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Tas
5th October 2005, 20:15
Can anyone help me with some info or a replacement muffler? The Fizzer is in need of a new muffler to replace the original one. Im prepared to do some cutting, mods and welding, as the original is all one unit, but I'd like to know if there are mufflers off other bikes that would need the least mods. I dont have a fortune to spend otherwise I would be fitting a new Neptune or similar. Any help appreciated.

limbimtimwim
5th October 2005, 20:53
Can anyone help me with some info or a replacement muffler? The Fizzer is in need of a new muffler to replace the original one. Im prepared to do some cutting, mods and welding, as the original is all one unit, but I'd like to know if there are mufflers off other bikes that would need the least mods. I dont have a fortune to spend otherwise I would be fitting a new Neptune or similar. Any help appreciated.My books on engines tell me (See, I don't actually have much practical experience with this stuff) that if you get something with the closest possible internal length and diameter, you can't muck things up too much. Look on trademe, ask the seller to measure the internal diameter of the engine end and have a shot at measuring the length. I would imagine mufflers off other similar generation 4cyl 750's would be close to the mark.

But then, that's just what my books tell me, and you probably knew those things already.

Getting the hanger to line up with whatever you bolt your muffler too could be a real bitch too.

riffer
5th October 2005, 22:01
You're opening up a real can of worms there buddy.

You see, your FZR750 is a 2LM model, right? The Japanese domestic model, restricted to 77BHP?

So, the exhaust is part of the derestriction. It's got more twists and turns than a Tarantino script... You put another exhaust on it from a different bike and it'll have your bike running really lean - you'll know it because about 6-7000 rpm you'll get it pinking (that nasty ball bearings in a tin drum-like sound) which isn't good for it.

Best bet for you if you're going to change the exhaust and you have to put in a less restrictive one is to make a few alts at the same time.

There's a restricting plug in the airbox. It's in the air inlet - a long rubber bung which is held in with a huge metal clip. You get to the airbox by taking off the tank. Pull it off and junk it.

Next step is to get some bigger jets in the carbs. Undo the carbs at the joints to the inlet manifold (more metal clips) and pull the float bowl cover off (one at a time!). Replace the 80 mains on the inner cylinders with 105's and the 82.5 mains on the outer cylinders with 107.5s. You won't ned to change the float levels, but depending on how easily it idles and revs up you may want to take the pilot airs up to maybe 115s.

This will take care of the leaning problem, and also give you a decent horsepower increase.

The only other step in the puzzle if you wish to continue further, is to swap out the 2LM ignitor with either the 2NK ignitor from the FZR750R (1987 US model) or the 1FM ignitor from the FZR1000 (87/88 model). This will remap the ignition so that it gives you more advance and will liberate even more power.

Even if you don't do the ignitor, the derestricting will bring the bike up a good 20HP.

Good luck. It's really not hard to do at all.

Tas
5th October 2005, 22:48
thanks guys. I'll go down the road of re-jetting if needed. Thanks for the details Simon. I suppose the chances of finding a muffler than only requires slight mounting mods is like finding the proverbial rocking horse crap.
Hey Simon did you actually change your muffler when you did your tuning or did you leave it stock?

DEATH_INC.
9th October 2005, 10:00
I dunno if it'll fit(riffer???),but I think (I'll have to check Kerrys' still got it) I've got a full muzzy system off a genesis thou you could have fairly cheap.It's a bit loud as all those old muzzys were but it was magic on the thou.

Tas
9th October 2005, 23:14
I dunno if it'll fit(riffer???),but I think (I'll have to check Kerrys' still got it) I've got a full muzzy system off a genesis thou you could have fairly cheap.It's a bit loud as all those old muzzys were but it was magic on the thou.

Thanks DEATH INC I'll send you a PM