Topic: 1977 CB750 K7 Resto-mod, Knoxville

[Restoration Fan]

What do you mean by the rods are down in the case?  If you turn the crank, two of them should rise up at a time to allow you to put the pistons back into the cylinders.

[AintNoEasyWay]

I mean that the rods are attached to the crankshaft. If you see Dino's video that I linked to, he already has the rods off the crankshaft & can use the Lisle ring compressor to fit the rings inside the jugs pretty easily.

In my case, since the rods are still attached to the crankshaft down in the cases, I can't really see a way to use the ring compressor I bought.

[AintNoEasyWay]

Ron, I know you guys used the Honda tools to install your pistons into the jugs, I'm just looking for an alternative method. The other methods I've seen explained all seem to involve having the rods already removed from the crankcase, connected to the pistons. For an example, see the Hack-a-week video on the previous page.

[Restoration Fan]

Nate,
You're not going to be able to use the same technique that Dino used in those videos if your rods are still attached to the crankshaft.

You're going to need to use the same technique we used, even if you don't have access to the Honda tools like we did.

Raise the #2 and #3 cylinders by turning the crank and take a couple of pieces of wood and slip them beneath those 2 pistons.  Then take a hose clamp with enough thickness to cover all 3 rings and tighten it up on each of the 2 pistons.  But leave it loose enough that it can slide down the piston when pressure is applied from above.  GENTLY tap the center of the cylinders down until it barely covers the bottom piston rings on both #2 and #3.  Remove the clamp (you will have to take it completely apart and then re-insert the loose end when you put it on cylinders #4 and #1.

Now, move the blocks out from under 2 and 3 and very gently turn the crank to raise #1 and #4 until they're as close to the cylinders as possible.  Repeat the same process with the clamps for #1 and #4 to get the piston rings in those cylinders but note that you won't be able to put those blocks beneath the pistons for 1 and 4.  That should get your pistons back in the cylinders with the new rings on them and it will only take you between 15 and 30 minutes if you do it right.

Only other thing I'd add is that DON'T bang on the cylinder top to get them down.  If it seems like you're having to smack the jugs to get them to go down, you're probably getting something stuck somewhere and something is wrong.  So stop and evaluate what could be catching....fix that...then proceed.

[AintNoEasyWay]

Awesome. Exactly what I needed, Ron. Also for further reference, some of the guys helped me out in the thread too: http://forums.sohc4.net/index.php/topic,107040.msg1688707.html#msg1688707

Baby steps...

[enwri]

Was wondering how this was going, getting to the good bit now. The four studs in Brandons leak thing, I thought he meant the ones in this photo.
I think in manufacture the stud holes can break through to the underside and weep out underneath, right next to the pucks.
I'd stick with the old chain too, do it next time, when you go for the hot cam and heavier valve springs.

[AintNoEasyWay]

Cool, thanks enwri. Just to confirm, you also believe that those 4 cam tower studs should be removed & retightened with thread sealer?

Hope you're doing well. It's good to hear from you again.

[enwri]

Yep, I'm going ok thanks, how about you? Still helping the bloke with the old bike collection?
    I really don't know about the stud thing. Someone may know that all of them run through, or only some, or if you can only tell by taking them out and looking.
Does happen if people have mentioned it, and a way to stop it. How do you feel about Murphys' Law? If you don't, it will leak, if you do, what are the chances of the studs breaking off or threads coming out with them? probably come out easy, (the studs, not the threads) they've been in a nice oily environment their whole lives so far, but wait,,,, now that I've said it...

[AintNoEasyWay]

Went through everything last night to make sure I had all my parts ready before I put the cylinders over the pistons. I'm missing one o-ring that goes on top in the back of the jugs, there are two that go over the studs on the top back of the crankcase & two that go on the top back of the jugs. Unfortunately I only bought three so I'm gonna call the local honda shop today to see if they have one I can run by & grab. Hopefully they'll have some Hondabond as well?

In brandEn's leak free thread, he tells you to check to make sure the four dowels, all the #3s in the diagram below, sit flush with the head surface. Mine do not, as I've tried to show in the photos below. Is this an issue? The head gasket I bought seems to fit perfectly around the dowels despite them sticking up IF I remove the rubber rings that fit around them (I can try to measure how many millimeters that may be if that'd help). I've also attached a photo of the case where I leave the rubber rings around the dowels. There's a significant rise in the head gasket off the surface because the head gasket isn't cut on the two front center holes to accommodate for the rubber rings. Any answers you guess can provide would be great!

Just to summarize the photos below, 1st & 2nd photos show the dowels sticking up WITH the rubber rings also in place around them. The 3rd photo shows the head gasket sitting nicely against the cylinder because the dowels do not have the rubber rings in place.

[enwri]

The gasket I have has big holes there. the O rings have to stick up higher than the gasket through the big holes, but the short dowels mustn't be able to touch the head when its torqued down, flush is best. It can hold the head up off the gasket otherwise. make sure the long dowels have enough room to never bottom out their holes in the head either.

[AintNoEasyWay]

Ok, maybe I will try mocking up the head with the cylinders tonight & see what type of feeler gauge I can fit in between? I guess it wouldn't be a true reading though since nothing would be torqued down. Damn. Not sure if I'll need a new gasket now or what to do. I ordered this one: https://www.davidsilverspares.com/CB750K7-FOUR-1977/part_8011/

Which in the photo appears to have the same size holes for each of the for inner dowels. I still have the receipt from last fall. Maybe they sent the wrong gasket??

Also, what fix is there if the short dowels stick up to far into the head? Do you just shave the dowels down somehow? Haha, so much confusion.

[enwri]

Without O rings and gasket, head should ideally sit flat, no gap. over the no.8s poking up.

The no.3s in the diagram are there to stop the no.2s, (O rings) squeezing out.

 The short dowels, no.3s, cannot stick up more than a torqued down gasket thickness, (flush with block is best) the O rings must stick up MORE than a torqued down gasket thickness. (To seal against head.)

The no.8s are the ones that slip into the head to locate it and stop it moving around.  These long dowels stick up into the head, and must not bottom out in the holes in the head.(front corners)

The no.7s are the oil supply O rings, also sticking up higher than the gasket to seal against the head. none of the O rings sit ON the gasket, must be through a hole.

That diagram doesn't show the no.8 in the left front. both front corners should have one.

have you had them all out and compared lengths, you would have used some under the cylinders too if you're missing shorter ones. can't remember how different, if at all.

If they machined the surface of the cylinders they might be too long now.

And yes you may have to trim then, they all came out of there before though, they should go back in.

Bike bandit shows the no.8s as 18mm long x 12 diam.  The no.3s just show as 12mm, could be length or diameter.

[AintNoEasyWay]

have you had them all out and compared lengths, you would have used some under the cylinders too if you're missing shorter ones. can't remember how different, if at all.

If they machined the surface of the cylinders they might be too long now.

And yes you may have to trim then, they all came out of there before though, they should go back in.

I have 4 longer dowels & 8 shorter dowels, the 4 longer dowels go out on front corners, on the top & bottom of the cylinders (the two that go beneath the cylinders are the ones that were rusted into the head & were culprits for me not being able to get the jugs off).

I've compared the old 8 shorter dowels to the new 8 & it does seems like the old are ever so slightly shorter than the new. I can take a picture later on, but when I put those old dowels in the cylinders to test, they still sat slightly above the surface. I'm wondering if they machined too much off my cylinders?

[enwri]

Grinder, belt sander, file, concrete floor.
Listed in order of efficiency.
Shouldn't really use the side of a bench grinder stone but it's a flat surface, may be a bit aggressive though, I don't think the short dowels are a hard steel anyway.
 Drag them up A nice sharp file, should cut them pretty easily.         

[AintNoEasyWay]

Thanks, enwri. I'm going to leave out those 4 center rubber rings that go around the short dowels. The popular brandEn's leak free top end thread shows him leaving out those 4 inner rubber rings & just using some non-hardening gasket sealant around the short dowels instead. I guess I may try that. He says it's common to get gaskets that don't have holes large enough to accommodate the 4 inner rings.

I started getting my cylinders down over the pistons last night. I got #2 & #3 in, but then it got late & pistons #1 & #4 weren't cooperating. So instead of letting my frustration get to me, I went on in to bed. I will play with it more tonight & hopefully get the remaining two pistons up in the cylinders.

[AintNoEasyWay]

Not much luck getting #1 & #4 pistons up into their cylinders. Seems like it's a tough job to do alone. I can't be on both side of the cylinders at once to make sure everything is matching up properly.

The main issue is that I was able to put blocks under #2 & #3 to keep them from moving around while I got them in, but even after turning the crankshaft up, #1 & #4 pistons don't go high enough to put anything under them to keep them steady. I will try again tomorrow, but for now is giving me a fit.

[Restoration Fan]

It's definitely easier as a two person job.  But the key thing is that you just need to get it so the pistons aren't moving.  You may be able to put something beneath pistons 2 and 3 still that keep them from moving.  Potentially even something as thin as a pencil.  But you just need to lock the pistons from being able to move up & down.  If you can lock down 2 & 3, it might keep 1 & 4 from moving as well.

[AintNoEasyWay]

Cool, thanks, Ron. I may be able to get some extra help come Sunday when my dad gets back in town. I'm waiting on 1 more o-ring to put at the top of the cylinders anyway before I can move on to the cylinder head.

[AintNoEasyWay]

Got my pistons in but I've got a significant gap between my cylinder head & the cylinder block. I can get a .65 mm feeler gauge in between them if I have the dowels in but leave the rubbers inserts out. I'm going home at lunch to re-check, but I've started another thread for the time being to get more input about it: http://forums.sohc4.net/index.php/topic,148540.msg1693109.html#msg1693109.

Here's a short video of me explaining the issue:

I'm also going to call the local bike shop that did my head work & sublet my cylinder head out to a machine shop for work. I'm not sure exactly what type of work the machine shop did & hopefully they'll be able to let me know.

[Restoration Fan]

Here's a short video of me explaining the issue:

Yeah, that's not good.  The head should mate flat against the top of the cylinder jugs.
First thing I would do is have them contact the machine shop and get them to tell you the exact thickness that was removed when the head was decked.
If they give you a number that doesn't explain the gap, then the only other thing I can think of is that you may have the wrong sized dowel pins.  But weren't these the ones that used to be in the engine back when it was running?

[AintNoEasyWay]

Here's a short video of me explaining the issue:

Yeah, that's not good.  The head should mate flat against the top of the cylinder jugs.
First thing I would do is have them contact the machine shop and get them to tell you the exact thickness that was removed when the head was decked.
If they give you a number that doesn't explain the gap, then the only other thing I can think of is that you may have the wrong sized dowel pins.  But weren't these the ones that used to be in the engine back when it was running?

Unfortunately I had this work done way back in early November. Ah!!!

I've checked to make sure I have the correct dowels. I bought new dowels, but they're the same size as the old. Yesterday I tried putting the old dowels in to see if it made any difference, but I still have the same gap, whether I use the new or old dowels.

[Restoration Fan]

Well, worst case, I know Bill Benton has other heads so you could always get a replacement head if they truly did screw the pooch on that one.  Of course, that would mean cleaning, replacing the valve springs, etc and would absolutely suck.  But that beats putting an engine back in that you know for a fact is going to leak. 

And, just my own personal opinion, but there's no way I would try to make up that much of a difference with a built-up head gasket.  Even a copper one isn't really intended to cover up a gap that large.

[AintNoEasyWay]

I just went home for lunch to check things. The two longer dowels that sit at the corners of the cylinder block aren't causing any trouble. I just put them in & the head is able to sit flush with the block.

So, it's the 8 center dowels that are causing the issue. The holes in the head aren't large enough to go over them, so the dowels have to sit completely down into the holes on the cylinder block, otherwise there's a gap. Like enwri said, I am wondering if I can just shave these dowels down & not have any consequences?

[AintNoEasyWay]

Powderman & madmtnmotors confirmed that I can just shave the dowels and be ok. I'm going to practice with the old dowels I have first to make sure everything looks good. If things seems ok I'll operate on the new dowels I bought & move right along.

[AintNoEasyWay]

Just finished shaving the dowels down & now the head sits flush against the block. Awesome. Thanks enwri & others who suggested I go this route.

Hondaman & madmtnmotors suggested I go ahead & punch out the holes in my head gasket that aren't cut to accommodate the rubber inserts, just as security. I'll see about doing this tomorrow. Then I hope to move on to the head.