Topic: Re: cb750 dunstall exhaust..? *updated with pics*

[jneuf]

I'm going to look at a '71 CB750 tomorrow that has been sitting since the '80's. Amongst some other old speed parts on the bike, it apparently has a Dunstall exhaust system...were all dunstall systems 4-2 with upswept pipes? I haven't found a bunch of info on them, so I'm just curious as to what I'm going to see.

I'll post up some pics after I check out the bike tomorrow.

[Rookster]

There are 3 basic kinds of Dunstall exhaust for the CB750K.  They are all a 4 into 2. 

Early (rare crossover)


Most Common


Last version (1 & 4 pipes ran outside the frame rails)


Scott

[jneuf]

Thanks a lot for that info...If those dyno numbers in the second ad are accurate, that's a pretty serious increase for a small jetting increase and exhaust.

That crossover pipe on the first system looks pretty wild...I'm curious to see what system will be on the bike tomorrow.

Are these exhausts considerably louder over the stock 4-4 system?

[Rookster]

Yes they are louder but its not obnoxous.  They have a nice sound to them but they won't get you pulled over or anything.  Dunstall used those horsepower numbers to market their exhausts for the CB750.  I'm not sure which system produced those gains though.  I almost think it was the crossover system as this was the first one they came out with.  If the bike has the Dunstall exhaust make sure it has the rear passenger plates as the mufflers cover the passenger peg mounts.  The centerstand doesn't have a stop on it either which will foul the chain without the Dunstall plates.





Scott

[jneuf]

So I went to go check out the bike this morning...Seeing as it's sat outside for years (tarped), it's in pretty good shape.

Anyway, the exhaust was interesting, see the pics attached. As per the info above, dunstall only did 4-2 pipes...but this is a 4-1, with the "Dunstall Power" tag on it.

Anyway, I couldn't pass up a complete K1, so It'll be in my possession as soon as I can drag it home.

[Rookster]

What you have there is a Dunstall Power silencer attatched to another makers headers.  The Dunstall Power silencer came in a few different inlet sizes to fit many bikes/systems.  The Headers are not Dunstall.  The Power silencer is a decent muffler.  It is louder than the Decibel and was marketed as the high performance option.





Scott

[fire113]

...5 weeks ago I was thinking to buy this K0, it has a complete dunstall exhaust.

[Rookster]

...5 weeks ago I was thinking to buy this K0, it has a complete dunstall exhaust.

It sure does.  The mufflers aren't Dunstall but that bike has a bunch of goodies on it: Kimtab wheels, different gas tank, oil cooler, enclosed chainguard, frame for hard bags and it almost looks like a different front end.
Scott   

[fire113]

...5 weeks ago I was thinking to buy this K0, it has a complete dunstall exhaust.

It sure does.  The mufflers aren't Dunstall but that bike has a bunch of goodies on it: Kimtab wheels, different gas tank, oil cooler, enclosed chainguard, frame for hard bags and it almost looks like a different front end.
Scott

Hi Scott,

...it has the Dunstall mounting plates and I look into the end of the pipe and it was looking like on the picture that You have posted. A kind of bigger tube and several smaler tubes inside the end of the pipe.

I thoght that there was mounted BMW "Snowflake" wheels and a Marzocchi fork.

Have a good one...Georg

[754]

 Look like BMW mags to me .. looks like Krauser racks for bags.. is it a K1.. it has some K1 parts on it.

[fire113]

...but is build in 69 and has an 12xxx frame No