Topic: I Must Have Missed Something

[Dr. Frankenstein]

I'm working on my '72 CB500/4 and got all excited today because I got the pistons back into the cylinders and thought it was coming together well, but when I try to turn the engine over by hand via the clutch pack, it will barely budge! I wanted to make sure the pistons would go up and down smoothly, but I can barely get them to move a quarter inch! I thought it might have just been in gear, but now it seems the shifter is not engaging either, it looks like it's pulling way to the rear and not engaging the drum ... could I have put the gears back in wrong? I was very meticulous about which way they came out and went back in, and I was able to shift through the gears before...what do you think - take it apart and start again? Could it be the new rings I put in are creating a drag on the cylinders? ("Always time to do it TWICE, never time to do it Right!" as they say...) It should be able to turn over by hand easily, yes? It's not the cam chain getting in the way, I made sure of that...plus when I DO pull on the cam chain to try to get the pistons to rotate, it won't do that either! It's like it's stuck or something...

[bryanj]

Has it been rebored?
If not is it new rings
If so did you clean the grooves out properly
If new rings are they the correct size and did you check ring gap

[Dr. Frankenstein]

No, Yes, Yes and Yes...

[Don R]

   What Bryan asked and, are the plugs in it and are you trying to turn the clutch basket by hand? Are the cylinders oiled? Did you use thin three-piece oil rings or one-piece oil rings?

[Dr. Frankenstein]

No, no plugs - I have just fitted the cylinders over the pistons, there's no top end on it yet; yes, the cylinders are oiled, and I used the 3-piece oil rings. I should be able to at least spin it over, yes? It's super tight! 

[Rayzerman]

I would think not the pistons/rings holding you up that bad... however.... when you say you were able to shift gears etc. were you able to turn over the engine (i assume with no pistons or cylinders) a half or full revolution in any gear?  I'm thinking something just not quite lined up there at the moment...  any chance of being able to jiggle the clutch basket a bit and shift a gear or two?  If you now removed pressure plate, can you now spin the engine?  Tranny would not be engaged in that scenario.  Hopefully that will narrow it down some.

[Jerry Rxman Griffin aka MuthaF'er]

Did you gap the new rings?

[bryanj]

As to shifting both shafts have to be rotated to get all the gears

[Dr. Frankenstein]

I might just go back in and do it again; something isn't right, and better to do it now than put it all together and have to take it apart again... I know I have all the shift dogs where they should be...could I have driven the mainshaft in too much?

[M 750K6]

Just take the cylinder barrels off and try again, before opening the bottom end?

[Dr. Frankenstein]

Yeah, that's what I will try to do. Here's hoping.

[kerryb]

You could put a socket on the alternator rotor bolt and try turning the crankshaft directly.

[BenelliSEI]

Just take the cylinder barrels off and try again, before opening the bottom end?

+1 to “do this”. Somethings not right.

[Dr. Frankenstein]

I'll probably try that; I'm not too sure about rotating the crank though - as tight as it feels, those little teeth on the spark advancer have a tendency to break off really easily, and spark advancers aren't cheap. 

[MauiK3]

absolutely, check the rings, measure the bores and pistons, eliminate doubts, makes sleeping easier.

[RAFster122s]

You do Not want to try and use the spark advancer side, it's nut, to turn over the motor, you will be d the shaft causing a wobble which screws up the points opening you will have to straighten it if runout is too great.

[Dr. Frankenstein]

So I finally got a chance to get back out to the garage and took some measurements - the cylinder bores spec out at 56.01 +/-, and the pistons are at 55.46 +/-, so they look good. I took the cylinders back off and put a strap wrench around the clutch pack and everything seems to spin fine, but I noticed that when I took the cylinders off the pistons were still pretty tight in the barrels.

The rings have a good gap - I think they were at 0.23, I'll have to check again before I put the cylinders back on - and I deglazed the cylinders too before I put them on the first time, so what I'm thinking is that with the new rings, they probably just have to 'seat in' through the normal action of the pistons going up and down to travel really smoothly. And part of the problem with the shifter arm appears to be that it was somehow pushing out towards the outer part of the barrel - I simply pushed it back in, away from the clutch pack and it seems to shift thru the gears fine - so unless there are some other observations, I think I'm just going to put it all back together and see how she does.

[bryanj]

It may be the 3 piece rings were not seated quite right, it should turn over ok

[Dr. Frankenstein]

I'll scrutinize them before I put them back in; I did notice the first time that those 'sandwich' rings did have a tendency to slip out of place. All things being equal, I'll try the strap wrench again when I get the head back on.

[BenelliSEI]

I hate to ask the obvious. You lubricate the rings, pistons and bores? Lots of assembly lube every where else?

[Dr. Frankenstein]

Yep; sure did. Actually, it went together a lot better this time.

[BenelliSEI]

Yep; sure did. Actually, it went together a lot better this time.

Good to hear.