Topic: an idiot with a cb750 (resto-mod/brat/tracker build)

[mannydantyla]

Hi guys! New SOHC owner here!

I brought this 1978 CB750k home the other day:



It looks good in the back of my truck  - a 1973 Chevy K10. In fact, I wanted a truck in the first place to haul motorcycle arounds! Then I just had to go and restore one... but now I'm done and can focus on bikes again!



This will be my second build. My first build, a 74 CL200:



The CL200 is what gave me the confidence to tackle a large project like the truck. Now the truck has delivered me my next project. It's come full circle 







The oil filter bold was stuck. Apparently, a rite of passage for all SOHC CB750 owners is to deal with an oil filter bolt that's siezed up. It's soft and was quickly rounded. With the exhaust off I had plenty of room, so I used an angle grinder to grind two flat spots that a pair of vice grips could grab well. It worked but the bolt is ruined. Thankfully I was able to find one on Amazon for around $10.



Upon closer look at the supplied mufflers, two them have a different flange than the other two.



So clearly this bike is going to be a real piece of work. I don't plan on restoring it to any original glory. This is the perfect opportunity to go full on custom! But i'm going to keep it classy. I'm thinking a resto-mod/brat/tracker/thingy. I'm still deciding...

[mannydantyla]

Rule #1 by SteveD in the FAQ section (yes, I've been doing a lot of reading) is "Never commit to a bike you know nothing about."

... WHOOPS!

I've been reading about these 750s. The k8 is the best one.. right guys?! There seems to be an unlimited number of things I gotta look out for. Fork tube bearings.. generator windings.. float levels.. clutch disk thicknesses.. OH JOY!

Gotta decide how much dough I wanna drop into this project. I could have a really #$%*en ride for $1000 + the original $500 I payed the man for the turd (you think I got ripped off?). But I want do drop some money into my truck as well.. a transmission swap and trade the carb for a throttle bottle EFI unit. Those two things will cost $2500 at best. I think I'll go with the #$%*ing motorcycle!

Good news! I have the stock air cleaner box! That apparently will make tuning much much easier. Same was true with my CL200.

 

[calj737]

It doesn't look like the motor has ever been opened. All the screws are still in tact and not buggered up. They're not Phillips, they're JIS. So do yourself a favor and buy some JIS screwdrivers to work on the bike and the carbs. The carbs probably need a full clean, new steering bearings, swing arm bushings and new tires! (No Firestones  )

Open your headlight and commence cleaning all the connectors, plus under the left side panel, and the fuse block. These things cost very little but make a huge difference in the reliability of your bike. And change the fork oil. Theres a small bolt on the outside of the lower leg (it has a crush washer beneath it). Open that bolt and drain the fluid. Then remove the fork tube bolt up top (its holding a spring so be mindful) and rinse the tubes out with some Acetone or Diesel or degreaser. Then refill with proper weight and volume of oil.

Some simple things that just make a bike much safer and more reliable. Even before the #$%*in' custo-mod endeavor.

[mannydantyla]

Thank you Cali, good advice! Yeah you're right, those screws look great! I replaced all the screws on my CL200 with allen buttons, and all the screws on my 73 ATC90 three wheeler are all destroyed  Looks like I won't have any problems with this 750 motor with bolts.

The engine is getting very good compression I believe. I used a reliable, USA-made compression guage. However, we could not open the throttle because the push-pull throttle grip is in a box somewhere. So we did it anyways and I guess I could add 20psi to the readings maybe? Each cylinder recorded 130psi. With the throttle closed! So I think that's pretty good.

The guy I bought it from said that the guy he bought it from had restored the carbs while taking great care not to ruin their balence by taking them apart from each other. My hope is that I don't have to do much to the carbs.

He also must have worked on the forks because they have new oil in them and the seals look brand new. Hopefully he replaced the fork tube bearings too. How can I tell without taking it apart?

[calj737]

Fork tube bearings? Steering head bearings perhaps ?  Bike on center stand, weight to rear wheel, push the bars to left. Does it feel "notchy"? Does it flop over or fall over smoothly? Test to right side also.

When good, it should be smooth and neutral, no tendency to flop to the side or feel gritty.

[SOHC4 Cafe Racer Fan]

$500 is a pretty solid deal.  The bike is close to all there.  The motor has decent compression and sign of significant leaks.  I say get this one back into running shape and enjoy.

[mannydantyla]

$500 is a pretty solid deal.  The bike is close to all there.  The motor has decent compression and sign of significant leaks.  I say get this one back into running shape and enjoy.

Thanks you! And there's no oil leaks either

BTW, yesterday I watched a youtube video featuring your bike (I recognize it from the links in your footer) and I was like "that one is awesome! i want mine to look like that" so don't be too surprised if I "borrow" some of your design choices

[Desert-SOHC]

$500.00 was a good deal, I paid 1K for mine, but it ran...poorly, but it did run. Yours looks a lot like mine when I first got it.

[mannydantyla]

Focusing on just getting the bike ride-able and running reliably

The bike has 21,807 miles showing on the speedometer, BTW.

Things to buy:

• battery (check)
• oil filter (check)
• oil filter bolt (check)
• oil (check)
• fuel filter (check)
• fuel lines
• spark plugs (check)
• spark plug caps
• points
• exhaust collar joints
• exhaust crush gaskets (check)
• air filter element
• brake pads
• tires
• grips
• POR-15 fuel tank liner
• bearings and bushings

Things to do

• prep the engine (new oil, filters, battery, spark plugs, etc. Put air cleaner and exhaust on)
  
• get the engine running
• ensure good oil pressure (might install a fixed oil pressure gauge)
• fine tune the engine (tappets, air/fuel screw, cam chain, throttle position, clutch adjustment, etc)
• clean inside of fuel tank and line with POR-15
• install tires
• assemble front brakes
• rebuild master cylinder
• go over all electricals
• get a temporary seat on there
• install bearings and bushings
• ride the bike around!?
• get it registered and insured and all that boring crap

Anything I'm missing?

Just working on getting it ride-able at this point. I don't know yet but I will probably get clubmans or clamp-ons, new tach and speedo, new rear shocks and springs, a custom seat and rear hoop kit, side covers and emblems, aftermarket turn signals and tail light, paint the tank, etc. But my main concern with this build is FUNCTION over form! Not going to put stupid firestone tires on it or anything... also not going to make it a crazy race bike. GOOD performance over HIGH performance. And make it a SAFE bike to ride.

[SOHC4 Cafe Racer Fan]

Good goals. Make it a solid non-pretty runner first. Then mod to suit function.

[calj737]

Things to do

• replace master cylinder

with a repo unit from David Silver Spares

• go over all electrical and clean the harness and every connector

Ahhhh, thats better