FRANKENHONDA II the 1982 DOHC CB 750F2 Build

Maritime

Well-Known Member
Fill with oil, button up, leave carbs off. pull plugs, put guage on cylinder 1 turn motor over with the starter and battery, read, rinse repeat for each cylinder.

I've done this to 2-3 engines before I bought them to know what I was getting. really simple.
 
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teazer

Well-Known Member
DTT BOTM WINNER
just out of idle curiosity, why are the bores in that head gasket so much larger than the actual bores? Is it for a 900 or 100 by any chance? When a gasket is that much larger than the bore, the motor will have a tendency to blow gaskets or to detonate. Suzuki had that problem on the GT750 for years.
 
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Jimbonaut

Well-Known Member
DTT SUPPORTER
...turn motor over with the starter and battery
This is the part I'm curious about Mike. Dumb questions maybe, but where exactly do you connect the red and black jumper? The starter motor and starter clutch assembly all needs to be installed too right?
 

Maritime

Well-Known Member
yep. you ground the black(neg) to the motor on a bolt usually not connected to the starter then touch the red(pos) to the nut on the starter where it would connect to the wire from the solenoid if installed on the bike. that turns the starter and you let it go for 2-3 revolutions then read your compression gauge.
 

Jimbonaut

Well-Known Member
DTT SUPPORTER
yep. you ground the black(neg) to the motor on a bolt usually not connected to the starter then touch the red(pos) to the nut on the starter where it would connect to the wire from the solenoid if installed on the bike. that turns the starter and you let it go for 2-3 revolutions then read your compression gauge.
Cool, thanks - that explains it. One more thing - if it's a brand new engine (like Frankenhonda and my build) is there anything else you should so before jumping it? Or just fill it with oil and grip it an' rip it?
 

Maritime

Well-Known Member
Id lube the cam up with break in oil fill the head and oil pockets but you arent going to run it so it will pump oil in while you turn it over. The numbers will be lower that speced for a warm engine but high enough to know its ok and also within the +- 5 psi between cylinders. When I did thw 450 twin it was 120 and 121 psi cold and freshly rebuilt by seller. After installed and runnin it went to 150 each which was right on factory spec.
 

Jimbonaut

Well-Known Member
DTT SUPPORTER
My engine was rebuilt using assembly lube, but I didn't realize there was a special kind of break-in oil. What is that? Thicker?
 

Maritime

Well-Known Member
I got a jug of it years ago. Lucas engine break in oil with ZDDP. Not sure you can still by it but older engines like it for cam and valve protection the zinc is good. There are threads on it here. They stopped putting zinc in oil and it was good for older engines. Pre 90's I think so a squirt of the lucas with zddp(zinc) is a little extra love for a freshbrebuilt engine
 

Jimbonaut

Well-Known Member
DTT SUPPORTER
Think I was told to use a mineral oil for break in. Since being told about it when working on Rhonda, I've always used Rotella T4 on all my bikes. Break-in oil though is new to me.

(sorry for the hijack, but hope this info is useful to you too)
 

Maritime

Well-Known Member
Think I was told to use a mineral oil for break in. Since being told about it when working on Rhonda, I've always used Rotella T4 on all my bikes. Break-in oil though is new to me.

(sorry for the hijack, but hope this info is useful to you too)
You don't fill the bike with it and assembly lube likely has the zinc in it too. I just add a few table spoons to the mineral oil for the old bikes. The 1L bottle has lasted me 8 years and still 1/4 full. a drizzle over the heads moving parts is a little extra love, may do fuck all but the zinc thing is well documented to help prevent wear on the older cams etc.
 

Maritime

Well-Known Member
Oh and just to add controversy about oil, I just did the Yaris's annual oil change. Been using Mobile 1 since I got it and change it once a year or 32K clicks. I've put 138 K on it and it uses about 1 L in between changes, car has 368K Kms on it now. That's a modern engine and modern oil vs the old stuff. I do dino 5w40 Quaker state in the GL and once a season or if I get a lot of miles on 2X a season. Add the ZDDP in it as well.
 

cb250nproject

If you can make it better do so
just out of idle curiosity, why are the bores in that head gasket so much larger than the actual bores? Is it for a 900 or 100 by any chance? When a gasket is that much larger than the bore, the motor will have a tendency to blow gaskets or to detonate. Suzuki had that problem on the GT750 for years.
The guy who I got my last gasket from said this would be ok, I’ll be pretty pissed off if he has stitched me.


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cb250nproject

If you can make it better do so
I’ve just reviewed my pictures, the gasket is way off, F$@k looks like I’m going to have to strip her down again and do it all over... that’s pretty frustrating I did explain that it was bored out to 823 cc and that I needed the same gasket as last time... he said this one would be fine.. looks like I’ll have to get Rex to make me up a copper one maybe.... spewing I fly out in a week, there goes another day, I guess on the bright side I’ll become better at replacing head gaskets that’s for sure


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cb250nproject

If you can make it better do so
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Well OMM was hard at it and more successful than myself thankfully

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He nailed the sump modification, hopefully the hoses that I ordered will arrive soon, then I just need to wait for Rex to make me up a new oil pump and we will just about be away... well as long as I can finally manage to button up this motor.


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cb250nproject

If you can make it better do so
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offending gasket out.

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and Steve down at Old Gold Motorcycles managed to find me a set of second hand oil lines

So we’re just about in business for this oil cooler upgrade.


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