Topic: Yet another F2 Top End overhaul... Cam chain probs

[pdeg]

To follow on from

Yet another F2 Top End overhaul... Where do the o-rings/restricters go ?  http://forums.sohc4.net/index.php?topic=138202.0

Assembled pistons  .. yada ... yada...

Got the barrels on .. but could not get them to go all the way down.  After hours of scratching around .. I pulled the barrels off and  tried
to see why they would not go down all the way.  The 2 pins on the front guide would not go into the slots in the bottom case, when I trying to seat
the barrels.  And they were not caught on the gasket..

Checking out the photo... the clearance between the front guide and the roller is too small, compressing the cam chain.
I can get a screwdriver in there and get clearance by pushing hard and it is compressing the rubbers on the tensioner shaft.
In the picture notice the tensioner shaft rubbers are out of place..

I verniered the old parts and the new.. and they measured the same...  It is a heavy duty cam chain, but the only difference is the width of the
plates on the side.  New roller and guide are exactly the same. The tensioner shaft rubbers are new too.

At this stage, I intend to put the pins in the guide in while there is a gap... and then force the rubbers on the tensioner wheel  shaft down and in.
And turn the idle up for a bit until it settles down 

Thoughts ... ?

[dlhoulton]

From what I can see in the picture you are trying to install the cam chain guide into the top of the crank case. It should be installed into the "barrels". The end with the metal pin should be pointing down. It also looks like you have all of your cam chain crammed into your crank case. Cam chain should be pulled out and secured with a wire or something not allowing it to fall back in into the crank case.

[madmtnmotors]

From what I can see in the picture you are trying to install the cam chain guide into the top of the crank case. It should be installed into the "barrels". The end with the metal pin should be pointing down. It also looks like you have all of your cam chain crammed into your crank case. Cam chain should be pulled out and secured with a wire or something not allowing it to fall back in into the crank case.

I concur. The "slider" is upside down and needs to be inserted from the top of the barrels (before installing the barrels). The "tongue" of the slider (as shown) extends too far into the bottom case and takes up too much room.

[pdeg]

Sorry .. should have been a bit more specific..

I did try to install as you said... with the guide inside the barrels and all the other things that you said.

But when I had problems ... I pulled out all of the bits (tensioner and what not)  and put them into the case to try and find out why
it was binding...

Are you sure that the removeable metal pin goes into the case ... ?  That is not my understanding of the thing,
and different to what I pulled out.

and when I said I put a screwdriver in there. ...  I take the chain off the tensioner pulley and off the guide, so that I put the
screwdriver blade in where the chain would go and try and lever it to see how much clearance I can get....


When I siad I would put the pins in the case... that is when I have the barrels on and down as far as to leave a small gap.  Then
put the guide pins in.  At this stage .. the tensioner rubbers would be half in- half out of their position in the case .. .and force them
in with barrels coming down on the case..

The fact that other guys do not seem to have this problems is a bit worrying.



Cheers
Peter

[madmtnmotors]

Okay, so you made me reference the pitcher book. Here ya go:




Notice the long "tail" sticking out of the top of the barrels. Hard to see in such a small picture, but it's just as we described...

With the long "tail" pointing down you are trying to cram too much material into the bottom case. The parts fiche shows the same thing. 

[dlhoulton]

Here's another visual that might help. Long end of guide pointing up.

Plus, what is that "disk" holding the cam chain? That's not supposed to be there. You should be working with these parts:


Look at the schematic of parts. Take part 11, 9, 8, 10 and 11 and install them into part 3. Look at your picture. Take the parts I circled and install them into the part the arrow is pointing to. Don't forget to thread the cam chain through part "3" before assembling.
 

[madmtnmotors]

What is that "disk" holding the cam chain?

I'm pretty sure that's part of Kenny's (CycleX) cam chain tensioner. I'll bet the rest of the tensioner assembly was merely left off for the photo op. Good pictures by the way dl, I think once the slider is oriented properly things should fit better.

[dlhoulton]

My mistake. Didn't realize he had that kit. Just went back and read his link.

[pdeg]

So you are saying that the removable pin in the front guide goes into the case... ?  And that I have the front guide in up side down !!

I am so glad  I asked.  In a previous life .. . I would have just forced it   

In my  (pathetic) defence.. that was how it came out .. and the plastic pin has the flat parts to prove it. It  must have been
put in wrong by the guy that did the engine the last time !

The whole thing makes more sense.....

It a credit to the robustness of these motors.

Will get back to you guys .. .and very many tx

BTW... yep it is a CycleX tensioner...

Your barrels look outstanding btw.

Peter

[pdeg]

Ah  ha.

here is the picture of the the guide put in the correct way around.
And the chain slide beautifully..  Like it should.

Now to the story. 

Notice in the picture... the slot where the pin goes ?  Arrowed.

Well... before the picture... this slot was too shallow ..

Measured at 5.8 mm deep.  The one on the left was 6.5 mm and the pin measured at 6 mm.

Had to do some grinding with dremel to get it deep enough, and match the other side.

This would probably explain why my predecessor had put the guide in upside down.  With the rubber
pins you can "squash"  them down to fit in too small a slot.. Hence the flat spot on the rubber pin on my
old guide.

Now to press on ... except I have broken a ring.  ARRRRRHHHH...   Thought I have outgrown the bigger hammer
stage........  Grrrrrrrrrrrr.  Or maybe the good Lord did this to show me that I broken one.  I remember bending it
when the barrels went on the first time....

Cheers and tx guys...

[garyS-NJ]

Hey peter - those 410 pistons look good.  How did you clean them up (or did you get all four new from CMS)?  and where did you get rings???.  I'm doing top end on my '78 CB750F3 and looking at rings from metric cycle and also the 13011-392-004's from partzilla but think the oil rings might be off.  otherwise hats off to you for asking and sharing here knowing that I'm studying a little so my stuff goes together easier.

[pdeg]

Cheers mate...  sorry about the delay...

I am a sucker for punishment 

Yep .. got the new pistons from CMS.   Thought I got the last pistons in captivity....
If I had to bored it out would have gone for the 830  kits ....

 RIngs sourced from the a local Aussie SOHC guy..... not sure where he gets them from, but they
venier the same as the old ones....
 
Am stuck whilst waiting for them to get here... Want the same as the ones already on the pistons...
When I get them .. will post the part number and make..

Spend this weekend getting the stripped screw that holds the speedo cable into the hub out. First time
that I have managed to use an easy-out without breaking the thing in the drill hole and causing more stress 
Giving it a fry-up with a propane torch first may have helped.. 

And put the re-chromed forks back in as well ... at $300 plus freight... they better be good.
Now for the front calipers re-build...  sigh...

Never ends... once these things start to sulk .......

The guys on this forum have been really helpfull, and go to a lot of trouble.  Which I really appreciate.

[pdeg]

Got the new rings last week.

They are NPR.. Nippon Piston Ring Company. http://www.npr.co.jp/english/company/business.html


The end gap was 14 thou. and they look pretty good ... but have not started the motor yet ... so cannot vouch for it..

After all of the help.... the barrels slipped on as if they were meant to...



Joy.

Now for the head...

Peter