Topic: Hot Street Motor on a Budget

[MRieck]

Couple more questions.  Is there a good place to get those CBX exhaust studs to replace the four 6mm head bolts?  And do you install the studs with anything, like locktite?

Any recommendations on what would be a reasonable amount to advance the webcam 41 to move the powerband down lower (going in a chopper)?  I'm considering drilling a stock cam sprocket to get between 5 and 10 degrees advance.

I assume I should be fine using the Kibblewhite chromed stem SS valves in the cast iron Kibblewhite guides.

I have studs on hand if you need them. Yes...blue Locktite. It's a blind hole so don't over to it with the Locktite.
The lobe centers on the 41A are low to begin with ....I'd stay with recommended cam timing. It is a mild cam so compression and torque will stay up. Just use a slotted sprocket or cut an early sprocket on a rotary table.
Use the Kibblewhite Black Diamond valves....coated valves work better in iron guides.

[TurboD]

I agree with Mike on the cam timing, you might advance it 1-2 degrees if you like, you may see a couple more HP down low as well as slightly better throttle response.

To address earlier questions. I would clean the ports up and retain the stock valves if possible. Couple of reasons, first as you said and I pointed out. You are wanting a street chopper on a budget. Secondly the stock valves provide better flow, the shape of the heads (this is why I asked you) out flow the flat aftermarket valve with all things being equal. I have done back to back tests to confirm this, typically the loss is about 2 cfm per port on the intake side. If you are not going over size on the valves (I would not on this given project), you are better off staying with the stock valves.

If I were helping you build this setup, I would simply recommend a 836 kit , 41 (cx-1) cam with a good port clean up, make sure the valves all seal up good and have fun riding.

[MRieck]

I know we talked about F2 valves, aftermarket shape and flow loss. The stock shape Kibblewhite intakes seem OK with a backcut but I"ll defer to your testing Turbo. When I see the word "budget" I always think "that's a good start".

[TurboD]

I have not tested the stock shape Kibblewhite's, I'm sure if they are similar to the stock valves they are good. The Honda designers (along with many other motorcycle company's) did their home work on these old bikes.

In my testing I took good ports (decent amount of work) and tested them with both stock valves and a available aftermarket back cut stock size valve. In every instance I seen 2-3 CFM loss per port, to do math this would equate to 4-5 HP. To gain this back more port work and or larger valves would be needed.

[MRieck]

The Honda designers (along with many other motorcycle company's) did their home work on these old bikes.

I agree...especially with those F2 valves. Unfortunately they weigh a ton.

[RAFster122s]

So, an aftermarket company needs to build a set of F2 knock offs in head shape with madern lightweight materials.  I presume since we are not dealing with a turbo they do not need to be sodium filled?  Or, do aircooled motors run hotter where the additional cooling by a sodium filled valve would be of benefit.  Or is it also a function involving compression affecting heat?  Curious on the need for sodium filled valves , guess I need to find some reliable info on the interwebs...

[TurboD]

Yes the aftermarket needs to copy the stock valves, both K and F. Unfortunately yes it would add weight. This said a lighter valve is a benefit in a high reving engine, how ever when using a stock or heavier valve there are things to keep in mind that will keep everything together and valve float down. First is of coarse is good springs and staying on top of them, second and just as important is cam selection. Some cam designs (lobe shape) are simply parts killers, with little to no benefit in a SOHC Honda. The cylinder head flow sets the baseline on how much power a given engine will produce, continuing to add more cam (lift and duration) than said engine can use will only make for a lower performing engine, many times at the expense of parts.

[stikman]

That would be great, Mike.  I'll take 4 studs and nuts off you, just let me know what you need for them.

I appreciate the input, Turbo.  What about the fact that a few of the valve tips have been hammered by the rockers from excessive lash?  And those nasty raised letters on the heads, should they be ground off? 

As a note, any port work is free since I'm doing it myself.  Is a quench band worth adding?  Now I'm second guessing everything I was leaning toward doing.  It's good to get these other perspectives though, especially experienced ones.

As for degreeing the camshaft, I guess I'll just slot a stock cam sprocket and advance the cam a few degrees if anything.

[TurboD]

Your welcome. Depending on how bad the stems are you could face them, many times it does not take much. The numbers on the bottom will have no effect on flow what so ever. If you want you could dress them smooth on a belt sander to remove them.

I personally would not do anything to open the chamber up and lowering compression, thus helping with low end and throttle response.

Yes as I posted, advancing 1 maybe 2 degrees at the most. I don't think you will see mush improvement beyond that.

On exhaust studs. The O'reilly auto parts stores here stock replacement studs with nuts that work good on the SOHC Honda's, a 10 pack with nuts is like $8.

[MRieck]

Your welcome. Depending on how bad the stems are you could face them, many times it does not take much. The numbers on the bottom will have no effect on flow what so ever. If you want you could dress them smooth on a belt sander to remove them.

I personally would not do anything to open the chamber up and lowering compression, thus helping with low end and throttle response.

Yes as I posted, advancing 1 maybe 2 degrees at the most. I don't think you will see mush improvement beyond that.

On exhaust studs. The O'reilly auto parts stores here stock replacement studs with nuts that work good on the SOHC Honda's, a 10 pack with nuts is like $8.

He is talking about replacing the 4 bolts through the center of the head with studs. I believe I mentioned this in a thread quite a while ago.

[Medyo Bastos]

Under the rubber nickels?


Sent from my iPhone using Tapatalk

[MRieck]

Yes...

[TurboD]

Your welcome. Depending on how bad the stems are you could face them, many times it does not take much. The numbers on the bottom will have no effect on flow what so ever. If you want you could dress them smooth on a belt sander to remove them.

I personally would not do anything to open the chamber up and lowering compression, thus helping with low end and throttle response.

Yes as I posted, advancing 1 maybe 2 degrees at the most. I don't think you will see mush improvement beyond that.

On exhaust studs. The O'reilly auto parts stores here stock replacement studs with nuts that work good on the SOHC Honda's, a 10 pack with nuts is like $8.

He is talking about replacing the 4 bolts through the center of the head with studs. I believe I mentioned this in a thread quite a while ago.

Yes sorry for the confusion. The studs I mentioned are for the exhaust.

[stikman]

Your welcome. Depending on how bad the stems are you could face them, many times it does not take much. The numbers on the bottom will have no effect on flow what so ever. If you want you could dress them smooth on a belt sander to remove them.

I personally would not do anything to open the chamber up and lowering compression, thus helping with low end and throttle response.

Yes as I posted, advancing 1 maybe 2 degrees at the most. I don't think you will see mush improvement beyond that.

On exhaust studs. The O'reilly auto parts stores here stock replacement studs with nuts that work good on the SOHC Honda's, a 10 pack with nuts is like $8.

He is talking about replacing the 4 bolts through the center of the head with studs. I believe I mentioned this in a thread quite a while ago.

Yes sorry for the confusion. The studs I mentioned are for the exhaust.

Ah no worries.  I've been doing a bunch of research which has taken me back to alot of older posts.

[Big Jay]

This new motor I'm building is a K4.  Still up in the air whether to go with the cruzinimage cast 836 pistons or forged with deep valve reliefs.  I'd really like to run a bigger cam but it's definitely more costly to go with the forged pistons.  Are they a pain to run on the street, with the heat/cold cycling and piston slap??  Or does it mainly mean you have to wait longer to warm up before riding, and longer to cool down before starting back up?

We set the Wiseco forged 836s up at .0015/.002. You will not get and piston slap or rocking with that.

If the head still has the oem iron guides, they will no doubt be shot.  We have a rebuild service where the seats are opened to modern specs, bronze guides, stainless chrome stem valves ( same as in the new RC fuelers) and Serdi valve job. Check it out  http://cbrzone.com/sohc.html 

[MRieck]

This new motor I'm building is a K4.  Still up in the air whether to go with the cruzinimage cast 836 pistons or forged with deep valve reliefs.  I'd really like to run a bigger cam but it's definitely more costly to go with the forged pistons.  Are they a pain to run on the street, with the heat/cold cycling and piston slap??  Or does it mainly mean you have to wait longer to warm up before riding, and longer to cool down before starting back up?

We set the Wiseco forged 836s up at .0015/.002. You will not get and piston slap or rocking with that.

I agree....he showed an ancient Wiseco box is this build thread. I thought he was going to use.  Now I don't know what the hell is real or not. I'm out and I bit pissed off.

[Bill/BentON Racing]

CBX exhaust studs which can be used under the rubber pucks are no longer available from Honda !

[stikman]

This new motor I'm building is a K4.  Still up in the air whether to go with the cruzinimage cast 836 pistons or forged with deep valve reliefs.  I'd really like to run a bigger cam but it's definitely more costly to go with the forged pistons.  Are they a pain to run on the street, with the heat/cold cycling and piston slap??  Or does it mainly mean you have to wait longer to warm up before riding, and longer to cool down before starting back up?

We set the Wiseco forged 836s up at .0015/.002. You will not get and piston slap or rocking with that.

I agree....he showed an ancient Wiseco box is this build thread. I thought he was going to use.  Now I don't know what the hell is real or not. I'm out and I bit pissed off.

Sorry, Mike.  Jay was quoting my post from a month ago before I had bought the old Wisecos off Bill P.  You were correct to think I am using the Wisecos.

[dragracer]

Couldn't he just machine those stems enough to install lash caps??? It would save the valve.

[TurboD]

He could, although they may only need to be lightly faced to make them usable.

[dragracer]

He could, although they may only need to be lightly faced to make them usable.

I bought several sets of lash caps from Mike. The tips on my stock F2 valves are worn unevenly so to save the valves, when I freshen the motor up this winter, I'll get the tips machined per Mike's specs and install the caps. I'm running heavy springs and the RC327 cam. The stems are catching hell.

[PeWe]

He could, although they may only need to be lightly faced to make them usable.

I bought several sets of lash caps from Mike. The tips on my stock F2 valves are worn unevenly so to save the valves, when I freshen the motor up this winter, I'll get the tips machined per Mike's specs and install the caps. I'm running heavy springs and the RC327 cam. The stems are catching hell.

I had F2 inlet valves before in my K head as 34mm upgrade. The tips got dents very quick. One setup had to be grinded to remove them out from the steel guides. Used 2 setups of IN valves during max 35.000 km.
Not used that long, mostly touring. Those valves have issues, right?
(Replaced a 3:rd time but with lash caps 2.5 years ago, now on the shelf since 5mm conv kit went in this year.)

I thought it was the lower/shorter stem that made the adjuster screw to dig into the valve stem with the edge. The adjuster screw should have a more rounded shape or elephant feet design as Porsche 911.
https://www.germansupply.com/home/customer/product.php?productid=16779&cat=372&page=1
Wrong thread for CB750 thgough, 8 x 1.0 mm

[BPellerine]

This new motor I'm building is a K4.  Still up in the air whether to go with the cruzinimage cast 836 pistons or forged with deep valve reliefs.  I'd really like to run a bigger cam but it's definitely more costly to go with the forged pistons.  Are they a pain to run on the street, with the heat/cold cycling and piston slap??  Or does it mainly mean you have to wait longer to warm up before riding, and longer to cool down before starting back up?

We set the Wiseco forged 836s up at .0015/.002. You will not get and piston slap or rocking with that.

I agree....he showed an ancient Wiseco box is this build thread. I thought he was going to use.  Now I don't know what the hell is real or not. I'm out and I bit pissed off.

the weiscos are the same as being sold today,same rings etc,pt no 4016,checked it out with weisco.billp

[stikman]

This new motor I'm building is a K4.  Still up in the air whether to go with the cruzinimage cast 836 pistons or forged with deep valve reliefs.  I'd really like to run a bigger cam but it's definitely more costly to go with the forged pistons.  Are they a pain to run on the street, with the heat/cold cycling and piston slap??  Or does it mainly mean you have to wait longer to warm up before riding, and longer to cool down before starting back up?

We set the Wiseco forged 836s up at .0015/.002. You will not get and piston slap or rocking with that.

I agree....he showed an ancient Wiseco box is this build thread. I thought he was going to use.  Now I don't know what the hell is real or not. I'm out and I bit pissed off.

the weiscos are the same as being sold today,same rings etc,pt no 4016,checked it out with weisco.billp

Yep, that's an old post Jay quoted and that issue has been put to rest.  A can of worms kinda got opened up there.  I appreciate the input on piston to wall clearance though, Jay.  And Bill, I'll be taking the pistons and jugs to my machinist this week.  I'll get your rings sent back then, just haven't had a chance yet.  Cheers bud!

[BPellerine]

cool,what is the advantage of the cbx studs?I have heard of using diff bolts for the adj cam sprocket.have a buddy with a lot of cbx stuff,he may have a set for me.billp