Lower End Rebuild

[JFunkadelic]

Hey Guys,

 So my full rebuild project is coming along (I'll be sure to post some pictures soon and progress soon), and I'm in the midst of rebuilding the seized engine I pulled off a 77 750K. Unfortunately, due to what looked like a lot of water in the cylinders, I'm having them bored out right now at 2nd oversize. I guess I have  a few general questions regarding engine rebuilding, and you're the guys to ask:

1. As for a head, since all the seats and valves on mine are shot, what would you recommend? Used off of ebay? (I've seen pretty clean heads on there without valves, any thoughts on a valve set?).

2. What would you replace without question in rebuilding an engine?

3. And lastly, more or less the same as 2, I have not yet pulled apart the bottom case, and thought it might be a good idea to order a few 'necessities' before I do in order to not have it apart too long. What would you replace just because you're opening it up?

 Thanks in advance. You guys rock.

[TOOLS1]

Before buying new valves. Pull them out, and check their condition. They might just need cleaned, and ground. However if you need new valves, CB750supply.com has them on sale right now. You are definitely going to need a gasket, and seal set. I would also check the cam chain, and tensioner/roller. I doubt the bottom end will need anything.
TOOLS

[JFunkadelic]

Thanks Tools. The mechanic I'm having bore the cylinders said the same thing about the bottom end when I dropped it off there today. I'm gonna look through the cylinder gaps in the case and if I don't spot any bad corrosion I think I'm just going to leave it as is.

About the head, we pulled two of the valves, and since the engine was seized for some several years with two of the valves stuck open, the seats and valves are shot on at least a few of them, for sure the two we looked at. All pitted and bad corrosion on the seat and valve.

What exactly do you mean gasket and seal set? I ordered a complete gasket set, with oil seals (which I'm sort of regretting right now since I might only need the three main gaskets (i.e. cylinder head, head, and cam cover), but were you referring to something more specific? The gaskets around the valves?

[TOOLS1]

The gaskets around the valves would be valve guide seals. When I say seal kit, I am talking about the shift shaft, clutch rod, counter shaft, and kick starter seals. Those can be replaced without splitting the cases.
TOOLS

[Re-run]

You WILL need the cam chain guides and stuff. Those rubber bits are long since dried up. A chain would be good too. All seals and gaskets including valve guides and seals should be replaced. I would do the springs too. Studs should be changed too. They do not like being torqued all these years later. It is best to do it right now instead of having to do it again in a couple years.

I wouldn't do used parts unless you have to. Things such as heads are unavoidable though.

[JFunkadelic]

Hmm… tough calls.

 Re-run, what do you mean about the studs? As the rule of thumb I'd hear bolts should be replaced but studs are alright? (I'm not even sure that's the right rule of thumb, haha), but what is the worry? That one of them snaps in a year or two due to new stresses and such on them? Once again requiring top end disassembly?

 Also, is it possible to run a new cam chain without splitting the case? That's really the hang up, is it even worth going in there? As Tools said previously, I can do all the seals without splitting it, and if it looks good (which I don't know for certain yet), I'm now sure it's worth messing anything up.

 At the same time, I like doing things right, and it's also a great learning experience at the moment. Have you guys seen lots of crank bearings and piston bearings (they're pressed in on these or something, is that right?) wear out? On another thread I saw somebody raving about how expensive rods are, so if I can avoid that I certainly will.

 Any good place to look for studs? I've seen sets for about $80. Does that sound about right?

[JFunkadelic]

And this head issue I'm still not sure about. I've seen some pretty clean ones on ebay without anything on them. I was thinking about getting one of these, along with valves, valve guides and stems, and just dropping my rocker box and camshaft into it? How does that sound?

And can I just measure my springs and if they're within the clearance in the manual run with it? Or if you're doing the heads do they just tend to wear out and it's something you do anyhow?

[shinyribs]

$80 is about as cheap as I could find them. Good luck getting the old ones out. Have your torch ready. They've been in there for a looong time and they aren't happy about coming out. It's totally doable, just be patient.

[shinyribs]

JFunkadelic wrote

And can I just measure my springs and if they're within the clearance in the manual run with it?

Yes. If they've lost their tension then they won't expand properly. As long as they're within spec they'll be OK.

Truthfully though, these motors are anvils. My chopper had sat for over 20 years. Cleaned the carbs,fresh oil and took off. Ran like a champ. Are you sure you have this many issues?

[JFunkadelic]

Am I sure? Haha, not quite. We had to disassemble the top end since the pistons were jammed, and also discovered the valves (at least two of them) are shot since they were stuck open for something like a decade. Those are the basic problems that need repair. Beyond that, I've just never rebuilt an engine before and I don't really know what's all entailed so I'm sort of just going all in, perhaps unnecessarily, probably unnecessarily in some aspects.

The cam and rockers all looked really good actually, just those two valves. You think I should have my local bike guy / machiner take a look and see if he could reseat just the two? Is that done typically? 2 of 8?

Thanks again, I'm a newb.

[shinyribs]

Well, if the pistons were jammed then yeah, that's not a good sign.

You really will just have to inspect everything piece by piece. Measure against factory specs and see what's reusable and what's shot. Then get to work!

[Re-run]

The studs go into the block and stick up. These are what go through the heads and then you use nuts on them to torque down the head. They are sometimes called engine bolts but studs is the name.

Age, heat, and past torquing weaken them and they can snap and are usually stretched.
If you take them out, use the double nut method. Put on the 1st nut part way down. Snug a second nut to the first. Put a box wrench on the first nut and turn it against the second. They basically lock together and allow the stud to be taken out. As Shiny said, heat may be needed.

You CAN put in a new chain without removing the head. Hook the new chain to the old chain and pull it through. Simple as that. Just make sure timing isn't messed up.

Rods ARE expensive. Falicon rods are cheaper than Carillos though. Carillo run about 1000.

cyclexchange runs rods a lot cheaper though. I forget how much and I haven't heard much about them but they usually don't sell crap.