Author Topic: race updates, nice hubs and CR's (Read 6143 times)

turboguzzi · « **on:** September 16, 2009, 12:16:36 am »

Another race, another 4th place and am still are 3rd in the championship with two races remaining. So far so good.

In the meantime, here are some pics of the most beautiful hubs I've ever seen for a SOHC. They are mounted on a friends 500 but he has no idea how or when were they installed on the bike. They were made specifically for our SOHCS in the seventies by SCARAB, an italian company well know for their early Ducati disc brake calipers.

Beautifully made, they are superlight and with conical construction. the front is especially nice as it is essentially hollow. the disc carrier is one piece with the whole hub. very smart, wouldnt be a bad idea to replicate them (if i had time....)

turboguzzi · « **Reply #1 on:** September 16, 2009, 12:24:32 am »

the rear is cool too, with integrated cush drive and disc carrier

there's an original SCARAB - HONDA 4 inscription on the hub

even the sprocket carrier is hollowed out!

square section swingarm is nice but not a bimota , those had eccentric chain adjusters, must be a period italian piece though

turboguzzi · « **Reply #2 on:** September 16, 2009, 12:30:27 am »

last

this is how my bike looks like with the new 29CR's.

Tried them out for the first time at the race and almost took the out and re-installed the old 27's.

Finding a steady idle speed was almost impossible, engine would either die or stay uo at 4K rpm.

A fellow racer gave me the tip of the day: these CR's (at least on a 500) need to have the air screw almost shut off! he reccomended ti close them to 1/2 a turn from fully closed (usually it's 1.5 turns) and hey presto! excellent idling and low speed response!

Still need to work on the needles and main jet but I am 90% there with the jetting.

voxonda · « **Reply #3 on:** September 16, 2009, 01:24:36 am »

Hey TG,

They look gorgious these SCARAB hubs. He needs to treasure them. Like your 500 too, glad to hear there is still much interest in racing these baby's. Bring that 3rd in the championship home!

Regards, Rob

DsKing416 · « **Reply #4 on:** September 16, 2009, 01:29:58 am »

Take a place then maybe we can all get reproduce race parts!!!

voxonda · « **Reply #5 on:** September 16, 2009, 03:05:38 am »

Quote from: turboguzzi on September 16, 2009, 12:24:32 am

the rear is cool too, with integrated cush drive and disc carrier

there's an original SCARAB - HONDA 4 inscription on the hub

even the sprocket carrier is hollowed out!

square section swingarm is nice but not a bimota , those had eccentric chain adjusters, must be a period italian piece though

BTW TG, do you have a overall picture of your friends bike?

Cheers, Rob

Rod · « **Reply #6 on:** September 16, 2009, 03:07:02 am »

Quote from: turboguzzi on September 16, 2009, 12:30:27 am

last

A fellow racer gave me the tip of the day: these CR's (at least on a 500) need to have the air screw almost shut off! he reccomended ti close them to 1/2 a turn from fully closed (usually it's 1.5 turns) and hey presto! excellent idling and low speed response!

It wasn't until after I'd sold the CRs that came with the bike that I found out that valuable piece of information - had already replaced them with 28mm Dellortos which was a world of pain, could never them to work across the rev range - back with CRs again now. TG I notice you're not running stacks on the carbs?

bwaller · « **Reply #7 on:** September 16, 2009, 04:23:46 am »

Those are trick hubs TG. I'm not even sure about what forks he's using, but good for him.

I can appreciate the sorting needed to make the CR 29's work.

I know you were short time, but ideally it would have been cool to get a before & after Dyno look at what performance difference they offer alone.

After your overall engine/carburation changes do you feel a difference in how it pulls?

MRieck · « **Reply #8 on:** September 16, 2009, 05:08:39 am »

I run 31's and have no problems with idle etc. Several of us went to a bike meet this past weekend, got in a traffic jam but the bike idled well for extended periods of time. 1/2 to 1 turn out is normal if you have the right pilot jet. Any more than 1 turn and I'd reduce the pilot jet size.

turboguzzi · « **Reply #9 on:** September 16, 2009, 07:12:33 am »

Mrieck, manual says 1.5 turns so that's why i was kind of surprised, this guy said tha it wasnt even a matter of jet size, just that it required the minimum amount of air possible.

Brent, a dyno session os of course on the list, I can certainly feel a difference in the way the motor 'sing' up high as well as in throttle response, sharper. They are also easier on th ehand and much more easy to reach WOT when coming of turns. I did lighten spring preload on the VM's but this is still like half the effort.

Not running stacks at the moment as I have no idea what works and with my previous set up they actually made things worse. planning to lend some sets from a friend before shelling out the money for a specific length.

Forks on that bike are the usual 35mm Ducati bits with Grimeca calipers.

Bob, other than those hubs and S'arm, it's a pretty stock CB500 with very good looking fairing and plastic parts. will look for a pic.

paulages · « **Reply #10 on:** September 16, 2009, 09:46:19 am »

wow, nice pics yossef. those hubs and swingarm are quite droolworthy. what's your steering geometry setup now? 14" rear and dropped a bit through the trees? yours looks steeper than mine. with the steering damper all instability is gone now, and i could see going even steeper a little to smooth out the ride and turn in quicker.

congrats on your ranking!

HedNut · « **Reply #11 on:** September 16, 2009, 09:55:18 am »

HEy TG! Very cool indeed... It's awesome to see you're racing and doing well. I'm newer to the forum and am all over the vintage love now.
I have a question for you!... if you don't mind me asking, what kind of tires are you running on your 500? I love the look!....and since you race them, I'd bet they work damn well too. (which is the most important aspect I suppose)

Cheers!!

turboguzzi · « **Reply #12 on:** September 16, 2009, 11:40:25 am »

hei paul

Im not really dropped much on the front as you saw to keep good ground cleareance. for the back i'd have to measure but am away form the bike back in SF.

hed, in genenral for vintage racing it's either Avon AM20, 22, 23 in sprint compund or Dunlop KR 124 , 164 etc. Both are not DOT legal, only for racing. that's the only race compund stuff in 18" size

I am running a 90/90-18" AM20 fornt and 130/650-18" AM23 rear.

Essentially you could run the same setup in regular compound for the looks.

Other pretty sporty stuff is Bridgeston BT45'sand Conti TKV11/22

HedNut · « **Reply #13 on:** September 16, 2009, 12:02:08 pm »

Sweet! Thanks for the direction.... I like your style.
Cheers!

paulages · « **Reply #14 on:** September 16, 2009, 12:22:51 pm »

Quote from: turboguzzi on September 16, 2009, 11:40:25 am

hei paul

Im not really dropped much on the front as you saw to keep good ground cleareance. for the back i'd have to measure but am away form the bike back in SF.

hed, in genenral for vintage racing it's either Avon AM20, 22, 23 in sprint compund or Dunlop KR 124 , 164 etc. Both are not DOT legal, only for racing. that's the only race compund stuff in 18" size

I am running a 90/90-18" AM20 fornt and 130/650-18" AM23 rear.

Essentially you could run the same setup in regular compound for the looks.

Other pretty sporty stuff is Bridgeston BT45'sand Conti TKV11/22

Still in the states, huh? Or back again? I'm curious, so let me know whenever you get back. have you read the artcile about steering angle experiments in one of those foale links? From that data, I'm just as interested in smoothing out road irregularities as I am making the bike turn in quiker with the steeper angle.

lordmoonpie · « **Reply #15 on:** September 16, 2009, 01:24:14 pm »

Hey TG - coul dthat swingarm be a Segale? Is he still making wonderful unique bikes in Italy I wonder? I had a Segale 650 Honda dominator engined bike for a week once and have wanted one ever since...

turboguzzi · « **Reply #16 on:** September 16, 2009, 03:18:53 pm »

nice catch, all but forgot about segale but his shop is just 25 miles from home, should visit him one of these days.

Dont know if he was so much into hondas back in the seventies, might be worth checking. Will ask him about sohc parts while I am there

lordmoonpie · « **Reply #17 on:** September 18, 2009, 04:47:05 am »

Hey TG - if you do drop in on him, find out for me if he will still make a Segale 650 Honda and how much it'll cost

turboguzzi · « **Reply #18 on:** September 18, 2009, 07:52:57 pm »

Quote from: lordmoonpie on September 18, 2009, 04:47:05 am

Hey TG - if you do drop in on him, find out for me if he will still make a Segale 650 Honda and how much it'll cost

dont count on it.... the site shows massimo segale as the owner,

luigi, the father and outstanding builder doesn't show even

you would expect the son to show some respect for the amazing history but the site says nothing about the beautiful bikes that were built there.

http://www.hondasegale.it/index2.htm

Still, will give it a try in the winter time when I have more time

davesprinkle · « **Reply #19 on:** September 19, 2009, 12:45:07 am »

Quote from: turboguzzi on September 16, 2009, 12:30:27 am

last

this is how my bike looks like with the new 29CR's.

Tried them out for the first time at the race and almost took the out and re-installed the old 27's.

Finding a steady idle speed was almost impossible, engine would either die or stay uo at 4K rpm.

A fellow racer gave me the tip of the day: these CR's (at least on a 500) need to have the air screw almost shut off! he reccomended ti close them to 1/2 a turn from fully closed (usually it's 1.5 turns) and hey presto! excellent idling and low speed response!

Still need to work on the needles and main jet but I am 90% there with the jetting.

I'll confirm your finding regarding the CR airscrews. I'm running about 1/4 to 1/2 turn on my CR26s (CB400F). It has to be this rich to get a decent, but not great, idle. You'll find, though, that the airscrew has most of its impact on the 1/4 throttle region. You run the screw in to get a good idle but at the expense of a low throttle rich misfire and sooty pipes. Dropping the needle can help this.

This is fundamentally due to the poor design of the idle circuit. Keihin decided to keep all of the main and idle circuits in the jet-block, a replaceable section of the carb body that sits just below the slide. I presume they did this for ease of manufacturing, but the unfortunate consequence is that the idle circuit enters the port on the upstream side of the slide edge. Thus the idle circuit doesn't see full engine vacuum and it resultingly acts more like a venturi-driven main circuit, ie. ineffective at low airflow, and, even worse, far too effective as airflow increases. When the CR evolved into the FCR, the idle circuit moved to the downstream side of the slide, so it's obvious that Keihin realized just how poor a design compromise they'd made.

A true fix would require a substantial effort to redrill the idle circuit. Not sure it's even possible. Screw it, I'll idle the damn thing at 2500 and wipe the pipes occasionally.

turboguzzi · « **Reply #20 on:** September 19, 2009, 12:56:56 am »

wow, thats good to hear,

didn't go that deep into figuring out all what you are saying, just assumed initially that they should be set as in every other cab i know.

wonder how much pain this feature has caused to many sohc'ers

tg

lordmoonpie · « **Reply #21 on:** September 19, 2009, 01:57:18 am »

Quote from: davesprinkle on September 19, 2009, 12:45:07 am

I'll confirm your finding regarding the CR airscrews. I'm running about 1/4 to 1/2 turn on my CR26s (CB400F). It has to be this rich to get a decent, but not great, idle. You'll find, though, that the airscrew has most of its impact on the 1/4 throttle region. You run the screw in to get a good idle but at the expense of a low throttle rich misfire and sooty pipes. Dropping the needle can help this.

This is fundamentally due to the poor design of the idle circuit. Keihin decided to keep all of the main and idle circuits in the jet-block, a replaceable section of the carb body that sits just below the slide. I presume they did this for ease of manufacturing, but the unfortunate consequence is that the idle circuit enters the port on the upstream side of the slide edge. Thus the idle circuit doesn't see full engine vacuum and it resultingly acts more like a venturi-driven main circuit, ie. ineffective at low airflow. When the CR evolved into the FCR, the idle circuit moved to the downstream side of the slide, so it's obvious that Keihin realized their mistake.

A true fix would require a substantial effort to redrill the idle circuit. Not sure it's even possible. Screw it, I'll idle the damn thing at 2500 and wipe the pipes occasionally.

Dave - this is interesting stuff. I'm having problems getting my CR31s to idle on the 750 and my air screws are one whole turn out. I guess I shuld try reducing that to at least a 1/2 turn if not a 1/4 turn from fully in based on your findings?

davesprinkle · « **Reply #22 on:** September 19, 2009, 07:46:21 am »

Quote from: lordmoonpie on September 19, 2009, 01:57:18 am

Dave - this is interesting stuff. I'm having problems getting my CR31s to idle on the 750 and my air screws are one whole turn out. I guess I shuld try reducing that to at least a 1/2 turn if not a 1/4 turn from fully in based on your findings?

Moonie, all my insight (can I call it that?) regarding the CRs is from running a rack of 26s on my CB400, so I can only speculate about how your 29s would run on the 750. I will say this -- MReick has been able to get his bike to idle and run quite well with CRs. Don't know where his screws are.

Setting aside the differences between our bikes, our carbs are definitely manufactured the same, so they'll have the same fundamental idle challenges. I think you should run the screws in. Be aware that you'll likely pick up a 1/4-throttle rich misfire. Lowering the needle can help address this. Good luck.

Joksa · « **Reply #23 on:** August 14, 2010, 04:22:28 am »

Nice hubs. ISR makes a bit similar conical / hollowed hubs:
http://www.isrbrakes.se/products/hubs/

Hmm.. speaking of Scarab... my CB 500 has Scarab rear disc brake, but wheels is also non-stock (Ronal alloy)

wookie · « **Reply #24 on:** August 14, 2010, 07:52:27 am »

Quote from: davesprinkle on September 19, 2009, 12:45:07 am

Quote from: turboguzzi on September 16, 2009, 12:30:27 am
last

this is how my bike looks like with the new 29CR's.

Tried them out for the first time at the race and almost took the out and re-installed the old 27's.

Finding a steady idle speed was almost impossible, engine would either die or stay uo at 4K rpm.

A fellow racer gave me the tip of the day: these CR's (at least on a 500) need to have the air screw almost shut off! he reccomended ti close them to 1/2 a turn from fully closed (usually it's 1.5 turns) and hey presto! excellent idling and low speed response!

Still need to work on the needles and main jet but I am 90% there with the jetting.
I'll confirm your finding regarding the CR airscrews. I'm running about 1/4 to 1/2 turn on my CR26s (CB400F). It has to be this rich to get a decent, but not great, idle. You'll find, though, that the airscrew has most of its impact on the 1/4 throttle region. You run the screw in to get a good idle but at the expense of a low throttle rich misfire and sooty pipes. Dropping the needle can help this.

This is fundamentally due to the poor design of the idle circuit. Keihin decided to keep all of the main and idle circuits in the jet-block, a replaceable section of the carb body that sits just below the slide. I presume they did this for ease of manufacturing, but the unfortunate consequence is that the idle circuit enters the port on the upstream side of the slide edge. Thus the idle circuit doesn't see full engine vacuum and it resultingly acts more like a venturi-driven main circuit, ie. ineffective at low airflow, and, even worse, far too effective as airflow increases. When the CR evolved into the FCR, the idle circuit moved to the downstream side of the slide, so it's obvious that Keihin realized just how poor a design compromise they'd made.

A true fix would require a substantial effort to redrill the idle circuit. Not sure it's even possible. Screw it, I'll idle the damn thing at 2500 and wipe the pipes occasionally.

Now that is the kind of information i have been scouring the web for. Maybe i can get my 29's to idle a bit lower now.

If there isn't one already, this info should be moved to a cr tuning thread.

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Author Topic: race updates, nice hubs and CR's (Read 6143 times)