Author Topic: I would like to hear your .02 on my 75 cb750ss. 1st timer here, looking to learn (Read 5407 times)

75 super sport · « **on:** February 25, 2012, 02:33:53 PM »

I recently bought a 1975 Cb750 super sport that has been sitting a very long time (10+ years.) Cosmetically the bike looks very sound, it has good compression and has just over 13,000 miles. I have not tried to start the bike yet, I was thinking about just pulling the motor, inspecting valves, pistons, rings and replacing the seals for the top end before I even attempt to start the bike. I'm just not positive on where to start, I feel since its been sitting so long it would be the right thing to do, any advice? Like I said, I am new to the hobby and I am ready to start learning about my Cb750. So any advice is greatly appreciated. I do know basic knowledge of motors, carbs, little of electrical, etc... Thanks!

seanbarney41 · « **Reply #1 on:** February 25, 2012, 02:49:52 PM »

if it has good compression...why? Make sure you got oil circulating, check for spark, throw some gas in and fire that bad boy up...it will probably run bad...then you have to do the whole 3000 mile tune up regimen (get a manual!) after probably cleaning/rebuilding the carbs

75 super sport · « **Reply #2 on:** February 25, 2012, 02:56:20 PM »

Thanks man, any advice helps. Probably would be smart to just make sure I have the 3 elements of a running engine and see where that takes me.

Stev-o · « **Reply #3 on:** February 25, 2012, 03:04:49 PM »

first off, welcome!

+1 try tostart that bad boy. At 13K miles, it should not need a rebuild of thevtop end.
But your carbs may if they have been sitting with gas in them.
Get a new battery, then check spark...

grcamna2 · « **Reply #4 on:** February 25, 2012, 03:10:23 PM »

I would shoot a bit of light weight oil into each intake port when the carbs are off and spin it over for a while to start the juices flowing...and a fresh oil change w/ 10/30 before starting.

75 super sport · « **Reply #5 on:** February 25, 2012, 03:27:27 PM »

Awesome guys, great pointers. Keep em' coming! Thanks alot

bharvey60 · « **Reply #6 on:** February 25, 2012, 03:32:15 PM »

If it sat with gas, you'll need to clean and possibly rebuild carbs. also take the bowl off the fuel petcock, clean screen and check for correct operation, replace spark plugs, oil, oil filter and air filter, clean and gap points. Connect to a decent battery. After that, you'll have a much better chance if success when you hit the starter. Get Hondaman's book and follow it. Just went through this with a K3 that sat for close to 15 years with gas in it. Amazing how strongly old gas bonds carb slides

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I am here: http://maps.google.com/maps?ll=40.783211,-77.907215

75 super sport · « **Reply #7 on:** February 25, 2012, 03:37:46 PM »

So @bHarvey, did you get the bike running after just the tune up? and how did it run after you got it started?

RSchaefer · « **Reply #8 on:** February 25, 2012, 05:04:10 PM »

I too have a "75 SS with just under 13K that I am rebuilding. When I got it (circa '95) I took the carb's apart and cleaned and put back together and got her running albeit not really well. I did run through the gears for sure. It then set for another 15 years, I got interested in a total restoration, found this forum (best thing that ever happened) and I went back to it early last year. I decided to pull the motor and do a variety of upgrades, paint frame, upgrade swingarm, put in All Balls in the triple clamp, and generally try to do reliability and safety upgrades, electronic ignition. One of the 1st things I did was to purchase Hondaman's book, which you should consider.

When I pulled the engine I decided NOT to pull the head. I did compression checks and they seemed OK, not great. I continued to work on various parts, speedo faces, etc. and for some reason finally decided to pull the top end (kept gnawing at me). Boy am I glad I did. Turns out the valves and seats are spotted (rust), probably from moisture. Obviously not all valves were closed while it set for 15 years. I am now in the process of having a valve job done, milling .0010 of the head and .0005 off the cylinders, ordered new rings and will hone the cylinders. Also as Hondaman recommends, porting the inlets and exhaust and removing flow issues on the chambers and cylinders for the inlet valves.

I am going to feel much better about this motor once I get it back together so if I were you I would take the top end apart. Pulling and replacing the motors is a real pain, might as well do it right while you have it apart.

octagon · « **Reply #9 on:** February 25, 2012, 05:37:12 PM »

i think - this is about 2 cents right - if the motor turns over and you have good compression you're crazy to pull it and take it apart. if you're just learning, learn how to do carbs, a tune up, oil change.

brandEn · « **Reply #10 on:** February 25, 2012, 05:47:20 PM »

Sounds like you got a good bike. 13000 is just broken in. I would clean the carbs, put a new battery and plugs in it, change the oil and fire it up. Flush the tank and be sure to check the tank and make sure there is no rust floating around. If all is well then brake rebuild, new fork oil, change the tires and ride it! Spend a weekend working on the routine stuff and you will have a runner.

75 super sport · « **Reply #11 on:** February 25, 2012, 06:07:54 PM »

Thanks for the advice fellas! I agree, the best thing to do is get my spark, fuel, and air situations worked out and try to fire that bad boy up. It's a much better way to get a grasp on things then to pull the motor right away, especially @ 13,000 miles. The bike still has a long way to go from what i hear. Thanks again guys, keep it comin

Stev-o · « **Reply #12 on:** February 25, 2012, 06:24:26 PM »

Can you post some pics?

Flying J · « **Reply #13 on:** February 25, 2012, 06:28:38 PM »

Im with brandEN. I just went through the same thing with a 550. My list for a new bike is:
Try and start it..
Clean the carbs... try and start it
adjust points and timing...try and start it, usually by this point it starts and i ride around the block a few times to see what rattles loose, how the bike rides and any funny noises or handling issues.. Then i do all the other adjustments like valves and timing chain.
And then i move on to replacing consumables like brakes, chain, tires, air filters. So that i know how many miles those things have on them.

Thats how i do it.

tlbranth · « **Reply #14 on:** February 25, 2012, 07:09:31 PM »

I'd also pull the plugs and shoot a little oil in each cylinder, let it sit a day or two and then kick it over a few times without ignition or fuel - just to get the rings & cylinders lubed a bit. If ambitious, you could undo the valve adjustment caps and shoot some oil onto the valve stems and cam lobes too. I'd put new oil in before firing and change it after running the engine for a few hours.
I'm sure you'll have to mess with the carbs eventually but right off, I'd put in plugs and clean the points, lube the point cam and static time the engine.

BeSeeingYou · « **Reply #15 on:** February 25, 2012, 11:00:16 PM »

I have a 76 750SS that sat for 25 years and this is what I did. It had been stored with gas in the tank but the petcock was shut off so gas had not evaporated and made a mess of the carbs. Pull the carb bowls off and this will tell you how bad they are. All I had to do was remove the jets for cleaning and only one slow jet was blocked. I did not have to remove the carbs. The tank had a lot of varnish from the gas but minimal corrosion but it took awhile to get it clean. After the tank cleaning get a new petcock filter. My brakes were locked up so I rebuilt both MC's and the calipers. Pull the plugs and put a small amount of oil, tranny fluid, or 2 stroke oil into each cylinder. Drain the oil and change the filter. When you add the new oil save a quart and put it into a squeeze bottle so you can squirt oil into the top end through the tappet covers. Just put in the required amount. This is a dry sump engine but when they sit the oil can drain into the crankcase so it can look like it is low. It's not a problem but always check the oil right after running the bike. With the plugs still out use the kicker to turn the bike over 10-20 times. Clean the plugs regap and install or get new ones. Check the points and clean them off with a point file. Mine fired up on the third kick after that and has been running fine for 3 years with no problems or issues. You will want new tires and change the fork oil too. Check the air box to make sure no mice have made a home and put a new air filter in. It might smoke a bit for a short time (mine did for a few hours) if the rings need to reseat.

bluesmoke69 · « **Reply #16 on:** February 25, 2012, 11:20:15 PM »

Buy hondaman's book sold on this site.

750K · « **Reply #17 on:** February 25, 2012, 11:28:29 PM »

Quote from: ffJMoore on February 25, 2012, 06:28:38 PM

Im with brandEN. I just went through the same thing with a 550. My list for a new bike is:
Try and start it..
Clean the carbs... try and start it
adjust points and timing...try and start it, usually by this point it starts and i ride around the block a few times to see what rattles loose, how the bike rides and any funny noises or handling issues.. Then i do all the other adjustments like valves and timing chain.
And then i move on to replacing consumables like brakes, chain, tires, air filters. So that i know how many miles those things have on them.

Thats how i do it.

+1 to that, I bought my wife a 78 cb400t last year for a friend. He left it outside all year uncovered, gas tank half full with the petcock on for 2-3 yrs...

I cleaned the tank, rebuilt the carbs, new fuel filter, adjusted the valves, fresh plugs, new battery & unstuck the rear brake. Put fresh gas in it and it fired up on the second kick, great little bike once we undid all of his neglect.

75 super sport · « **Reply #18 on:** February 25, 2012, 11:42:02 PM »

Tomorrow i am getting a new battery, plugs and oil. Plan to clean/inspect the carburetor's as well. I have only kicked the motor over and made sure it turned freely, tomorrow I will check for spark, fuel, and air intake issues and see what i come up with. Wish me luck, i'll keep you guys posted.

trueblue · « **Reply #19 on:** February 26, 2012, 01:11:20 AM »

+1 to most everything that has been said, just try and start it up, the only exception is don't use 10w/30 oil it is way too light, these engines need a 20w/50 weight motorcycle oil, whatever brand you like, but if it has been sitting for a long time I would avoid synthetics because it just runs through old seals like they aren't even there.

grcamna2 · « **Reply #20 on:** February 26, 2012, 05:05:51 AM »

I was thinking of having him put in the 10/30 oil just to get it running...just use it to flush out the engine initially...then change the oil and filter after bringing it up to full operating temperature...or after a nice ride

.

Kurt V · « **Reply #21 on:** February 26, 2012, 07:05:05 AM »

I guess it depends on how it has been stored over the years. If it was run into a shed and parked with gas in the tank an carbs you might have to pull the carbs to get the crap out of them. May have rust in the gas tank. Just depends on how exposed to the elements it was.

On the other hand, if the carbs were run dry, the petcock closed, and the gas tank emptied, all you might have to do is just get some new gas and oil in it and off you go.

75 super sport · « **Reply #22 on:** February 26, 2012, 08:35:37 AM »

Thanks for all the help you guys. Off to the store i go to get all I need to see if this bad boy has spark, fuel, or intake issues. Ill let you guys know what happens.

BeSeeingYou · « **Reply #23 on:** February 26, 2012, 11:15:45 AM »

Oh no...the dreaded oil subject. Don't just put anything in there. Some oil has additives that make it slippery which can cause problems with the clutch in these bikes. Oil that seems to be recommended are Castrol GTX, Rotella, Honda and Yamaha have their brands for bikes too but cost more. Add Seafoam to the oil and run the bike for a bit, drain and change again. It's great for cleaning out gunk.

75 super sport · « **Reply #24 on:** February 26, 2012, 01:08:21 PM »

well i am trying to post pictures but its not letting me. it says entity too large. Anyways there is ALOT of white build up in the carbs, is this from old gas or?? any help is appreciated, thanks

Flying J · « **Reply #25 on:** February 26, 2012, 01:37:58 PM »

Get a photobucket account and then post pictures from there. The white stuff is normal. Do you know how to clean the carbs? Its not just the bowls you need to clean. You need to pull every jet and clean every hole to be sure they are clear. Do a search to see how its done.

75 super sport · « **Reply #26 on:** February 26, 2012, 01:48:53 PM »

I am able to clean carbs, it seems like water corrosion, doesnt want to come off worth anything. Are the carbs toast? thanks guys

BeSeeingYou · « **Reply #27 on:** February 26, 2012, 01:52:59 PM »

You can post pictures directly here but you need to shrink them down to under 254k in size. Using photobucket you can post them whatever size they are. If the carbs are really gunked up you may have to do a more complete tear down and cleaning than I had to with mine. Mine were fairly clean when I first opened them up. Let's see what your pictures look like and go from there.

75 super sport · « **Reply #28 on:** February 26, 2012, 02:08:17 PM »

http://i1054.photobucket.com/albums/s492/75supersport/carbcb750.jpg There is carburetor #1 i believe(far left), this is the worst one. The others arent much better. Almost look pitted $:-\$

LesterPiglet · « **Reply #29 on:** February 26, 2012, 02:10:52 PM »

Waters been in there. The brass will be fine but whether you can recover those I don't know.

75 super sport · « **Reply #30 on:** February 26, 2012, 02:16:14 PM »

Here's another. On this carburetor the stop for the floats looks like it may have been eaten away? so the floats just stay wide open and the float valve keeps falling out. http://i1054.photobucket.com/albums/s492/75supersport/IMG_2443.jpg

75 super sport · « **Reply #31 on:** February 26, 2012, 02:19:38 PM »

Whats to say about my motor?? Is that a real bad sign as far as haveing to pull the motor completely apart?

LesterPiglet · « **Reply #32 on:** February 26, 2012, 02:30:55 PM »

Do I see one of the posts for the float pin eaten away? If you have drained the oil and didn't find any water I think the motor is probably fine.

BeSeeingYou · « **Reply #33 on:** February 26, 2012, 02:48:21 PM »

The fact that the motor turns over is a very positive sign at this point. Did you check the compression with a gauge? The carbs look like you may have some problems depending on how bad the aluminum is pitted or eaten away. Never had to clean one as bad as that but I wonder if something like CLR would remove the white oxidation so you can see what you have. Simple Green is often used to clean carbs of gas varnish but not sure if it will remove this. We have seen some pretty wretched stuff brought back to life here so don't get to far ahead yet.

75 super sport · « **Reply #34 on:** February 26, 2012, 02:50:42 PM »

not the float pin itself, but the two towers or supports for the float pin are just about deteriorated. I am pretty convinced a new set of carburetors will be my first investment for the bike. I am more concerned about the other side of those carbs, the motor. What should I look for? Obviously, this is because water had been there, but is my motor going to look the same way? Thanks for the help guys.

Stev-o · « **Reply #35 on:** February 26, 2012, 03:17:26 PM »

To post pics:

Open a free acct at photobucket.com
Then, look here...

http://forums.sohc4.net/index.php?topic=70243.msg779527#msg779527

The white stuff is corrosion.

News:

Author Topic: I would like to hear your .02 on my 75 cb750ss. 1st timer here, looking to learn (Read 5407 times)