Topic: 77 CB750A need advice

[broshae]

I picked up a 77 CB750A last weekend that needs some work.  I was told that it hasn't run since 1977 when the original owner took a spill in the ditch with it, shortly after buying it.  The speedo has been changed (headlight and speedo were damaged in crash) so the odometer only reads 0.9 miles.  The guy I bought it from said it has less than 400 miles on it, he bought it as a project about 15 years ago and never got around to working on it.

So my first question is:  What should I do with a 37 year old engine that hasn't run in 37 years?  Supposedly the engine was running fine when the original owner parked it back in 77.  gas tank was disconnected and carbs drained.  I pulled out the kick starter and turned it over a few times and its very smooth.

Thanks in advance for your advice

[broshae]

I will be posting some pictures later today

[broshae]

I should add, I'm mostly wondering about the bottom end (varnish, dry seals, etc.) I haven't pulled the dip stick, but from turning it over Im sure its full of oil.  Should I fill the crank case with any type of product to clean/flush it?  Or something to condition the seals a bit?  I've read some suggestions to fill with diesel oil and stop leak and let it soak for a week, turning over often.  I've also read about using diesel fuel or kerosene instead. Not really sure what to do.

But also any other recommendations would be appreciated (carbs, etc.)

[nixon]

hey

im no mechanic but your on the right track im sure. whatever you do with that engine will have its pro's/cons. but im guessing you dont want to sink alot of $ in it!

Personally, id drain oil..use some cheapish 15-40w for a short period and change again.

maybe just get it running then manage any problems..it may have zero issues!

[raymond10078]

Personally, id drain oil..use some cheapish 15-40w for a short period and change again.

+1

[Johnie]

Welcome to the forum:
Drain oil pan and oil tank, change filter, save a little oil to add to the top end by removing the valve adjustment caps on the cover. Then use a syringe from a farm store to squirt oil in the head area. Get a new battery. Confirm the tank is clean before you put gas in. Be sure gas petcock is in the OFF position. Might want to pop off a carb bowl just to confirm the carbs are clean. Once that is all done make sure the kill switch is in the OFF position. Spin the motor over a few times either with the starter or the kicker to get the fresh oil distributed a bit. Once you have that done then turn the kill switch ON, petcock ON and key ON...then fire it up. These bikes were made so well I would be surprised if it does not start for you. Let us know how you come out.
On a side note, there is a gas filter screen in the bottom of the petcock bowl area. You could check that if you want or not. If you want to give it an even better chance to start toss in some new spark plugs.

[brooze72]

+1 Johnie, it's a Honda so I'm guessing no major issues, fire it up! ( after following recommendations, of course)

[broshae]

Thanks for the replies guys. I will be doing those things while I wait for a new tank and some other parts. After further investigation I have found out that this bike used to have a fairing on it. It seems like it was crashed in to something like maybe the back of a big truck.  The fairing was the point of impact. Some damage to the speedo and gauge bracket. bars are a little bent and a few dents in the headers. Then the bike fell over and bent the rear signal light. The rider's legs must have driven the fuel tank in to the frame at the front, its all dented in around there. I'll attempt to post some pics.

[broshae]

pics

[iceman321]

Hello
        post sounds like you have not run it yet. 1st thing to do is test the compression to see if the rings have frozen up.Fill cylinders  with mystery oil over night to free them if no compression.

[POPS 911]

Put some mystery oil maybe a table spoon full in each hole.  If you do not have a remote gas tank , sit a small gas can/ WITH SOFT PLASTIC LINE on a stool or chair higher than the carbs, siphon some fuel to get it flowing and plug line into fuel intake line. I use a car battery [ out of car ] with jumper cables has more cranking AMPS. Make sure there is no rat nest in air box =  Pull choke out and hit start button, it will run rough if the low jet is plugged with 15 year old fuel but if it starts it will be a while until the rust on valves burns off Honda hard seats and valve head = remember some of those valves were open for all those years... I done this a 100 times over the past 58 years spinning wrenches on OLD BIKES. DO-NOT PUT ANY FLUSHING  IN THE MOTOR AS THIS WILL BREAK UP THE CRUD AND FLOAT IN THE OIL TO EVERY HOLE THAT OIL RUNS THRU.  If you pull those carbs remember if you bust one of those 1-2-3-4 boots no one has them for sale  37 year old boots can be very brittle , heating boots with a HAIR DRYER can soften them up a little to pop them out, drain all gas out of bowls with fuel bowl drain screw first.  I have a garage full of Hondamatic'S  400-450-750cc  and have drag raced one for many years.