Topic: '72 CB750K1/2 First time project

[MadDogCanada]

I picked up a bike and frame, no history on it, missing lots of part non runner.  This is the test bike to learn how everything work, Make it into Frankenbike since there's so much missing. doing it on the cheap to get it back together and running down to work and back, 25km


Here's some pics of what I'm dealing with.

My first question is, the broken bottom case bolt hole, is it fixable? will it piss out oil or cause serious problems down the road other than look ugly!?

I already got a line on a top case without broken fins.

So the biggest question is.. where do I begin? what to check first to see if it's worth salvaging the engine or loooking for a replacement power plant..

Thanks,
M

[timbo750]

I can't actually tell which bolt it is thats broken but generally it can welded up and then use a file to reshape.
Does the engine turn over? If its not siezed then its a good start.  How far you pull apart one of these depends on 3 things, how much patience you have, how much mechanical skill you have or are capable of learning and what is the end result you are looking for. There is also money but generally if have a desire for it you will find a way to fund it.

[MadDogCanada]

hey timbo,
Its the bottom right front bolt hole on the crank case. 
I've got the time and the desire, and a lil bit of mechanical skill...I've managed to keep three bikes on the road for years. Time to test the skills and learn a bit more....  I am economical and practical, so I wont replace things just so that they are new. but change things that need to be done.

PLus it's expensive as hell getting parts in Canada, between the exchange rate, shipping costs and border taxes...

I'm thinking of starting with the top end checking gaps and rockers and cleaning up the gas tank since it's caked in bondo.

[MadDogCanada]

here's a better picture. I'm a bit annoyed I didn't notice this before buying it.
Anyone got an opinion if this will be a major issue or how it's fixable thx.

Plan on bench testing the bike this weekend.
will check top end gaps,rough balance the carbs and chuck some oilfuel in it and see where it leaks... from everywhere most likely.

Feel free to post any comments or tips.

[timbo750]

That is critical, it is actually one of the main bolts that keeps the crank torqued up and place. I would not suggest running the engine with that in that state. It can fixed but most likely not with out pulling the engine apart. It also looks like there is crack travelling upwards as well. Does the engine turn over by hand?

[MadDogCanada]

Yah can't believe I didn't see it. Or that the guy didn't at least warn me... I'm thinking jb weld. And Helicoil may do the trick.  Don't know if I want to pull everything apart for something that can be fixed.... but it'd be a learning experience.
How would you fix it?

[timbo750]

That bolt is about 6 inches long so the thread should be fine. I have used JB weld on a few things but have also found a better option for this sort of thing. Get some 'Sun Fix' its 2 part and stiff to start with and guaranteed to dry rock hard, just make sure the case is spotless and free from any oil or grease residue, it is also better on a rough surface.

[MadDogCanada]

Step  2!

took engine out and put on a table with support brackets! i only took out two long engine bolts. isn't there three?  and I don't trust the two that were in there.

anyone know the sizes, lengths and proper placement of the long engine mount bolts.?

Here's a pic of my work bench.

So i'm checking the top end, gaps then starting to look at the carbs.

just want to hear it cranck over and see what I'm dealing with and see if I need a full rebuild or just a different engine!


Any advice or tips on things I should check before cranking it over? ALL tips Welcome!

[BPellerine]

cant see if you have an oil tank hooked up,but if you are going to turn it over with the starter,it might be a good idea to hook it up and run some oil through it,you will be able to see if oil is reaching the top end,also I think you would only have to remove the lower case half to get that welded it looks like,lots of good welders in alberta I would think.bill

[754]

Just so you know,
Three long bolts hold the engine in plus a few shorter ones
Of the long ones two have a bolt head and are I think 10 mm.
The other is I think 12 mm, and has thread on both ends, its lwer rear mount, and holds the footpegs on. Very often one end is bent, mostly still useable, but do not try to pull bent end through the motor.

[MadDogCanada]

still hooking things up.  will get the oil tank on. and use the kick start to get some oil going through things.  need to do a compresion test and set the carbs up.

SO I'm missing tht 12mm bolt... any Idea how long those bolts are? 

Where in Canada do you guys get your parts?  Gaskets, carb kits?  engine parts.
trying to find stuff local to canada and not pay US prices, transport and border taxes.

hope to have this putting by Sunday.

Any other tips before I crank it over? feel free to share.
thanks

[MadDogCanada]

so I've  gone through the valve clearances, most were pretty good, think I got them to spec. did cam chain tension. didn't notice any movement or change from before or after,  a tiny bit of play on rear of chain when at TDC, but tight to sprocket. the Manual wasn't much help.

So it's time to check out the electrical system. Never worked with points before so looking that up. pics and label of wires where they are on the bike. I'm thinking of minimizing the wire harness.  engine, headlight turnsignals and make it a kick start.

First things first, hook up wires to engine out of frame and see what happens.

Checking the points now, look decent enough. new battery but will get a smaller 8 cell Lith battery, or see if i can do it without a battery!? as my buddies trying to get me to do.\

let u know how it all goes.

[754]

It always needs a bit of juice to start.
Do you ever get to CowTown ? A buddy may have a 73 motor available later this year. He knows where a guy had 3 motors foe salem they were outside.. He did not check them over.. I am trying to get him to go check them out in the next few weeks.
 What you really need is cases, or lower end and at least a head.....correct ? If you cant find a complete motor..

[MadDogCanada]

That'd be pretty cool man keep me posted. It'll depend if this thing turns over or not. May need the whole thing.

What frame kits do you do?

[timbo750]

Franks frame kit works well, I can vouch for itt, easy to use and no welding.

[754]

I will be back making frame kits soon.
It allows you to cut the two lower frame rails under the tank, then remove the section to access topend in the frame. Then it clamps rigidly back in place.. Without having to weld  sections into the frame to allow that. The brace section has a bolt in element, that ties that back together.

[MadDogCanada]

yah I'v seen those around. makes taking of valve cover a bit easier, is there a bolt on hoop for the seat frame with that?

[754]

No bolt on hoop..

[MadDogCanada]

This engine is fighting me every inch of the way. I went to torque on oil drain plug and found it striped oh and no washer. The PO has screwed everything up that I've looked at so far.

The  bolt looks decent so thinking it's the inside threads....Will try and get a bolt to test it out. but there goes my plans bench testing this engine.

But I have always wanted to learn to Tap out holes.. s i'm staying positive.

[BPellerine]

sorry it is going badly!

[754]

It always needs a bit of juice to start.
Do you ever get to CowTown ? A buddy may have a 73 motor available later this year. He knows where a guy had 3 motors foe salem they were outside.. He did not check them over.. I am trying to get him to go check them out in the next few weeks.
 What you really need is cases, or lower end and at least a head.....correct ? If you cant find a complete motor..

 Looks like there may be at least the parts you need ora motor available in Calgary for you , either a 73 or 72.. Pm me if you need more info.754

[MadDogCanada]

It always needs a bit of juice to start.
Do you ever get to CowTown ? A buddy may have a 73 motor available later this year. He knows where a guy had 3 motors foe salem they were outside.. He did not check them over.. I am trying to get him to go check them out in the next few weeks.
 What you really need is cases, or lower end and at least a head.....correct ? If you cant find a complete motor..

 Looks like there may be at least the parts you need ora motor available in Calgary for you , either a 73 or 72.. Pm me if you need more info.754

Thx man any info would be good. Stripping my bike down into bits to ship... Any tips on what to take or leave behind to save on cost...

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[HondaMan]

My welder (he's a good aircraft-certified welder guy) would fix that bolt tower up for me in an hour and charge me $40 in the end.
The fins would be a little more (probably $60-$80), but do-able: the hard part is in taking the time to file them down to look like the others. It takes about an evening for me to do 2 fins.

[MauiK3]

For a start on what parts are and what they look like you can go to the Yamiya web site

http://www.yamiya750.com/

They have the pictures and sell a lot of the parts you will need.

[MadDogCanada]

For a start on what parts are and what they look like you can go to the Yamiya web site

http://www.yamiya750.com/

They have the pictures and sell a lot of the parts you will need.

I'm tearing the engine apart to salvage as much as I can. And ditch the case. Any parts you think are more important than others. I.e. Rare /hard to find/expensive... I got limited space to ship...

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[MauiK3]

Transmission parts that are in good shape
Oil pump, especially if the screen is sound
Crankshaft
Kick start parts
Alternator parts
Camshaft
Points advancer

[BPellerine]

depending where you are going,alot of parts can be hard to get,I would try to keep all of the engine parts,and covers as they are all from the same engine,bill

[MadDogCanada]

Is it worth taking the gear box apart? Thinking as I'm a newb to get a whole engine to slip in. And just keep external engine parts and top end....
Pulling piston out tmrw.
I still can't get the exhaust valves out, they don't slip out of the guides like the intakes do!?  Any advice is welcome pls!

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[BPellerine]

if you have the springs off the valves they should come out,sometimes the old valve seals hold them a bit,or there could be some carbon or rust,a little wd and a light tap and they should come out,can you not take the bottom end as a unit?bill

[MadDogCanada]

if you have the springs off the valves they should come out,sometimes the old valve seals hold them a bit,or there could be some carbon or rust,a little wd and a light tap and they should come out,can you not take the bottom end as a unit?bill

All the valves hit the guides badly. But I'll give it a few wacks. Not keeping the cases  fins cracked...bottom cracked too

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[MadDogCanada]

From what I see on YouTube. I just smack the valve guides with an 8mm socket to pop them out!? Comments?

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[BPellerine]

are you trying to take the springs off ?not sure what you are doing,you can use a socket to give the springs a little wack with a rubber mallet,but the collets will fly out if you are not careful,a pic would be helpful

[MadDogCanada]

are you trying to take the springs off ?not sure what you are doing,you can use a socket to give the springs a little wack with a rubber mallet,but the collets will fly out if you are not careful,a pic would be helpful

Removing exhaust valves. Won't fit through sleeve
Here's a pic

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[BPellerine]

they should come out,they maybe mushroomed a bit,so check how far they go down,maybe a little,emery paper to polish a bit,and if that head is bad,those oiljets in there are very hard to get,some would take the head just to get the jets.by the way I am from nova scotia,bill

[MadDogCanada]

they should come out,they maybe mushroomed a bit,so check how far they go down,maybe a little,emery paper to polish a bit,and if that head is bad,those oiljets in there are very hard to get,some would take the head just to get the jets.by the way I am from nova scotia,bill

Just smacked them. One out one seized...Strange. They must have warped...

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[BPellerine]

yeah you could have a bent valve,usually destroys the guide getting it out.bill

[MadDogCanada]

yeah you could have a bent valve,usually destroys the guide getting it out.bill

Think all 4 of them were.. bigger hammer worked. Thx man

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