Topic: New Cam!

[JerrodR]

What's up everybody, so I tried out Lucas Oil treatment for Motorcycle in my 74. Its always been good in my Car, but I do not recommend it for a CB-750. It blew my head gasket which led to a completely destroyed Cam bearing. But this is where it gets interesting. I bought a replacement Cam off eBay for 50 buck's, installed it today. And it transformed my bike into a Fire breathing monster. I finished setting the valve's and started it and it sounds like a different bike. And I took it out just babying it didn't take it over 4000 RPM cause the new Cam and Rocker Tower. And there was a noticable power increase. I'm honestly just confused, it was not advertised as anything but a CB-750 Cam and was the Cheapest available. Does anyone have a theory as to why this 50 dollar "Stock Cam" completely transformed my 50 Y/O Bike?

[ekpent]

 Maybe is wasn't running on all four cylinders before you fixed it.

[caluser2000]

Because the old one was stuffed

[Alan F.]

Without measuring the cam who knows? Do you have any photos of it? Could be a performance part or you could have had a problem waiting to happen with your old cam that was sapping performance.

[JerrodR]

No, it wasn't down a Piston or anything. It ran pretty good actually. It's Jetted with a 4 into 1 with a straight pipe with no baffling. Made 73 HP on a Buddy's Dyno last Spring. And no didn't take Pictures. It had an R9 on it, but I've been told the casting Marks on these Cams don't mean much. I did consider that maybe the Guy was parting out a Bike that didn't run or something. And he thought it was a stock Cam when it wasn't. I'm gonna have it Dynoed again when I get it broke in. I'm curious.

[seanbarney41]

No, it wasn't down a Piston or anything. It ran pretty good actually. It's Jetted with a 4 into 1 with a straight pipe with no baffling. Made 73 HP on a Buddy's Dyno last Spring.

Damn! Cool story bro!

[JerrodR]

I just looked and it was advertised as a 73 Cam, it has an R9 Cast Marking right next to the timing Sprocket. But I guy on here told me a little ways back that those Cast Marking's aren't really for identification, but more for when and where the Cam was manufactured.

[JerrodR]

One thing I would like to know, is how long should the break in period be for a new/used Cam. I replaced 1 of the Rocker Tower's too. New to rebuilding Motor's, this was my 3rd time. And I'm getting pretty decent at getting things together and timed in. But I don't know the small but important details like how long I should go easy on it..

[dave500]

just dont peak it out,never load any motor until its fully warm,how many in the day bought their new 750 and just started racing every car from the red lights?just ride it normally for a few days,change oil often.

[Old Moe Toe]

Maybe the cam you got was an F2 type cam?

[Jerry Rxman Griffin aka MuthaF'er]

Or F0/F1 cam

[MauiK3]

How does an F0 cam compare to a K3 cam?

[Jerry Rxman Griffin aka MuthaF'er]

Early F's brought back the "lost" HP. The cam is an upgrade to the middle K's. My bike is an early first year. I measured the cam lobes and discovered the exhaust lobes are 0.1mm taller than all my other 750 cams. Intake the same. It always (until I blew it up with a missed shift) ran like a scalded ass dog.

[PeWe]

Cant be a hot cam since they need pistons with deeper pockets.
I guess the cam now works as it should, your old cam the problem
or leaking headgasket causing low compression. CB750 really like compression.
Or a valve did not have proper lash, open all the time....

[L5wolvesf]

One thing I would like to know, is how long should the break in period be for a new/used Cam.

Just curious about the new/used Cam. In auto motors a used Cam should not be used with different used rockers or lifters because of the different wear patterns. That can be done if the lifters are resurfaced. Does that apply to Honda motors?

[caluser2000]

One thing I would like to know, is how long should the break in period be for a new/used Cam.

Just curious about the new/used Cam. In auto motors a used Cam should not be used with different used rockers or lifters because of the different wear patterns. That can be done if the lifters are resurfaced. Does that apply to Honda motors?

Another myth like using nylocks only once. If the cam is in good condition and within factory specs it will be fine in any vehicle  engine of the same type.

[754]

Maybe you had an A cam in it  and ended up with a CB cam.
 I wish you had a pic, 9 some guys did rework stock cams , sometimes welding them..

[PeWe]

One thing I would like to know, is how long should the break in period be for a new/used Cam.

Just curious about the new/used Cam. In auto motors a used Cam should not be used with different used rockers or lifters because of the different wear patterns. That can be done if the lifters are resurfaced. Does that apply to Honda motors?

Important that the rockers pads are OK without scratches, flaking chrome.
If valves are new, new adjuster screws can be a good idea.

Then an oil with API class that allow ZZDP as this engine design need.

Good description of it despite it is for cars.
https://www.transdiesel.com/blog/passenger-car-motor-oil-blog

"API SG and SH were the last PCMO service classifications where the zinc level in the engine oil was any reliable indication of anti-wear performance.  These PCMOs had zinc levels of up to 1200 or 1300 parts per million (ppm)."

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On top of this for wet clutch to be sure that no additional antifriction additives will make clutch to slip.
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More...
"So, from the mid-1990s, zinc level could no longer be taken as a reliable indication of the anti-wear protection the engine oil provided.  The level of engine oil anti-wear performance also doesn’t need to be as high in modern engine oils because engine designs have evolved.
 So while API SJ, API SL, API SM and API SN PCMOs are perfect for modern petrol engines, they may not be ideal for older engines, especially those fitted with flat tappet cam followers.

Because of the high sliding load of flat tappet cam followers on the camshaft in older engines, a higher level of anti-wear agent is desirable to prevent cam lobe wear.  The perfect anti-wear agent for this job is our old friend ZDDP.  And ZDDP at the concentration of previous API SH engine oils.  Larger engines also seem to benefit from higher viscosity engine oil, such as an SAE 20W-50."


There are  motorcycle oils that have loads of phosporous and zinc.
Spectro and Red Line are the ones I know.

Higher lifting cams using harder springs will need really good lubrication.