Topic: Picking the best bottom-end for a high-hp engine?

[JLeather]

Well, the turbo-matic project has hit a snag.  The bottom end of that 'matic engine is totally trashed.  Both clutch packs (hi and low) are finished.  The fiber plates are worn out a flaking, and the steel discs are worn through the plating to the base metal.  The input shaft damper had all the springs broke out of it.  Some of the bearings are questionable.  Long and short of it is if I can't find a better bottom end to start from the 'matic isn't happening.

So, I have a stash of standard-shift motors that I could also use for this turbo build.  Problem it, none of them have ever run while in my posession.  The 'matic was a non-runner when I got it, and look how it turned out.  So, how do I figure out which of my other bottom ends is best for a bike?  Are there procedures for making sure the shift forks and everything are good without ever having the engine running/shifting?

Which year did they stop putting the auto-oiler in the output shaft?  I've got two '78F engines that are both locked up.  Now, I'm working on a regular K-model top end with some early model cylinders ('74 I believe) for the turbo.  Will that work out OK with a '78F bottom end?  Is the '78F bottom end stronger than one of my early K's (72-75)? 

The '78F bottom ends I've got haven't run in years.  How do I make sure that when I'm done putting it together it'll work right/shift?  I'm certainly planning on replacing the primary chains, cam chain, tensioners, checking the main bearings, replacing the rod bearings (new rods anyway), etc.

Anyone know of a good running 'matic engine near MD?

[JLeather]

Anyone?  Bueller?  Bueller?

[MRieck]

 A 77or 78F crank and clutch set up would be the best bet. An automatic crank with the HyVo primary would be better but more involved. Lordmoonpie has developed a nice system but hasn't run it yet.

[HondaMan]

The auto-oiler final output shaft changed in the K7/K8 with the 630 chain drive. Prior to that, the late K2-K6 output shafts were all the same, with dual-row final bearing. Before that, the output shaft had a longer shoulder and a 1-row bearing. If you use the shaft and bearing together, they will all interchange.

To use the 2-row bearing on the earlier shaft, you can cut back the shaft to fit the bearing (but I'd rather trade one with you, if you find one), and you must make a spacer to use the newer 2-row shaft with a 1-row bearing.

The 1-row bearing puts a bit more HP on the pavement, in the end. It will handle up to 90 HP at the shaft, which is about 105 HP at the crank, the 2-row even more. If you use the 2-row output bearing, check for a good inner bearing on that shaft, too. It's much smaller, and runs in dirty oil, so they tend to wear quite a bit, and generate and audible howl at around 30-40 MPH. Kawasaki sells this bearing for one of their bikes, while Honda doesn't carry it anymore. If you need it, I have the part # written somewhere in my notebooks, thanks to another SOHC4-er who found this for us.

[JLeather]

So I can put a K top end onto a 78F bottom end?  All the oil passages and everything match up ok?  I seem to recall reading somewhere that the F-model gearbox ratios are different as well.

I cracked open another K-model bottom end today (used to be a dragbike engine) and unfortunately one of the bosses that holds the points in place had cracked and came off with the points plate.  Another set of cases for the scrap pile I suppose.  I did find a very nice lightened rotor though.  I'm gonna dive into an F-model bottom end shortly and see what it looks like inside.  But since I've already got a set of bored jugs I gotta make sure they'll still work.  I know Honda changed to jugs a lot from year to year, but is there anything that has to be done (or can be done) to run a top end from a '73 on a F?