Topic: Who can tell me whether this rockers, camshaft and pistons have some life left?

[Raul CB750K1]

I'm going to start the reassembly of my CB350 soon. I've been gathering all the parts in dire need of replacement. As the bill is getting real high (I've preferred not to add up the total until everything is done) I want to reuse as many parts as I can.

I think this information can be useful for everybody, but, if Mr. Moderator believes this thread belong in the NON-SOHC4, please feel free to move it there (won't you do it anyway?)

In every manual they say "replace the rocker arm and camshaft if the contact surfaces show evident wear of pitting. A little pitting is tolerable". So, how much is too much pitting.

Here I post some pictures of the rocker arms and the camshaft. Only the lobe shown have pitting. The other three are pristine. The rockers have no pitting at all, but the surface that has rubbed has different brightness. I don't know if it really makes a difference or not.

As you say, OEM Honda rockers go for about 55 bucks each, and the camshaft is about 200-300 bucks, so I rather use mine if I can.



Now let's move to the pistons and rings. They are 0.25 oversize, so it means the engine was rebuilt. As I have seen many hand-fisted things on the bike, I really don't know how skilled the mechanic was.

Both pistons had a lot of carbon deposit. I've cleaned with sandpaper one of them. I've posted two pictures of them, showing both sides. Is that skirt scratching tolerable? I think so, as the cylinders look fine.

What amazes me are the rings. In theory, rings have a letter that identifies the make, and it should face upwards (the opposite side to the piston skirt). The upper ones have no letter at all. It could be that it has been rubbed down, but it could also be that the profile is symmetrical and it doesn't matter the installation position. But I would say that one of the sides have a little lip, so I guess it should face the skirt side to "sweep" the oil downwards.

The second ring have a clear ridge or lip, and the letters are visible. They were facind upwards, so the lip faces downwards, scraping the oil towards the oil ring. That makes sense.

The oil control ring seems symmetrical, but they have a letter on one of the side, and it was facing downwards!!! (facing the piston skirt).


But it doesn't end up here. I've checked the gap, that is, inserting the ring alone in the cylinder by the bottom side, pushing it with the piston to leave it parallel and checking the gap. It should be between 0.2-0.4 mm, with a maximum of 0.8. Ring #1 was smaller than 0.2 -so no gauge from 0.2 up would fit-. Ring #2 have a 0.9 gap!!! Could that be the reason for the carbon on the piston side between #1 and #2 in the picture? Ring #3 (oil) was fine.

BUT, the ridge clearance was not between tolerances at all. That makes me believe that either the rings are not Honda, or the mechanic didn't file the ends to set the gap, or maybe both.

Valve stem diameter are between tolerances. Valve springs free length are just in the minimum, but still between values. Piston (gudgeon) pin have marks on the crank arm position, but the diameter at the ends are perfect. If I rub my nail I can feel just a slight ridge, but they don't look bad at all (I forgot to take a picture).


So, my questions are:

Can I reuse the camshaft? And the rockers?
Can I reuse the pistons?
Can I reuse the piston pins? If not, how much do they cost?
What's the right position of the rings? Letter facing up or down? Should first and third ring have symmetrical profile? To which side should the lip face?
Do i have to replace the springs if they are almost at the minimum length?

Thank you everybody


Raul

[ElCheapo]

I will comment based on my years of engine building in the automotive world.

One of the things that you should be doing with those pistons is taking the time to mic them across two points to see if there is a size difference as there is from time to time on pistons with skirt scratching. Some is normal, but you must know that the piston is round not egg shapped. This is impossible to see by just the naked eye. There are tolerances for this spec. These you will have to find in the manual. Measure these at the skirt across from one side of the wrist pin to the other and then 90 degrees of that.

Camshaft lobes must be smooth. Otherwise these will eat the rocker or follower that the lobe rides on. Pits in a camshaft are created by rust left way too long or piss poor casting of the part which was evident in the 70's. Pits happen when the part is not allowed to get up to full temp before pouring when they are casting it. This biggest problem is that the pitting is in the path of the wear mark on the cam shaft. Were it outside this area I would say that it would be safe to use.

You may find if you use this camshaft you will be doing very frequent valve adjustments as it wears into the rocker or follower. Luck you Raul I have a 70 CB 350 I am parting out and would make you a killer deal on the camshaft. The pistons I can't help on that as my motor is locked. If there are other parts you need just drop me a line and we can do the impossible deal.

Your rockers have a pattern that does not appear to be uniform. If you look closely at the wear pattern it looks like they were riding more on one edge than the other. I might be wrong. These I also have from a low miles bike that is barn stuck.

Some rings have a slight tapper to them. If memory serves me right they should be big end of the tapper down. Not sure on the numbers/letters.

[Lumbee]

...OK, I'll throw my 2 cents in.  CheapO gave u a pretty good synopsis.  I'd say the cam is the only thing u'd have to really worry about.  The pistons look OK...I rebuilt my 750 in the spring and I had plenty of wear marks on the skirts.  You won't really know unless you get a caliper and check it out.  As far as the rockers...yes, the uneven wear is a concern, however since rockers are manally adjusted, as long as your gap is correct, then you should be good.  Its something to note, and therefore be sure you regualarly check the tappets for the correct gap.

[Raul CB750K1]

I have the original Honda manual and everything is between tolerance but the ring gap and the ridge gap, that's what makes me think the rings were not Honda. I'm going to err on the safe side and replace them all. Pistons are also in tolerance, having into account that they are .25 oversize.

The point is that I don't mind in reusing a easily replaceable part, but the inner parts that mean a complete engine dissasembly are something that you better be sure they are in top shape.

For example, the head cover nuts were a little rusted. I tried the phosphoric acid and they came out great, with a dull gray color but it matches the aluminium cover. That's when I enter the "ethic" part of the resto. If I find a good thing to restore an old machine, why replacing nuts and bolts, even when they are not "new", if you can reuse them? Of course nuts and bolts are cheap, but weren't they part of the original bike? I don't know, probably I will buy new ones and will decide at reassembly time.


Raul

[Terry in Australia]

That's when I enter the "ethic" part of the resto. If I find a good thing to restore an old machine, why replacing nuts and bolts, even when they are not "new", if you can reuse them? Of course nuts and bolts are cheap, but weren't they part of the original bike?
Raul

To me, a "restored" bike, is a bike that not only looks like new, but is in excellent mechanical condition too. Sure, you have to draw a line in the sand and say "This is my budget and I'm not gonna fudge it" (I'm a poet) but you just can't slap the engine back together knowing that it's clagged, unless you're just a "Trailer Sailor" and the bike will be proudly parked in your garage for all to see, but none to ride. I think we'd all agree that mechanical efficiency and road-worthiness should always take priority over shiny new paint and chrome.

Looking at those parts Raul, there's not much I'd consider re-using. The cam lobes appear burned and scored and the tappets (rockers etc) look like the hard chrome has worn off them. Buy some new rings mate, and install them correctly with letter/numbers facing up. Re: the pistons, you didn't mention (or i might have missed it) whether you measured the "piston to bore" clearance, where you stick a feeler gauge between the piston and the cylinder at the "thrust faces"? 1.5 thou gap is perfect, and any more than 3 thou and they're only good for ashtrays.

If you don't replace the pistons they'll slap around in there big time. You could take them to an engineer and have him "Knurl" the skirts which slightly increases the OD and stops piston slap, but eventually they'll wear back to the point where you'll have to replace them. If there's any detectable wear on your gudgeon pins (wrist pins) give them the "heave-ho" as well mate, it just aint worth the worry.

Obviously you'll use new piston circlips, and I imagine a nice new camchain while you've got it apart? I can't help but wonder whether you've suffered an oil starvation problem on that bike looking at the damage on your valve train, so make sure that your oil pump and rotary filter thingy are both serviceable, or you'll be doing this all again real soon.

Ask Tom (Cheapy) how much for the complete head Raul, and swap the lot over, that way all his used parts have "bedded in" together, and more than likely his rockers and valve springs are showing a lot less wear than yours, and most importantly it's easier for him working in freezing conditions, so he can knock your order over and get back to the priority task of stripping his K1 for me, ha ha! Cheers, Terry.

[MRieck]

That's when I enter the "ethic" part of the resto. If I find a good thing to restore an old machine, why replacing nuts and bolts, even when they are not "new", if you can reuse them? Of course nuts and bolts are cheap, but weren't they part of the original bike?
Raul

.



If you don't replace the pistons they'll slap around in there big time. You could take them to an engineer and have him "Knurl" the skirts which slightly increases the OD and stops piston slap, but eventually they'll wear back to the point where you'll have to replace them. If there's any detectable wear on your gudgeon pins (wrist pins) give them the "heave-ho" as well mate, it just aint worth the worry.

Cheers, Terry.

Just an FYI. The piston skirts can be built up to .004 by a company here called Swain Tech. They use a "Poly Moly'' coating. I had them apply it to my 915 pistons on they last rebuilt just to replace the .0005" I lost through normal wear. It works well and resulted in a quieter engine. A nice process if you are dealing with unobtainable pistons. 

[Terry in Australia]

That's good to know Mike, what sort of money are we talking about? I saw an article somewhere about "Metal Spraying" pistons to build them up, but in Rauls case the OEM or aftermarket pistons are still available, my suggestion (for what it's worth of course) would be to go up to the next oversize and bore his cylinders to suit, the cost for a twin wouldn't be that prohibitive, and there's always a few oversize piston kits on Ebay, the old CB350 (boat anchor) wasn't really all that collectable, and a gazillion were built for third world commuting, so parts should be cheap? Cheers, Terry.    

[MRieck]

That's good to know Mike, what sort of money are we talking about? I saw an article somewhere about "Metal Spraying" pistons to build them up, but in Rauls case the OEM or aftermarket pistons are still available, my suggestion (for what it's worth of course) would be to go up to the next oversize and bore his cylinders to suit, the cost for a twin wouldn't be that prohibitive, and there's always a few oversize piston kits on Ebay, the old CB350 (boat anchor) wasn't really all that collectable, and a gazillion were built for third world commuting, so parts should be cheap? Cheers, Terry.    

Terry, it cost me 18.00 per piston. They do nice work. I've had them do a few sets with a dome coating as well. Did you receive the cam timing articles??

[Raul CB750K1]

Thanks for the advice guys. I have been unable to trace the history of the bike, but during disassembly I found out that the engine has been rebuilt.

Actually, the pictures show a worst state than the actual state. The camshaft lobes are perfect except the one shown, and as Cheapo said, only in the non-running side. The rockers have a different shade, but the surface is smooth.

The pistons are in tolerance. I will check the piston-to-cylinder clearance. There was no indication on the manual, as it only said the expected diameter and out-of-round but I don't have a inside micrometer.


Unfortunately, Spain is not a country of DIY on things mechanical, so availability of machinist shops or aftermarket parts is scarce. I buy everything out of eBay or original Honda. I already bought a new camchain, of course new circlips, new gaskets, new tensioner rollers and blades. I guess that if the piston-to-wall clearance is 1.5 thou -you are talking inches Terry, don't you- piston slap will be negligible.

As Terry pointed out, the CB350 is a workhorse. I know the resto will cost more than it is worth, so I'm not trying to save money on the key parts, but simply being practical and trying to reuse anything that have some life left and whose replacement is expensive. I also find it an exercise of knowledge, because it's very easy to replace everything. It's harder to be able to tell when something is still usable or when it's not. When I say "usable" I mean it will not need replacement in then next years or 30.000 km...

So, up to know, new camchain and tensioner, rings. Same camshaft -unless Cheapo offers a really good deal... ;-) -, and pistons only if the clearance is good.

I'm going to take the cylinders to a machinist for the honing, so I will take the pistons, camchain and the like for them to have their opinion. That's something I don't like to know because taking those parts for them to tell you wether they are reusable or not is like opening your wallet in from of them and telling them if they mind to count your money for you because you are blind...


Raul

[ElCheapo]

Ok Raul I have good and fairly goos news. First I must say DAMN HONDA AND THIER CRAPPY CASTINGS!!

Ok I got the cam out. I too have a small spot. It looks like my imperfection on the cam lobe is less than yours. I can tell you it is polished over at the imperfection. You can rub your finger on it and not feel it. Would I install it in my bike? YES, I would.

3 out of four of my rockers are perfect. 1 has the lovely high quality casting pits on one end. Bright side is that the wear is even on all of them. I was looking at how the 350 is laid out and the only reason I can give you for the weird wear pattern that you have on your rockers is that the adjustable rocker shafts are worn or the rockers themselves are worn inside. My rocker shafts are nice and I can include them in the deal.

These parts come out of a motor with 9,160 miles exactly.

[Terry in Australia]

Those look heaps better Tom, geez the rockers still have the hard chrome in place! Now listen mate, you've done enough for Raul, so don't forget your regular customers, and I hope you're not supplying him with any Cheese treats  are you? Ha ha, Cheers, Terry.

[bryanj]

Raul, from the pictures bottom right rocker is toast as it looks like its worn into the "pad" and i suspect that was on the worn cam lobe (also toast as i can see "galling") pistons need accurate micing but visually look OK Replace the rings. Suspect bad oil flow to the cam and lack of changes/oil filter cleaning (suction AND centrifugal) The worn top ring would be relaced, if you were using it again, with the worn bit upwards, dont know exactly why but thats the way they always wear--also logical as it WOULD have had a mark and that should have been on top. If you can get me som better pictures diirect to me please do so. I am not "on line" as often just at present but if it comes direct i will get back to you.

[Raul CB750K1]

Well, thanks everybody again for your advice.

I have to say that my pictures doesn't really show the actual condition. I would say that the rockers are reusable. I was this morning in the machinist shop to have the cylinders honed (and the broken fin welded), took the pistons, valves, rockers and camshaft for them to inspect. They told me the rockers are reusable, the lobe pitting is an issue but it is not too rough, the valves nead refacing and so the seats (I didn't take the head with me but, for just a few bucks, they will do it so there we go). The pistons are usable too.

They didn't have the rings so I will have to buy original honda (about 60 bucks for both sets). Checked yesterday the clearance. My thinner feeler gauge is 20 thousand inches. I was unable to insert it in the front and back with the piston in the cylinder. If I removed it I could insert the piston with the gauge in place but the piston would stuck, so that means the clearance is lower. But, I could insert the 20 thou gauge on the sides, that makes sense so i would say pistons will be reinstalled.


Cheapo, I read your message. If the pitting in your camshaft is, as you say, not noticeable with the finger or fingernail then you've got a deal. BUT!!!!! you have to send me a can of easy cheese too, otherwise the deal is off  !!!!!

If you send the rocker shafts that would be great too. Don't be afraid to send along some other parts that can be usable or good enough to keep as spares, as long as the box doesn't get too heavy....  of course as freebies  HAHAHAHAHA or send me some pictures of the parts and maybe we can make them part of the deal. Blinkers, mirrors, carbs, just tell me what you have or send me a picture of the carcass.


I picked up this morning my order of allen screws. As Murphy stated, you never find all the parts you need in one single trip...


Holy sh1t, this bike is getting more expensive every day!!!!!!!!!!


Raul


P.S. Bryan, thanks for your kind offer for assesing the condition. As you said, the camshaft is toast, and provided that Cheapo will send it cheap with a can of EC, how can I say no?   HAHAHAHA

[Terry in Australia]

Well, thanks everybody again for your advice.

Checked yesterday the clearance. My thinner feeler gauge is 20 thousand inches. I was unable to insert it in the front and back with the piston in the cylinder. If I removed it I could insert the piston with the gauge in place but the piston would stuck, so that means the clearance is lower. But, I could insert the 20 thou gauge on the sides, that makes sense so i would say pistons will be reinstalled.


Cheapo, I read your message. If the pitting in your camshaft is, as you say, not noticeable with the finger or fingernail then you've got a deal. BUT!!!!! you have to send me a can of easy cheese too, otherwise the deal is off  !!!!!

If you send the rocker shafts that would be great too. Don't be afraid to send along some other parts that can be usable or good enough to keep as spares, as long as the box doesn't get too heavy....  of course as freebies  HAHAHAHAHA or send me some pictures of the parts and maybe we can make them part of the deal.

Raul

Hey Raul, check those piston to cylinder clearances again mate, the most you want is about .003" (three one thousandths of an inch) .020 (twenty one thousandths of an inch) or "20 thou" as you put it means that your pistons are screwed beyond redemption. I suspect you actually mean .002, but you need to measure them at the most worn part of the bore (about half way down)between the piston skirt and the cylinder wall. I'd be extremely surprised if there's only .002" clearance looking at the wear on the pistons in the pic, but if that's the case, well done.

Now just a quick word on the conventions of scrounging. While it is perfectly acceptable to hint that free stuff would be great to have, you must be aware that it is NOT acceptable to threaten to renege on a deal if the seller won't include a can of Easy cheese, particularly when he's doing you a favour!

We all understand that Spain is a third world backwater haven for communist terrorists and Nazi war criminals, and is devoid of decent food or flushing toilets so begging is the norm, however it lowers the whole tone of this site to do so here, and if you continue to publicly break Tom's balls about sending you a care package of Easy cheese, I'll have no option but to report you to one of Glenns hall monitors, er, I mean, Global Moderators, to have your offensive freeloading posts removed completely. You have been warned!

Tom, please pay no attention to Rauls wheedling for EC, you've already said that this wouldn't happen, and I know that as an ex Marine you have integrity "up the whazoo" and won't succumb to his hollow threats. If push comes to shove, I'll pay for all those boat anchor CB350 parts and you can send them to me mate, and I'll just throw them out and eat the EC! Cheers, Terry.