found a motorcycle in a shed ADVICE
I found a motorcycle in a shed and I need advice. It's a '77 Honda cb750 and I think the pistons are seized from sitting for 20 years. The owner told me it wasn't seized when he stored it. Neither the starter or the kick start can move them. How do I break them free? PS I got it for free so don't think I'm an idiot for buying such a hunk.
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fill the crankcase with kerosene, squirt some penetrating oil in the cylinder, then screw an air fitting in the sparkplug hole. Set the regulator on 100 PSI and go for it. 0 -
pull out the plugs and squirt some marvel mystery oil in the holes let it soak..buy new plugs..drain the tank and carb bowls..get a new battery..change oil..roll over the engine w/plugs out first several times..the tank should be removed and cleaned out w/gas remove the petcock from the bottom of the tank also flush it out..if it will roll over freely..put gas in the tank 1/4 gallon will do..put in the plugs and try to crank it up..use the choke..hopefully it will break free let it set a couple days w/the marvel mystery oil in it..Loko[:D] 0 -
MARVEL MYSTERY OIL...Put 4 oz. in each "plug-hole", wait 48hrs, then "BUMP" it over,just to break it loose.
Reapply Myst.oil, wait 24 hrs. turn-over a few full revolutions...Check for spark, tumble fuel tank and "cream" it.Add fresh tires, and go for a ride!![;)]You may also need to clean the carbs ..
Jeff0 -
Restored 70' vintage CB750's are worth lots of money. It may be the valves stuck in the heads rather than the rings stuck to the cylinder walls. Either way, remove the plugs and fill they cylinders with a good penetrating oil or diesel fuel. Remove the cam covers an see it you cam move the valves. Soak them down with the oil too.
If all the parts are there, a up end rebuild is pretty simple and a good investment.
How about some pictures?
PS, Marvel Mystery Oil is good too. Lot's of good advice so far.0 -
let us know how it turns out
Taz0 -
Well the price was right! These things are a dime a dozen. They made so many for so many years that they are everywhere. As you, as my forum name implies, know that I am a Honda fan.
First thing (and you have good advice) is to pour penatrating oil in the sparkplug holes. Pour a lot since the engine isn't a vertical config. Next is let it sit - perhaps a long time. Try to turn it with the kick starter now and then but don't rush. I've been soaking a frozen slide on a civil war pistol for over a year!
Even if you free it up (and do all the fuel cleaning as others have mentioned) you still may have a bad piston ring/cylinder wall seal problem. Rust on the walls will keep you from having a original powered engine.
Let us know how things turn out.0 -
Look for some penitrating oil called "kroil" recommended by members of Farmall Cub, put some in and wait a few days then add some more and wait and add some more. Don't get in a hurry, let the oil work. Even if you can't get it to spin you have a lot of parts to sell on eBay. 0 -
quote:Originally posted by dheffley
Restored 70' vintage CB750's are worth lots of money. It may be the valves stuck in the heads rather than the rings stuck to the cylinder walls. Either way, remove the plugs and fill they cylinders with a good penetrating oil or diesel fuel. Remove the cam covers an see it you cam move the valves. Soak them down with the oil too.
If all the parts are there, a up end rebuild is pretty simple and a good investment.
How about some pictures?
PS, Marvel Mystery Oil is good too. Lot's of good advice so far.
Smart guy. Somebody finally mentioned good old fashion diesel.
I think diesel and patience is great.0 -
All good advice.
Worst case scenerio is an engine tear down. I have seen them stuck bad enough the pistons had to be drilled full of holes and collapsed. The engine had to be sleeved.0 -
Owned my own shop for 4 years. We used brake fluid for soaking. use the foot starter not the electric. Any time a bike sits the problem is when turning it over just to see if its free, that wipes the oil off the cyls. Then it will freeze up in a day or two. You must turn the 750 honda about 10 times to get oil to the top. Do not fill the case with anything it WILL lock up. Leave the plugs out till your ready to start it. You can check the spark by grounding the plug to the motor. Do not touch the biles bare metal while doing this test. Carbs will need cleaning for sure.
Above all else get a manul. You can do all this your self, don't pay somebody to do it cus they said its hard and you'll ruin it. They only want the job for the money.0 -
make a footnote....
DONT USE THE ELECTRIC START! kiss it goodbye if you do with a seized engine!
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quote:Originally posted by Da-Tank
Carbs will need cleaning for sure.
Tank Too. Everyone always does a simple rinse to the tank, cleans the carb, then 2 months later they have to clean the carbs again because they didn't get the buildup out of the tank and the new gas and engine vibration broke everything loose again.
In fact, after you have it clean and running, put an inline filter on the gas supply for at least a year. It will save you having to do the carbs again, and even again.0 -
The guy didn't know much about fogging cylinders[:0] 0 -
Now you guys got me thinking about my own '74 CB-750 K-4.
Thing is, I haven't even started it since around 2003. Last time I looked inside the gas tank I saw some kind of rank smelling fluid and everything was covered with a powdery amber stuff similar to a greasy soot. I bet the carbs are worse. I guess new lines will be needed. Ah, yes. The front brake hydraulic reservoir is empty ... I wonder about the condition of that brake caliper and piston.
So there is more to worry than just frozen pistons ...[B)][:(]0 -
need advice on a cb750 go to hondachopper.com
it is a bunch of us (tho i havent been there for a while) who have and chop STRICTLY cb750s
as for breaking it loose, carefull is the word
fill all cylinders with wd or pther solvent and re-fill for several days as it works through to the crank through the rings.
after about 4 days to a week put it in gear and GENTLY rock back and forth putting gentle strain on all pistons and crank at the same time
i have done 4 750s and all have come around to be good motors0 -
Automatic tranny fluid is a cheap and plentiful substitute for Marvel Mystery oil. 0 -
All this is also makes sence as cures for rusty barrels.
But breakfluid just gets the rust going after u clean it away,so some other threatment may be adviceable.0 -
cheeze,
The CB 750's were a breeze to work on and they used to be an easy motor to build up. They were a well balanced bike, and extreamly dependable. There are still lots of parts to be found for them. The heads come off easy enough. I would try and pull them and put a new jug & piston kit on it. The only tricky area is making sure the cam chain gets put back together correctly. You can even find used ones that may work well, and cost less. The weakest area on these bikes was the case strength. The main drive chain must be kept tightened. If it gets lose, and it raps around the front sprocket it will crack the case. I had this happen to my 1975 CB 750. Seeing how I had to tear it all down I went ahead and upgraded it to an 836 kit, and added an ATC turbo charger. After everything was said & done this bike was a 10 second ride. That was quick for a bike back in 1978, but these days they come off the show room floor smaller & quicker.
Warning, if you do a build up make sure you put stronger head bolts in to hold it all together. I didn't do this on my first up grade, and after the Turbo was finsihed tearing things up I went to a beefed up 1100 kit. This caused me to have to beef up the swing arm, clutch, and many other parts a swell. The thing was a beast, but fun to ride.[:D]
Good luck, and send us some photos.
Trinity +++0 -
clean the gas tank with electrolysis:
http://twinoak.altelco.net/~jacil/clay/motorcycle/KElecSetup.html0 -
There is nothing more expensive than a free motorcycle. [:D] 0 -
quote:Originally posted by Jgreen
There is nothing more expensive than a free motorcycle. [:D]
[:D][:D][:D]0 -
why spend the time on it? sell it to a motorcycle junkyard and buy one that runs. 0 -
Alright! Thanks to everybody for the good info, except buschmaster jeez. I'll keep coming back with updates and hopefully post pics for you! 0
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