Topic: 1976 cb750A barn rescue, running but chatter/rattle at low RPM

[tittymonster]

I was hoping to find an educated guess on where to look..the bike has been sitting for 15 years, YES 15 years in a barn in North Florida..so long the brake fluid turned to dust, didn't know hydraulic fluid did that..Anyway, I got her running in about an hour and at low RPM it has a metallic rattle like a cam chain is loose...I have done 3 oil changes on her after a 15 min warm up between oil changes, it still looks like coke-a-cola...before I tear into it (if its worth tearing into) is there anywhere else it might be coming from?
>>ALSO I understand the carbs on the 1976 are 24 MM and they don't make a rebuild kit for it, the 1977 & 78 are 28MM and the kits may not be interchangeable...any advise or websites to order a kit from..
Thanks

[tramp]

you really need to go into everything on that old of a rest period, to be safe
even the wheel bearings and tires because they are probable dry rotted

[nickjtc]

What tramp says. Plus do a complete tune up before you start tearing into anything: plugs, points, condenser, balance the carbs etc etc. Check the state of the air filter. You might want to put some Sea Foam into the oil just before you do the next oil change. Sea Foam in the gas won't hurt, either.

[tittymonster]

YES the tires are trashed, the top end was rebuilt before it was stored and all new cables and brake lines were installed.theres no rust in the tank and no smoke when running, they put marvel mystery oil in the cyl's.of course the started relay went out on the thing after a few times.this is my first rehab project of a bike, i always screwed around with the honda z50's when i could find them.. stupid question, what is sea foam?

this is a great site, thaks for the advice

[nickjtc]

http://www.seafoamsales.com/buy.htm

Previous thread here:  http://forums.sohc4.net/index.php?topic=13927.0

[sidematic]

I rebuilt and sold a 76 750A last year.  The chatter at idle is normal and coming from the tranny on the right side.  In gear it will rattle much less.  If you decide to rebuild the motor buy a head and carbs from a CB750, you will pickup more lower end power and the 2 speed auto needs it.  If you have other questions, I will try to answer them.
                    Barry

[fuzzybutt]

i know on the 5 speed 750's poor carb sync will make it rattle badly.