Topic: What aftermarket camshafts work with stock rockers (CB750K2)?

[FridgeRaider]

I was talking with Calj737 and he mentioned that hardwelded camshafts require hard welded rockers to match.... makes sense to me. There are a couple of vendors selling new "billet" cams which don't require you to send in a core to be hardwelded. Will these work with the stock rockers in a '72 CB750K or is it the same philosophy to upgrade rockers with any new aftermarket cam?

Vendors that sell such cams:
http://www.cyclexchange.net/camshaftpage.htm

http://www.speedmotoco.com/product-p/22-25-2.htm?1=1&CartID=0

Sidenote: has any one had any experience with CycleX's CX1 or CX3? If so, let me know what you think of them. I'm trying to figure out what to drop in my CB750K2 with a Cruizin_Image 836 kit and probably some light porting.

[Davez134]

I have a Webcam 41 (similar to CX-1, as stated in their description)  in my 1972 cb750 with 836, ported head, otherwise stock valve train. Smooth, even power, smooth idle. I personally think it is a great cam for a daily ridden street bike. Also, I just had to replace a valve seal. While I had the cover off, I inspected the cam and rocker arms. Virtually no wear at all after 5000 miles.

[PeWe]

Std rockers works fine as long as the chromed surface against lobes is OK. Check for flaked chrome.
I think it is mostly Megacycle that sell welded cams. Webcams all cam and Dynoman's DP295, 315 (made by webcam) are all billet cams, welded is optional. My old Action Fours SS-1 cam (billet) has been used for over 40.000 km without any mark on lobes or less lift.
Maybe only racers that need a welded cam?

[Terry in Australia]

As has been said above, hardwelded rockers are unnecessary if your stock rockers are in good condition. (some of the cam suppliers sell hard welded rockers, so go figure...........) I bought a Megacycle 125/75 billet cam and noticed in the instructions that Megacycle recommend hard welded rockers, but (in my opinion) that's more of an insurance policy for Megacycle in case some tool uses buggared rockers and blames the ensuing damage on the cam manufacturer.

I rode that bike like I stole it for several years with that cam and when I pulled it out to use a more sensible street cam it was unmarked, and my 40-odd year old rockers were still fine too. Cheers, Terry.

[BPellerine]

I did notice that very few people change rockers,or have them hardwelded.bill

[MRieck]

About the only thing that will destroy a hardweld rocker is lack of oil. I have seen NOS rocker arms ruined in short order by more aggressive cams. Sam Green's auto drag bike is a great example.....the engine only had about 15 actual miles on it (if that).

[754]

Do you recall what the valve lash was.
At .012 on an RC 315, the engine is not overly loud. I suspect the big clearance allows easy oil access, and might actually cushion the blow.... Pity the guts that go...oh too much, lets run it tighter.

[MRieck]

Do you recall what the valve lash was.
At .012 on an RC 315, the engine is not overly loud. I suspect the big clearance allows easy oil access, and might actually cushion the blow.... Pity the guts that go...oh too much, lets run it tighter.

Lash was generous Frank as we backed off for more torque using a 125-75. Later ran a 295 cam.

[HondaMan]

When considering meshing the valve train parts, keep the old "bearing materials axiom" in mind, which is:
Never run similar metals, nor similar hardness, together. One side of the bearing must be softer than the other, whether it be a softer metal, or one being non-hard. Running 2 non-hard metals together is fine.

The reason, stated succinctly in the Machinery's Handbook (circa 1992) is: one material must yield to the other in order for a bearing surface to be created that can then be lubricated effectively.

[bwaller]

I've seen more than SOHC4 engines suffer from used rockers & hardweld cams, and it doesn't take long, but go ahead give it a try! I've pounded on an engine with hardweld cam/rockers for a few seasons now & both surfaces look like new. It's not Megacycle making up this claim.

[HondaMan]

Maybe consider adding some extra zinc (ZDDP) additive during the break-in phase, as this will help burnish and seal the surfaces together better.

[FridgeRaider]

Thanks for all the technical knowledge! My stock cam is toast and I will have to spend money on something....might as well give it a little boost. I've just about decided on following Davez's build and putting in a webcam 41 equivalent since it's destined to be a daily rider.

Maybe consider adding some extra zinc (ZDDP) additive during the break-in phase, as this will help burnish and seal the surfaces together better.

I read your write up on it a while back and have subsequently started putting it in mine and my dad's bikes.

Sam Green's auto drag bike is a great example.....the engine only had about 15 actual miles on it (if that).

Would you say that this was an extreme case due to the drag racing nature of trying to get every bit of power out of the engine? It's tough for me to justify spending $400+ on new rockers to prevent this from happening with a mildly modified motor.

[PeWe]

If all your std rockers are not OK, check for used ones on eBay where you can find good ones for not much. As said earlier, aggressive cams will cause more wear. This is cams with high lift and relatively short duration where the lift accelerate very quick.

RC/DP315 cam is specified with a lot of lash, 0.012" which is 3 times more than other hot cams. Must have more space for oil to lubricate the rocker as Frank wrote. I ran DP315 with 0.04/0.05" as I used on other cams.

I read Franks ideas about better lubrication with more lash as RC specified. That cams overlap was rather much so it was easier to change to specified 0.012" lash with decreased overlap, duration and also lift. Longer cooling time for valve in the seats must be good too, especially for EX valves.
The forces on valve train including the rockers will be less too.

Engine has a different behaviour with DP315 (much smoother) compared with a 295 or my other cams as Action fours ss-1, CX-7, Megacycle 125-20 that all have a sudden power increase around 6000-7000 rpm. CX-7 and 125-20 suddenly wake up at around 7000 rpm.
I'll see later on dyno if I'll compare the cams. DP315 will go in next.
Dyno before was 80rwhp with SS-1, 83 with 125-20 that have a fun behaviour exceeding 10.000 rpm like tacho going crazy

Wecam 41, 41a are all mild cams in comparison. Some of the other hotter cams need more cc and cr to work as designed. High CR need a cam with more overlap, later closing of IN that reduce the pressure (dynamic compression ratio) and less risk for pinging.

Note! My engine is tuned with ported head, 34mm inlet, opened chambers, bored, 32mm carbs, lightened crank (APE), carillo rods.
Most cams need ported head and pistons with higher CR and deeper valve pockets.
For more job the owner need deeper pockets!!

[grcamna2]

subscribed

[rotortiller]

When we were teenagers and popped in a high lift cam in we installed helicoils at the rocker boxes  regardless if we installed stronger valve springs or not (which we also did most times). Seemed to avoid stripped threads in that area, still appears like a good idea, especially when you are in that area and the fact that pulling a engine again sucks.

[calj737]

There is a great deal of knowledge from experienced guys being submitted here, Fridge. But for my $, I'll follow Mike Rieck's and Brent Waller's counsel. They tend to deal with "built right, last long" engines. Yep, hard weld rockers cost some money, but I'd rather spend the money now, than to spend it later and pull the motor, head, repair the cam towers, and replace parts.

[MRieck]

Hardweld rockers from Megacycle retail for about 95.00 ea. Hardweld cams just went up and retail for 549.00. It is investment quality work and like I said only a lack of oil will kill them.

[grcamna2]

As has been said above, hardwelded rockers are unnecessary if your stock rockers are in good condition. (some of the cam suppliers sell hard welded rockers, so go figure...........) I bought a Megacycle 125/75 billet cam and noticed in the instructions that Megacycle recommend hard welded rockers, but (in my opinion) that's more of an insurance policy for Megacycle in case some tool uses buggared rockers and blames the ensuing damage on the cam manufacturer.

I rode that bike like I stole it for several years with that cam and when I pulled it out to use a more sensible street cam it was unmarked, and my 40-odd year old rockers were still fine too. Cheers, Terry.

thanks

[Don R]

 I always use a quality assembly lube so the new parts get a chance to know each other upon first start and break-in. The oil additives probably help as much after the engine is warmed up and oil is flowing.

[gschuld]

I’m bringing this thread back from the dead.  I’m curious to get opinions on how the use of beehive springs could effect the big cam to rocker wear issue.

Beehive springs are well known to reduce overall spring pressure so in theory at least they should reduce the wear on any rocker/cam combination.  This is not meant to be a crutch for poorly selected or inferior cams or rockers, but an extra level of insurance.

Thoughts?

George

[Terry in Australia]

Probably a good idea George, the post-Buell Harley Sportsters are producing decent HP with redesigned heads and bigger cams, and running beehive springs.

[PeWe]

I saw that CycleX has a page about old cams with their data. Also the thoughts of Action Fours how a good profile should look like for a long life
http://www.cyclexchange.net/Tech%20Tips%20Camshafts.htm

This is exact how my old Action Fours SS-1 cam lobes look  like. Lobes are not agressive or steep change from top to bottom with valve float either.
My stock rockers were OK after 35000 km.  I replaced a few when I had others looking better. Still no flaked chrome where rocker meet lobe.

It's different on a racer where an agressive cam is used combined with constant agressive way of riding. Lack of time and money to NOT use hardwelded, right?

Scheisse, threads like this will create a sudden need of more. My billet block K6 has all except good hardwelded rockers :-)
I hope the 5mm Kibblewhite valve kit has softer springs and will save the stock rockers. I heard that before. Possible due to the lighter valves.
- What about hardwelded rockers on billet cam? Or is a hardwelded cam a must?

Stock on billet, hardwelded on hardweled is  a must?

It has been discussions before about the hardwelded rockers vs billet cam, hardwelded  cam vs stock rockers with different thoughts

[Terry in Australia]

Oooher, that's a nice looking cam you've got there Per, it looks similar to the "No Name" cam I had in my K1, it was the same profile as the stocker, with a couple more mm lift. Sweet.........

[PeWe]

Yes, that is a good cam that has served me and the engine well. Perfect with 836 + ported head. Made my bike to a good tourer that could keep up the pace with Kawasaki 1000 and similar from the early 80's.

This little fellow below is hardwelded and might need hardwelded rockers.
"only a lack of oil will kill them" I have seen NOS rocker arms ruined in short order by more aggressive cams. Sam Green's auto drag bike is a great example.....the engine only had about 15 actual miles on it (if that).

I'm sure that will pop-up in my mind in the middle of the nights hereafter so I have to fix it to get piece.... Facts by experience is a heavy argument.  Try to save some hundreds will probably cost much more later on.
This is not that aggressive with its sweet ears. Ex open up rather early. This cam did not respect the tacho at all, just passed the red area into the green just like that! 836 + ported head + 4-1 

OK, the HW cam will go in later on...

[Terry in Australia]

Nice! It's a pity though, that you can buy a cam for 250 bucks, then have to fork out another 800 for rockers, once upon a time I could buy a running CB750 for that much......