Topic: Starting Cb750 that hasnt run in 15 years - advice!

[andyvclifford]

Hey all,

My name is Andy Clifford, I own a 1975 Honda cb750 that runs well and that I have done most of the work on myself.  I recently picked up a 1978 CB750 F2 (F3?) with 26,000 miles for a very good deal that has been sitting in a heated basement for the past 15 years.  The motor turns freely and theres really not much / any rust since it was stored inside for about half its life.  This will be my first time really restoring a bike and I was wondering if i could get tips on what to do first?  Should i try to get it running before I tear it down?  I know these bikes have issues with their valve guides and often need replacement. 

Any tips of bringing an engine that hasn’t run in 15 years back to life would be greatly appreciated. 

So far i have -

Completely cleaned / rebuilt the carbs and got them to stock settings
Dismantled, cleaned, and assembled the stock air box

I'm thinking about making a build thread also, and any tips on that would be helpful!

Pictures of bike below and also embarrassing picture girlfriend took of me sitting on it :| for good measure.


Thanks!
Andy

[scottly]

Should i try to get it running before I tear it down?

Yes.

[seanbarney41]

not really seeing any reason to tear it down...get it running, fix what is broke, ride, improve what needs it, repeat...

acetone and atf or marvel mystery oil through plug holes helps unstick piston rings...once it is running be sure and pull an inspection cap to confirm oil in the valve train

[grcamna2]

You can drain out as much of the old oil as possible from the oil tank on the frame and put in fresh motor oil enough to get on the bottom of the dipstick while the bike is level,open up all the 8 valve adjustment caps and use an oil can w/ the same motor oil to squirt a little oil around inside on the camshaft and lifters and then about an ounce+ each of Marvel Mystery oil in each of the spark plug holes/cylinders(let that MMO sit at least overnight in the cylinders)using a thin,tiny funnel and then 4 fresh spark plugs.Check/clean the ignition points and clean/spray WD40 on some of the electrical wires such as the battery cable ends after you clean the metal contacts to make them bright and shiny.
When you start it go slow and steady(about 2-2500 rpm) on the engine speed for about 5+ minutes or until the crankcases are warm enough for an oil and filter change and then do that. oh yeah make sure you have a good battery 
I think it would be good to remove the fuel tank and put enough fuel in it to wash it out toward the petcock hole(remove the fuel tap for this),roll the tank around all different ways to rinse it out well,this way you won't fill up your freshly cleaned carbs. w/ sediment.

[Jerry Rxman Griffin aka MuthaF'er]

Check the oil level, put gas in it, fill the bowls then try to start it.

[PeWe]

It should be OK if it has been stored in a warm and dry place with stable temperature and humidity.
If forgotten outisde in a garden with hot summers, rains and heavy winters..... why start it? Tear down direct.....

[evanphi]

If it ain't broke... don't fix it.

How do you find out if it's broke?


RUN IT.

[andyvclifford]

You can drain out as much of the old oil as possible from the oil tank on the frame and put in fresh motor oil enough to get on the bottom of the dipstick while the bike is level,open up all the 8 valve adjustment caps and use an oil can w/ the same motor oil to squirt a little oil around inside on the camshaft and lifters and then about an ounce+ each of Marvel Mystery oil in each of the spark plug holes/cylinders(let that MMO sit at least overnight in the cylinders)using a thin,tiny funnel and then 4 fresh spark plugs.Check/clean the ignition points and clean/spray WD40 on some of the electrical wires such as the battery cable ends after you clean the metal contacts to make them bright and shiny.
When you start it go slow and steady(about 2-2500 rpm) on the engine speed for about 5+ minutes or until the crankcases are warm enough for an oil and filter change and then do that. oh yeah make sure you have a good battery 
I think it would be good to remove the fuel tank and put enough fuel in it to wash it out toward the petcock hole(remove the fuel tap for this),roll the tank around all different ways to rinse it out well,this way you won't fill up your freshly cleaned carbs. w/ sediment.

Thanks you!  this is exactly the type of advice i am looking for!

Unfortunately i had to move it from his nice heated basement to my not heated garage so there is that against me!

Once i get my new carb packing kits and air filter i will give this a try. 

Is there any sort of substance to put in with the oil that might break up any old gunk that has accumulated in the oil passages in the engine ?

[evanphi]

Is there any sort of substance to put in with the oil that might break up any old gunk that has accumulated in the oil passages in the engine ?

Seafoam is supposed to be good for this.

[Phinn]

Old gas is a potential source of problems from sitting that long: solids and rust. For a bike that old, I'd start there -- pull the petcock off (and replace, along w/ the built-in filter, if your model has one), clean the interior of the tank thoroughly. Then pull and clean the carb bowls, which will develop varnish & goo after that long.

If you have good, clean fuel flow, working carbs and a functional electric system, I wouldn't rush to open a free-turning engine unless it appears necessary.

[SOHC4 Cafe Racer Fan]

Clean out your fuel and fuel delivery components (gas tank, petcock, carburetors, fuel lines); drain and replace your oil (drop the pan and look for any signs of metal particulate matter); lube cam and lifters from above (through tappet holes).  Cycle the starter thoroughly (a few minutes) with the RUN switch OFF to get oil cycling throughout the engine and up into the valvetrain; new spark plugs; fresh battery; a little starter fluid spray into the carbs.

[grcamna2]

When you drain out as much of the old oil as you can and then add fresh oil before you start it for the first time this fresh oil has detergents in it and then run it until good and warm and drain it;just do a couple oil and filter changes after you take it for the first rides,that will wash it out.

[andyvclifford]

Parts arriving next Wednesday, ill give an update about whether I was able to get it running then!

[CB650CPastor]

So....? Running?

[Stev-o]

Parts arriving next Wednesday, ill give an update about whether I was able to get it running then!

Hope you didn't buy aftermarket carb kits. They are crap and will cause tuning problems.

[andyvclifford]

Thanks Stev-o for the recommendation!  I only bought the gaskets and o rings i needed for the carbs as i was able to fully clean all of the jets and passages and needles.

[Stev-o]

Thanks Stev-o for the recommendation!  I only bought the gaskets and o rings i needed for the carbs as i was able to fully clean all of the jets and passages and needles.

Perfect

[andyvclifford]

Thanks for all the advice - Carbs rebuilt, Airbox rebuilt, oil changed with new filter, new spark plugs, and full tune up started up easily after about 10 seconds of holding the starter button!  Pretty good for 15 years of sitting in a basement.  Now I'm not sure what to do next - any advice would be much appreicated!  Its not driveable at the moment since I am rebuilding the brakes and suspension, ect.  That being said, should i keep running it?  What kinds of things should i be looking for to indicate what kinds of problems it might be having while running?

Thanks!
Andy

[Don R]

 If you have a volt meter you could check the charging voltage, check the condition of the fuse box and all the  lights. Looks like a nice find. I'm a fan of the dual disc front brakes and especially the triple disc bikes. 

[Stev-o]

Have you given it the 3000 mike tune up?

Place a fan blowing on the motor whenever idling for extended amount of time (for cooling)

[Kevin D]

Andy, congrats on the startup. Mine was also parked for 15 years - fresh gas oil change and new battery goes a long way! For your first ride I'd have clean brake fluid, new tires and make sure the brakes are decent, then circle the neighborhood for an hour. Watch for fuel leaks from sticky floats/needle valve. Maybe new chain, clean/lube/adjust anyway.
 My circles got bigger and bigger, but the feared breakdowns/problems never happened. These days I ride all day, my body gives up the sun goes down and the CB doesn't break a sweat. I put new wheel bearings in after I figured out that the grease inside them was 40 years old - but the old ones weren't complaining. Tapered roller bearings in the steering head and Hondaman swingarm bushings. Braided brake lines, rebuilt MC and caliper, spokes tight, wheels true, think I have touched everything over the years.
 So I'd say ride it 10000 miles and then check back.