Bought my first bike, woohoo!

[SFRT - Frenchy]

I bought my first bike ever, a 1975 CB750F from a guy that ran the bike to the ground and couldn't get her to go anymore. After cleaning her up for a couple of days, changing the coils, spark plugs, new A & B throttle wires, redoing entire electrical thanks to oldmanhonda.com, and cleaning the carbs thanks to SohcCBs, I finally got her to run.

Throttle response seems great, I do have some issues that maybe some comunity member can help with.

1/ When I rev up the engine, the RPM increase fast, but when I left the trottle snap back to idle the RPMs decrease very slowly. Takes about 5-8 secs to come back from 4K to 1.5K. I do see the slider cylinder rod push all the way back in, so I'm thinking the "butterflies" close.

2/ How can I adjust the tension of my cam chain? I ear a pretty loud rattle from my engine.

3/ My left side case was leacking oil from the bolts. I opened it to find what seems to be an alternator mechanisum. Is it supposed to be drenched in oil? Same with the clutch mechanisum? I attached some pictures.





Hopefully will daily ride the thing soon so I can learn how to ride.

[FrodeMk3]

I might ask you if that's an electric clutch, Frenchy, but I don't know enough about Bikes to say for sure.

[MiloMorai]

Clutches are usually 'wet' clutches.

There should be an tension adjustment roller for the cam chain.

[dkff49]

congrats on your first bike.

My first was a yamaha 450  man that thing had so much vibration at 55 that my feet were numbfor an hour after riding for only half an hour.Anyway Inow have a Yamaha V-star 1100 and love it.You will really love that thing after you get the hang of it.

As far as your  questions go. I am no expert and I am sure someone here will be able to help more than I can.

My bike has a fairly loud vibrating noise coming from the engine as well (well maybe not loud but definitely noticeable). I have been told by several people that that noise is slop in the valves, that is put there on purpose. Since the engine is air-cooled they put the slop in there to allow for expansion and contraction. Not sure if that is the case with yours or not but maybe.

don't know about any of the other questions though.

[mora]

1/ When I rev up the engine, the RPM increase fast, but when I left the trottle snap back to idle the RPMs decrease very slowly. Takes about 5-8 secs to come back from 4K to 1.5K. I do see the slider cylinder rod push all the way back in, so I'm thinking the "butterflies" close.

Check for intake leaks and check that idle mixture screws are not broken. Screw them out and inspect them. Setting the idle speed as low as possible might help, but there certainly is a real cause somewhere. I had the same problem with my bike, but it's a single carb and so it's much easier to troubleshoot.

[Maverick]

The Hondas definitely had "wet" clutches. They are supposed to be in oil. I am not sure about the alternator however.

The slow responding throttle could be sticking cables, weak return spring, dirty butterfly mechanism but very doubtful to be air leaks unless it's spitting and backfiring too.

If you can find one I'd get a copy of the Clymers manual for your year and model bike. If not check the used book stores and maybe even the public library for a copy to look at for more info about the bike's internals.

[SFRT - Frenchy]

I did put the carb appart and cleaned/ dipped cleaned everything already. I set the fuel screew to 1.5 turn. Went to ride her, and the thing is screaming with great acceleration (as far as I know about acceleration and bikes as I don't know how to ride). But engine definitly sounds healthy accelerating.





They do look much better after cleaning:







I cosmetic side, I removed the high handle bar and replaced with clubmans. I removed the highway floorboards and replaced with regula pegs. I'm building the tail with fiberglass as a side project. She's going to look like, a 55FG inspired paint. And here's a squetch I did :

[SFRT - Frenchy]

The Hondas definitely had "wet" clutches. They are supposed to be in oil. I am not sure about the alternator however.

The slow responding throttle could be sticking cables, weak return spring, dirty butterfly mechanism but very doubtful to be air leaks unless it's spitting and backfiring too.

The throttle has new cables (both A & B), when I accelerate and let go, they snap right back to idle, I can see the htrottle assembly attached to the carb snap back to idle, I can see the butterflies closing also. Acceleration is immediate, deceleration of the RPM is very very slow back to idle despite evrything "moving right". I was thinking a timing issue, but I would think that would affect both deceleration and acceleration.

thx 4 for the brainstorming 

[Mustaine]

Mine does the same thing... idles 3k + if I let the clutch out a bit with the brake on I can bring the RPM's down to normal idle, and it will stay there.

really odd.


I do know my throttle return cable is stretched out, and I have a replacement, but the throttle arm does go all the way back and it is still doing this.

[633DH98]

Nice looking paint scheme.

Google CB750 groups for help with your troubles.

[mora]

The slow responding throttle could be sticking cables, weak return spring, dirty butterfly mechanism but very doubtful to be air leaks unless it's spitting and backfiring too.

He told that he had checked that the throttle returns. This is a common problem and unlikely to be caused by slow return, as the slowing down period is so long and apparently the idle speed is at a correct level. Little spitting and backfiring goes pretty much unnoticed in an old bike like this. It's not a bad idea to check for them anyway as there more than likely is some. Obviously the problem is caused by fuel mixture entering the engine uncommanded, and it can't be caused by many things.

[mora]

Mine does the same thing... idles 3k + if I let the clutch out a bit with the brake on I can bring the RPM's down to normal idle, and it will stay there.

really odd.


I do know my throttle return cable is stretched out, and I have a replacement, but the throttle arm does go all the way back and it is still doing this.

As I wrote earlier, check your idle mixture screw(s). If broken you'll need to fish out the broken tip somehow. Very common with Mikuni's. Then check the fuel level in the float chamber and check for intake leaks.

[mora]

Oh and congrat's for the purchase! I love old Jap bikes, but I won't get one as they reguire far too much work for every mile driven.

[Mustaine]

As I wrote earlier, check your idle mixture screw(s). If broken you'll need to fish out the broken tip somehow. Very common with Mikuni's. Then check the fuel level in the float chamber and check for intake leaks.

Yeah I have been reading in the Clymer about doing all the carb set up, tools I don't have, don't know, and don't have anyone I know to borrow them from

I plan on trying to tackle it this winter when I have time, now I have to ride it just to survive, otherwise I can't afford food.

[Swoop]

Frenchy,

1st congrats!  Welcome to the fraternity.


The "slow return to idle" issue means the bike is running rich, adjust your carbs and turn down your fuel / air mixture a little.