Topic: Drag Bike / The Big 4 Express.

[Don R]

[Don R]

[Don R]

Of course with it apart the kickstart works perfectly. I need to go through the spare parts boxes to look for a kicker mechanism. If I don't find one I need to split another old engine. I have a frozen K0 that needs to come apart anyway.

[Don R]

LUCK!  A couple years ago I bought an F2 trans on E bay for $30. The seller included the kickstart mechanism, so I aced that.
 I traded a $20 (what I paid) henry abe 900 kit to Big Jay for backcutting this transmission so my decision now is, do I use the backcut F trans in the dragbike or just put it back together and save the backcut trans for a bike I'm going to ride more.

I'll check rod bearings once I determine the rod bolt torque value. I'm getting the Hondaman book out to see how to swap the kick start mechanism. Then I'll get my brother over to look inside before I put it back together.

[Tintop]

subscribed

[Jerry Rxman Griffin aka MuthaF'er]

Good question. Think I'd use it in a rider. How much will you have that bike on the track?

$20, huh?! And to think I thought you were givin it up on that swap. You coulda gotten more  but we all came out good. Thanks again for doing that. All I need to do is prime and install the oil pump then see how your kit pieces do.

[Don R]

Awesome Jerry. I knew what the big bore kit was worth but did get it almost free. You gotta help a fellow muthaF'er and a sohc4 vendor when you can.
 When I saw the braze spots on this crank I thought of you.

 Since I'm telling my secrets, I got the sandcast and dragbike for,,, nope, some guys would hate me. I think I can have the dragbike complete for 3-4K depending on paint and rear rim/slick.

I got the kicker swapped out. One of my brothers old manuals had the secret of loading the spring. You slip in the gear/spring, use a screwdriver to push the tang down past the pin, you hold it down and then slide the kicker shaft in, the last thing is to tap down the roll pin to hold it all together.

[754]

I got a sandcast complete for 500, so go ahead..make me feel bad..

 What kind of oil is in that motor..looks familiar like maybe Pennzoil GT or ..Torco or ?

[MoMo]

subscription sent in.  Have fun with the build Don...Larry

[Don R]

 I think it had Kendall 50wt. It's green and clings to everything. 
 We just finished a funny car front half chassis. The top frame rails vent the crankcase to the seperator tank in the back. When they welded the old frame they drilled random 1/8" holes to vent the tubes for welding, so the vented oil goes everywhere inside the frame. That thing dripped oil non stop the entire time it was here. That was 70 wt Valvoline with a small amount of gear oil mixed in to provide extra zinc and moly. I think they mix 2-3 qts per barrel.

[andy750]

Some great info here - subscribed! I want to see this thing run!

good luck!
Andy

[EnginebyAdam]

Sorry Don R, I read the info over here so I'll post the question and my response over here too.

EnginebyAdam-
"Don R, I'm following both your threads, great info Sorry if I missed this but, is this engine a F2/F3 base?"

DonR-
"Sorry, auctually it's a K2 Titled as a 73. It has the early front forks and for some reason a two hole rear hub."


The reason I ask Don R is that you mentioned about putting in a F2 tranny. Were you talking about just the tranny or the output shaft as well? More of a follow up to my F2 tranny thread. 

Cheers.

[Don R]

 Yes, I'm still assuming it will work. pics at 9.
Update-

 The F2 final drive gear (output shaft) does not fit into the K2 case, the bearing is located farther outboard and doesn't leave room for the retainer or the seal. I don't have a K6 case and that, I think was your question. I wonder what year Honda widened the case?
 The F2 output shaft final gear also does not mesh properly with the corresponding gear on the K2 countershaft either so at least those gears will both need to be from the K. (on a K2)

Sorry I'm not more help. I don't think I'm going to use my backcut f trans in the dragbike. Just because the dragbike is being rebuilt on the premise the PO's family wants to buy it back. There's no upside to me using my good trans in it.

[EnginebyAdam]

Yes, I'm still assuming it will work. pics at 9.
Update-

 The F2 final drive gear (output shaft) does not fit into the K2 case, the bearing is located farther outboard and doesn't leave room for the retainer or the seal. I don't have a K6 case and that, I think was your question. I wonder what year Honda widened the case?
 The F2 output shaft final gear also does not mesh properly with the corresponding gear on the K2 countershaft either so at least those gears will both need to be from the K. (on a K2)

Sorry I'm not more help. I don't think I'm going to use my backcut f trans in the dragbike. Just because the dragbike is being rebuilt on the premise the PO's family wants to buy it back. There's no upside to me using my good trans in it.

Thanks for the info Don R. As far as I know the K6 was the first year of the new engine cases and I believe they went to the double row bearing as well. As soon as I get this engine torn down I will be able to confirm. Sorry for the detour

[Terry in Australia]

G'Day Don, that looks fantastic mate, I love the work you did on the rear fender, you've inspired me to shorten one for my bike. Geez that crank  is stroked to the max, I was trying to understand how you'd get 1188cc out of an SOHC4 until I saw those pics, that is amazing!

Good luck with your project Don, and FYI, the F2 trans will work with a K or early F output shaft, (I just ran out to my garage and checked in reverse, the F2 output shaft gear meshes with the K transmission fine) so for the insurance of not missing a gear at high RPM and doing some top end damage alone, I'd use that APE transmission, for sure. Cheers, Terry.  

[Don R]

 Thanks Terry. For the encouragement and the info! After all, those ugly F's have to be good for something right?

 Some of the drag racing Aussies were talking about a busa starter in a cb750. I just ordered one. My goal is self starting a stroker motor. Magneto, LED lighting and a total loss electrical system. Might make a lap through town.

[Don R]

 I've dropped the F2 output shaft into the K2 several times and the gears don't mesh right when I turn them. The f2 gear bottoms in the mating gear on the K2 countershaft.
 When I measure with a dial caliper the root of the gear diameter appears slightly bigger on the F2 than the K2. This doesn't agree with Terrys findings.

I believe the sprocket shaft gear must match the corresponding gear on the countershaft. That could be as easy as pressing the bearings off, swapping the gears and pressing it back on.  That makes the gears all match and the sprocket shaft correct for the case.

[HondaMan]

I've dropped the F2 output shaft into the K2 several times and the gears don't mesh right when I turn them. The f2 gear bottoms in the mating gear on the K2 countershaft.
 When I measure with a dial caliper the root of the gear diameter appears slightly bigger on the F2 than the K2. This doesn't agree with Terrys findings.

I believe the sprocket shaft gear must match the corresponding gear on the countershaft. That could be as easy as pressing the bearings off, swapping the gears and pressing it back on.  That makes the gears all match and the sprocket shaft correct for the case.

The F2 output gear should be 50 teeth. The earlier ones were 56T. The shafts space the bearing out further on the early ones (stepped shaft) and have to have their shoulder turned back to fit the 2-row output bearing instead of the 1-row type. Of course, the cases must also hold the 2-row: the ones from the last K2 until the K6 held the wider bearing there. The K2-3 versions had retainer grooves to fit either output shaft-bearing combo, too.

[Terry in Australia]

I've dropped the F2 output shaft into the K2 several times and the gears don't mesh right when I turn them. The f2 gear bottoms in the mating gear on the K2 countershaft.
 When I measure with a dial caliper the root of the gear diameter appears slightly bigger on the F2 than the K2. This doesn't agree with Terrys findings.

I believe the sprocket shaft gear must match the corresponding gear on the countershaft. That could be as easy as pressing the bearings off, swapping the gears and pressing it back on.  That makes the gears all match and the sprocket shaft correct for the case.

That's interesting Don, all I did was take the output shaft (sprocket shaft) from an F2 and mesh it with the K transmission I've got set up in the bottom case and it worked fine, but there might be a difference when done in reverse?

Well curiosity got to me so I went back out to the garage (it's around 100 deg F in there today so I'm trying to stay away) and had a closer look. Both the K2 and F2 output (sprocket) shaft gears are 50 teeth, but you're correct, the deepest part of the teeth on the F2 gear are around .5mm deeper than on the K2 gear, but the OD of the K2 gear is around .5mm larger?

Regardless, as you've already said, just swapping the gear on the countershaft would solve that problem, I'd reckon? Cheers, Terry.

[Don R]

 Mine clinks as it's turned, the F2  output shafts teeth are bottoming out in the K2 trans gear. Maybe just a tolerance stack. I agree, swap the gears to the original shaft and viola!
 I may still do it. Undecided.

  Edit: gears did not match.

[754]

Swap the gears.
 No sense in putting big bucks in it to sell back to them...hope that does not happen..

[Don R]

 The trans question is mostly to help Adam and some other guys that really want to throw F gears in a K. I think I can but don't want others spending $$ on my best guess.
 
  I'm in a lucky place right now but there are too many toys in the shop for me to afford to finish, I'm going to be forced by reality to choose between them. Very difficult to let one go, they're all special in one way or another or I wouldn't have them.

[Don R]

I've dropped the F2 output shaft into the K2 several times and the gears don't mesh right when I turn them. The f2 gear bottoms in the mating gear on the K2 countershaft.
 When I measure with a dial caliper the root of the gear diameter appears slightly bigger on the F2 than the K2. This doesn't agree with Terrys findings.

I believe the sprocket shaft gear must match the corresponding gear on the countershaft. That could be as easy as pressing the bearings off, swapping the gears and pressing it back on.  That makes the gears all match and the sprocket shaft correct for the case.

The F2 output gear should be 50 teeth. The earlier ones were 56T. The shafts space the bearing out further on the early ones (stepped shaft) and have to have their shoulder turned back to fit the 2-row output bearing instead of the 1-row type. Of course, the cases must also hold the 2-row: the ones from the last K2 until the K6 held the wider bearing there. The K2-3 versions had retainer grooves to fit either output shaft-bearing combo, too.

Here you go Adam!

[EnginebyAdam]

Thanks Don R

[Don R]

Thanks Hondaman!