Topic: high speed weaving.... disconcerting.....

[Henry Dorset Case]

I did 410km (say 250 miles) on my 400F on Saturday.

observations:  I had a little givi  aerostar fairing on the bike but I find it better to ride without the fairing... plus the bike looks better with it off.

at a 100kph (say 60mph) cruise there are few worse places in the world to be than riding an old honda SOHC.

a 400cc motorbike goes pretty damn well, considering its nearly 30 years old and all.

the one dark spot in an otherwise bright day was when tapped out (say 150kph) when passing an idiot who decided he wanted to race.... (and by that stage I was COMMITTED ! ) was a low frequency weaving.  Its about the same frequency as the 60kph deceleration wobble that most old hondas I have ridden seem to have.

and thence to my question:

steps to cure the weaving:

remove fairing (yes)

check steering head bearings
check swing arm bushes
check forks are straight.
check wheel alignment
ditch comedy 30 y.o. shocks.


any thing else I should try?

(It has near new, well balanced tyres  Pirelli City Demons... they're excellent)

[bwaller]

 Are the wheel bearings ok, are the spokes tight, are the rims true?

[Lumbee]

..I'd say if you truly want a smooth ride at hi speeds cover all the basics first:

-good tires
-rims balanced/trued
-rear wheel centered and true
-good bearings...

...I'd think that would do it.  I always feel like the front end of my 750 gets "light" over 80mph.  I've only been riding these bikes less than a year, but I find my self getting increasingly confident the more I ride.  I was rolling around 85mph on the interstate pretty comfortably today.  The actaul speed doesn't scare me as much as how the bike would react if an anomoly would occur at that speed.

[Terry in Australia]

G'Day Henry, I reckon you've answered your own question, but the first thing I'd do is ditch the fairing, most handlebar mounted fairings will induce a weave at high speed, whereas a well designed OEM frame mounted fairing (like my old BMW R100RS item) will generally be of benefit.

I took the "full fairing" off my "boomer" (a "beemer" is a car) one summer and fitted a genuine R90S fairing with fatory brackets etc, and nearly killed myself at around 130 Mph when it got as close to a "tank slapper" as I ever want to experience. I sold the bike with the bikini fairing in place but warned the buyer to keep to highway speeds, but never heard from him after that, so I hope he's ok?

I bought my Suzuki GS1000S (Wes Cooler replica) with the fairing already removed, so I put it back on, and by christ, it nearly happened again! Bugger that, I took it off, hung it on the garage wall, then took the bike out again and crept up to 145 Mph, and it's as stable as a mack truck. All the other possibilities are certainly contributing factors, but my guess is that the fairing is the culprit. Cheers, Terry.  

[carsholduptraffic]

i pulled a 230kph run out of the 836 when she was fresh, and it meant taking off the mirrors! it pulled 210 with them on, but with a big slow weave, that was getting wilder as i went faster. with the bike on 7500-8000 in top (things were shaky) it was scary. this was on a freeway (south of tweed heads). no mirrors on the return had it hauling smooth as a cb will ever get. it pulled to 230 but that was 8k and i thought that was enough.
p.s. noticable wear noises from motor after that.

[Terry in Australia]

p.s. noticable wear noises from motor after that.

I reckon I'd be making noticeable noises from my trousers, ha ha! Cheers, Terry.

[78 k550]

Terry,]
 You have a r100? I have a chance to get one. It is in a Junk yard. It is ok shape but he want's 1,100 for it.

Paul

[Terry in Australia]

Terry,]
 You have a r100? I have a chance to get one. It is in a Junk yard. It is ok shape but he want's 1,100 for it.

Paul

What model mate? Mine was a 1979 R100RS, great highway bike, torquey engine and  handled really well once I ditched the Metzlers and fitted Bridgestone BT45R tires and Koni shocks and progressive fork springs, and with that beautiful fairing I could ride it in a torrential downpour and as long as I didn't have to stop anywhere, I'd stay as dry as dust! I think I might have to buy another one, ha ha!

$1100.00 is ok if the engine's good, mine wasn't and it cost me 4500 for a "specialist" to rebuild the engine and 'box, but the bike had done over 120,000 miles, and hadn't been well maintained by it's one careful owner and the other 11 careless ones! You could rebuild it for a lot less now that Ebay is the first place to look for spares, but this was pre-internet days, (I owned it for 12 years) so I paid for it "through the nose", ha ha!

If you can get them to start it mate, don't be worried by top end rattles (they are noisier than jap fours but with the valve clearances done properly they're quiter than Moto-Guzzi's and Ducati's of the same era) but beware of bottom end "rumbles", they're expensive! Lemme know how you go? cheers, Terry.

[damn_yankee]

That's a very good price out here in California for an R100 (any model).They are very solid and easy to work on. First gear will make a loud thunk when engaged but that is normal.