1982 CB750F... The resto-not

The Jimbonaut

Well-Known Member
Chatting with a moto guy today, told me in order to repair the crooked spark plug thread I have to pull the head, no matter what. Folk here have said that this is a job that can be done - carefully - without pulling the head. The thread is totally crooked, easily 10-20 degrees off true. Helicoil is the way to go I'm told, bit what gives? If I drill out the new hole for the helicoil very slowly, and with the bit covered in grease, that should do it, no? Obviously I want to avoid shit from falling ito the cylinder, but I've never installed a helicoil before so trying to get the skinny on how to approach the job.

Again, to pull the head or to not pull the head - that is the question.
 

pidjones

Well-Known Member
Nice vice. I think if your plug is that far off, you might at a minimum consider a Timecert. It's possible that the head may need welded up and redrilled, however.
 

jordandogtown

Washed up Weekend Warrior
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I think I would bite the bullet and pull the head. I'm the type that no matter how careful I was with drilling, I'd always be paranoid something slipped by and I would be sitting on a time bomb.

That thinking has also led me to a lot of unnecessary work/frustration, so...
 

adventurco

Nick Ol' Eye
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The Jimbonaut said:
Chatting with a moto guy today, told me in order to repair the crooked spark plug thread I have to pull the head, no matter what. Folk here have said that this is a job that can be done - carefully - without pulling the head. The thread is totally crooked, easily 10-20 degrees off true. Helicoil is the way to go I'm told, bit what gives? If I drill out the new hole for the helicoil very slowly, and with the bit covered in grease, that should do it, no? Obviously I want to avoid shit from falling ito the cylinder, but I've never installed a helicoil before so trying to get the skinny on how to approach the job.

Again, to pull the head or to not pull the head - that is the question.
If its me I'm not gonna risk it for the biscuit, I'd pull the head.
 

The Jimbonaut

Well-Known Member
Not gonna risk it for the biscuit. Shit man, I'm stealing that.

Pull the thing? Think that's the best option? Weighing everything up it makes sense on many levels. I'm listening to some righteous dub, makes any decision easier.
 

adventurco

Nick Ol' Eye
DTT BOTM WINNER
The Jimbonaut said:
Not gonna risk it for the biscuit. Shit man, I'm stealing that.

Pull the thing? Think that's the best option? Weighing everything up it makes sense on many levels. I'm listening to some righteous dub, makes any decision easier.
Its not a whole lot of extra work, and not much to mess up. While its out you can do the valve stem seals, and do the alcohol test to make sure your valves are all sealing properly.
 

The Jimbonaut

Well-Known Member
advCo said:
Its not a whole lot of extra work, and not much to mess up. While its out you can do the valve stem seals, and do the alcohol test to make sure your valves are all sealing properly.
That's the plan - once I pull it then I can do the valve seals as well, maybe do a bit of porting and sort out the spark plug snafu of course. Not to mention it'll make painting the lump a bit easier.

Scoping out the best option for a gasket kit, but to be honest I'm not sure exactly what I'll need (other than the obvious). I know for example there are some copper crush washers that need to go under the cylinder stud nuts but I don't see them in any gasket kit. This kit for example -

https://www.ebay.com/itm/Engine-Rebuild-Kit-Honda-CB750-C-F-K-L-SC-1979-1982-DOHC-Gasket-Set-Seals/173035071895?fits=Year%3A1982%7CMake%3AHonda&hash=item2849b1a997:g:pX4AAOSwdTJaa7w9:rk:1:pf:1

- seems complete but not sure if there's anything else I need to order. Any ideas?
 

jordandogtown

Washed up Weekend Warrior
DTT BOTM WINNER
Can't help with the gasket kit - but you might as well throw in a big bore kit while you're in there? ;D
 

The Jimbonaut

Well-Known Member
Built a workbench yesterday for the bench grinder and vice I scored last week -




Ye gads that vice is h-e-a-v-y, but the workbench is a stout little bugger so all should be well. My garage is starting to look like a workshop now. I feel...promoted.
 

Maritime

Well-Known Member
Nice, I need the grinder/polisher for my shop. Have the vice on a rolling tool box and wouldn't give it up for anything. Super handy. You'll find you use that vice all the blessed time.
 

The Jimbonaut

Well-Known Member
Picked up the grinder from kijiji for $30 CAD - result.

My wife got me a welding course for Christmas which happened on Saturday, loved it. Learned about MIG welding and got to grips with the basics, even managed some half-way decent welds by the end of the day. I didn't realize that the steel that you're welding actually melts and fuses with the wire - now I understand why a decent weld is so strong. Now just need to find me a useable welder and I'm off to the races.
 

Maritime

Well-Known Member
Nice, that's something I'd like to do soon as well. My wifes uncle is a pro welder, been doing it for a living for 50+ years, he's still working in his late 70's because he's a fabricator, not just a welder and he has customers who don't trust anyone else. He told me he'd show me some Mig someday, I need to take him up on that offer before he's not able too.
 

The Jimbonaut

Well-Known Member
For sure man, you should. It's really, really satisfying - very visceral and, well, who doesn't love a ton of sparks. Cleaning the welds up is cool too - I need to get me a welder.
 

trek97

No Custom Title
DTT BOTM WINNER
The Jimbonaut said:
Also scored a free monster vice -

I think it's about 2000 years old and weighs as much as my car. Seems legit.
OH hells to the yes.
 

The Jimbonaut

Well-Known Member
Was going to clean up a few frame parts, get them ready for paint, but when I got to the garage all my cleaning products were frozen solid. So this happened instead -



The "ahh, fuck it" argument won the day.

Got the timing marks all in the right place before I dove in, but buggered if I could get the exhaust cam drive chain off its sprocket without moving the cam. I understand the principals now of the timing chain/cams/valves but a bit misty on how important it is to keep the timing mark in the same position throughout the procedure. Very misty truth be told.

Also, the base gasket separated a mm from the crankcase - does this mean I have to pull the cylinders and replace the gasket? It's not torn or anything.
 

The Jimbonaut

Well-Known Member
For documentation purposes - and so that perhaps more proficient mechanics can offer any insight - here are the steps I took

1. Got the timing marks lined up (on this CB it's the "T 1 4" you're looking for) -


2. Removed the cam chain and tensioner guides -


3. Removed the cam holders in the correct sequence, the cam sprockets and the cams -


4. Removed the valve shims and buckets, bagged and labelled them

5. Removed a few bolts, tapped around the jugs with a rubber mallet and lifted the cylinders off the crankcase -


Head/valves -


One of the guide dowels is stuck in the cylinder case, the other one stuck in the head. PB blasted them and will see what gives.
 

trek97

No Custom Title
DTT BOTM WINNER
Looking good dude. Keep track of them dang insulators, both, where they go and orientation.
 
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