Topic: '76 CB750K Project #3 - Long and Low - Final thoughts and pics

[Stoli]

Thought I would tear down this bike to see what I had to work with.

Engine and carbs aren't too bad. Haven't cracked the case open yet but the head is useable - although, I do have a '74 head  that needs less work, so I will probably use that if it is compatible with the '76 - need to look into that.

Frame is decent and I can use the wheel hubs. Fork cases are OK but need new tubes and a new tree. Just about everything else is useless. Tank is rusted through on the bottom rear.

Total cost to date: $0
Estimated final cost:  Probably more than I could sell it for but that's not the point

[SOHC4 Cafe Racer Fan]

Yes, the 74 head is compatible with the rest of the 76 engine.

[Stoli]

Yes, the 74 head is compatible with the rest of the 76 engine.

Thanks for the reply. My research indicates that the only differences between my K4 engine (2338396) and K6 engine (2442357) is in the cylinder block. Specifically the K6 has knock pins and seals where the K4 just had o-rings between the cylinder and the head. I was scratching my head for a while and doubting what you said, but I think those knock pins recess fully into the cylinder block so the old head would go on the newer cylinder like you said.

Do you know if all the internals are interchangeable between the two engines?

If I had to guess at this point, I think my plan is to use most of the K4 engine with the following parts from the K6:

carbs
clutch & cover
alternator & cover
head cover
mission cover
sprocket cover
and possibly the cylinder block

[iron_worker]

Much work to do INDEED!

 

Good luck.

IW

[goldarrow]

wonder how much rust if any in the bottom end........

[bjatwood]

Look at those frame tubes for rust very closey. That baby has lived outside for a "few" season eh?

[Stoli]

Look at those frame tubes for rust very closey. That baby has lived outside for a "few" season eh?

That is certainly a big concern. Do the CB750 frames have a history of rusting from the inside out? Most of the external rust looks superficial but I am worried about what's on the inside.

[Stoli]

My other project was at the powder coaters, so cleaned up the frame on this one and increased the neck rake by 9-10 degrees.

[Stoli]

Here is the neck after the wedge was closed up. Tack welded in place for now. Will get it properly welded later.

[bjatwood]

The place to look for rust is on the tubes under the motor. Water can collect in these spots and can cause havoc...

[Don R]

 Your honda is like my 40 chevy. The restorer crowd gave me a hard time about making it a street rod. I told them it was saved from the junkyard twice, none of those guys would have saved it, so kiss my, you know.
 You're making something special out of what many wouldn't be brave enough to tackle. So when the restorers cry after it's beautiful laugh at them. I started a long and low project but got sidetracked. It's hanging on the wall in the shop. +4" swingarm and raked too.

[Stoli]

Thanks for the encouragement Don. There seems to be a lot of incomplete project threads of bikes with increased rake. Maybe there is a  hidden message there??

This project was a perfect candidate for me to get more creative with since there were so many parts that were going to come from salvage yards and internet sites. Not sure exactly where I am going with it but one way or another I hope to have it on the road next summer.

[Stoli]

Starting to take shape. Scored the tank off ebay. Shipped to me with gas in it. Gotta love that. Thanks to Stevo for the triple tree and Tom W. for the 650 swing arm. The tank isn't as long as I had hoped for this bike but this F model is the longest stock tank made, I believe, and the price was right.

The swingarm gets me an additional 2" in length and the rake mod about 4". Even more if I go with longer tubes. I just stuck on these tubes from one of my other projects to see what it looked like. I think I might stick with the stock length as it will drop the bike 2.5" if my math is right. I will be going with a slightly bigger tire radius, so the net drop won't be quite that much.

[BPellerine]

looks good so far.bill

[SOHC4 Cafe Racer Fan]

Starting to take shape. Scored the tank off ebay. Shipped to me with gas in it. Gotta love that. Thanks to Stevo for the triple tree and Tom W. for the 650 swing arm. The tank isn't as long as I had hoped for this bike but this F model is the longest stock tank made, I believe, and the price was right.

The swingarm gets me an additional 2" in length and the rake mod about 4". Even more if I go with longer tubes. I just stuck on these tubes from one of my other projects to see what it looked like. I think I might stick with the stock length as it will drop the bike 2.5" if my math is right. I will be going with a slightly bigger tire radius, so the net drop won't be quite that much.

I am partial to Super Sport tanks over the K tanks. 

[Stoli]

I think I may have to move the petcock bung. I am moving the tank back an inch or two to accommodate the mod to the neck and I think the petcock will be hitting the #1 carb body.

[Stoli]

Bought a new 16" Harley rim (Drag Specialties). Kind of a pos but for $72 delivered, couldn't expect much more. Took me a little while to lace up (Buchanan's pre-packaged spoke kit) since the pattern was a little different than the stock rims  but in the end it came out pretty good. True enough.

[Stoli]

Wish I could say the same for the front wheel. It appears that unless you send Buchanan's a sample of the exact spokes you need (or ship them the hub and rim), they have a hard time making a custom set for you.

I bought a new 19" Harley rim for the front wheel. Drag Specialties again ($95) but this one is a lot nicer quality than the 16" rear. This required a custom spoke set and after a few emails to/from the Buchanan's tech support folks, they said all they needed was a few dimensions of the rim and we'd be good to go ....  Not so fast.

Maybe I laced it up wrong, but the spokes are too long. If someone sees something wrong with my pattern, please let me know and I'll offer up a big mea culpa to Buchanan's. Otherwise, I'm a bit disappointed with them as this is the 2nd custom spoke set from them that I've had a problem with. They got the bends wrong on a set I ordered for my first project bike.

[G3]

Thought I would tear down this bike to see what I had to work with.

Engine and carbs aren't too bad. Haven't cracked the case open yet but the head is useable - although, I do have a '74 head  that needs less work, so I will probably use that if it is compatible with the '76 - need to look into that.

Frame is decent and I can use the wheel hubs. Fork cases are OK but need new tubes and a new tree. Just about everything else is useless. Tank is rusted through on the bottom rear.

Total cost to date: $0
Estimated final cost:  Probably more than I could sell it for but that's not the point

I think the worse they are to start with, the more satisfaction you get in the end right? 

[SOHC4 Cafe Racer Fan]

That's a rough one!

[USCG_C130]

wow looks like  you have a handful there, wish my balls would have been big enough to cut my frame, i love the long and low look! best of luck!

[Stoli]

I think the worse they are to start with, the more satisfaction you get in the end right?

Something to be said for that. It would be more impressive if I was keeping more of the original bike but most stuff is just too far gone. If the soul of the bike lives in the frame and engine, then this project is certainly a worthwhile endeavor.

[MoMo]

You are a brave man attacking that rust pile.   Subscription sent in....larry

[BPellerine]

hope you are the one to finish a raked bike and get it on the road.bill

[KB02]

Check out my build thread. They can be brought back from worse.

I will be interesting to watch this unfold.