Topic: CB750 "R1" camshaft

[MCRider]

Whew! My head is spinning. Suffice it to say, the 69s were the fastest and some cams are different from others.     

No, the fastest stock 750s were the 77 and 78 Fs. They were also the heaviest. According to Cycle's test of the 77K it was also faster than the 69 they tested way back when and heavier too. Some here dispute the tested 1/4 mile times of the 69 (ragged out bike, improper technique on this new kind of beast etc etc) but who knows as there seems to be a good bit of nostalgia mixed in. I would think that with the higher compression in the late Ks combined with the better breathing heads and pumper carbs that more power was being generated.  This was certainly blunted somewhat by the weight gains and perhaps by the quiet exhausts. . . .

OK I understand and can accept that. They are just not in my personal knowledge base. Thanks for getting me up to "speed".

[lwitchey]

Thanks guys! even know that I am not getting rich off of a R1 cam, I have really got educated on CB750 cams. I have some other parts that will help build a performance cb750 motor. But I have some other projects before I get to building this motor.

[Jerry Rxman Griffin aka MuthaF'er]

My vote is with Bodi. These markings are just casting numbers and not final grind designators.

My 78 K cam is R1

My 75 F cam is R9

 

[GammaFlat]

I have an R5 and R7 (both K0 engines).

[mick7504]

Found a R13 today,.... what is that from..

..Freakin EH model..

Found an R14 in amongst the collection.

[HondaMan]

I just measure the lift. That separates them best. 

[bucky katt]

one of the r1 cams i have has considerably more lift and duration than the other. too bad the one with all the lift and duration is trashed with scored bearing surfaces and lobes.

[garyS-NJ]

If anyone is still looking at this thread, here goes...(posted as a new thread without much response)

I had some sort of top end failure where a loose nut got under my #3/4 rocker holder and busted things up.  rockers, holder, & cam wiped.  and one rocker hold down stripped out the head.  So I had a basket 78 F3 motor in my cellar and grabbed the cam from that (already out of the motor).  My wiped cam is stamped R2 and this basket cam is stamped R1.  I'd like to have the same cam back in the bike (I think) but would also like to know what I have in my hands.  Supposedly the seller took a worked on 1978CB750F motor apart and this is the cam he found.  The basket engine has VIN that shows its a '78 but who knows about the cam (and he also gave me some K model parts).  I did a quick/dirty comparison and the cams look about the same and I measured lob heights (only the bearing (bushing) surfaces of my cam got totaled). I can't measure the degrees. 

So my motor before (as much as I know) was stock with the airbox and the stock 4 into 1 pipe.  I knocked the baffle out of the pipe and it ran good.  I ran the points for a year or so and then put in a dyna S when I had to do points again.  I bought an aftermarket copy of K&N pods along with the next size up main jets and I'm only getting to that now.

except for some wear on the #3 & 4 cyclinder cam lobes, the cams lobes have about the same height (within a few thousands).  1.425" IN and 1.405 EX.  But I looked at my Honda "official Shop Manual" for '78 K8/F3 and it only lists one set of cam specs (doesn't list for F and K models) and it shows 1.4173" IN and 1.3976" EX.  I guess these are the K model specs and the F model specs were "secret".  Eyeballing the profiles, the cams look the same but I don't know if any differences could be detected.  Am I safe to put this R1 cam in my 1978F3??

Also, when the rocker holder broke, it trashed the cam hold down clamps too.  I have two rocker holders (with rockers) from my basket motor but no cam hold down clamps.  the manual says the clamps are matched to the holders with stamped numbers but I didn't see any matching numbers on mine.  In fact, the holders are stamped 1, 2, 2, 2 (respectively going from # 1 cyclinder to #4.).  Am I good to buy new old stock or aftermarket cam hold down clamps (and where to get aftermarket>?).  and then rather than measuring cam bearing OD and the clamp ID, do folks use plastic gauge now??  My basket cam reads 0.864", 0.858" 0.858", 0.864" going #1 cyc to # 4cyc and the manual says 0.864" down to service limit 0.861" but I'm thinking my 0.858" on the inside cyclinders might be OK...

last thing, when the rocker holder broke free, it also stripped out a hold down bolt (head threads stripped).  I planned to repair the head with a 6mm helicoil .

Inputs on the cam ?? and any other recommendations on motor work to do while the engine is out?

[Old Scrambler]

Just got in from my garage.............I have 4 F2-3 motors/heads and all have or had R-1 cams indicated on the #3 side of the center-sprocket; PLUS the F identifier on the #2 side of the sprocket. These cams also have small horizontal 'bars' on the casting between #3 & #4.  If your spare parts are within spec.........they should make for a good exchange.

Your central cam bearing races are worn so the cam should be replaced because that is the area of greatest 'flex' and strain caused by the cam-chain.  Yes, you could plasti-gauge the fit when you get new caps or install an entirely different cam-tower.  If the cam-races are within spec.........you might tighten the caps just a bit if they are slightly worn.

I would suggest a 'time-cert' versus a heli-coil thread repair. 

[bryanj]

The cam caps are matched and lettered BUT over the year i have found that if you drop them on the carrier the edges will either be way off or so damned close you cant feel a step, if the latter they will normaly run OK

[KayOne]

Here is a picture of a Webcam 41, F3 and unknown post 1974 camshaft. The post K4 cam looks pathetic compared to the F3 and 41. The Webcam is a slight upgrade from the F3 visually but made a sizable increase in power on my 836. I originally ordered a 41a but the vendor messed up and sent the 41 instead. Kind of glad because I am really happy how much low and midrange power it makes. The combination of higher compression/displacement with a moderate performance cam is ideal for my style of riding.

[edwardmorris]

..........
By the time of the K2 mid-year, these numbers were approximately:
IN  .3010"
OUT  .286"
as measured across several bikes at the time.
..........

This is just what I was looking for. So I have a NOS R2, which is correct (based on the numbers above) for the K2!! Thanks to Frank who sold it to me, and as always, the best info from Mark.

[PeWe]

Measure the cam(s) when mounted will answer the questions.
Degree wheel will tell when open and close, dial indicator will tell the lift and when open and close happen.