Rejet issues maybe.

[lookoutdriftmike]

I just had to put a new muffler on my 81 GS450 because my MAC literally fell off and got destroyed. I used a 2" exhaust pipe and made a baffle old school hot rod style with a pipe and washers and drilled out a few holes in the washers to give it more flow. Big mistake. Now I need to jet since at about 5k it seems to hit a wall that sounds like a rev limiter. Before the new muffler, it would rev all the way out. It runs great below 5k by the way so I have been riding it around a little but it wants to go I just know it. I just put in a 20 pilot and a 125 main and while the idle is better and it warms much faster, the wall is still there. Everything else is stock on the motor as far as I know and it was running well under stock specs before. Do I really need a bigger main than 125 for just a muffler? Seems crazy, I read tales of 135 mains for pods and exhaust. This is my muffler:

[cableguy]

I'm no expert but I would start by enriching your mixture before rejetting. Did you rejet when you went from stock to MAC? If no, does the DIY baffle you made flow better than what you had in there?

[chef1366]

If the spark plugs are white I'd increase the main jet until you can hit redline and you get good color on the plugs.

[pete]

Definitely plug chop time!

Also, on my '82 450E I discovered the needles are adjustable, so if it's quarter to three quarters throttle opening where the wall is, you'll need to do something with your needle, and again a plug chop will show you if you need to raise the needle (richer) or whatever.

[hampshirehog]

When you get the rev limiter effect as you describe it's more likely that you are running too rich. Either that or the pipe flows really badly (like it's partially blocked).

[lookoutdriftmike]

When you get the rev limiter effect as you describe it's more likely that you are running too rich. Either that or the pipe flows really badly (like it's partially blocked).

Interesting, it appears to have more open more open pipe than the MAC which was designed to be equal to stock. Guess it's chop time and maybe a new pipe again. Thanks for the thoughts guys.

[Big T]

Stuff the pipe with steel wool and see if that doesn't get you closer to where you started

[lookoutdriftmike]

Ok I tried a few things. I tried removing the baffle and still had the same problem, so no to the blockage. and then noticed another thread about a fuse filament being loose in the tube and shaking helping. I checked my fuse which has been replaced with a blade type but as I was pulling off the rubber cap I noticed my gauge lights blink. Looks like the PO had twisted the wires together and taped them but did not solder. I just soldered them together and whoa!!1 1st and 2nd winds up good but I get a bog at 6k in third and up so onward to the chopping now that I can get it to rev out under light load. Thanks again for the help. I am still toying around with a better pipe but now that the electrical signal is solid, the bike purrs real nice.

[pete]

Nice find! Glad to hear it's running now

Definitely time for plug chops and don't forget the masking tape to work out throttle openings so you know which circuit needs adjusting.