Topic: CB500/4 racer resurrection - airbox finished, didnt quite work....

[turboguzzi]

last race of the season in Misano is next week, but like a good schoolboy am thinking already what to run next year.
After carefully assessing possibilities among race bikes i have or building yet another one, i decided to pull out of pension my good ole CB500/4 racer.
After bringing me a 3rd place in the 500c.c. 4 stroke 500cc championship back in 2009, I put it aside when i built my GPZ750/810 racer. After that one i built a complex Supermono but regretfully the class has proven very unpopular, so ended up with a great bike with no class to properly race it.
So it's back to the old lady and for those who are relatively new to the HiPo section, i can tell that it was the work on this on this very bike that prompted me to ask the moderator of the technical forum to open a dedicated racing section....
Anyway, work to get her back to track starts today!


 

[bwaller]

About time!   

[turboguzzi]

ok brent, i owe you the first pic from the teardown
remember i never got around to tell you how the CBR600 cam chain tensioner held?
so it's finally out of the motor!
perfect i would say...hardly a sign on the sliding surface.
to see the complete idea behind this:
http://forums.sohc4.net/index.php?topic=55162.0

[bwaller]

Right on TG, looks good indeed. Not sure what the issue was with Gerrit, maybe too tight. I'll show you what mine looks like after a second season but it surely is still quiet.

Have you any plan for change?

[gschuld]

Great to hear your pulling the cb500 our of mothballs.

I'm curious to know how you feel about the Koni shocks.

George

[turboguzzi]

george, i would say that koni (now ikon) are fine for street use, have them on my kz750e, but as race bike shocks too basic: heavy steel body, emulsion type, very approximate rebound damping. Suspension is definitely an area i want to improve, those konis where simply what i could afford back when i built the bike.
Going to try latest generation of alloy bodied bitubos which separate the oil and air through a De Carbon type floating piston, quite like Race Tech's IFP shocks. Riccardo is using them on his 750 and is quite happy (and fast...)
http://www.bitubo.com/Bitubo/cms/ENG/content/129-wmeo.html

Engine teardown revealed some good news and some not so good news.

on the positive side, the thailand made Hi-Speed brand pistons are in great shape, actually some of the graphite layer is still intact, and clearance is fine. i might hone and re-ring just for a fresh up. they held much better than the japanese made TKRJs i used before them that galled and smeared under pressure. being slipper type, they are a good 20% lighter than the stock ones.
As a side note, the wear pattern on the graphite coating lets you see how it's only the central part of the skirt that does any work.... having a skirt under the sides is indeed pretty useless and simply adds weight and friction.

camshft looks great, ditto  for the rockers, but not everything was fine... all will be revealed

[livefast_dieold]

I need to come visit you one of these evenings and see what you are up to!

As for rear shocks, we have been testing a new brand, cheaper than bitubo. They seems quite effective.

[gschuld]

TG,

If I understand correctly, the rebound adjustment on the Bitubo shocks you referenced is a 1-5 soft to hard setup below.  I am curious to how they perform compared to the alloy body Koni rial a ride shocks.  The dial a ride shocks have the 1-4 rebound adjustment under the rubber boot as below. 

The Bitubo shocks certainly have a finer spring preload adjustment than the 4 positions available on the Konis.

My interest in the Konis has far more to for with keeping the parts on the bike more vintage visually rather than using the highest end modern parts available.  Voxonda has preferred these Koni shocks on his race bikes so I'd like to thank they still have some value to a racer.

George

[Camrector]

Works built me a set for the “605”. Super lightweight body, preload and rebound adjustment galore. $800

[turboguzzi]

wow, hope this doesnt turn into a "best oil to use" style thread about shocks
George, rob is a friend and he sure knows best whats best for him, so please dont put me in that corner of contradicting him
sure both dampers have adjustment, thing is that the range of the koni goes from super soft to rock hard in four steps, good for the street where you need to cover anything from single skinny rider to two-up fully loaded bike, less for the track where you want fine tuning. in practice the 4 position adjustment in my konis had only one setting that was usable for me ...
koni is emulsion, bitubo (and some others ) separate oil from air/gas. not much point in arguing what's better really. On a personal level, I experienced in at least two races severe shock fade due to foaming/frothing after 20 minutes in hot weather, in one case  lost a podium because of rear shocks misbehaving in the last corner.
Again, not an issue in street riding or track parading and please dont let my humble opinion discourage you from using them.

Camrector, I am simply envious of your shocks! Bringing those to europe would be in the 1K$ range or more.... Now just tell me how to make that kind of money, that's what i really want to know

[MessnerMoto]

Yoss you need cb750, you are to big  for a cb500

[turboguzzi]

Yoss you need cb750, you are to big  for a cb500

indeed mirko, i just heard that a fresh bike ready to race will be available in Belgrade

[gschuld]

Sorry, I have no intention to make an oil thread argument out of the subject of rear shocks.  Perhaps I should have sent you a PM .  I enjoy learning about the differences between the shock designs.

I have 5 sets if vintage Koni shocks, their primary propose is ultimately street use. 

Again, great to hear you are back in sohc4 mode....

George

[turboguzzi]

now to the not-so-good stuff....

after freeing the cam from the chain i causally put it back on the head and noticed this strange rock movement when pressing side to side.

it's about 0.15-0.1 up/down at the cam's end.

initially thought cam was bent but it does the same things after rotating it to different positions, so my takeaway is that the head got distorted somehow.
will still going to check cam straightness  on V-blocks on a marble table but from my quick check with a steel ruler it looks like a mistake while milling the head
have to think about how to solve, might need to do a new head  

[turboguzzi]

and as if that wasnt bad enough, found this sitting at the bottom of the sump...

having it wedge between teeth at 100 mph would be no fun, so was lucky there.

clean fatigue break, sump was free of any metal particles or silvery deposits.

it's the 5th gear on the output shaft, the 29T one. anybody got a spare?

[MessnerMoto]

...

Yoss you need cb750, you are to big  for a cb500

indeed mirko, i just heard that a fresh bike ready to race will be available in Belgrade

...Solved the problem with primary tensioner. I managed to get it out while engine was still in frame...nobody will believe that you can do that on cb750
and we did some additional changes to case so I can now it is easy to take out the primary chain tensioner while engine is still in
frame.... looking forward to you build

[bwaller]

I'll certainly have that gear. PM your address again.

[turboguzzi]

ah! sweet! tnxs brent

let me see first how to avoid banging my head against the italian customs system....will get back to you.

another positive piece of info, the DID 219 FTH (flat side plates) cam chain that came already used from a GSXR750 shows virtually no wear after four seasons.... the 7.77 pitch gives me 155.4 theoretical length for 20 links, i measure 156mm, wear limit is 158mm... not hard to see that these flat links give an easier life to the plastic cam tensioners.

[bwaller]

Absolutely true about those flat link chains, plus the 500 slipper style tensioner is easier on chains too.

I'll wait for your ok to ship. It'll wait until we're back from Barber anyway.

[NobleHops]

Works built me a set for the “605”. Super lightweight body, preload and rebound adjustment galore. $800

Works closed up shop a few weeks ago. Sad to see that.

[slikwilli420]

Works built me a set for the “605”. Super lightweight body, preload and rebound adjustment galore. $800

Works closed up shop a few weeks ago. Sad to see that.

Where did you see that? A quick google search says they are closed but their website doesn't indicate anything other than that they are still open and operational.

[NobleHops]

Starting a new thread Cam, apologies for hijacking this one.

N.

[gschuld]

Starting a new thread Cam, apologies for hijacking this one.

N.

http://forums.sohc4.net/index.php/topic,168659.0.html

George

[turboguzzi]

well, here's the offending bastard of a dog... this is one of three passing the power of 3rd gear, means it's the one most banged about when up-shifting/accelerating out of slow turns, i.e. most likely to break according to tuner flavio crispi.
not surprisingly, in most spares sites it shows as "no longer available".
following Flavio's advice i went for a new one rather than the used brent offer. logic being at least to start with a fresh one.  Managed to find a new gear in a little shop in a forgotten corner of europe, really by chance...

[scottly]

What does the shift fork look like? Excessive wear on one side, or bent?