Topic: Exhaust Swapping

[Burke]

Does any have a general "knowledge" of what exhausts from certain years will fit other years?

Reason cause, I am in need of one for the a 77' 750K I picked up, and in my e-bay searches have found quite a few that span the years.

I'm thinking that the header fit wont be an issue, but more of the brackets and mounts lining up. am I close on this?

[HondaMan]

Well, you're on the right track, to a point. I think all of the "F" and K7-K8 head joints are similar (Eldar, are you there?). The K0-K6 heads are all similar, also. The twain shall never meet, though, as the "F" signalled the beginning of the "second type"' of head pipes. Those 4-into-1 pipes from Honda fit only the "F" models, and the K7-K8 pipes do not fit the earlier "K" bikes, nor vice-versa. I don't know if the K7-K8 and the "F" 4-1 pipes will fit each other, though.

[754]

With spigots Anything might fit..

I am running F or K7/8 turbo pipe on a 73 motor..

[eurban]

Right, at the head, all the SOHC 750 pipes will fit all years.  You would just need spiggots and clamp style exhaust "flowers" to attach 76 and earlier style pipes or studs and the latter style exhaust flowers and shims to attach 77/78k or f stuff.  However, I don't know how well the exhausts fit around the frame bits and or line up with the rear mounts as you mix and match years. . . . .

[azuredesign]

Am I mistaken? I thought that early heads had exhaust ports where the angulation between #1 & 2 and 3 & 4 was greater than on later models. Will a 300 or 341 exhaust fit later year K bikes as well? Thanks for diminishing my dillema!

[Burke]

I believe the exhaust in the auction is off a K,. he has a bike pictured in the back ground and it looks to be a 78'K.
 I dont think its a stock pipe, after really looking, It looks like a mac

[754]

I am not saying stock pipes will swap from early to late or vice versa. But I think a lot of the headers would, but I would try them first. Might have to remove centerstand.

[rbmgf7]

i'm running the stock 78F 4-1 on a 75K. Just had to remove the spigots on the K engine, either install studs or get bolts, and the headers bolted right up.

[HondaMan]

Am I mistaken? I thought that early heads had exhaust ports where the angulation between #1 & 2 and 3 & 4 was greater than on later models. Will a 300 or 341 exhaust fit later year K bikes as well? Thanks for diminishing my dillema!

Nope, you're not mistaken. Even when swapping spigots, there are some tiny differences that, if not monitored, cause header leaks. Sometimes I have fixed such a leak (after a full rebuild) by rotating the center 2 spigots, since I screwed them in upside down. It seemed to slightly change the angle, causing a departure angle leak. Personally, I think this was a production tolerance side effect from Honda, but never studied it close enough to nail it down for sure.

IIRC, fitting the K1 (HM300 style) pipes to the K2/K3 frames (common when I raced) caused the pipes to run closer to the oil filter housing. I do remember trying to swap the spigots to alter this, with no improvement, due to my other experience with the "angles". My main concern at the time was the extra heat this applied to the oil at the filter during long (100 mile) races. Not that it really mattered that much, just one of those late-night-before-the-race musings.... 

[KRONUS0100]

hey.  My 76F original motor was swiped during a frame off.  The MAC 4 into 1 header pipe slid right into the ports on the 72 K2 replacement motor. I have seen this a couple of times, all the ports seem to match from the early K's to the F's.  I have only seen a few of the spigot types, and even they matched up.