what could cause this? burnt valve?

[heath]

Hi I just purchased a 1998 black vmax with 15000 miles. The bike has cobra 4 into 4. The left rear cylinder(right side rear exhaust) will make a piece of paper slap the exhaust(suck it in). Hoping for the best. Hopefully valve out of adjustment. I didn't think anything major could be wrong with low miles but now im wondering.

 

[The Beekeeper]

Have you done a compression test?..........What were the results both wet and dry?..............Tom.

 

[davesax36]

Have you done a compression test?..........What were the results both wet and dry?..............Tom.

And leak down. At least you'll be able to hear where the air is going. Does the other exhaust blow a lot/ Sporadically?

Sent from my Galaxy Nexus using Tapatalk 2

 

[bazwell]

Try a compression test to begin with.

 

[heath]

Hi thank you for your replies! I have not been able to do a compression test yet. And the other rear cylinder does hit hard/sporadic.

 

[alorio1]

A compression test is definately in order, you could have a broke valve spring and a very remote possibility of a broke camshaft. Someone tore their engine down and found their camshaft was broke just recently. If your compression is down you may be able to borrow a bore scope and have a look around in the cylinder chamber.

 

[alorio1]

Edit; I stated that someone posted their camshaft had broken recently, but I did a search and found it was an old thread, but here it is,,,,a very rare but one of the possibilities in your case. I'm just throwing it out there for a FYI.

http://www.vmaxforum.net/showthread.php?t=4636&highlight=broke+camshaft

 

[buckridge]

i bought a 98 with the same exhaust system as yours ,it had a foam uni filter on it that was so dirty that it did not flow air properly ,was super rich and unburnt fuel started to leave a deposit of carbon which built up so much on the piston crown and combustion chamber surface that it started hitting the carbon and took the big end bearing out on the connecting rod which means engine rebuild . see if you have lots of carbon build up the slapping sound could be what happened to this engine this lesson taught me to always keep air filter clean lol