Weird engine noise.. So build the Maxim with Seca internals?

I got my 82 Maxim xj550 up a running, but it seems it has a weird noise at low RPM's that shuts up about 2500+RPM. But sounds like knock so before I toast the engine I might as well dump another couple hundred bucks in it right? (So far a money pit) But I have looked around and foundthe Seca cams are more aggressive, But not too sure on the piston compression ratio or even if the Seca parts will be a direct swap in the Maxim case? Does anyone have knowledge with this?

http://www.youtube.com/watch?v=WSoP59xL_CM

Figured some more compression, more aggresive cams, Ported head, new gaskets, Might hit 100mph lol

 

I've noticed this too but its only when the bike is idling low, and sounds as if its about to die. Maybe 1300 rpm. It goes away at about 1500 so I'm thinking it will stop once I get the idle fixed. We'll see atleast.

 

The 550s have a "true" primary chain that actually drives the transmission (not just the jackshaft like on the bigger bikes.)

This primary chain has an hydraulically-activated tensioner, operated by engine oil pressure.

At idle, the primary chain will make one heck of a "slap-slap-slap" racket that will immediately go away as soon as you rev the bike, as the oil pressure comes up and tightens the chain. Pulling in the clutch will "change" the sound slightly but only because you take the clutch and trans out of the mix that way.

If this is what you're hearing, it's normal.

That being said, the racket can be greatly diminished by getting the bike running right, the carbs sync'ed and getting the "lump-lump-lump" out of the idle. Get it idling smoothly and it'll sound like a sewing machine and not a farm implement.

For reference sake: The 550 Seca has slightly "hotter" cams and different pilot air jets/needles and that's about it. Compression ratio, pistons, etc., all the same. Mechanically, the motors are otherwise identical.

 

Posted a quick Video...