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Author Topic: CB550 front improvement?  (Read 1322 times)

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Offline vintage_racer

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CB550 front improvement?
« on: August 13, 2007, 02:12:57 PM »
During the last race weekend I experienced a speed wooble going down the main streight at Mosport (around 190 km/h) This bike is in a high state of tune with Yosh pistons, modified camshaft, head porting, large carbs etc.. probably a stock CB550 wouldn't reach a speed where stability is an issue.

Is there a way to improve the stability of the front or I simply experienced flex in the frame?

I'm using a steering dumper already but it wouldn't do much for this type of problem.

Thanks in advance,


Dan
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Offline TwoTired

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Re: CB550 front improvement?
« Reply #1 on: August 13, 2007, 03:05:49 PM »
Do you have a stiff fork brace that goes across the lower legs?
Tight bearings?
Tight spokes?
Tight swing arm bushings?
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Offline bwaller

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Re: CB550 front improvement?
« Reply #2 on: August 13, 2007, 06:58:52 PM »
Hey Dan,

TT hits on the important stuff but a fork brace is a must. Spend some time to check wheel alignment too. Frame flex..maybe but not apt to lead to this problem on a straight.

Are there still some ripples on that back straight to help get the bike to unsettle? If so are you using the original fork damper pipes and on what year forks? Switching to another model damper(CB500 twin) gives more compression damping than the stock pipes. Interconnecting the forks and adding 10psi helps some too. 

When & where is the next vintage event, Shannonville??

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Offline vintage_racer

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Re: CB550 front improvement?
« Reply #3 on: August 15, 2007, 12:22:19 PM »
Well,

I'm not using any fork brace, my fork is in a good shape (as far as I can tell) and is of a CB750 K2.

Spokes are tight, swing arm bearings are OK, will check head bearings. The steering dumper is of an old Kawi, it's of the piston type.

Dan

P.S. our next Vintage race is at North Bay Ontario at the air field.
I may run at Shennonville late Sep with the RACE organization, may rebuild the motor early Sep (have a fresh set of Yosh pistons 560cc and will play with some porting on the intake side of the head).
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Offline oldbiker

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Re: CB550 front improvement?
« Reply #4 on: August 16, 2007, 01:34:26 AM »
A good stiff fork brace is a must have item.
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Offline Caferacernoc

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Re: CB550 front improvement?
« Reply #5 on: August 17, 2007, 01:23:21 PM »
At the very least you should use the fender brace/bracket from a stock fender.
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Offline bwaller

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Re: CB550 front improvement?
« Reply #6 on: August 17, 2007, 02:22:13 PM »
If you're using a set of 750 forks changing fork dampers isn't necessary. I thought if you had a set of 404 forks from a 550 then it would help tremendously.

One other thing that might cause a HS wobble is if the front wheel is slightly offset from the original position with the 750 front end, and not in alignment with the rear?? Does the weave lead to a tank slapper? Does it take something to upset the bike to lead to this or does it come on gradually? I'd take a close look at your rear to front alignment.
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