Topic: Final Generation of Billet blocks??

[Don R]

 Does anyone have a motor project underway to slip their new big block onto?

[MRieck]

I have all my parts to start. I'm using an F2 head and F2 bottom end. Have a 6mm striker crank Marine Crankshaft did for me. The stroker crank and 72mm pistons give almost 1125cc's. Counting on some nice torque.
I'm going to document the build too.

[PeWe]

Any clutch modification, Mike?

[MRieck]

Any clutch modification, Mike?

Replace the primary Cush drive pieces. Transmission is a very low mileage F2 undercut by Fast By Gast. The original style HD primary chains from Germany. I'll probably have the basket unit balanced as well.

[bigutah]

Does anyone have a motor project underway to slip their new big block onto?

I do


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[newday777]

Does anyone have a motor project underway to slip their new big block onto?

I've been collecting the bottom end speed parts but haven't pulled the motor out of the 76 F1 yet. I've been busy off doing some work to be able to collect the parts. So no, it's not ready to slip the shiny new big block onto.

[Don R]

  I've collected too many projects that I've become attached to, mostly because of who owned them before me, that made a decision difficult.
  I'm planning to use a low mile K6 case and crank with a back-cut F2 transmission by big Jay. I'm putting it in my first project bike, the blue green K0.
  It hasn't had the original engine since the 70's so it's not like I'm ruining its value. If I ever get too old to ride it, I'll keep it just to look at.
  Rods are still to be decided on, I have a set of MTC steel rods, a set of RC rebuilt rods, and I won't use them here but a set of allegedly new aluminum MTC rods. I tried to buy a set of nice used Carillos but they were apparently sold out of all of the rods on the web site I was looking at. 
 

[MRieck]

My buddy picked up the blocks today for bead blasting. Should be done in a couple of weeks.

[newday777]

👍

[PeWe]

Any clutch modification, Mike?

Replace the primary Cush drive pieces. Transmission is a very low mileage F2 undercut by Fast By Gast. The original style HD primary chains from Germany. I'll probably have the basket unit balanced as well.

- No mods for better grip, less prone to slip?

I think my engine should cause clutch slip with 6-7mm longer stroke.
Dyno runs at 105-107.5whp, 68.5 ft lbs torque.
My K6 has got the late clutch from an F2 with double metal plate, glass beaded metal plates. EBC fibers, the heavier black Barnett springs middle number -66-.

I changed front sprocket to 18 from 17. Clutch gave up at next dyno run a day later. I could verify the most important needle change though.

Bike behaved not as fun on stock 18-48 as 17-48. Noticed when passing a queue of cars. I had to gear down for a quick pass when earlier not.

New EBC fibers and fresh glass beaded metal discs back in. 17-48 sprockets. This was late 2024.

My slow going engine project that has the upper case milled for the billet block has a good stock crank.
Later undercutted transmission 2-5, final shaft is from a K2-K6 trans, the gear part of the late K7 trans.
Gear 4 and 5 will rev a little more with late transmission compared to K6
Super rods.

I have a new Megacycle 125-70 on the shelf. Standard rocker arms.

It would be nice with a balanced stroker crank with rods. 

This might be another thing. My K6 has one
https://good-bits.co.uk/product/cb750-sohc-clutch-actuating-hub/

I do no not like how fast they years passing by.
Winter rest (waste) of 5-6 months every year  start to be stressful. Riding half life only.

[MRieck]

Any clutch modification, Mike?

Replace the primary Cush drive pieces. Transmission is a very low mileage F2 undercut by Fast By Gast. The original style HD primary chains from Germany. I'll probably have the basket unit balanced as well.

- No mods for better grip, less prone to slip?

I think my engine should cause clutch slip with 6-7mm longer stroke.
Dyno runs at 105-107.5whp, 68.5 ft lbs torque.
My K6 has got the late clutch from an F2 with double metal plate, glass beaded metal plates. EBC fibers, the heavier black Barnett springs middle number -66-.

I changed front sprocket to 18 from 17. Clutch gave up at next dyno run a day later. I could verify the most important needle change though.

Bike behaved not as fun on stock 18-48 as 17-48. Noticed when passing a queue of cars. I had to gear down for a quick pass when earlier not.

New EBC fibers and fresh glass beaded metal discs back in. 17-48 sprockets. This was late 2024.

My slow going engine project that has the upper case milled for the billet block has a good stock crank.
Later undercutted transmission 2-5, final shaft is from a K2-K6 trans, the gear part of the late K7 trans.
Gear 4 and 5 will rev a little more with late transmission compared to K6
Super rods.

I have a new Megacycle 125-70 on the shelf. Standard rocker arms.

It would be nice with a balanced stroker crank with rods. 

This might be another thing. My K6 has one
https://good-bits.co.uk/product/cb750-sohc-clutch-actuating-hub/

I do no not like how fast they years passing by.
Winter rest (waste) of 5-6 months every year  start to be stressful. Riding half life only.

I'm currently at that 107 RWHP with 74 lbs of torque if I remember correctly. I have the black Barnett springs but always use OEM steel and fiber plates. Bead blasted steel plates too. The clutch holds very well. There isn't much else to do. I have a billet actuating plate too....it can't hurt.
 
 Lock up clutches are not good on the street as it becomes very difficult to changes gears at higher RPM's....you really need an air shifter to drive the gear change home and it's much harder on the transmission.
 I honestly can't remember the sprocket ratio but I did go down a couple of teeth on the rear because the engine was revving too high at 75 to 80 MPH.
 I'm using stock length rods. I had the piston pin moved up 6mm to compensate for the extra stroke.....I don't like short rods or the problems like extra length cam chain with stroker plates under the cylinder. My billet block also has shorter cylinder flanges for rod clearance.
 There will be a few more 100+ RWHP CB750's on the road once I ship these cylinders out.😉

[PeWe]

Nice numbers, Mike. Your stroker engine will increase it even more.
It will be interesting to follow the builds.
Compression affect the hp.
I had initially thick gaskets.
Later thinner gaskets, around 215-220 PSI with a cheap tester.  200PSI needed to enter 100WHP.
Cam timing affect that, when in valve close. When timed too late, power was very dull. Too advanced not good either.
I hoped for a later DOHC clutch to just pop-in with small adjustments.

Anyway, the torque will make the bike bigger.

[MRieck]

Nice numbers, Mike. Your stroker engine will increase it even more.
It will be interesting to follow the builds.
Compression affect the hp.
I had initially thick gaskets.
Later thinner gaskets, around 215-220 PSI with a cheap tester.  200PSI needed to enter 100WHP.
Cam timing affect that, when in valve close. When timed too late, power was very dull. Too advanced not good either.
I hoped for a later DOHC clutch to just pop-in with small adjustments.

Anyway, the torque will make the bike bigger.

I agree Per...you get 210 PSI and over and you start making real power. Squish is very important.😁 That 125-70 is best at 105 LC.....that's what I've found. That 105LC was standard for Yoshimura cams back in the day.
 If I have problems with the clutch I guess I'll have to explore options.😆

[PeWe]

My last cam timing
0 lash: 1mm lift:
IN 27/54*   9.98mm lift
EX 57/22*   9.38mm lift 

This ends up in
IN 103.5 ATDC
EX 107.5 BTDC

I see that LC will be closer to 105 by retarding 1 degree.

Running lash
0.10/0.15mm
(0.004/0.006")
24.5/51*    9.82mm lift
54/17*       9.15mm lift

It runs fine as is and my degree wheel is not the highest tech. My goal was relative timing OK, consistent timing. Maybe not absolutely correct.
If I retard 1 degree, the engine will run smoother with less dynamic compression.
I noticed the compression felt harder with last timing.

If I give full throttle on 5th gear at around 5000-6000 rpm, I'll hear pinging at 7000 rpm.
If I only give 3/4, wait until 7000rpm for the last 1/4. No problem. The acceleration is good anyway.
I need to do it properly:
Gear down to 4th and WOT, 5th gear in at 9000 rpm.
Give too much throttle too early on 5th gear seems to overfill the chambers, "over boost"

I' m sure this will be smoother if I retard the cam 1 degree.
No plugs in when I fine adjusted according to photo.
Kick starter used and also rolled rear wheel with gear in.

Small wheel to adjust with engine in frame. I have no other wheel either ..

[MRieck]

Larger wheel equal better resolution. I have an 11" and 18" Moroso. The 18" makes half a degree look huge. I saw a pic of a Nascar shop years ago and they had a wheel that was like 4 feet in diameter.....holy $hit.🤣 Now it's all electronic measuring devices....final word in accuracy. Always remember.....when that engine is spinning at 7,000, 8,000....15,000RPM everything is moving around, charge is going in both directions and things just "kinda" stay the same.😉

[bigutah]

It’s not much, but it’s good enough for me.


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[PeWe]

I made punch marks in the cam and sprocket before taking it apart the first time.
New photo after each timing.
I tested different settings on dyno when testing carb jetting. I have a photo with 10whp less when advanced too much

When I compare this photo with an earlier with its numbers, timing can be in the mentioned good lobe center.
Below last setting that work fine. I doubt I can change it to get more than 107.5whp. 970cc (70 mm pistons)
I have Mike's numbers as a reference too.

[willbird]

Interesting side note is that many machines I have worked on over the years had very accurate vernier angle setting methods built in to them that would resolve degrees, minutes, and seconds of angle. They were pretty small physically too, not any bigger of a degree circle than a small lathe compound rest has.

Gear hobbs being just one example. A common surveyors transit has these features as well. Friend was going through Carpenters apprenticeship and had a class on transits, she was doing homework and I noticed and said "oh yea that is an angular vernier"....she got pissed and said "do you know EVERYTHING?" LOL. Not quite but I do know a few things :-).

Some older machinery I worked with had vernier scales maybe 8-10 feet of table travel with a lighted magnifier included on each scale to read the verniers. We never used that feature, those that needed any precision they had added digital readout.

[MRieck]

Interesting side note is that many machines I have worked on over the years had very accurate vernier angle setting methods built in to them that would resolve degrees, minutes, and seconds of angle. They were pretty small physically too, not any bigger of a degree circle than a small lathe compound rest has.

Gear hobbs being just one example. A common surveyors transit has these features as well. Friend was going through Carpenters apprenticeship and had a class on transits, she was doing homework and I noticed and said "oh yea that is an angular vernier"....she got pissed and said "do you know EVERYTHING?" LOL. Not quite but I do know a few things :-).

Some older machinery I worked with had vernier scales maybe 8-10 feet of table travel with a lighted magnifier included on each scale to read the verniers. We never used that feature, those that needed any precision they had added digital readout.

You have a lot more experience with machining then I do for sure😉 I imagine it really gets down to the precision drive mechanisms for the small vernier measuring tools in terms of accuracy. Still....DRO's etc are pretty convenient. I can't remember the last time I used an analog mic or vernier. I'll be honest I don't miss them either.🤣