Honda-SOHC

SOHC.co.uk Forums => CB350/400 => Topic started by: ricardo on May 04, 2019, 08:18:50 AM

Title: Front forks /wobbly steering
Post by: ricardo on May 04, 2019, 08:18:50 AM
Hello everyone.
I've removed my front wheel to investigate. Pads are good. bearings seem to be ok but how can I be sure? I noticed that with the wheel off the forks will rotate independent of each other . Is that correct. I always imagined that they would stay in the alignment they are in when the wheel is in place.

Ricardo
Title: Re: Front forks /wobbly steering
Post by: K2-K6 on May 04, 2019, 09:19:25 AM
The bottom of the fork legs are effectively "floating" with no rotational location,  that's correct.

They are only aligned by clamping the wheel spindle when correctly assembled and tightened. So all ok if clamps and threads are in good order.

The front mudguard is considered as brace to help,  but if it has rubber mounts it can't really contribute much.

Initially you've not flagged anything untoward there.
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 04, 2019, 09:27:43 AM
Many thanks
Ricardo
Title: Re: Front forks /wobbly steering
Post by: TrickyMicky on May 04, 2019, 09:41:56 AM
Whilst you have the front wheel removed, it's nice and easy to check if it is out of balance. Hold/support the wheel spindle, and just give the wheel a gentle spin, when it stops, make a chalk mark at the 6 o'clock position. Repeat this a few times, if it stops at the same place each time, then your chalk mark is the heavy spot and a balance weight should be affixed diametrically opposite, correct weight determined by trial and error I'm afraid! When giving the wheel its slow spin, if the wheel bearings are in good order, you should not be able to detect any noises or feel any harshness when holding the axle. As you have the front wheel removed I assume the front of the bike is supported leaving the forks free to  move, Slowly move the handlebars from lock to lock, there should be no resistance or roughness throughout the travel, especially at the straight ahead position. Lastly, once again as the front end is free to move, ensure the bike is secure, then grasp the bottom of the fork legs and push and pull them in the fore and aft direction, if your steering head bearings are good there will be no movement at all.
   Eons ago, when I had a CB750, it had a front wheel which was only very slightly out of balance. Did not take any notice until one day when going on holiday, two up with a very heavily loaded rear carrier, i closed the throttle at about 40MPH and took my hands off the bars to adjust my goggles, HOLY SHIT! It went into the biggest tank-slapper I've ever had. Please take those few extra minutes to check those few items. Happy riding, and stay upright. Michael.
Title: Re: Front forks /wobbly steering
Post by: K2-K6 on May 04, 2019, 10:53:40 AM
The point Micheal made about checking the smooth turning of fork yokes has particular significance in this problem. Absolutely any roughness however small can cause error.

The original headstock bearings are ball and race type.  If there is an indentation just very slightly off true straight ahead geometry (you'd feel this in checking) then it can cause the front forks to "sit " in that alignment,  which would turn the bike in one direction slightly.  The natural steering geometry will "try" to make the bike go straight down the road with no input to the bars.  The conflict between the two can make the forks oscillate in and out of that bearing dip,  making the steering wobble. Even adjusting the chain and getting a slight bias on rear wheel alignment can bring this in or out of play.

The headstock bearings are ideally replaced for taper roller bearings which ordinarily resist deterioration under use much more effectively.

Something else to look for in detail,  the wheel spindle clamps look universal but are directional.  There's an arrow cast into them that should point forward in direction of travel,  they would be clamped first by the leading stud to get them seated metal to metal ( that part of the casting in longer to facilitate) and only then the rear stud tightened to finally pinch the spindle.  It's a subtle design,  but often missed.

Title: Re: Front forks /wobbly steering
Post by: ricardo on May 04, 2019, 01:43:32 PM

Many thanks. I'll run-through that lot.

Ricardo
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 04, 2019, 03:25:14 PM
I've just checked the steering. From neutral position theirs drop all the way round to the left. Extreme to the right its a little stiff at the end of the range.

What should do please.
Ricardo
Title: Re: Front forks /wobbly steering
Post by: TrickyMicky on May 04, 2019, 03:28:50 PM
Make sure it's not cables/wires/brake pipes bunching up in one direction.
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 04, 2019, 04:08:35 PM
I think that's the reason for the R turn stiffness. I'm not sure how it affects the swing to the left
Ricardo
Title: Re: Front forks /wobbly steering
Post by: taysidedragon on May 05, 2019, 12:37:34 AM
The only way to be sure that it's not being caused by wiring or cables is to disconnect them all from the bars and then turn them from side to side.
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 05, 2019, 08:34:29 AM
Wow. Quite a job!  Sound advice though. I'll investigate
Title: Re: Front forks /wobbly steering
Post by: Rob62 on May 05, 2019, 08:51:10 AM
Removing the cables is a bit ott in my opinion... so long as there is no free play or notchyness and the steering moves freely it is ok.
Title: Re: Front forks /wobbly steering
Post by: K2-K6 on May 05, 2019, 09:14:50 AM
As above,  agree that cables although you can feel them at max turn have little effect when riding.

At most you're going to be 10degree each side of straight ahead,  unless manoeuvring at very low speed.

Although I took "wobbly " to mean the handlebars are shaking when you ride it,  rather than just staying straight if you take your hands off the bars. If that's the case then it is just the central range of bearing movement you need to inspect with the most scrutiny.
Title: Re: Front forks /wobbly steering
Post by: TrickyMicky on May 05, 2019, 09:21:59 AM
Don't worry about the steering falling to one side or the other. If you look at the steering set-up, you will see that the forks are forward of the steering stem/axis point, so when you turn the bars the forks actually move round in an arc. Because the steering stem is at an angle, this means that the forks actually drop either side of centre. When it is all re-assembled, take bike off the stand so it is on its wheels, then turn the bars from lock to lock and you will see that the bike actually moves from side to side roughly at the point in line with the front of the tank. This set up is to give the optimum steering and handling response for a road bike. If you look at a speedway bike the forks are very close to the vertical, no good in a straight line but good for drifting, drag/sprint bikes are totally the opposite, acutely angled forks for straight line running.
   Just as an aside, if you've ever wondered what keeps your bike so stable, whilst you have your front wheel removed, using both hands hold it up by the wheel spindle and rock it about. Now get a mate to spin the wheel and then try to move it about and you will feel the gyroscopic effect. Be lucky, Michael.
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 07, 2019, 03:18:49 PM
Bikers thanks.
No the steering doesn't vibrate or shudder. It feels as if the steering is imprecise. I seem to have to always be turning the bars  to keep the bike on a straight line. Probably more noticeable while on a bend
On another bike I once had with excellent steering it behaved like this  when my front tyre was below pressure
Does that mean anything different.?

Ricardo.
Title: Re: Front forks /wobbly steering
Post by: Bryanj on May 07, 2019, 03:45:43 PM
How old and what type is the tyre? Has this happened suddenly or always been there? Have you altered or adjusted anything recently?
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 21, 2019, 07:32:30 PM
hi. thanks for reply. Apologies for late response.

It was there when I drove the bike away. I thought tyre might have been a bit flat. it was a little. Toppoed air up and it helped somewhat. I have been doing other stuff since but all suggested investigations have not resulted in a solution. Tyre and wheel off so I;ll look at tyre and let you know.
Ricardo
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 21, 2019, 07:43:09 PM
tyre is 'hent (or Heng) sinh

Lettering a bit weird.
Tyre in good condition but the 2 parallel lines near the edge of the tyre seems a bit off centre. A clear gap between the inner one and the rim but not visible gap on the opposite side of the tyre.
Ive made no adjustments
Ricardo
Title: Re: Front forks /wobbly steering
Post by: hairygit on May 21, 2019, 08:27:03 PM
Well you may have found your problem, the tyre is not mounted correctly! Deflate the tyre completely, and push the beading in the rim a bit. Smear tyre soap or similar around the inside of the rim walls/along the tyre bead, and re inflate until the tyre bead sits evenly around the rim, then adjust to the correct pressure and go for a test ride. If no improvement,get the tyre changed, it's probably knackered.

Sent from my X6pro using Tapatalk

Title: Re: Front forks /wobbly steering
Post by: Bryanj on May 21, 2019, 10:36:50 PM
Also very cheap tyre. Did not have a good rep
Title: Re: Front forks /wobbly steering
Post by: Nurse Julie on May 21, 2019, 10:45:15 PM
Also very cheap tyre. Did not have a good rep
Nowt wrong with cheng shins, I have one fitted to the front of my CB400/4 , best tyre i have ever had for stickability to the road. I have a Mitas or however you spell it on the back, and once again, absolutely fantastic. The only problem now is that my 400/4 handles so well with this combination, it makes me want to ride fast all the time 😁😁😁😁
Title: Re: Front forks /wobbly steering
Post by: Bryanj on May 22, 2019, 03:04:58 AM
Must have changed Julie, when i was fitting them, admittedly many eons ago, they were marginaly worse than the original Japanese rubber!!
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 22, 2019, 08:53:41 AM
Thanks to both of you. I have a spare used tyre which came with bike. Seems to have very little wear on it. As I'd be taking tyre off anyway should I replace it with this one?

Ricardo
Title: Re: Front forks /wobbly steering
Post by: hairygit on May 22, 2019, 09:46:26 AM
If you have another tyre, then yes, change it. While it's off check the inner edge of the rim for rust or the likes. If there is any, clean it off, as it needs to be a smooth surface for the tyre to seat itself properly.

Sent from my X6pro using Tapatalk

Title: Re: Front forks /wobbly steering
Post by: Moorey on May 22, 2019, 10:45:18 AM
Also very cheap tyre. Did not have a good rep
Nowt wrong with cheng shins, I have one fitted to the front of my CB400/4 , best tyre i have ever had for stickability to the road. I have a Mitas or however you spell it on the back, and once again, absolutely fantastic. The only problem now is that my 400/4 handles so well with this combination, it makes me want to ride fast all the time 😁😁😁😁

Well Julie I have been away in Devon and Cornwall for the last 5 weeks and have had the 400 superfour with us and done quite a few miles on it. On Monday I went out on the 350 and couldn't believe how bad it feels. I have been kidding myself about the Cheng Shings. Now awaiting new tyres been delivered.  4.00x18 and 3.50x18 if you have use for them you are more than welcome to them, seems such a shame to scrap new tyres. T don't blame the fact they are Cheng Shings I am just going to put the correct size tyres on the bike. :D
Title: Re: Front forks /wobbly steering
Post by: Nurse Julie on May 22, 2019, 10:52:18 AM
Yep, agree totally. The correct size tyres always help 😀😀😁
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 22, 2019, 07:06:53 PM
Thanks Julie.
Ill check in the manual and be sure that the right tyre is going on

Any views on using paint stripers to remove the black paint sprayed in the hub and rim. It seems the cheapest option?!
Title: Re: Front forks /wobbly steering
Post by: ricardo on May 22, 2019, 07:27:34 PM
Now I'm confused. As usual.

Tyre spec according to Haynes is  front 3.00 S18 (4PR).

The spare tyre is 90/90-18 M/C 57P

I suppose the M/C is motor cycle but the rest is Chinese to me.

The existing Feng shui tyre is 3.00 -18. 47p

Advice please or I will have to walk everywhere
Ricardo

Title: Re: Front forks /wobbly steering
Post by: ricardo on May 23, 2019, 09:03:05 AM
Many thanks for all the advice. I now have a plan
Ricardo
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