Need Some help

[78cb750ss]

hello and thank you all for taking the time to look and hopefully help me out a bit. I just bought a 78 CB750 super sport from some guy for 300 bucks. it was sitting in his garage for the past 10 years. i brought it home put some gas in it checked the oil and gave it a try. She fired right up but sounds like the timing chain is ratteling. The bike has 26k miles on it. It only rattles real bad at like 1200 rpm and less. i was looking though the old repair manual i got with it but its not a very good one. And i was wondering what all else i should do to this since it has bin sitting for so long. I am pretty good mechanicly but this is my first bike and im used to cars, so all the help i can get would be awsome. Thank you

[pat english]

78cb750ss wrote

hello and thank you all for taking the time to look and hopefully help me out a bit. I just bought a 78 CB750 super sport from some guy for 300 bucks. it was sitting in his garage for the past 10 years. i brought it home put some gas in it checked the oil and gave it a try. She fired right up but sounds like the timing chain is ratteling. The bike has 26k miles on it. It only rattles real bad at like 1200 rpm and less. i was looking though the old repair manual i got with it but its not a very good one. And i was wondering what all else i should do to this since it has bin sitting for so long. I am pretty good mechanicly but this is my first bike and im used to cars, so all the help i can get would be awsome. Thank you

dang bro,you scored.i just got a 74 for 1600.it seems like you already know whats wrong with it though.if you think the timing chain is loose or the tensioner is worn out,then you should open it up and check it out.
im new to these bikes too,but i think you gotta drain the oil first to do this.dont be scarred to brake somthing just take it apart.i mean,you ony paid 300 anyways.OPEN THAT BITCH UP AND POST PICS IN THE BUILD THREAD!!!!!!
                                 

[Re-run]

Good chance the cam chain is rattling but it is likely to be a good chunk of clutch rattle too.
Get things cleaned up good first. From there, pull of the cam chain tension unit. There is a gasket here, it is not very important just do not tear it. hold your hand over the open and and slowly loosen the lbolt that holds the tensioner. The rod might be stuck but if not, it will spring out. If stuck, twist and pull and it will pop out. Clean it and put it back together. Stick it on the bike and loosen the bolt to give it a base line tension.

From here the next thing is to pull the carbs off and clean them. Now the air box gives people trouble, remember that it splits in half! You have 2 bolts that hold it to the frame, well immediately below those bolts are 2 more bolts, 1 on each side. It you loosen these, the bottom half will come off.
Once the air box is off, loosen the manifolds on the carb side so they stay on the engine.

Now at this time, download the manual here for the 78k/f and clean them carbs till you would drink out of them and then clean them again. Clean EVERYWHERE, the fuel lines, the accel pump unit(might need to be replaced if any tears), clean everything! I can't stress it enough on the 77/78 bikes. I have seen many times where even a shop cleans them and there is crud left over. A very common place is the idle jets. Being pressed in, many think they cant be removed. BUT they can! Just wrap a cloth, piece of rubber, something, around the jet and grip with pliers. Twist and pull. You might have to twist back and forth a bit. Do not wiggle them side to side if you can help it, You could crack the housing and that means in most cases, replacing that carb.

Now get a couple strands of fine copper and gently clean each and every hole twice and spray with carb cleaner to wash out.

From there, follow the manual and it will tell what all your base settings should be.

This is your starting point for tuning the bike.

Above all, get the manual. It will save you some head beating!

[78cb750ss]

kk thank you all for the advice so far. I do have a manual but its not a good one. The cam chain tensioner is located under the silver plate on top of the bottom end correct? just want to ask that and get ready to start working on it. i wanted to start today but it rained so i should just get all my facts stright and be as ready as i can before i start.

[Re-run]

Down load the manual we got here. It is the actual honda manual, not a clymer or haynes.
That cover is for the starter. The cam chain housing is mounted to the jugs.

[spliffy]

hi the one thing with cb750 is the engine rattle it normally is the clutch plates if you start engine then pull clutch lever in you will find the rattle goes i have been told although i have never tried it you can subbstitute goldwing clutch plates for 750 ones i have just got one that was stored for 10 years by my nephew who spent a thousand pounds rebuilding engine with new cam chain still rattles but goes quiet when pulls clutch in just buy loud pipes for it and carry on riding

[Re-run]

The main reason for clutch rattle is carbs not being synced. A good sync will get rid of much of the noise.
After that, the k7/8 77/78 clutch packs have an extra plate in them which cuts down on it too.You will never totally get rid of it though. Just the nature of the engine.

[vern401]

they have the honda shop manual on this site for your bike I sugest downloading it. I have the same year and model you do. When I got mine I started by going through it and looking for anything that just wasent quite right. Cam chain carbs new battery cleaned wiring connections, New plugs, new Air filter and changed the oil and filter. Rebuilt the front master cylendar It was nasty, the calipers were ok but I rebuilt and cleaned them any way to avoid future problems. working on the rear master now.
Very true ReRun