, just got some plugs.

Edit: Just replaced the plug that was loose, not the main problem. Sounds like its coming from the top end. I can't get it over 6k rpm. Could it be a valve? It does also smell "gassier" too. The noise is a mix of a tick and buzz.

I will record the noise if that would help. Thx for reading!

Johnj · #4 Unread post by **Johnj** » Thu Jul 10, 2008 2:55 pm

You might want to go ahead and tear it down before something breaks.

MrShake · #5 Unread post by **MrShake** » Fri Jul 11, 2008 4:50 am

is your bike an overhead cam bike?

HYPERR · #6 Unread post by **HYPERR** » Fri Jul 11, 2008 4:59 am

MrShake wrote:is your bike an overhead cam bike?

Yeah those are the DOHC V4s. I know the earlier ones had big time cam bearing problems...

#7 Unread post by **fireguzzi** » Fri Jul 11, 2008 5:05 am

I would not suggest running it anymore it could make things much worse. Go ahead and take a look in there.

MrShake · #8 Unread post by **MrShake** » Mon Jul 14, 2008 6:39 am

You may want to check a service manual on your cam chain tensioner. Though pulling the valve covers off and taking a look could give you a clue.