CB550 Wild, Wobbling and Bouncing all over the place.

[Freak_Hybrid]

Hey guys, So I bought this trike project to give a go and I've gotten to the test ride state and it's positively awful. In it's life it's been on he road for several years before holding up so i'm hoping it's nothing catastrophic w/ the chassis.

The build;

1983 CB550sc Nighthawk bike frame and a reliant rear diff w/ wheels off a mini (I think).

The problem(s);

The handling on it is truly terrifying, It's heavy to turn the bars and on corners and the slightest bump/dip in the road has the front end feeling light and the bars wild while the back end bounces all over the place. In it's life it's been on he road for several years before holding up so i'm hoping it's nothing catastrophic w/ the chassis. If you hold the front wheel and try and shake the bars the bike part of the frame will wobble/almost twist where it should be solid.

Problem solving;

- I've replaced the headstock bearings and adjusted those so that there's no forward/back movement and the bars move freely either side.

- I ratchet strapped the back end down (Theoretical hard tail) and that removed all the back end and chassis wobble but the front end steering was still light and a lil wild. So i'm thinking the rear shocks are shot and i'm just looking at what shocks to put in there place.

- I've replaced the fork seals and oil (10w, 375 ml as per manual) but there's ~2 inches of travel on the forks. I increased the preload by maybe an inch to see if that helped and i think it did slightly, so i'm thinking maybe worn main springs or just knackered forks in general?

- Have boxed it up w/ chalk and the tracking on the back looks good.

I'm sure there are things I've forgotten to mention but i think that's most of it. Basically, it handles like a potato and i'm not sure why. Any help would be appreciated

 

[FuzzyWuzHe]

Sounds like shocks and springs would be a good start. Also, you might play around with the rear tire pressure see if lowering it helps. There's almost no weight on the rear.

Welcome to the Gang from Western Colorado.

 

[wehrme]

I'd try the rear tire pressure. From the pic, it looks like the tires are riding pretty high. Most trikes usually have 22~24 lbs in the rear.

 

[Freak_Hybrid]

Wow, quick response.

I've just lowered the rear tyre pressure to 24 psi (Was set at 40).

Any suggestions on what shocks to go for? Will any new shocks work? Also, i've got like a wooden frame w/ an army ammo box i'm working on to go on the back and cover the diff and give me a bit of a boot, that should add some weight to the back end.

Thanks guys.

 

[Lee H. Mann]

Wow, quick response.

I've just lowered the rear tyre pressure to 24 psi (Was set at 40).

Any suggestions on what shocks to go for? Will any new shocks work? Also, i've got like a wooden frame w/ an army ammo box i'm working on to go on the back and cover the diff and give me a bit of a boot, that should add some weight to the back end.

Thanks guys.

After viewing the pix, I would run 18 - 20 psi in the rear tires. Start the suspension on soft and work your way up one notch at a time to improve the ride.

 

[Jack Klarich]

Welcome to Trike Talk

Looking @ the photo I see the rear shocks @ a pretty severe angle

The rear ride height is TOO high, that throws the front fork out of whack causing hard to steer and high speed wobble

IMO get the rear end down, move the shocks closer to the wheels if you can

Lowering the back should give you better steering and less wobble

JMO

 

[Gideon]

Welcome to Trike Talk

Looking @ the photo I see the rear shocks @ a pretty severe angle

The rear ride height is TOO high, that throws the front fork out of whack causing hard to steer and high speed wobble

IMO get the rear end down, move the shocks closer to the wheels if you can

Lowering the back should give you better steering and less wobble

JMO

I agree!

Move the shocks from under your butt to under the passenger seat, the rear is much to high.

Please fix it before taking it out on the road.

God bless,

Ride safe

Gideon

 

[Freak_Hybrid]

Edit: A quick google says I should aim for 15 - 20 degrees, I think mine are closer to 45.

Thanks again guys. Is that change the angle of the shocks or just move them further back? (Maybe both?) There's a bar going across further back i should be able to reinforce and weld some mounts for the shock, then just try and attach the top end further up by the sides of the grab rail.

(Ignore the scattered wiring, I was in the process of wiring the back lights)

 

[Jack Klarich]

Is that change the angle of the shocks or just move them further back? (Maybe both?) There's a bar going across further back i should be able to reinforce and weld some mounts for the shock, then just try and attach the top end further up by the sides of the grab rail.

Moving the shocks back will set them at a better angle in affect lowering the back end

However you may have TOO long of shocks also

Too long will keep your rear ride height to high, you want to drop it down to let the front end take control whilst you ride ( may have to get shorter shocks eye to eye and different springs)

I hope this helps and makes sense

The only other and expensive option is cut your neck on the frame and change the front rake kicking the front wheel further out to ease the steering and make the ride more stable

 

[Freak_Hybrid]

Moving the shocks back will set them at a better angle in affect lowering the back end

However you may have TOO long of shocks also

Too long will keep your rear ride height to high, you want to drop it down to let the front end take control whilst you ride ( may have to get shorter shocks eye to eye and different springs)

I hope this helps and makes sense

The only other and expensive option is cut your neck on the frame and change the front rake kicking the front wheel further out to ease the steering and make the ride more stable

So, I've just opened up the back a lil and there's a nice bit of chassis i can drill a hole and weld a new mounting point for the shock. I've also had a look online and there's a host of shorter shocks i can fit for a reasonable price. I was just wondering how much you'd recon i should lower the shocks by. I think the stock ones on there are 340mm (Currently compressed to 310mm but i think they're knackered) and the shortest I've found so far are 280 mm. Before i buy any i'll retry my current shocks w/ the new mounting points and see how much that lowers the back end and how much it affects the heavy steering (A bit of rough trig says the back end should drop by about 20 mm).

Once again, thanks for all the help.

 

[FuzzyWuzHe]

I think I'd wait before moving the rear shocks until you see what the wood rear does to the geometry. THEN make shock adjustments. The wood will be heavy and lower the rear quite a lot.

 

[Jack Klarich]

Look @ mounting your shocks @ the sissy bar bolt, that looks to be a pretty good angle

Try a level on your seat, I bet it is WAY off, if you can drop the rear of the trike so the bubble shows level from what I see in the picture you could get a pretty close idea of your rear shock height JMO