Topic: Camshaft removal

[Mark K]

In the process of a complete tear down and rebuild of a "73 CB750. Engine is removed and on a modified HF eng stand. Engine is locked (and did not know about trying to "rock it" to break it free before starting tear down).
My questions - does the camshaft have to be aligned to the timing index line before removal? It appears that two of the valves are partially open as they're on the lobe. The engine is stuck and I'm unable to turn the crank either direction. Also, do you have to use the rocker shaft removal tool to remove the shaft or is there another way that does not require a special tool?

Thanks in advance.

[madmtnmotors]

Back the valve adjusters all the way out. This should relieve the tension on the valve springs enough to get the rocker shafts out. The problem I had with the seized engine on my latest project was that one of the cam sprocket bolts was in the 6 o'clock position. The cam chain tunnel is too narrow to allow removal of this bolt in that position. I finally decided to back the bolt out as far as it would go and went at the shaft of the bolt just under the bolt head with an 1/8" diameter carbide cutter in the die grinder. Once the head was liberated from the bolt I was able to remove what was left of the bolt and continue tear down. I preferred this approach as opposed to cutting the cam chain since I want to avoid splitting the lower cases. I rotated the engine on the stand during the cutting process so the chips would fall out instead of into the bottom end.

EZPZ 

[Mark K]

Thanks Wilbur, I'll attempt it, although I don't own a carbide cutter...

[70CB750]

You can always align the camshaft with the crankshaft when you assemble it.  The how to is available on the forum and in the shop manual, etc. 

[madmtnmotors]

Thanks Wilbur, I'll attempt it, although I don't own a carbide cutter...

I didn't have the one I needed either, but it was cheaper than a cam chain and way easier than splitting the cases. Are you saying one of your sprocket bolts is buried in the cam chain tunnel as well? After backing out the bolt there was a little less than a 1/4" between the head of the bolt and the cam sprocket so I went with an 1/8" diameter cutter. Took about half an hour but I won!

[754]

If its seized, and you get the bolts out , get chain off sprocket,  the keep turning cam to slide rocker shafts out.. don't break the ears off the cam. You may have to put sprocket back on , less chain to turn cam.
 I should add, if it turns over........ I probably left chain and sprockets on the cam, then turned it into position to slide rocker shafts out.
 And I assemble same way

[Mark K]

You can always align the camshaft with the crankshaft when you assemble it.  The how to is available on the forum and in the shop manual, etc.

Thank you. I did not want parts to come flying off if I try to disassemble with the cam not aligned per the tech manual.

[Mark K]

Wilbur,

 My cam chain sprocket bolts are exactly horizontal and accessible! Just looked to check. I appreciate all of the suggestions, recommendations and help that anyone and everyone here can provide. I've never torn an engine down this far before. The '72 Honda CL70 I did a partial restore on did not include an engine tear down. So this is all new to me.

Thanks again to all of you, I appreciate your knowledge and wisdom!

Mark K.

[madmtnmotors]

Once you remove the cam sprocket you can use the bolt on the left side of the cam to turn the camshaft, but do so SLOWLY because these are "interference" engines. Since you would be turning the cam without turning the crank with the rockers still in place you can hit the piston with the valve by doing this. Go slow, relieve as much tension as you can by relieving the spring tension by backing off the rocker adjusters, and go from there. Personally, I would relieve the spring tension and drive the rocker shafts out before removing the cam sprocket. Brass drift pins work well, just make sure the center bolt is out.

[Mark K]

This is what the bike looked like when I bought it.

[Mark K]

And this is where I'm at with it.

[Mark K]

Sidebar to tear down - every morning when I'd go into my garage, I'd find many little spiders all over the bike. Each day I'd suck them up with my shop vac. Next day same thing. As I tore the bike all apart, I figured the momma spider would find better digs elsewhere. When I was removing the starter, I took off the front sprocket cover and this is what I found.

Needless to say, the momma spider died an unpleasant death at my hands.

[newday777]

Sidebar to tear down - every morning when I'd go into my garage, I'd find many little spiders all over the bike. Each day I'd suck them up with my shop vac. Next day same thing. As I tore the bike all apart, I figured the momma spider would find better digs elsewhere. When I was removing the starter, I took off the front sprocket cover and this is what I found.

Needless to say, the momma spider died an unpleasant death at my hands.

EEKS! Good find. Hopefully, no more spidies.

[Mark K]

Thanks to all the suggestions. Once I removed the cam sprocket bolts, I was able to turn the cam (slowly) to align camshaft for removal. Loosened all the valve tappet adjusting nuts then I removed rocker arm shafts (basically slid out once I removed ALL the bolts). Got all the head bolts removed after removing the cam holder assemblies and then started on the head. Again, it's amazing how much hold one bolt can have. Missed one bolt, which kept us from removing the head. Once we figured that out, the head came off pretty easily. The cylinder was a bit more tricky as #1 & #4 pistons were "stuck." The guy I bought it from had filled the cylinders with ATF some time ago, I believe that helped to make it easier to unstick the engine. So the head and cylinder are removed. Next will be the pistons. Have to see about a micrometer and a dial gauge to check all the measurements per the tech manual.

[BenelliSEI]

Congrats! Nothing like good old perseverance.

[70CB750]

Way to go!

[ekpent]

 Got her all bagged and tagged. What your big picture plan for it in the end ?

[Mark K]

Got the pistons off tonight, I removed 1 & 2, my son did 3 & 4. Lots of carbon on piston tops, rings are stuck on 1 & 2. Soaking 1 in chem dip, we'll see how that works. I'm keeping all parts together (piston, pin and clips) for each cylinder. The tech manual doesn't say if the pistons are interchangeable between cylinders.

Are the pistons interchangeable between cylinders?  Reason I ask is, if they are interchangeable, then I could put them all in the chem-dip can to soak at the same time.

Plans for the bike after total tear down is to rebuild into a cafe racer style or as back to original as close as possible. One mistake made already was I threw away the seat, tore to hell and the seat pan extremely rusted. So I definitely need a seat of some sort.

Thanks for all the encouragement!

[onepieceatatime]

Like any parts that wear together, it is best to keep the pistons with the cylinders that they have been run in already.

[Mark K]

That's what I was thinking, but since I'm a novice I had to ask.

Thanks!

[bryanj]

If the pistons were stuck on cylinders chances are the rust will mean a rebore and new pistons

[70CB750]

When I took Dorothy apart I marked pistons on the bottom with numbers 1 to 4.