So I received my Dyna mufflers from EBay and upon inspection it would seem that the seller drilled 3 1/4" holes in the center plate of both -- of course not mentioned in the auction.  Before I bother to install them, I have read about every thread in the tech section about it and according to Lancer and OF the lack of restriction of this is pretty much going to make the bike run like S#*!, or as if I've added a straight pipe.  Is that correct?

I'm running stock air and jets right now, planning on rejetting once installed, but haven't opened up the carb yet, and I'll probably leave stock air for now.

Any advise on how to proceed would be appreciated.  Is there any easy way to "fill" the holes or add a plate in front of the original plate to block the holes back up, keep in mind I don't have access to welding or machining equipment?  Thanks all

I can't imagine that  3 1/4" holes are going to make that much of a difference.  If it was so significant that guy wouldn't have upgraded from those pipes.

I ran a straight pipe until recently and I can promise you it will be nothing like that.

The Dyna muffler I have has the baffle welded in and you cannot see through it... that's why I'm interested in what these holes are all about.. I guess to produce a louder sound?

Got an update.  Got the muffler installed and rode it a couple of times the other day.  Sounds great!  Purrs at idle, growls up to about 60, then just screams.  Didn't have to rejet at all.  Was at 1 1/2 turns out, stock jets (I think, still haven't opened the carb up), tuned it according to the threads on here (by ear) and the sweet spot seemed to be at about 1 3/4 to 2 1/4 turns out, dies off at 2 1/2 turns.  Running stock air still.

Doesn't seem like those holes did much to it, runs great.  I do get a rapid grumble (bop-bop-bop) on decel and downshift, but when I richened it to 2 1/4 turns out that pretty much goes away.  It isn't the loud, high-pitched pops I used to get with the stock setup either.  I kinda like it. Gets the attention of people around me when I'm slowing down

Does it seem weird that I wouldn't have to rejet though?

It's not completely gone, but it's just tamed a little bit so people don't veer off the road in shock when I engine break.  It goes away completely if I pull the clutch, so it's like a bonus feature!

I probably will rejet now that I re-read some of the jetting threads.  My upper end throttle seems to be responsive, but it seems to hit a flat spot around 60-65 now, where it used to pull right through into the 70's-80's.
Thought maybe I'd richen the main jet a little see if that helps.  The low and middle is running great so far though, so I'll leave that alone.

Can anyone explain to me in small, easy to understand words, exactly what the white spacer mod does?  I know most people around here have done it and that it allows for more fuel to flow through the carb at all times, right?  Does that just richen the whole throttle range as opposed to specific ranges (ie. jets)

Quote:
Can anyone explain to me in small, easy to understand words, exactly what the white spacer mod does?
--------------------------------------------------------------------------------
-
Doing the white spacer mod,.....(making the white spacer thinner) raises the tapered metering rod that controls fuel flow in the low to intermediate throttle range. Older carbs used to have slots in the rod w/ a clip for adjusting the rod up and down.
If your engine runs smooth under light load,.... 1/8 to 1/3 throttle range,.......while just kinda loafing along about 20-40mph, my advice is don't touch it. Many do the mod because another guy did it,.... while not really knowing why.
Same w/ rejetting,......have a reason for doing it, not just because another did it,......or just because you opened up the air or exhaust a little. Some bikes need.... what others may not need.