Topic: The Hot Mess - 1975 CB550F1 Frame/1981 CB650 Engine

[calj737]

Cal, totally unnecessary bud, the swingarms we are using are designed to accomodate18 inch wheels, I have a 4.5x17 rim with a 180 slick on it and it fits in a stock arm, plenty of room in front of it for the 18, which is only half inch or less bigger in that area... Most classic race 500/550/750 run 18/18 combo, look at the continental road or race attack tires designed for these applications...

Yeah, I'm well aware of the road racers setup preference. Not sure what Don's intentions were though. And, he's not using a stock swing arm, so as a precaution I'll measure it for him as "his" swing arm is sitting on one of my bikes  I will say this. I've got a 130-16 on there now, and while I don't see any clearance issue to the frame of the arm, the stay rod (for drums) will be quite problematic without modification for a 150/160 tire.

As a reference, the dimensions I got from Devin was 13" radius from the CL of axle to peak of tmounted tire, and 5-5/8" for overall width at the peak. We all know that can differ slightly based upon which tire, but it should be close enough for local government work 

A 180 on a stock 750 arm? Hmmm, sounds "snug".

[P.abrera]

Related to this, at what point in tire width on the stock 550 hub/swingarm do you have to start thinking of offset sprockets?


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[calj737]

Right at 160, Paolo

[P.abrera]

Always ready with the info, cal. Thsnks

Theres always a lot of debate on how the different offset and angles a modern fork has will affect the steering behavior of the bike, wont a switch to a smaller wheel diameter also steepen steering angles and amplify the already quicker steering gsxr front end geometry? How did you compensate for that, Don? ...keeping notes for a future project


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[calj737]

It does/will. Earlier he cited that he had custom offset triples made by Cognito to achieve his desired geometry. Scroll back up

Edit: actually his custom trees were documented in his Bionic Mongrel thread. Sorry.

[knottedknickers]

Theres always a lot of debate on how the different offset and angles a modern fork has will affect the steering behavior of the bike, wont a switch to a smaller wheel diameter also steepen steering angles and amplify the already quicker steering gsxr front end geometry? How did you compensate for that, Don?

I think you're correct that a smaller wheel will decrease rake ('steering angle') and trail. Increased offset will also decrease trail (though my understanding is that most sportbike forks have less offset (~ 30 mm)  than our CBs (~ 60 mm), which will increase trail). See http://www.autoevolution.com/news/a-quick-guide-to-motorcycle-rake-trail-and-offset-part-1-83482.html and http://bikearama.com/theory/motorcycle-rake-trail-explained/.

[SOHC4 Cafe Racer Fan]

Knotted.

I'm not sure which model CB uses 60mm offset.  550's use 45mm.  750's use 2 different offsets depending on the model and year.

Cal is correct.  I specifically ordered custom offset triples from Devin/Cognitomoto to compensate for the GSXR front end, the TTR400 swingarm and 18" wheels.

And yes, I am also using custom offset triples in my Bionic Mongrel CB750K2 build (with a 2008 CBR600RR front end).

[Retro Rocket]

Cal, totally unnecessary bud, the swingarms we are using are designed to accomodate18 inch wheels, I have a 4.5x17 rim with a 180 slick on it and it fits in a stock arm, plenty of room in front of it for the 18, which is only half inch or less bigger in that area... Most classic race 500/550/750 run 18/18 combo, look at the continental road or race attack tires designed for these applications...

Yeah, I'm well aware of the road racers setup preference. Not sure what Don's intentions were though. And, he's not using a stock swing arm, so as a precaution I'll measure it for him as "his" swing arm is sitting on one of my bikes  I will say this. I've got a 130-16 on there now, and while I don't see any clearance issue to the frame of the arm, the stay rod (for drums) will be quite problematic without modification for a 150/160 tire.

As a reference, the dimensions I got from Devin was 13" radius from the CL of axle to peak of tmounted tire, and 5-5/8" for overall width at the peak. We all know that can differ slightly based upon which tire, but it should be close enough for local government work 

A 180 on a stock 750 arm? Hmmm, sounds "snug".

Have a look at the CycleX racer Cal, the F bike, it uses a stock swingarm with wide tires, not sure the exact size... Here's a pic of the 750 with a 180 race slick on a 4.5 inch x 17 wheel with stock swingarm, its tight, but it fits....Not the best pics but I still have the tire in the shop..

[Retro Rocket]

Knotted.

I'm not sure which model CB uses 60mm offset.  550's use 45mm.  750's use 2 different offsets depending on the model and year.

Cal is correct.  I specifically ordered custom offset triples from Devin/Cognitomoto to compensate for the GSXR front end, the TTR400 swingarm and 18" wheels.

And yes, I am also using custom offset triples in my Bionic Mongrel CB750K2 build (with a 2008 CBR600RR front end).

K0 to K6 use 60mm offset, F1 to F3 use 50mm offsett, I think K7 and K8 also use 50mm offset   

[P.abrera]

Cool. Lots to catch up on. Always an education hangin out with you guys

[knottedknickers]

Knotted.

I'm not sure which model CB uses 60mm offset.  550's use 45mm.  750's use 2 different offsets depending on the model and year.

Cal is correct.  I specifically ordered custom offset triples from Devin/Cognitomoto to compensate for the GSXR front end, the TTR400 swingarm and 18" wheels.

And yes, I am also using custom offset triples in my Bionic Mongrel CB750K2 build (with a 2008 CBR600RR front end).

K0 to K6 use 60mm offset, F1 to F3 use 50mm offsett, I think K7 and K8 also use 50mm offset   

Yeah, sorry--I should have been more specific about which bike I was referring to (my 750K6). Especially since I don't really know about 550 / 650s...

I snapped a few pictures of my 750K6 upper triple with my 1996 GSX-R750 lower, for what it's worth:





I'm sure you've probably seen Sam's Fork Chart, but just in case anyone else would benefit here's the link. Lots of good info there.

I'll just sit back and watch now...

[SOHC4 Cafe Racer Fan]

650 cam and rockers packed and ready to mail to Mike Rieck (to send back to Megacycle in CA) for hardwelding on rockers and new hardweld/grind cam.   

I might take one last crack at blaster soak and ULTRA heat to try to extract this bugger.  If not, off to the machinist it goes for removal. 

[flatlander]

what grind are you getting? one of their 550 ones?
bummer about that stud. good luck with it!

[SOHC4 Cafe Racer Fan]

Yes, Megacycle 126-20. 500/550/650 cam.

[calj737]

Yes, Megacycle 126-20. 500/550/650 cam.

That will wake up that motor!

[SOHC4 Cafe Racer Fan]

Cal: Yes, that's definitely the intention!

IF anyone has a 1975 or 1976 rear CB750 Super Sport Wheel Hub & Brake they don't need  and that's in good condition, please PM me.  I reached out to Bill Benton (CB parts accumulator extraordinaire) but have not heard back yet.

[SOHC4 Cafe Racer Fan]

Stud soaking in penetrating oil.

Newest speed bump is trying to source a new output shaft seal. They are no longer made. Western Hills may have them.

91205-426-013   OIL SEAL (36X57X13)      

[bwaller]

Don, have a weldor weld a nut to the exposed stud. Spritzing a little water on the stud after welding will shrink the stud and help it back out of there. Safest bet man.

[SOHC4 Cafe Racer Fan]

I will give it a go, Brent.

On the good news front, I found a NOS output drive seal. Rare little bugger. It has a groove in the inner diameter for oil flow so you cannot use a generic seal.

[SOHC4 Cafe Racer Fan]

Bill Benton was able to find a 1975-76 CB750F rear wheel in his treasure trove of parts.

image_zpsbuahuzwi by Donald Leonhardt, on Flickr

image_zpsx2iofncd by Donald Leonhardt, on Flickr

Nothing a little bead blasting and powdercoating cannot fix.  I am also looking into swapping the rear disc for a EBC pro-lite lightweight rotor like the ones on the front of my CB750 (with GL1000 front end).  This will reduce a few lbs. along with the aluminum rear rim.

195327_zpsata1fljk by Donald Leonhardt, on Flickr

[MessnerMoto]

Bill Benton was able to find a 1975-76 CB750F rear wheel in his treasure trove of parts.





Nothing a little bead blasting and powdercoating cannot fix.  I am also looking into swapping the rear disc for a EBC pro-lite lightweight rotor like the ones on the front of my CB750 (with GL1000 front end).  This will reduce a few lbs. along with the aluminum rear rim.

What rim size you are going to use for rear at the end?

[SOHC4 Cafe Racer Fan]

I am not completely decided but very likely an 18" Sun 4.25" width. It will fit the Bridgestone BT016 and the Continental Cont Road Attack 2 CR.

[SOHC4 Cafe Racer Fan]

For those interested in shaving some weight on their CB750F bikes, EBC make a pro-lite rotor that fits all 1975-78 CB750F models - Part No. MD1064 (http://www.dynoman.net/brakes/ebc-apps.html).  I found one for $120.

[MessnerMoto]

I am not completely decided but very likely an 18" Sun 4.25" width. It will fit the Bridgestone BT016 and the Continental Cont Road Attack 2 CR.

I like more BT016 design. But personally I would choose sport touring tire

It is hard to get something wider then 18"x4.25"... There are excel rims wider then 4.25 but they are non dimpled. I just don't like non dimpled look

[SOHC4 Cafe Racer Fan]

I am not completely decided but very likely an 18" Sun 4.25" width. It will fit the Bridgestone BT016 and the Continental Cont Road Attack 2 CR.

I like more BT016 design. But personally I would choose sport touring tire

It is hard to get something wider then 18"x4.25"... There are excel rims wider then 4.25 but they are non dimpled. I just don't like non dimpled look

I would agree on availability.  I really don't want anything wider.  I have Excel high-shoulder rims dimpled rims on my 9 Lives CB750 bike. 







They are nice-looking and lighter wheels. 

Sun also makes a slightly more affordable 4.25" wheel.  http://www.buchananspokes.com/categories/rims_sun.asp