Topic: Rattle from 750 Hondamatic

[vintage3448]

Hi everyone, My first time on this site. I have a 1977 CB750A Hondamatic. I live in Australia, These were never sold here it was imported from California so no one really knows about them here. It's in very nice condition, Only 8,000miles. Engine sounds great but there's a rattle from the torque converter area. I've pulled it apart and can't find a thing wrong with it( There's really nothing to go wrong it's so simple). Noise disappears as revs increase. Any suggestions please? 

[hendrcs]

That's very common on the 'matics with a few miles on them - rattling sound from the lower end at idle - especially when cold. Goes away as revs increase.
Nothing to worry about unless it starts getting really bad.

[Spanner 1]

I had a '77 'Matic too.  I'd bet ya a case of '4x' the rattle is the primary chain.... very common in the A's.  Unfortunately, the A doesn't have a primary chain tensioner like the K bikes due to 'no room' in the lower crankcase with all the oil pressure lines, oil pump and gubbins for the auto transmission.
It is considered the only weak point on the A motor.   Mine was really rattly, but improved when motor warmed-up, also a carefull carb sync, will also diminish the rattling considerably.... Good luck with your A   

Oh , and welcome to the Forum.......

[vintage3448]

 Greetings from Australia.Thank you for replies, I will have the carbs. tuned and see how that goes.

[dave500]

gday vintage,where are you in aus?im on the gold coast.

[tomsweb1]

Yup, mine clacks a bit 'till you put her in gear. From one I've seen and heard, a good portion of them do!

[jonnycakes]

My "new" '76 does it too.........53,000 miles on it.

[Danno]

my 76 always rattled at idle it would stop when you put it in gear my rattle was from the torque converter and with the few miles on yours it probably is too in one of my manuals it said this was normal till you put it in gear it does not get enough oil so the plates in the torque converter rattle it improves with being warmed up and being ridden more frequently as it is really just a dry condition often from sitting to my knowledge unless it was the primary chain nothing to do about it accept ride it more frequently

[slipnot]

My 77 did the same but after cleaning the oil strainer it improved immensely.  It too had sat for long periods and had low miles when I bought it.  A pain to remove the lower oil pan and get to the strainer but it was pretty gummy from sitting so long, supposed to help engine run cooler too....

[zboy]

My "77 had a rattle at idle and also at about 45 mph. changed the oil to the honda GN4 10w-40sj, the same thing I run in my honda 450 forman 4x4. after riding about 4-6 different times I noticed the noise has now gone away, and the bike really runs quiet and smooth.

[trueblue]

Welcome to the forum, I have only seen one of the A's in Australia, it was at a bike, car and plane show at our local airport.