Topic: CB750 Motor rebuild... for dummies

[Honda?]

Don't forget assembly lube when you get to that point.

[legendary]

Thanks Guys,
                    yep I need assembly lube and plasti-gage. Just got back from buying stripper, scraper, brushes.

How is your piston dilema coming along Honda?? Every time I see another cylinder head on E-bay I think of your motor....

Are you still committed to going 836, or what?

[Terry in Australia]

Good work mate, keep it up and don't forget some pics! Re: the "cam vs porting" dilemma, you're not gonna get much port work done for 200 bucks, so I'd buy the mildest of the three cams that CycleX sell, (good price too for a new billet cam) if you can afford another 50 or 60 bucks get some heavy duty valve springs too.

I installed a mild (stock lift, longer duration) Andrews cam in my first K1 back in 1982, and I could feel the difference, it had much better low and midrange "grunt" than the stocker, and that was with a stock head and only first oversize pistons. You don't need new tappets unless the hard chroming on yours is worn through. Keep up the good work!

Heavy duty studs are really worth their weight in gold regardless of your application, but if the engine's staying stock, and money is running low, you won't need them. Cheers, Terry.

[SandwichEnthusiast]

Hey guys, I'm almost ready to break open the crankcase, I had some problems with stripped screws on the alternator cover.

I'm trying to get the AC rotor off the bike, but the big bolt is on tight and the engine turns when I try it, is there a magic trick to hold the engine in place while I do it?

also on the points plate, the 6mm hex nut comes off before that special hex washer... right?

I had one top ring seize in a piston, I'm soaking that, i hope it's not bad news.

[Patrick]

You can split the case without taking off the alternator rotor. It's much easier to get the rotor off while the motor is in the bike. Hit it with an impact driver. And yes, the 6mm nut comes off first. It holds the other in place.

[Kevin D]

Well.... I got the rusted knock pin out - 1/2 hour with a rotary stone. Cases are apart and I'm prepping them for paint. I'm not sure if the oil pan is a painted or polished item.

I've made a couple mistakes (at least):
1) Too much gasket glue last time in. Probably don't need the stuff at all, let the knock pins locate the gasket during assembly. I'm spending a lot of time scraping gaskets. The base gasket was a real bugger. Permatex gasket remover is helping.
2) Should have washed the motor thoroughly before removal.

Just those two little things would have saved me a lot of time.

[Sweep]

I made the same mistake with the sealer and regretted it on the 2nd teardown.  This time I barely touched the stuff.

I painted my oil pan and I'm pretty sure it was painted in the first place.

[Terry in Australia]

The oil pans aren't painted out of the factory, I've got a new one hanging up and it's bare alloy. Cheers, Terry.

[Honda?]

Thanks Guys,
                    yep I need assembly lube and plasti-gage. Just got back from buying stripper, scraper, brushes.

How is your piston dilema coming along Honda?? Every time I see another cylinder head on E-bay I think of your motor....

Are you still committed to going 836, or what?

Well yes when I finish my rebuild it will be an 836cc BUT I just ran into money troubles (paying for my Bachelors Degree classes) I just put my BMW up for sale this weekend and once I sell that I'm going to have to settle for an econobox car for a while. It sucks a lot but I have been through worse so I'm not worried. In the mean time the 750s engine sits in a room dedicated to its rebuild and the rest of the bike has it's space in the garage. I just need time to recover.

So I guess it's up to you guys to build the rest of this thread. I will drop in and help out any way I can every now and then. Good luck on your rebuilds guys!

-Tyson

[Kevin D]

Tyson - Sounds like you have your priorities well in order. Don't do like I did - leave the Honda for 15 years. One of my BIGGEST mistakes.

I measured ring end gap at 0.013", service limit is 0.027". These rings have 30000 miles on them. Compression good. So I'm thinking....what might the end gap be with new rings? Cyl also measured OK. I went into this thinking hone and new standard rings. I don't want to to skimp on important stuff.

Also, I have the old type 1 piece oil ring. I don't think it's available anymore. Will the new 3 piece oil ring work with my old piston?

[jerry194]

Guys,
          I need a little timely tech assistance. Too cold today for the garage so I am ordering my parts.

Here is what "Terry from Australia" provided on page 1 of this thread- and what I have done

Full gasket set (CycleX, $59.00)- Ordered
Set of Piston Rings (Rusty Riders $30.00) Couldn't find them on RR ordered from Cycle X
Cylinder Hone (buy the tool to fit your cordless drill, around $10.00)- had it done for $40
Heavy Duty Tsubaki Cam Chain (Z1 Enterprises $28.00)- Ordered
OEM cam chain tensioner, wheel, and guide (Z1 Enterprises $61.00) Ordered
Engine seal set ($20.00 from Rusty Riders) Couldn't find them on RR ordered from Cycle X
New OEM Primary Chains (Terry Quail, $70.00 per set) Ordered from Terry I also got the primary chain tensioner
New NGK Spark Plugs ($10.00 from your nearest auto parts store)Not yet
New points ($10.00 from Rusty Riders) Still looking
Engine Enamel ($10.00 from your nearest auto parts store) Today

I am also considering this cam from Cycle X- # EN-617 about 2/3 of the way down the page here:

http://www.cyclexchange.net/Engine%20Parts%20Page.htm.

Does the benefit of a cam on an otherwise stock engine justify the $200? Or would the money be better spent on porting the head.  Do I need to replace the tappets if I replace the cam? I know on a V8 engine new cam means new lifters???

Anything else I should be getting??

Jury still out on all new cylinder studs?

Thanks All,   Steve

can you tell me how to get a hold of Terry Quail to buy some primary chains from him thanks

[jerry194]

Well done guys, I'm looking forward to seeing your progress! The good thing about the legendary CB750 engine is that it is dead simple to work on, and to bring back to "as new" condition. I've recently (in the last 12 months) built 2 engines, one stocker, and one "competition", and so all I reckon you'll need parts wise for a "rebuild" is the following:

Full gasket set (CycleX, $59.00)
Set of Piston Rings (Rusty Riders $30.00)
Cylinder Hone (buy the tool to fit your cordless drill, around $10.00)
Heavy Duty Tsubaki Cam Chain (Z1 Enterprises $28.00)
OEM cam chain tensioner, wheel, and guide (Z1 Enterprises $61.00) 
Engine seal set ($20.00 from Rusty Riders)
New OEM Primary Chains (Terry Quail, $70.00 per set)
New NGK Spark Plugs ($10.00 from your nearest auto parts store)
New points ($10.00 from Rusty Riders)
Engine Enamel ($10.00 from your nearest auto parts store)

There's probably one or two items that I've forgotten, but as you can see, for around 300 bucks you can do a full "rebuild" that a shop wouldn't do for under 1000 bucks. Spend the other 700 on good quality tools and better quality booze, and give yourselves a pat on the back! Cheers, Terry.

::)can you tell how to contact Terry Quail to buy a set of primary chains thanks

[Terry in Australia]

G'Day Jerry, I think his EBay handle is Iron_Horse_Honda, I'll check when I get home. (No EBay allowed on my defence force compuker..............) 

[legendary]

Terry Quail is:

 Quail "Owner of the comfortable k8"     on this forum.

I bought my primary chains and a chain tensioner from Terry and they are beautiful. Still in the original bags and they look great.

Waiting on some other parts from Z1 Enterprises and Cycle Exchange.

I'll post some pics and prices soon. Progress has taken a big hit due to "real life"   Problems- un-related to rebuilding a CB750 motor and hence not worth mentioning

Steve

[seebee750]

How much for the pair of primary chains from Terry ?
I paid $93 for a pair from Honda 

[fang]

Helloooo all.  I too am building up a few CB750 motors now.  I am sure there must be a Honda factory manual or two floating around out there as .pdf files.  Can some one please post links to them? Thanks!

Sadly I do not have a camera at the moment, but I will introduce my motor to you.  I bought most ot the parts for this build several years ago, so some of the details are a little foggy....  From the bottom up:

RC crank (a little lighter and balanced)
Forged aluminum rods
stock tranny
new primary chains
upgraded primary chain tensioner
new bottom end seals
copper base gasket
cylinders punched out for 1000cc sleeves, but sleeves bored to fit 900cc pistons - that way I can re-bore larger if I want.
top crankcase half machined to fit the large sleeves
Henry Abe 900cc piston kit
Tsubaki HD cam chain
M3racing.com cam chian controller/tensoiner
copper head gasket
Web-cam steet/strip big bore camshaft
HD valve spring kit
Titanium valve retainers
Mildly ported
fresh valves
I think that's it, but honestly I can't remember anymore. 
I'll find out for sure what all is there as I go through the boxes again.  Seems like I have a mint invested in this mess!  All the machine work is done and I am buttoning up the motor right now. 

At the moment I am in the middle of trying to match up correct bearings.  Of course the "color coded" stuff is all LONG GONE.  I hate plastigauge.  No!  I mean plastigauge is my friend.  Assemble, torque, disassemble, inspect, adjust, re-assemble, torque, disassemble, re-check, repeat, ad nauseam ....

But soon it will be a very nice 2-up cafe bike for me and the Mrs.  The bike is a '69, but the motor is a k1-k8 mutt.
I am glad I am not the only one out there who is enjoying this process!

Peace and grease
-fang

[TwoTired]

 A note about assembly lubes.  I was under the impression that a lot of them used Moly as an anti-friction agent.  This is great for the engine, but not the clutch.  Could someone list some assembly lubes that do NOT have moly in them?

Thanks,

[MRieck]

A note about assembly lubes.  I was under the impression that a lot of them used Moly as an anti-friction agent.  This is great for the engine, but not the clutch.  Could someone list some assembly lubes that do NOT have moly in them?

Thanks,

Redline. Torco. Spectro.

[Terry in Australia]

How much for the pair of primary chains from Terry ?
I paid $93 for a pair from Honda 

I had to laugh, Terry sent me a "pair" and I asked him how much and he told me $160.00. I thought, "Geezus, that's expensive" and told him so, but he said, "well that's just what they cost".

I paid him, and when they arrived, I realized that there wasn't one set, but two! If you order the part number, you get two chains, but we didn't know that, so Terry ordered two, and I got 4 chains! No biggie, I needed another set for my K3 engine, so now I don't have to order another set. Cheers, Terry.

[TwoTired]

A note about assembly lubes.  I was under the impression that a lot of them used Moly as an anti-friction agent.  This is great for the engine, but not the clutch.  Could someone list some assembly lubes that do NOT have moly in them?

Thanks,

Redline. Torco. Spectro.

Redline looks good

Looks like Torco does have moly in it.
http://www.onoffroad.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=TORCO-LUBRICANTS-ENGINE-ASSEMBLY&Category_Code=TORCO-AUTOMOTIVE-LUBRICANTS

Spectro won't list ingredients for their assembly lube... even in their MSDS!  If it is black or gray, I'd be suspicious of moly content.

Cheers,

[fang]

I sometimes use Torco "MPZ Spray Lube" as a chain lube. 

I was reading the can last week and noticed that is is strongly advertised as an assembly lubricant.  I saw no reference to any ingredients.... nor any Molly.  I have always used the stuff  in a tube, but it sounds especially convenient to have the stuff in a spray can.  Has anyone here used a spray assembly lube?

I prefer to use AMSOIL Heavy Metal Protector as my chain lube. 

I especially like and trust AMSOIL products.  I know it is supposed to be 10% synthetic, but I don't know about its molly content.  I imagine it might make a good assembly lube.

[MRieck]

A note about assembly lubes.  I was under the impression that a lot of them used Moly as an anti-friction agent.  This is great for the engine, but not the clutch.  Could someone list some assembly lubes that do NOT have moly in them?

Thanks,

Redline. Torco. Spectro.

Redline looks good

Looks like Torco does have moly in it.
http://www.onoffroad.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=TORCO-LUBRICANTS-ENGINE-ASSEMBLY&Category_Code=TORCO-AUTOMOTIVE-LUBRICANTS

Spectro won't list ingredients for their assembly lube... even in their MSDS!  If it is black or gray, I'd be suspicious of moly content.

Cheers,

The Spectro basically looks like a very light colored oil. It is very viscous and comes in a squeeze bottle.

[SandwichEnthusiast]

Yay progress.

Some of my parts arrived for the bike from Z1, cam tensioner and chain etc. I should have thought to look at the lights and harness because I will probably have to order some electrical connectors from them as well.
Still need primary chain and tensioner and the gaskets and oil sets, which I'll probably get from Cycle X.

So with only one rounded off bolt the crankcase has been separated.



It says in my Clymers that you can take that clutch base off, but i couldn't figure out how.
I skipped taking of the AC rotor off

and i couldn't get the neutral stopper plate off.

I was having some trouble getting the crankcase separated and I think it was because something was catching on this:


the oil guide?

[mal]

Hi All
I'm following this thread closely, as I am also in the progress of a rebuild of a K2 motor. Keep up the good work all of you who are helping out us dummies!

Can anyone give me any ideas on how to get the 4 countersunk screws out of the countershaft bearing holder (also described as the layshaft main bearing holder) and the single screw out of the end of the selector drum??? (see picture).

As you can probably see from the picture, I have tried to remove them with an impact screwdriver and it has completely rounded out one of the screws, and started to do the same with all the others. Damn!!

Do I actually need to remove these at all to split the case? My main reason for splitting the case is to replace the primary chains and the chain tensioner roller, which is pretty deteriorated.

Any help gratefully received.

Mal

[Sweep]

Hi All
I'm following this thread closely, as I am also in the progress of a rebuild of a K2 motor. Keep up the good work all of you who are helping out us dummies!

Can anyone give me any ideas on how to get the 4 countersunk screws out of the countershaft bearing holder (also described as the layshaft main bearing holder) and the single screw out of the end of the selector drum??? (see picture).

As you can probably see from the picture, I have tried to remove them with an impact screwdriver and it has completely rounded out one of the screws, and started to do the same with all the others. Damn!!

Do I actually need to remove these at all to split the case? My main reason for splitting the case is to replace the primary chains and the chain tensioner roller, which is pretty deteriorated.

Any help gratefully received.

Mal

From what I remember that countershaft holder bridges top and bottom cases and would have to be removed BUT do a search because unless I'm crazy I sort of remember someone saying it could be done.

As for the rounded screw I did the same thing.  I just drilled out the screw head and it just spun out easily at that point.  Just be careful to only drill the screw and keep those shavings out of the motor.