Topic: cam lobe and rocker pitting question

[my name is nobody]

This seems to be common on our bikes. There seems to be a lot of different opinions of what is acceptable.
Does anyone have a fix for slowing the process, short of having to have everything re welded? (Assuming the pitting is minor around the edges) Can the small areas be lightly filed or smoothed? If so, what is a good tool
to use? 

[BomberMann650]

Frequent oil changes, proper functioning oiling system, correct tappet clearances, and (hotly debated) zddp zinc oil additive can keep an sohc4’s cam and rockers happy for many many miles.

Post pics of yours if its a concern.

[my name is nobody]

750 actually, but rules are the same. Pitts are in early stage. Tempting to leave it, been watching for a good used F2 cam (and now rockers) No noise, and mostly in great shape. Good oil and frequent changes always.

[754]

I am pulling a top end off a black F and wil, likely be parting out most of it.
Should have cam out by tommorow.
 No idea of condition yet.

[my name is nobody]

I am pulling a top end off a black F and wil, likely be parting out most of it.
Should have cam out by tommorow.
 No idea of condition yet.

754.....please keep me posted. I'd be interested if the postage didn't cost too much. Thanks...

[seanbarney41]

Can you post a pic?  I have read that some experts consider a certain amount of pitting normal on these, never a good thing, but your engine is not gonna instantly blow up.  This acceptable pitting is caused by casting "inclusions", sort of a negative result of Honda's low cost casting methods of the time.  These casting methods later bit Honda on the ass when they tried to use the same type of castings in the early V4's...the difference with the v4's was an inferior oiling system mixed with more spring pressure and friction from 4 valves per cylinder.

If I had one apart, and found anything suspect, I'd grab a new camshaft or a better condition used one.  If I saw it in a bike that has been running fine, I would probably leave it.

[Yamahawk]

If you can afford a new cam, here is a good one for a little extra horsepower, and will work with your stock pistons/valve springs. I am thinking of installing a new cam, and I just bought an APE adjustable timing gear for $37.50 off eBay also, and am considering this cam for a little better running engine!

https://www.ebay.com/itm/Honda-CB750-High-Performance-Cam-Shaft-CX1-Drag-Race-Road-Race-Cafe-CR/201667874237?hash=item2ef4578dbd:m:m78dbFMp0Y3AIzFueBZpGEA

https://www.ebay.com/itm/Honda-CB750-High-Performance-Cam-Shaft-KHD-CX1-Drag-Race-Road-Race-Cafe/152729602152?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

Charlie

[HondaMan]

Pits in the 750 cams are REAL common, and cause no harm in most cases. Look to see if it was worn a groove (entering and leaving the pit), which could potentially start to "stripe" the rocker: other than that, they cause no troubles. My 750 went more than 90k miles with 2 pitted cams (#2 intake and #3 exhaust) and at 140k miles they had no grown, nor showed any marks on the rockers - which I re-used, along with a newer K4 cam, in the 2013 rebuild.

In the 500/550, I have seen more often that the pit turned into a ridge or groove, even in the rocker, and then it settled down, just losing a little bit of lift that way. This seems to occur more in this bike (by the numbers I have seen, anyway) than in the 750.

[PeWe]

My stock cam my CB750 K6 came with has some pits and rust. But that is after been stored cold with other parts in a box in barns between 1987 to end of 2009. It did 65.000km, most of it on cheap oils that caused foam in oil tank after the for the days wild riding with minimum of warming up.

I guess that having bike parked outdoors, sitting still for some time can cause corrosion.

I have had a few rockers where the chrome flaked on the sides of contact surface. I bought fresh low mile rockers with holders on eBay to have for replacement.
CMSNL has a complete set of NEW rockers for not that much.

I have doubts about Honda's valve lash of the IN valves. Only 0.05mm....How will this affect the oil to enter the lobes?
I'll try 0.1/0.1 mm (IN/EX) in my ongoing K2 project as hotter cams often have specified. Cam I use today, 0.3mm as RC Eng recommended.

[my name is nobody]

The wear that is most evident is on 4 of the rockers, primarily on the outer edges of the rocker pads, in early
stages of wear. My plan was to get a different cam anyway, and now at least, some younger rockers that don't
exhibit "flakiness". hadn't planned on different rockers due to added cost, but it is what it is. At least replace
the suspect ones and save the others?


EDIT pic of worst rocker. I'm thinking this one meets replacement criteria.

[my name is nobody]

Pits in the 750 cams are REAL common, and cause no harm in most cases. Look to see if it was worn a groove (entering and leaving the pit), which could potentially start to "stripe" the rocker: other than that, they cause no troubles. My 750 went more than 90k miles with 2 pitted cams (#2 intake and #3 exhaust) and at 140k miles they had no grown, nor showed any marks on the rockers - which I re-used, along with a newer K4 cam, in the 2013 rebuild.

In the 500/550, I have seen more often that the pit turned into a ridge or groove, even in the rocker, and then it settled down, just losing a little bit of lift that way. This seems to occur more in this bike (by the numbers I have seen, anyway) than in the 750.

This is good to know, thanks. Most of what I have going on is shown in the pic I posted.

[HondaMan]

Just remember one important thing about rockers and cams: at least one of them must NOT be hard. If you get a hardweld cam, for example, use a stock rocker, and vice-versa. Or, just use non-hard for both, which is what Honda did.

[754]

Your cam does not look bad in the pic.
 The one I pulled has one little pit.
 From what I can see your cam looks like mine.
Not sure though because I have had an F cam with huge lobes... but it may have been aftermarket and I bought into the F was hotter cam, and not realized it wasn't.
 Under the rocker inbthe pic or on other end of cam between 1 and 2 cylinders is there 4 little lumps cast into the cam?

[my name is nobody]

Your cam does not look bad in the pic.
 The one I pulled has one little pit.
 From what I can see your cam looks like mine.
Not sure though because I have had an F cam with huge lobes... but it may have been aftermarket and I bought into the F was hotter cam, and not realized it wasn't.
 Under the rocker inbthe pic or on other end of cam between 1 and 2 cylinders is there 4 little lumps cast into the cam?

mine is a K5. Between cyls #1 and #2 there are two separate bumps, stamped with letters, spaced 180 degrees apart. one is a "C", (spin the cam half turn) the other is a letter "G"

[Jerry Rxman Griffin aka MuthaF'er]

I hope you are not calling that as pitting under your magnifier! That lobe looks great.

[my name is nobody]

I hope you are not calling that as pitting under your magnifier! That lobe looks great.

pitts are at max lift on both extreme edges of lobe. middle of lobe is smooth. rocker arm is flaking on 1 edge, not able to show well in pics, altho somewhat visible when zoomed in, in my first pic, reply #10...
I have a replacement good rocker, but I will change cams for a hotter f version if available.

[Jerry Rxman Griffin aka MuthaF'er]

You will appreciate either F cam variant over the K5 cam. F2/3 preferable being better.

[my name is nobody]

Yup...just need to find one now, and not break the bank. Gonna degree whatever goes back in as well.

[HondaMan]

Your cam does not look bad in the pic.
 The one I pulled has one little pit.
 From what I can see your cam looks like mine.
Not sure though because I have had an F cam with huge lobes... but it may have been aftermarket and I bought into the F was hotter cam, and not realized it wasn't.
 Under the rocker inbthe pic or on other end of cam between 1 and 2 cylinders is there 4 little lumps cast into the cam?

mine is a K5. Between cyls #1 and #2 there are two separate bumps, stamped with letters, spaced 180 degrees apart. one is a "C", (spin the cam half turn) the other is a letter "G"

The one under the magnifier is ridge-raised where the rocker never rode on it. This happened quite often in the post-1974 750 engines where the rocker shafts are tightly locked down with the little 5mm bolts: the rocker towers may have a slightly raised edge where the rocker's bearing abuts them, moving the rocker over a tad and letting it ride off-center of the lobe. I just stone down the "high" spots on the rocker foot and cam lobe for the next round. The difference in heights that you see are the wear-in spec from the original Parkerizing of those surfaces, which mated them together in about 2000 miles.

[my name is nobody]

I micd the rocker shafts at 11.94(?) min spec... (mic doesn't go any lower) Would it be better to let them spin without the bolts? What do you use to "stone down" the high spots? I may need to go this route if I can't locate a good F model cam.
I will need to check the shaft towers for anything abnormal.

[754]

I can sell this cam , but Have to confirm  that it is an F cam.

I think I am having trouble recognising it because Ibhad one with very noticeably fat  lobes.. I was surprised.
 Pretty sure I checked the end and body for names or numbers, but its starting to look like it was maybe a hotter cam that I let go a few years back.
 Where are you located?

[my name is nobody]

I am about 25 miles west of St. Louis Mo.

[MRieck]

I haven't had any problems running hard weld cams with hard weld rocker arms. I have had notable problems with hard weld cams and OEM rocker arms (especially when spring pressure and lift are increased). I have seen new, OEM rocker arm pads severely flattened/grooved in very short order.I have never seen a hard weld rocker arm fail unless oil supply was cut off.

[kmb69]

Just remember one important thing about rockers and cams: at least one of them must NOT be hard. If you get a hardweld cam, for example, use a stock rocker, and vice-versa. Or, just use non-hard for both, which is what Honda did.

Mark's statements are not exactly true. 

The same argument can be made for running soft on soft as hard on hard. The real argument is running materials together with similar chemistry and like hardness will usually gall.

It appears that Honda may nitride or apply some surface treatment to some of their cams and apply flash hard chrome to the rocker faces. I have seen the hard chrome peeling from the rocker faces. And you can usually see the layered material when a rocker is worn through to the substrate.

I haven't had any problems running hard weld cams with hard weld rocker arms. I have had notable problems with hard weld cams and OEM rocker arms (especially when spring pressure and lift are increased). I have seen new, OEM rocker arm pads severely flattened/grooved in very short order.I have never seen a hard weld rocker arm fail unless oil supply was cut off.

Ditto. Good oil supply is imperative in either case.

[754]

 Good oil supply and don't tighten up the clearance on the big cams.. helps get oil in there.
 One of mine runs 12 thou clearance.