Topic: compatibility of K6 and K7

[johnyvilla]

Would there be any compatibility issues with nestling a K7 engine in a
k6 frame, as well as all the other K7 parts? I know the K7 has a different tank, carbs, side panels etc, but will these just bolt on? What about the swing-arms?
thanks

[GammaFlat]

I K7 engine will slide right in in terms of mounting.  There are 2 issues you might need to contend with.  

1) The output shaft is different.  The K7 "wants" a 630 sprocket.  A 530 sprocket will fit but the sprocket is wider where it meets the shaft.  My guess is (and folks here have said it in the past) that you can use the K7 bolt and washer arrangement to hold down the K6 style sprocket.  With the 630 sprocket (narrower), the washer seats up against the shaft and the sprocket.  When you use the wider 530 sprocket, the washer meets up with only the sprocket.  There may be compatible sprockets sold that take care of this issue (possibly cyclexchange.net). 

Here are the sprockets side by side to show the height difference:
530 on left, 630 on right




2) The K7 and K8 bikes have studs at the exhaust port where the pre-K7 has spigots held on with phillips screws.  This is relatively easy to remedy if you can get the studs out successfully and replace with the screws and spigot arrangement.  

[Laminar]

1) The output shaft is different.  The K7 "wants" a 630 sprocket.  A 530 sprocket will fit but the sprocket is wider where it meets the shaft.  My guess is (and folks here have said it in the past) that you can use the K7 bolt and washer arrangement to hold down the K6 style sprocket.  With the 630 sprocket (narrower), the washer seats up against the shaft and the sprocket.  When you use the wider 530 sprocket, the washer meets up with only the sprocket.  There may be compatible sprockets sold that take care of this issue (possibly cyclexchange.net). 

I bought a 530 conversion kit for my K7 from HavokTurbo, but I think he's out of the loop for a while. I believe the sprockets were made by Sunstar.

[KB02]

I think you will find the K7 swingarm to be wider as well. take a bunch of measurements to find out for sure, though.

[Toxic]

K7 swingarm will fit in an earlier frame but it is wider at the back so you would need to use a K7 rear sprocket carrier which is wider.

But honestly I was at the same point you seem to be and the only bad advice I can say I ever got from this website is that " There are not that many differences between th K7's and the earlier years"

If you want your bike to be a K7 , K8 then go for it, they are awesome bike in their own right.

If I were to do it again I wouldn't try mixing and matching parts from a K7 onto my 72-76.