Topic: 78 CB 550K motor rebuild

[AlekStooge]

Brent: Just curious, why would having plugs in make a difference in allowing you to rotate it backwards?

Dave: "When you use the alternator bolt, just be sure you don't unscrew the bolt as you turn it or the degree wheel doesn't rotate separate from the rotor."

That's what I wanted to do but when I turn it counterclockwise the bolt un-torques as soon as it gets hard to turn over. I could only get it so tight before the crank starts moving clockwise. What did you do?

Also can anyone tell me why it's so easy to turn it over in reverse regardless of which side of the engine I'm standing on and when I turn it forwards I get resistance half way up or down (which makes sense) like Dave mentioned. I mean the motion is the same so it shouldn't feel any different.

[DaveBarbier]

Dave: "When you use the alternator bolt, just be sure you don't unscrew the bolt as you turn it or the degree wheel doesn't rotate separate from the rotor."

That's what I wanted to do but when I turn it counterclockwise the bolt un-torques as soon as it gets hard to turn over. I could only get it so tight before the crank starts moving clockwise. What did you do?

You need to tighten the bolt more. I used a strap wrench on the rotor to hold it as I tightened the bolt.

Another thing, I "laminated" my degree wheel with packing tape to protect it. But the tape was under the bolt flange acting like a lubricant. It would twist the tape around and wouldn't allow it to grip. I had to cut away the tape around the bolt. Not sure if you have a similar situation. You could also stuff rope in a cylinder when that piston is at BDC so the piston has something to push against. Just don't stuff in all the rope so you can pull it out

Also can anyone tell me why it's so easy to turn it over in reverse regardless of which side of the engine I'm standing on and when I turn it forwards I get resistance half way up or down (which makes sense) like Dave mentioned. I mean the motion is the same so it shouldn't feel any different.

Shouldn't be. If anything it should be harder to turn in reverse if you have the starter installed because you're turning the starter too.

It's in neutral, right? Are you doing full rotations going backwards and forwards and feeling a big difference? Or are you just backing it up a bit and noticing it's fairly easy?

[DaveBarbier]

Regarding the rotor bolt, you could just do everything from the points side instead of the alternator side. As long as plugs are out.

[AlekStooge]

Brent: Just curious, why would having plugs in make a difference in allowing you to rotate it backwards?

Because you're building compression with the plug holes "plugged". If the plugs are out, the compressed air escapes more easily.

Ok makes sense, but why would the side you spin it from matter when the plugs are in or out?

I have the starter gear in but not the starter motor. I could spin backwards all day long with ease on both side the points side and alternator side. When I turn it forwards after about 3/4 turn I get resistance again on both sides.

Guess I'll look for a strap wrench, never heard of it.

[DaveBarbier]

Its just because of the size of the bolt. You're either turning a bit strong bolt (alternator side) or a little flimsy thing (points side). You don't want to bend the advancer shaft so only turn that if the plugs are out because you'll be fighting compression. See what we're saying?

[AlekStooge]

Its just because of the size of the bolt. You're either turning a bit strong bolt (alternator side) or a little flimsy thing (points side). You don't want to bend the advancer shaft so only turn that if the plugs are out because you'll be fighting compression. See what we're saying?

Ahha got you. How about the direction I'm turning in, is not having the starter motor that is making rotating it in reverse easier?  I got a strap wrench.

[AlekStooge]

Alright I put the starter in and the motor turned easy now forward. I didn't understand why so I took it out and it still worked??? I dunno when I did it this morning it took a lot to move it forward. Maybe the chain was hung up.

Use the alternator bolt not the points side bolt.

I'd tip that "piston stop" with something soft, like nylon or plastic. A bolt (should you jump the piston up into it) could damage the piston. And we know about that replacing a piston deal already.... 

How would you tip that piston stop with plastic or Nylon, Cal?

[DaveBarbier]

Alright I put the starter in and the motor turned easy now forward. I didn't understand why so I took it out and it still worked??? I dunno when I did it this morning it took a lot to move it forward. Maybe the chain was hung up.

How would you tip that piston stop with plastic or Nylon, Cal?

That's bizarre, if everything feels fine now rotating both directions I'd say it was the devil and you forced him out somehow.

Since the spark plugs go in at an angle and not directly above the piston I bet you can just slip some rubber hose over the threads and leave it sticking out 1/8" or so. I'd think glueing something to the bolt would just fall off after the first bump. Just keep in mind you don't want the piston stop to be too soft. You want to piston to bump against the stop firmly so it stops at exactly the same spot every time.

Honestly, all I did was round over the end of the bolt in the grinder and I didn't have any issues. As long as you use finesse when coming up to the stop you'll be fine. But definitely as you have your stop right now is too sharp.

[bwaller]

Yupper round the bolt end. Don't mean to disagree Cal but it has to be a "positive stop" so cushioning is no bueno. Just be careful in the knowledge you'll be contacting something hard. Finding absolute true TDC is the goal.

[AlekStooge]

Since I took that piston stop photo I have sanded it round and then smoothed it with a file. I think it's fine.

[RAFster122s]

If you want to get anal about it you could dip the end in Plasti-dip or liquid electrical tape. It should not have such a thick coating as to be too padded. But you should not be giving it enough velocity where it stops with a thunk. A long breaker bar give you leverage to move it slowly through and control any urge to roll past a point if you are going slowly.
What you have done is like other with more knowledge and experience have stated is enough...I'll quit beating the dead horse. 
How was your afternoon's progress after smoothing your new piston stop?

There is a fellow on the CX/GL forum that offers a nicely machined piston stop for $20. I think I'll stick with a homemade one. I can spend that much towards an mapp gas brazing setup. 
Time to finish up some computer work on a laptop...later!

[AlekStooge]

Made a bigger one, figured it be easier later on.

Pointy enough for you, Brent?

Smooth as it will get.

I had a bad piston laying around so I gave it a nice tap with the stop and got surface scratches. I'd say I'm good. See for yourself.

[AlekStooge]

Having a trouble putting my cam sprocket on my cam. My manuals aren't much help.

[DaveBarbier]

What I've done with the 550 and 650 is to take a big flat head screw driver, put some electrical tape over the end so it doesn't scratch anything, and push the tensioner away from the chain. Then, when the tensioner is pushed in, tighten the lock nut.

That gets my sprocket very close to being put on by hand. But a very slight amount of prying with a flat head gets it on the cam.

[flatlander]

align everything like this on the camshaft:


then do as the guys say.

[DaveBarbier]

And since you're degreeing,  I assume you've got a slotted sprocket. With the notch on the cam facing either 3 o'clock or 9 o'clock, #1-4 pistons at TDC, slide the sprocket on the cam so the bolt hole on the cam is in the center of the slot of the sprocket.

With the slots, you'll be able to have the cam and pistons in the right position and still be off a tooth on the sprocket. Just be aware of that. When you're degreeing, you'll see that your numbers are way off if that's the case.

[AlekStooge]

Thanks guys, I think I should get it now.

And since you're degreeing,  I assume you've got a slotted sprocket. With the notch on the cam facing either 3 o'clock or 9 o'clock, #1-4 pistons at TDC, slide the sprocket on the cam so the bolt hole on the cam is in the center of the slot of the sprocket.

With the slots, you'll be able to have the cam and pistons in the right position and still be off a tooth on the sprocket. Just be aware of that. When you're degreeing, you'll see that your numbers are way off if that's the case.

I thought you find TDC after putting the cam and sprocket on? Not sure what you mean by "off a tooth on the sprocket" I don't recall anything about keeping track of sprocket teeth when degreeing?

[DaveBarbier]

TDC just means top dead center. So when the piston is at the stop of its stroke, regardless if the head is on, that's still TDC.

Follow the manual to get the cam installed and while you're degreeing if you find your numbers are way off and you can't get it dialed in, then you're off a tooth.

[DaveBarbier]

I probably confused you by trying to make things more clear. Just install the cam and degree. If you have issues, deal with it then

[AlekStooge]

Here is what I did. I took out the cam and loosened the tensioner pushed it in with my finger and then tightened it. I put the cam in and let the chain lay like in flatlander's photo. I put the chain on the sprocket then lined the notch up so it's halfway above and below the head's surface. Next I lined the middle of the sprocket slots to the cam holes and slipped the sprocket on by slightly lifting it onto where it's supposed to be and then put the bolts on. Loosened the tensioner and then tightened the nut again.



I started to find TDC. I set it to 0 degrees. I used my torque wrench because it's the longest one I have to first turn it counter clock-wise till I hit the stop at 116 degrees then clockwise till I got 195 degrees. I checked both several times. So I got 155.5 degrees before and after TDC. If I'm doing something wrong someone please stop me!



My question is am I adjusting the tensioner right after I install the cam? If I am doing everything right I will adjust the wheel so the pointer is at 155.5 on each side. I'd adjust the pointer but it is too far away from 155.5 degrees on each side that it would end up crooked.. if that makes sense.

[flatlander]

it sort of makes sense, only the stuff about the pointer i don't get. you should adjust the pointer so that when the piston (no. 1 or 4, whichever you measure on for cam degreeing) is at TDC  it's at 0.
the tensioner during the whole process should be tight, to take slack out of the cam chain that otherwise would affect your readings.

[DaveBarbier]

Here is what I did. I took out the cam and loosened the tensioner pushed it in with my finger and then tightened it. I put the cam in and let the chain lay like in flatlander's photo. I put the chain on the sprocket then lined the notch up so it's halfway above and below the head's surface. Next I lined the middle of the sprocket slots to the cam holes and slipped the sprocket on by slightly lifting it onto where it's supposed to be and then put the bolts on. Loosened the tensioner and then tightened the nut again.

This is perfect as long as you had 1&4 pistons at the top of their stroke (TDC) also.

I started to find TDC. I set it to 0 degrees. I used my torque wrench because it's the longest one I have to first turn it counter clock-wise till I hit the stop at 116 degrees then clockwise till I got 195 degrees. I checked both several times. So I got 155.5 degrees before and after TDC. If I'm doing something wrong someone please stop me!

My question is am I adjusting the tensioner right after I install the cam? If I am doing everything right I will adjust the wheel so the pointer is at 155.5 on each side. I'd adjust the pointer but it is too far away from 155.5 degrees on each side that it would end up crooked.. if that makes sense.

If you can't move the pointer, move the degree wheel. Just don't accidentally rotate the motor. What are you using for a pointer? Most use a copper wire, yours looks like a piece of steel.

If you haven't seen, this was my setup:

[DaveBarbier]

And just to clarify, as i say in my degreeing write up, the cam chain has to be adjusted per the manual.

[AlekStooge]

In regards to the tensioner, when the tensioner is out it pushes against the chain making it tight? What I did was loosen the nut so I can push the tensioner inward (making the chain looser) with my finger making it easier to get the cam chain on the sprocket. After I did this I loosened the nut and in turn the tensioner moved outward (or tighter against the chain) and then locked the nut up again.

So I DO need to find TDC before I install the cam, I did it the other way around after the cam was bolted in.

My pointer is from a hanger. It is short so their isn't enough material for me to turn it all the way around the wheel from where I'm at... I'm saying I would not be able to get to 155.5 without turning the degree wheel loose or I could make another pointer.

Just to recap and make sure I understand correctly. My goal here it to find how many degrees I am away from TDC on each side and so those degrees are the same on both sides. I would adjust the pointer or degree wheel without moving the engine to get the same distance away from TDC on both sides. Correct?

[DaveBarbier]

In regards to the tensioner, when the tensioner is out it pushes against the chain making it tight? What I did was loosen the nut so I can push the tensioner inward (making the chain looser) with my finger making it easier to get the cam chain on the sprocket. After I did this I loosened the nut and in turn the tensioner moved outward (or tighter against the chain) and then locked the nut up again.

So I DO need to find TDC before I install the cam, I did it the other way around after the cam was bolted in.

My pointer is from a hanger. It is short so their isn't enough material for me to turn it all the way around the wheel from where I'm at... I'm saying I would not be able to get to 155.5 without turning the degree wheel loose or I could make another pointer.

Just to recap and make sure I understand correctly. My goal here is to find how many degrees I am away from TDC on each side and so those degrees are the same on both sides. I would adjust the pointer or degree wheel without moving the engine to get the same distance away from TDC on both sides. Correct?

Read the manual for adjusting chain tension.

Read the manual on how to install the cam.

After the cam is in properly, then fine tune it with the piston stop and degree wheel to get it perfect.

And yes, your last paragraph is correct.