Topic: Cb750f camshaft in k8 engine

[Dime]

In an ideal world I would drop a Webcam bolt in cam or similar into my k8 when I am doing the top end. However the f cams can be had alot cheaper when they come up.

With a ported head is the f cam worth doing in my k8 engine? Or just get the head ported and skip the cam for now?

This is based of a 836cc engine.

Thanks

[HondaMan]

Like a lot of things, it depends...on which "F" engine you're mentioning.
The F0/1 had the same cam timing as in the K0-K5/6 bikes, 5 BTC intake opening, 35 ABC closing intake. In the F2 and all later ones the intake changed to 0 BTC intake opening and 40 ABC closing, which caused the powerband to shift upward (and narrow a bit) and required carbs with better-controlled idle circuits to prevent intake spitback troubles and resulting poor idling situations (especially when hot).

So, it depends on which "F" cam you get?

The F2/3 cams also had slightly more lift (almost 0.5mm more on intakes), which was part & parcel with the more-efficient intake valves of the F2/3 heads. I have approximated that same efficiency with the earlier valves (and the K7/8 versions) by trimming the lip off the faces, but this reduces their ability to resist rusting over time when sitting too long. The valves themselves don't swap, as the F2/3 valves use different retainers from the "K" versions (among other reasons). There are aftermarket solutions to some of these issues, but require large bankrolls to employ. 

[Jerry Rxman Griffin aka MuthaF'er]

The K7 and K8 engines are basically derived or the same as the F0 and F1 engines. -392 engines.

With this being said, "when they come up", how will you actually know which cam you get unless you take it out of a known unmolested engine. They all look the same and do not have identifying markings like aftermarket cams do.

[scottly]

Or just get the head ported and skip the cam for now?

This is based of a 836cc engine.

Thanks

Even a mildly ported head will give more power increase than any cam alone.

[newday777]

I don't have an answer to your question on the F cam.
You mentioned Webcam, I have a new unopened Webcam 41a/CX2 cam available if that is what you want.
I'd let it go for $275 plus shipping.

[Dime]

Like a lot of things, it depends...on which "F" engine you're mentioning.
The F0/1 had the same cam timing as in the K0-K5/6 bikes, 5 BTC intake opening, 35 ABC closing intake. In the F2 and all later ones the intake changed to 0 BTC intake opening and 40 ABC closing, which caused the powerband to shift upward (and narrow a bit) and required carbs with better-controlled idle circuits to prevent intake spitback troubles and resulting poor idling situations (especially when hot).

So, it depends on which "F" cam you get?

The F2/3 cams also had slightly more lift (almost 0.5mm more on intakes), which was part & parcel with the more-efficient intake valves of the F2/3 heads. I have approximated that same efficiency with the earlier valves (and the K7/8 versions) by trimming the lip off the faces, but this reduces their ability to resist rusting over time when sitting too long. The valves themselves don't swap, as the F2/3 valves use different retainers from the "K" versions (among other reasons). There are aftermarket solutions to some of these issues, but require large bankrolls to employ. 

I was referring to the f2/f3 cam. I feel like my better money spent is to have someone rebuild the head and port it as well leaving the cam for a down the road upgrade.

[Dime]

The K7 and K8 engines are basically derived or the same as the F0 and F1 engines. -392 engines.

With this being said, "when they come up", how will you actually know which cam you get unless you take it out of a known unmolested engine. They all look the same and do not have identifying markings like aftermarket cams do.

True I think it would be trusting the listing which is a roll of the dice

[Dime]

Or just get the head ported and skip the cam for now?

This is based of a 836cc engine.

Thanks

Even a mildly ported head will give more power increase than any cam alone.

This makes sense. I am assuming that the head has to be rebuilt anyway so porting is the logical step even with stock cam.

[Dime]

I don't have an answer to your question on the F cam.
You mentioned Webcam, I have a new unopened Webcam 41a/CX2 cam available if that is what you want.
I'd let it go for $275 plus shipping.

That is an amazing offer. If I had the cash on hand I would take you up on that offer. Unfortunately I do not. Thank you

[Jerry Rxman Griffin aka MuthaF'er]

Install a frame kit and you will be happy when it comes time to swap out cams etc

[Dime]

Install a frame kit and you will be happy when it comes time to swap out cams etc

I was thinking about a frame kit. Any recommendations on a kit?

[Don R]

 I was under the impression the F2-3 cams have a "broken ring" around the shaft. They are still pretty old though. I have one with about 7K miles on it that I intend to use on a turbo engine.

[PeWe]

K7/K8 cam (probably F/F1 too is not a hotter cam. It has a molded ring beside tacho drive.

My K2 got one since I found a good looking cam cheap.
I have an extra.
Below with sprocket. The other cam my old stock K6.

I think the F2 has a squared shape mold instead of ring.

[Dime]

K7/K8 cam (probably F/F1 too is not a hotter cam. It has a molded ring beside tacho drive.

My K2 got one since I found a good looking cam cheap.
I have an extra.
Below with sprocket. The other cam my old stock K6.

I think the F2 has a squared shape mold instead of ring.

So just trying to understand. Are you saying you have an extra F2 cam? And that thr F2 cam has the squared ring near the tach drive? Thank you

[Dime]

So I pulled the valve cover off just to see if I could see any marking on the cam. It has R2 cast into it. As far as research goes that was used for the 77/78f engines and some of the 78 k engines, which is what I have.

Please correct me if I am wrong in my research. Thanks

[Dime]

K7/K8 cam (probably F/F1 too is not a hotter cam. It has a molded ring beside tacho drive.

My K2 got one since I found a good looking cam cheap.
I have an extra.
Below with sprocket. The other cam my old stock K6.

I think the F2 has a squared shape mold instead of ring.

PeWe if you are talking about what I have circled in your picture, my cam has that too

[Dime]

Pulled the cam from my engine and I am looking for a new cam either way. Mine is below service limits lift wise according to the manual.

[PeWe]

Yes, that ring.

The CX2 cam in earlier post is a better alternative if you have 836 with deeper valve pockets.
But make sure that head is good is more important. Valves, guides and seats.
Hotter cam need also better springs...

If doing a head restore, a port job can be done. A lighter job (less $)  for the worst anti flow metal inside.

[Dime]

Yes, that ring.

The CX2 cam in earlier post is a better alternative if you have 836 with deeper valve pockets.
But make sure that head is good is more important. Valves, guides and seats.
Hotter cam need also better springs...

If doing a head restore, a port job can be done. A lighter job (less $)  for the worst anti flow metal inside.

The plan is for a 836cc kit from cruzinimage. I don't want to get into a deep pocket piston setup.

I have been talking with Hondaman and I think I am going to send my head off to him to be reworked.

Here is the numbers from my cam lift wise. I found an old post of HondaMan's and he was saying of the cams he has measured in the later engines none actually measure out to the service limit, always below.

#1-Intake- 1.407" Exhaust- 1.3985"
#2-Intake- 1.410" Exhaust- 1.399"
#3 Intake- 1.410" Exhaust- 1.3985"
#4 Intake- 1.4125" Exhaust- 1.397"

PeWe if you have that spare F2 cam there would you be able to measure it to see how it stacks up against mine please? Thank you

[PeWe]

I have no F2 cam. Only the earlier K7/K8/F1 cam. Not higher lift than my old K6 cam.

Cruzin image pistons are good. Need tight clearance.
Their 836 not for higher lift cams. There is a long thread about those pistons in the SOHC Bikes forum.

My CB750 K2 has a Cruzin image set, +0.50mm, 392 type with a little higher domes than stock K.
It has the same type of cam as I showed.

A good head and not worn stock cam  will make it a fun bike.
An old head can be OK too

My K2 has 4-4, Yamiya No numbers (like HM300) and runs fine. Head  restored with new guides, valves and springs.
58 WHP on dyno a few years ago. It runs better now after carbs replacement.
From K6 carbs (086A) to better jetted CB750F-75 (064A) carbs, so maybe 60WHP. 17:48 sprockets and stock 4.0-18 tire make it to run fine.

My K6 with 970cc and +100WHP back to 17:48 sprockets. I tested 18:48 again during  a week or 2.
It felt not as fun anymore when I often need to pass slow going cars. I had to gear down when doing a caravan of cars....

Throttle response felt boring so the 17t front went back in. Rear tire wider 130/80-18, close to stock diameter.

[Dime]

I have no F2 cam. Only the earlier K7/K8/F1 cam. Not higher lift than my old K6 cam.

Cruzin image pistons are good. Need tight clearance.
Their 836 not for higher lift cams. There is a long thread about those pistons in the SOHC Bikes forum.

My CB750 K2 has a Cruzin image set, +0.50mm, 392 type with a little higher domes than stock K.
It has the same type of cam as I showed.

A good head and not worn stock cam  will make it a fun bike.
An old head can be OK too

My K2 has 4-4, Yamiya No numbers (like HM300) and runs fine. Head  restored with new guides, valves and springs.
58 WHP on dyno a few years ago. It runs better now after carbs replacement.
From K6 carbs (086A) to better jetted CB750F-75 (064A) carbs, so maybe 60WHP. 17:48 sprockets and stock 4.0-18 tire make it to run fine.

My K6 with 970cc and +100WHP back to 17:48 sprockets. I tested 18:48 again during  a week or 2.
It felt not as fun anymore when I often need to pass slow going cars. I had to gear down when doing a caravan of cars....

Throttle response felt boring so the 17t front went back in. Rear tire wider 130/80-18, close to stock diameter.

Thank you for the response. My apologies I misunderstood about the F2 cam.

I am not looking for max performance just want to do what makes sense while it is torn down.

I like the idea of the cycle x cx1 cam as it is bolt in. As of now it looks like over $700 Canadian landed to the door. A bit steep for my budget.

I will touch base with Hondaman again and go from there.

Thanks again for your time.