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Discussion in 'Old's Cool' started by myblubeemer, Oct 23, 2007.
I don't buy that "they all do that" because my '81 sure doesn't....
Maybe the problem is the '81!
Have you checked with Perry on this? I admire your desire to sort it out yourself but I would make the call.
A close comparision will show why the later models "all do that" to some degree
For some reason the second one did not come up. darn firewalls
Balancing and adjusting the carbs goes a long way towards eliminating the rattle at tickover. My 87 G/s used to rattle quite badly with the carbs out of sync until I rebuilt the gearbox. The roller bearing on the input shaft seems to be the culprit, since replacing the bearing there isn't a sound from my gearbox even when the carbs are out of balance.
My 91 Paralever GS has the same rattle even though it's only got 30k on it. I'm going to rebuild the gearbox over the winter, it will be interesting to see if it disappears on that bike as well.
They all do that sir.
Nature of the beast.
Don't worry about it.
Don't waste time mucking about with throwout bearings.
If you want to minimise the rattle, careful carb synching helps as Rob says above, and adjust the idle speed to where it is quietest, in the specified range of about 800 to 1100 rpm. The 1000-1100 range works better on the 81 and onwards light flywheel models, I have found.
Putting molylube gearbox additiive or colloidal graphite additive into the gearbox oil can help too. Seems to thicken up the gearbox oil and stops the gears and things rattling about inside quite so much.
If your cam chain is warn enough to be creating a ghost image when you strobe the timing marks, this is probably contributing to uneven idle and bouncing things around too.
Either way, it is nothing to be worried about.
Be more worried about loud whining noises coming from the gearbox under laod in the lower gears, indicating worn bearing or gears.
And be very very afraid if you find rough, abrasive, sandy feeling grinding paste stuck to the magnetic gearbox drain plug at oil change time. It is normal to have a light, feathery fluff stuck to it, but not the gritty bits that indicate gears or bearings inside coming apart.
Y0ur gearbox is the achilles heel of the Airhead, so change the oil with every engine oil change, not at every second change like the manual says.
And make sure that where the speedo cable goes into the gearbox, the rubber cover is in good condition, sealed up with Silastic and a cable tie. Water runs down the cable, past a perished or loose rubber and gets into the gearbox oil and breaks it down. This is a major cause of rapid wear.
A lot of Airhead riders swear by full synthetic gearbox oil and say it doubles the life of the box. I have no experience with it over long mileage, but have found that it is a bit "thin" - even the 90wt, and increases the rattle you are suffering.
HTH, and enjoy your great old bike.
Is that really in the manual?
Thanks for all the good advice! Makes sense as the rattling is not nearly as bad at 1100 rpm as it is at 800.....carb work and synching is also in order.
My Airhead has it .... exactly as you describe it. It's louder when the bike and trans are cold which rules out trans oil thickness and the noise being in the trans. It's loud at 800 RPM and gone by 1200 RPM. I keep the idle at 1000 RPM. Can't hear it with earplugs ..
Other BMW's I've had with dry cluthces also had clutch noise to some extent. I've experienced clutch noise with several bikes but never had a clutch failure over ten's of thousands of miles.
Pre 1981, the flywheel was actually a flywheel with some serious heft. I imagine it did a lot to smooth the engine pulses at idle. The stamped steel thing with a ring gear on the '81 and later makes shifting lighter and helps the engine acceleration but allows those pulses to rattle things unless things are synched really well.
Yep. For the Airheads, the BM owners manual specifies 7,500km engine oil change and 15,000km gearbox/shaft/bevel oil changes. Most old bikes with separate gearbox oil were like that.
But with the gearbox being the Airheads weak link, I reckon it is worth changing the gearbox oil at the same time as the engine. It allows you to keep an eye on the metal fragments on the gearbox drain magnet too. It can mean the difference between having to replace $300 worth of bearings and seals and having to replace $1200 worth of gears as well if excessive wear is detected early enough.
I change the engine/gearbox/shaft/bevel oils every 5,000km, which is once or twice a year for me, just to be safe.
Oil is cheap. BM gearbox parts and the special tools to install them are painfully expensive.
I change all the fluids from the tranny back once a year, but I didn't realize that the manual stipulated it. For me, my bike gets a little hard shifting toward the end of the season, and the oil change brings it back.
I just didn't realize I was doing right by the manual. I thought I was being a little anal...
My '93 R100 GS/PD has a clatter at idle with the clutch lever out. It goes quiet when the lever is pulled. It worried me for a while after I first bought the bike but I came to accept it and it doesn't seem to get any worse. If it annoys me sitting at a light, I just pull in the lever.
I know it's from a ways ago but reading all the posts has calmed me down about my clutch chatter! Thank you all! Best wishes.