Topic: 550 gearbox noise?

[Philly550K1]

is it normal for the transmission to be perceptibly noisier as it heats up?  i'm fairly certain it's the gearbox; it's definitely the left side of the bike as i ride.  my camchain and tappets are to spec and quieter now, so these things get noticed.  oh, and i repacked my megaphone. 

some time after i changed from 10W40 to 20W50 this spring, i noticed some gearbox noise (left side of bike) after a highway stint.  it was still unseasonably cool outside back then, so i switched back to 10W40 just to see.  the oil weight didn't seem to make a difference; there's just a noticeable faint hum/whoosh (i hesitate to say "grind"), in gear, rolling down the road, after a highway stint that remains until the bike cools for the next ride.  the manual says either 10/40 or 20/50, so i believe i'm "safe" on that issue.

i'm hoping it's just normal that as a gearbox heats up, things expand enough that they rub each other a little more, hence more noise hot.

anyone?

-jc
75 550K, 28,000 miles

[TwoTired]

Well, I don't want to start a rukus... But, are you using Auto oil or motorcycle oil?

Also, are you sure it's gearbox rather than chain/sprocket noise.

There is a metal "guide" mounted to the case in front of the sprocket.   I had a mounting tab break and that allowed the bracket to sometimes graze the chain.  Strange noise.

Er, did you put an oring chain on the bike?

[MetalHead550]

Yeah, you may want to pull your left engine cover and check your front sprocket for wear and make sure all is well there.  Is your chain properly adjusted and cleaned/lubed?  Like Two Tired said, beware if youre using an o-ring chain....believe me I know...

[Philly550K1]

i've used both types of oil.  now it's MC oil.  otherwise it's been Castrol GTX (mind you, i've only been the owner a few years, now).  i believe i've ruled out chain and sprocket noise.  yes, it is an o-ring, but it's a 520 w/520 sprockets; a whole trouble-free season plus on that.  and i just peeked in there recently, and nothing appears to have been rubbing anywhere it shouldn't.

this "guide", you mean the one on the cover, or on the engine case itself, lloyd?

-jc

[jsearle]

I have a similar noise coming from the gearbox on my 400/4 I use Castrol GTX.  the bike runs good, but when pulling away from a standing start it feels like the chain has jumped a cog.  The bike has new chain & sprockets and is adjusted correctly.  Any ideas ??

[TwoTired]

It's mounted on the cover.  If there is a problem with rubbing, you should see marks on it.  Unless you are really good with mirrors, you'll probably have to take off the cover to check it.  But, that's still much easier than splitting the engine cases to check for bent shift dogs.

Does the noise go away in some/any gears?
Does your shifter still feel solid?

[78 k550]

Isn't SAE 10-40 oil  oil. I didn't know they made a special m/c oil.

I just talked to my friendly Honda dealer ex Bultaco guy and knows his stuff and won't bs me. He say's the only thing he would use is GTX but not forever. Addatives in car oils will coat the cluth plates and is hard on trannies. especially penn. and Quaker State.
 I'm headed to the dealer for a filter and Motorcycle oil.

[78 k550]

How many mile's are on the Auto oil? I would say if more that 500 or 600 then your clutch plates might already be coated.

[Philly550K1]

my "peeking" alluded to earlier did involve removing the cover -- no scrapie scrapie.

golly, it's hard to keep that oil debate at bay, isn't it?

the more i listen, the more i think it's just me hearing what i couldn't hear before with a louder pipe and rattly chain and valves (although i can still hear the valvetrain making normal noise separately - this noise is further down, sounds like).  gears can't be expected to be silent, right? especially after 28,000 miles?  it's just a faint but discernible whine.  somewhere between a whine and a "shhh".  it's not just in one gear, but most noticeable in 5th, and more noticeable after running at high speed for a while.  that's the part that caused me to even bring it up, as it's not that alarming a noise.

the shifting is fine, no slippage, not much lash.

perhaps a tired bearing somewhere in there? are there particular parts that tend to be worn by now?  on my older cars, pilot bearings go into retirement and hiss until clutch time.  anyway, just something to talk about....

-jc

[dusterdude]

does honda use a throwout bearing?

[jsearle]

Ref.400/4 g/box. the clutch seems fine I like your idea about a cog being damaged
I think a stripdown is needed, pity cos the bike runs well.

[Philly550K1]

looking at the exploded diagrams in the 500-550 manual, there are bearings on the left side of the gearbox, two ball and one needle.  the 550 addendum shows a "trochoid pump" bearing on the right side.  the description states that the oil is fed to the right side of the countershaft.

continuing to ponder, listen, and peruse, it sure makes sense to me that i'm hearing a bearing. 

1) does anyone find "typical" bearing seizures on tearing one of these down?

2) is there a reasonable procedure to undertake short of cracking it open?  does that oil screen plug up?  i'm wondering if i can make sure the left side of the box is getting the oil it wants.  worth dropping the pan to inspect?   my valvetrain looks nice and oily up top, so i take it in general my oil supply is happening to a sufficient degree.

cheers...  -jc