Topic: I bought my first bike! ... and I have questions :D

[750fromhell]

Hey guys,

Great to be here. 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.





As you figured out, I'm not much of a mechanic, but I accomplished so much already thanks to Oldman and Socal, I'm looking foward to put her back on the road ... and even learn how to ride 

Thank you for having me here, cheers!

Oli.

[UnCrash]

These bikes have a "wet" clutch system so oil should be there.  If it wasn't it would be a problem 


Cam chain adjustment procedure can be found in the manual.  I found it to be pretty straight forward if your cam tensioner isn't frozen.  You can find more info here ---> http://www.sohc4.net/index.php?title=Cb750tech#Books.2C_Manuals.2C_and_Guides

If your cam tensioner is frozen, unbolt it from your engine and use some WD-40 to clean out and lube the sliding piston and pad.

Best of luck with getting her back on the road.

[MJL]

Clutch yes, alt/gen no.

Are the carbs snapping closed, or are they slowly closing themselves? If they snap closed I'd think they are on the rich side, maybe have the idle air screws too far open to.

I'm not a carb guy, I just know enough to make mine run.

[Johnie]

I see the shaft for your starter gear is still in the housing.  You may want to put that back in along with the washer before you lose it or the gear.  And just to save you some aggravation, be sure you put some sealant on the rubber grommet that holds those stator wires.  Those leak from time to time and you think it is the gasket when in fact it is that rubber area.  Here is a pic below of my grommet area that leaked until I resealed it.  This board advised me there is oil behind the clutch cover and the stator cover on my KO.  Someone will have to chime in about the 750F. 

[eurban]

Carefull y'all, wrong info can be worse than no info . . .On the left side of the engine there is the alternator cover and the shift mechanisim cover.  The clutch is on the right side of the motor.  On the 750, there is supposed to be oil behind both of these left side covers except behind the "wire chase" at the top of the shifter mechanism cover. . .  .Your engine's failure to return to idle speed could be a few things but a likely culprit is carbs that are significantly out of synch. 

[MCRider]

Clutch yes, alt/gen no.

Are the carbs snapping closed, or are they slowly closing themselves? If they snap closed I'd think they are on the rich side, maybe have the idle air screws too far open to.

I'm not a carb guy, I just know enough to make mine run.

OOps there, the 750 alternator does run in oil.

[mrbreeze]

I'm with Eurban....for sure carb synch.If everything else is in order (fuel,ignition,timing)....you should be golden after a proper carb synching.

[750fromhell]

You guys are awsome, I am so thankfull. So I'm just going to reseal the "alternator" cover, the shift mechanisum cover since oil in the alternator casing is normal.

The #1 carb is overflowing fuel by the fuel hose that connects to the bottom of the bowl when I'm not runing, maybe my float height is not correct.

So to do .....
Check the valve clearance.
Adjust the timing chain as per the link provided.
Do the timing.
The carb synch.

Thank you again, I'll post a picture to share when I'll get her runing right.

Cheers!

[eurban]

You guys are awsome, I am so thankfull. So I'm just going to reseal the "alternator" cover, the shift mechanisum cover since oil in the alternator casing is normal.

The #1 carb is overflowing fuel by the fuel hose that connects to the bottom of the bowl when I'm not runing, maybe my float height is not correct.

So to do .....
Check the valve clearance.
Adjust the timing chain as per the link provided.
Do the timing.
The carb synch.

Thank you again, I'll post a picture to share when I'll get her runing right.

Cheers!

Fix your overflowing problem(s) prior to synchronizing your carbs.   If you haven't cleaned and baselined your carbs yet, consider doing that too.  Your float levels may be out of adjustment but its just as likely that the float needle, seat, and or pivot pin may have issues. When you take your carbs off to clean / adjust / inspect  them, bench synchronize them (search this subject from the "SOHC/4 Bikes" page.) This will make the later gauge synching easier . . .A gauge carb synch should be done after a complete tune up and after you have determined that all of the bikes systems are actually functioning properly. 

Edited 6:30 on 8/7 to make sense!  Sloppy writing the first time . . .

[750fromhell]

Thx Eurban, I'm not a expert but I think I did a good job at cleaning my carbs. It must be my floats height then.

[mj_honda]

I haven't done a rebuild on your type of carbs before but on my 78K the slow jets needed to be cleaned. Mine are not supposed to be removable but they are. If they don't get cleaned the carbs no workey rightey. Yours might be different.

[eurban]

Thx Eurban, I'm not a expert but I think I did a good job at cleaning my carbs. It must be my floats height then.

Certainly check your float height.  If that doesn't take care of it, consider  . . . . It is fairly common for float needles to stick open upon carb reassembly.  A whack on the bowl with the plastic end of a screwdriver will sometimes get things into proper alignment. . . . There can be burrs on the float pivot pin causing sticky action. . . . When you start with badly mucked up parts, sometimes it isn't posible to clean them.  Things like pitting on the needle seats, and non functioning spring pins on the float needles (spring loaded pin that should move in and out of the non sealing end of the float needle <i believe your model has this type of needle?>) . . . . The fuel overflow standpipes can develop cracks allowing fuel to leak from them no matter how well the float is sealing. . . .Have fun and don't forget to bench synchronize the carbs while you have them off to work on.  That should eliminate synchronization issues as a cause of your bike's sluggish return to idle speed.

[bggann]

Add an in-line fuel filter if you can (I have a 400, so not familiar with a 750).  In mine, this solved the "overflow" carb problem which kept happening.  Would keep picking up junk from the tank.

BG