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CB350 top end tear down rebuild

5K views 27 replies 9 participants last post by  krukster86 
#1 ·
Decided to pull the top end off my second spare CB350 engine. It cleaned up good and turns over but I have no idea how many miles on it. Figured I would put it in projects because its the first time for me and I will take lots of pics and prob have lots of questions. First thing is to setup a workspace so I can store the parts safely and out of the way.
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#2 ·
Dang, it looks in better shape than my good engine on my bike, lol
 
#3 ·
Well it seems to me to be in good shape. I think it has just sat on some shelf for many a year. I would like to learn and investigate the engine, make sure that if I do need to swap it in, I am putting something good. So here we go. Took off the top cover, came off nice and seems pretty clean. Took off the points plate and have the screws holding the left and right shaft housing in some penetrant for today. The screws looks to have never seen a screwdriver look new. I do have the manual and have watched the videos but will still like to ask some questions from our experts.
First one, when removing the camshaft nuts, should the engine be at any specific orientation?
Second should I remove the camshaft tensioner before I remove the left and right holders?

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#4 ·
Question. Once you take out the center nut, does the advancer just pull straight off the shaft?
 
#5 ·
Ok I turned the barrel counter clock and it came off then the entire unit slid off. The barrel had a line pointing down and the unit has 286 in top left and a slot in the back that points NW when installed. Camshaft has mark /pin at the top also
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#6 ·
Ready to take the camshaft out tomorrow. The picture with the camchain wheel and the L and flat line. Is that how it should be lined up when it goes back together? If so should I mark the chain to either side with a marker or paint or such?

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#7 ·
The procedure for engine disassembly/assembly are in the factory service manual, I would follow that and if you need clarification ask here. The FSM is very good and it is very helpful to have a good understanding of it. You can find an FSM for your bike on common motor co website. The FSM will explain the procedure better than most of us can but can get confusing at times because it assumes we know certain things or leaves things out. The reason I suggest following the FSM is it also tells you the tolerances for many parts so you can check them as you go along and decide if you need replacements or not.
 
#8 ·
Got down to the bottom end. How much tightness do I have to keep on the chain when removing the bottom part? The cams looks to be nice condition.

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#9 ·
Any tips to remove the last part? The pistons move freely but I can't seem to remove the assembly. Seems to be stuck on.
 
#11 ·
Chain seems fine, moves easily when i give it a little tension and rotate the engine but it refuses to budge.
 
#12 ·
The base gasket was just on there like glue. I eventually managed to break the seal by lifting and then is smoothly came off.

The rollers seem to be solid and in good shape and then guide is smooth.

Other than cleaning everything up first, what should be my next steps?
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#13 ·
Just to be clear, I was interested in replacing the gaskets cause I could see some weep from in the past and check the rest of it, not build a race engine or such. The cam/rockers and rollers look good. Is it good practice to install new rings in the pistons?
 
#14 ·
While I figure out a plan everything gets its own box for safe keeping. They are all on sale at can tire.
Plastic
 
#15 ·
As far as the Cam Chain Roller go - it's not what they look like.

The problem is the rubber gets hard and cracks.

Unless they are known to be new replace them.
They are one part you don't want to have to go back in next year if that's when they decide to fall apart.
Think Rubber Bands - One day they are just fine and a week later they dry out crack and break.
 
#16 ·
What Yendor said ... when you get the new ones you will able to compare and see what they are supposed to feel like. Same with the cam chain. It is stretched after all the years of being under tension. Replace.

If the pistons and bores are reasonable then I buy a set of one oversize piston rings then file the ring end gap to spec. New ones also have the 3 piece oil control ring.

One of the followers has some pitting, clean and check the cam. You can use a flat diamond file to clean up minor imperfections on the cam and followers.
 
#17 ·
Do I need to open up the bottom end to replace the chain and rollers?
 
#19 · (Edited)
Cam chains don’t normally need to be replaced. If the horizontal line on the left of the cam sprocket lines up with the top of the cam box whe the crank is at LT then your chain is fine. If the horizontal line does not line up at LT (when the head is fully assembled and torqued) then replace

definitely replace the cam chain rollers though.

Using oversized rings is a solution of last resort; to be done only when you can’t find the correct sized rings. If correct sized rings for Your bore don’t fit then you need to overbore the cylinders and go up a size in pistons as well as rings.

while you motor is apart is a good time to inspect your valves, valve guides, springs and seats

never file your cam or rockers with anything. They have a stellite surface hardening applied and filing will remove the hardening and dramatically shorten the life of the component. If the surface needs attention have it replaced or rehardened by Delta or megacycle cams
 
#20 ·
Splitting the cases is MUCH Easier than the rest of the rebuild.
It also allows you to get in and clean out the sump which WILL be full of sludge and crud.

There is really no reason to take apart the transmission gears.
The both Shafts with gears in place can be removed and set aside intact.

There are a couple of things to watch out for but nothing difficult.

One of the biggest things to watch are the Alignment Pins on the Transmission Shaft End Cap Bearings.
The Bearing Caps have small Dimples and the Pins MUST be aligned to seat in the dimples.
If the cases are assembled and the pins are NOT in the dimples the Pins WILL break out a chip in the case.
This will allow the Bearing End Caps / Transmission Shaft to SLIP out of position and create shifting problems.
 
#21 ·
Thanks guys. Still thinking on what my plans are for this one. I don't have a good work space right now so taking it apart farther would require a new work space.
Questions.
1. I don't want to over bore the jugs and they seems to be in good shape. I see they sell standard size rings, can I just get a new set of those?
2. Cam rollers, the small wheel on the arm that touches the tensioner push arm. I seem to only see that as a full part replacement (arm and wheel). Do they just sell the wheel?
3. The manual says take a plastic scraper and remove the carbon build up on the piston. Is that good advice?
4. The valves have carbon build up on the area. Can i scrub that off with the valves in place?

All learning for me so if I am not saying the names of parts correctly please correct me.
 
#22 ·
“Seem to be in good shape” is a meaningless statement.

measure them or take them to a machinist to have them measured. They are either within spec or not. If in spec; run them, if not; replace them

if in spec, a new set of rings is a good idea

for the cam chain tensioner rollers you will need to buy the one roller they sell seperate and the one that is part of the assembly for a total of two rollers...should cost a bit over $100 for both.

i use a brass wire brush to remove carbon

valves are best decarboned once removed from the head. That will also allow you to inspect the valves, valve seats, valve stem, and valve guides
 
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#23 ·
Think this is going to take me longer than expected but again im in no rush. Can someone link me a good valve tool to replace and install the valves/springs? Something not too expensive. Id like to make sure I am ordering the right tool.
 
#24 ·
Quote from Outobie
never file your cam or rockers with anything. They have a stellite surface hardening applied and filing will remove the hardening and dramatically shorten the life of the component. If the surface needs attention have it replaced or rehardened by Delta or megacycle cams

FSM says soft nitride treatment on cam and special alloy on cam followers, stellite on valve faces.

Bottom of page 34 of FSM says minor defects on cam can be corrected with fine wet stone.

Properly gapped over sized rings in a vintage engine, common fix in my experience. I have had issues with new standard rings having excessive end gap out of the package.

As to the timing chain ...... well my experience tells me to change it out..... especially since it is minimal cost in time and dollars. Hard to explain to a customer that their engine has issues because of a $40 dollar part that will cost several hundred to replace.
 
#25 ·
Would this be possible? Get a new timing chain that uses a clip. Break the link on the original chain. Carefully wire the two together. Pull the chain through the bottom sprocket until it feeds the new chain on. Install the clip.
 
#28 ·
Yep I did that with my CB360. Note that mine was a "press-fit" master link cam chain. That means that I used the chain breaker tool attachments to compress the master link plate onto the pins of the master link to the same overall width as the other links on the replacement cam chain. I thought I would need to "peen"/deform/mushroom the ends of the pins to secure the plate, and ended up bending/breaking a chain breaker tool attachment. I contacted CMC about this and they said there was no need to deform the ends of the pins, as they are solid (not hollow to allow deformation).
 
#26 ·
Yes, that is how it is commonly done. Although I think cam chains always have a master link that needs to be riveted (not the clip type). I probably would not be confident in using a clip master link inside an engine in any case.


As for carbon deposits - clean them off with a brush if there is a lot of them, but otherwise no need to over-do it. These engines run fairly hot, and unless something is wrong (f.e. burning oil) there shouldn't be too much carbon deposits either way. Even if you clean it off completely, it will be the same in a few 1000km (and it won't really make a difference in how it runs). Be careful not to harm the gasket surface, or the side of the pistons. You'll probably have to have the head taken to a machinist to straighten the gasket surface, so clean the carbon first.
 
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