Topic: Does anybody know whether the CB350twin had an endemic front end wobble?

[Raul CB750K1]

I know, it's not a four, but as it is a frame issue it can have a common solution.

I took a test ride today in my recently-finished CB350 and I've noticed a front end wobble at about 60 mph. It starts as soon as you shake a little the handlebar. The bike, instead of centering itself, starts to wobble. Not to much, but enough to be annoying. Only reducing speed and leaning forward to put weight on the front end does the wobble disappear. At about 90 mph, the wobble starts by itself, much wider and dangerous.

I didn't ride the bike before I started the restoration so I don't know whether it was this way. The forks have been rebuilt, the wheel has been balanced - I've noticed a couple of loose spokes but the wheel is balanced and with the right air pressure-. The stem bearings have been repacked with new grease and correctly tightened -not to loose that the fork moves up and down, not to tight that the fork can turn either way freely-.

It escapes me what can the reason be. I thought that maybe it was a design flaw, and therefore, somebody who owns -or owned- one in the day can tell me whether it's normal or not. The axle clamps are well tightened. In this bike there was no gap on the clamp.


Thanks in advance

Raul

[dusterdude]

damn thats a good looking bike

[dusterdude]

raul,while i was drooling all over that pic i forgot to add,i had one of them 350`s back in the early 80`s and never had a front end shake issue at all.

[Raul CB750K1]

raul,while i was drooling all over that pic i forgot to add,i had one of them 350`s back in the early 80`s and never had a front end shake issue at all.

Thanks for your kind words Duster. It's been two years in the making, so plenty of time to get things right.

I'm preparing a before&after thread to be posted in a couple weeks, but here you have another picture for your viewing pleasure.




I also doubt it was an endemic flaw, but I don't have the slightest clue what the problem can be. This bike is not so powerful as to lighten the front end and causing wobble...

[SteveD CB500F]

Does it have an old ribbed front tyre?  If you've done the head bearings, it can't be them.

What about swingarm bearings?  I've heard that this can induce similar symptoms!

My VFR did this - it was a feathered front tyre.

[Raul CB750K1]

Does it have an old ribbed front tyre?  If you've done the head bearings, it can't be them.

What about swingarm bearings?  I've heard that this can induce similar symptoms!

My VFR did this - it was a feathered front tyre.

Front and rear tyres are about four year old. Metzeler ME33. What I don't know is whether that tyre is suppoused to be a front tyre. I will investigate. Bike came with them, they still had remains of the factory stickers so I kept them.

Swingarm bushings are brand new, Honda OEM. Rear tyre is 4.00 instead of 3.5, but I doubt it could have something to do with it. I guess it could affect handling in curves, but not in straights.

[Jay B]

I had a 350G back in the day. I ran the hell out of it, I don't recall any wobbling issues. And man, that is a nice bike. Maybe it is a front tire issue. As I recall, my old CB175 didn't like anything but the stock front rib.

[paulages]

it's been a while, but i used to notice a wobble when decelerating from 90mph or so speeds. not so much on the accel, but let me tell you it was scary. don't know if it's endemic to the bikes or not, but mine sure did it.

[Geeto67]

you have loose spokes in the front rim and you are riding it 

IT could be your wheel is walking when you get up to speed. Out of balance is usually a vibration, as is out of round. Rim moving off center is a wobble. I would go through your front end again.

[florence]

i have a cb350k which i use to ride a few years ago and the front end was fine until you got over 90mph when it would start to wander a little but I always put that down to the big rams horn handlebars i had on it.  I think there may be something wrong with yours.. maybe your head bearings aren't correctly adjusted or it doesn't like the front tyre.

[eurban]

Things that I can think of:
tires (seems most likely)
loose spokes
twist in your front fork tubes (upper and lower trees not quite lined up)
steering bearing issues (just cause you repacked your bearings doesn't mean that they are not worn/notched)
double check that the rear swingarm rebuild resulted in zero side to side play
front to rear wheel alignment is off (use string lines to line up the front and rear; the alignment marks on the swingarm are
often a good deal off!)

[Jerry Rxman Griffin aka MuthaF'er]

I had a 68 CB350 that would ton out but it never wobbled. Rode the hell out of it often. The only time it wobbled was in ~"73/'74 when I asked it to turn sharper half way through a sharp turn and the balding front tire didn't like what I was asking. Damn near side swiped a station wagon. My first brush with death. 

Nice looking bike! If you can find a cam from a '68 do it! Amazing difference. First year hottest cam - just like the 750K0. Nobody believed it was a stock 350. Especially the 450 boys.

[bryanj]

Raul, they were VERY finiky on getting head race correct( must be able to fall either way easily with no play) and old tyre stood for a while may well have a "hard" spot.

Also adjust your tyre pressures 2-3 psi either way as that can make a difference

[Raul CB750K1]

I tightened the two spokes that were loose -they wouldn't "ping" when hitting with the spoke wrench- and gave a go to a couple more that sounded at a lower pitch. No difference in handling, the wobble persist.

I was wrong about the tyres. They are Metzeler Perfect ME77. The front one is valid for front and rear, and is installed according to what the rotation marks say. Tyres are about 3 or 4 years old, and they have spent the last two years mounted on the wheels, but off the bike. My CB750 had 35-year-old tyres and it never wobbled, so I don't think it is a tyre issue.

I'm going to tighten the fork nut a little, just a little, and see whether it makes any difference. This is the only thing that worries me about the bike. The rest is just perfect; starts first try, runs like a champ, but the wobble is sometimes scary to say the least. Seem like if you are going to get a tankslapper at any moment.

I recall some old bikes had a knob at the top of the fork to tighten the steering; maybe it was to avoid the wobble. I'll keep you updated, and thanks for your help.

[mikedialect]

raul, looking forward to your before and after thread EAGERLY. I don't have any of the mentioned wobble. You obviously checked to see that the wheel is clamped to the fork correctly?

[seaweb11]

That turned out nice Raul

[Raul CB750K1]

raul, looking forward to your before and after thread EAGERLY. I don't have any of the mentioned wobble. You obviously checked to see that the wheel is clamped to the fork correctly?

Yes I did, the wheel is correctly clamped.

I'm waiting for some stickers to arrive and put in place -battery, tire caution etc- and then I will shoot the pictures. I took some pictures the very same day I bought it, so I plan to take the very same pictures in the very same spot, and put the old and new together to see the difference.

[mikedialect]

Well, I definitely will be happy to see those photos! I know it was a pretty obvious question. I've been guilty of missing the simple things lately. If the wheel is balanced and trued it has to be somewhere else. Frame? Forks?