Topic: CB550 Salt Flat Racer!

[B.O.X.N.I.F.E.]

After my last cross country trip on my poor old 550 I came home more determined than ever to run at Bonneville. I'd been thinking about it for 5 years, initially wanting to just visit as a spectator, but the bug to run had bitten about two years ago.

I've just rebuilt these, one of which I would have liked to have kept, to sell to fund the project. The nasty 550f is the bike I'll be running -





On the salt last year, showing off for the mountains -


I joined the landracing forum and was immediately referred back home to the SOHC4 boards, although I'll keep lurking over there. I need you racer guys to straighten out those twisties for a minute and think straight and fast.

Before I start bugging guys like Mrieck who hopefully will be doing some work on the bike, I'd like to have an idea of what kind of motor I'm building; where I want it to make power and what kind of chasis it should be slung in.

The salt is way up there, 4k plus feet. What means should I work with for moving enough air through the motor? I'll be boring up to 590 (because it needs rebored anyways), and was thinking a 650 cam (same as mild webcam 550 grind), 750 carbs if necessary and maybe those fancy new 1mm OS intakes. Are things like balancing the rotating assembly, shot peened rods, coated pistons, etc. also geared towards balls out top speed racing? I really want to know where LSR and roadracing differ.

Additional info, for no real reason...

Shop space -




Kimtabs!


Pipes and the bike, in a sad condition

[MRieck]

You will need all the port, all the cam, all the air you can get. You will also need custom pistons with all the compression you can get. Than there are gaskets............Starting point.

[B.O.X.N.I.F.E.]

So aggressive porting, lots of air and upped compression.

Considering I'm racing against myself, not in a competitive context, and on a budget that probably won't allow for huge pistons, can I gather some compression from something like decking the head/thin top/bottom gaskets?

I keep gravitating towards shoving a 650 motor in there, but I need to set some parameters and build the bike that feels right, not just crunching math and budgets until I find myself out there on a 'busa. A 550 taken as far as I can go with my current skill set still feels like the most fun option to me.

[754]

 Just get there , and do the run what ya brung... get a feel of the situation.
 Dont go overboard first time out.. have fun and learn... hope to see you there at BuB..

 I love the Kimtabs..anything you want to trade for one?... like billet stuff ?

 Remember weight at B,ville does not always hurt your speed, some add weight..

 Got your PM,  can probably help with that.. what disc and caliper, do you plan on running on the rear ?

[Flying J]

Im no race expert by any means but i do stay up on how to hotrod a 550 motor. Some things that might help would be a set of those pistons dynoman sells. They have higher compression. Also straightening out the intake track would help. You could run a set of the old KZ carbs or look at what funjimmy did with his CR26 carbs. doing it the way fun jimmy did it would also allow you to adjust the length of your intake to build the power where you want it. While your head is with Mrieck have him put in some of those new valves that hes got. I wouldnt mind running my bike at bonneville when its done.....wana race?

[jaguar]

love the wheels

[B.O.X.N.I.F.E.]

Just get there , and do the run what ya brung... get a feel of the situation.
 Dont go overboard first time out.. have fun and learn... hope to see you there at BuB..

 I love the Kimtabs..anything you want to trade for one?... like billet stuff ?

 Remember weight at B,ville does not always hurt your speed, some add weight..

 Got your PM,  can probably help with that.. what disc and caliper, do you plan on running on the rear ?

the kimtabs seem to get a lot of attention, they were an obsession and I jumped when a set finally popped up. They were embarrassingly expensive and I had to build and sell a whole bike to afford them. I haven't decided on a rear disc setup yet, for this season at least I'm just running the front. When/if I let the rear go consider that a first dibs to you Frank!

PM me back when you get a chance about the carrier for the front, Jimmy said you're the guy to talk to about that and I can't wait to get that wheel mounted up.

*looks like billy bob thornton already figured out the rear disc on kimtabs for me  . Looks like a Hurst or something fancy. Maybe machining a rear carrier to accept a 77 - 78 750F rotor would be a start, or possibly a Kawa Spectre or early 80's KZ1300....

http://garagecompany.com/bikes/custom/cb750racers/IMG_6232.JPG

Im no race expert by any means but i do stay up on how to hotrod a 550 motor. Some things that might help would be a set of those pistons dynoman sells. They have higher compression. Also straightening out the intake track would help. You could run a set of the old KZ carbs or look at what funjimmy did with his CR26 carbs. doing it the way fun jimmy did it would also allow you to adjust the length of your intake to build the power where you want it. While your head is with Mrieck have him put in some of those new valves that hes got. I wouldnt mind running my bike at bonneville when its done.....wana race?

I'd love to, we'll have to see which of Chris' MGPWerks pipes wins :-)

* Holy crap, I had never seen these kits. Thanks for the heads up. Considering I just got one of those Henry Abe kits, which will need the oiler groove worked and a new set of stock 750 rings, this is a good deal. I gotta be careful though, don't want to burn through my loot :/

http://www.dynoman.net/engine/pistons/dp-CB550.html

[754]

Are those Kimtabs unused?

 You will have to figure out the bore size, of the thru hole, and width of hub... and check if the holt pattern is for Honda discs.

 Hurst brakes are pretty primitive, most anythink will work as good or better. Grimecas are pretty reasonable..

[Flying J]

What is the weight of those wheels?

[jaguar]

What about old school brembos?

[B.O.X.N.I.F.E.]

Are those Kimtabs unused?

 You will have to figure out the bore size, of the thru hole, and width of hub... and check if the holt pattern is for Honda discs.

 Hurst brakes are pretty primitive, most anythink will work as good or better. Grimecas are pretty reasonable..

They're used, probably had a whole hub setup that was separated at some point. I'm getting 59.5mm on the bore of the thru hole, although if we machined up a bolt on bearing carrier like FunJimmy's Interceptor I'm not sure the bore would matter would it? Or are you thinking a sleeve for the thru hole? Width of the hub on the Kimtab is 86mm, not sure how that compares to the stock wheel. One side of the thru hole edge is beveled on both wheels for some reason.

I'll run the rear if it can be worked out in time, I'm most concerned with getting the front done first. Bolt hole pattern is the same, I slapped a 550 disc on there and ran the bolts through the hub for a perfect fit. Figuring out the spacers for centering the wheel in the forks and the offset from center of the disc seems complicated to my puny brain...

What is the weight of those wheels?

18" is 7.8lbs, 19" is 8.8lbs

[Greggo]

Subscribed.

[turboguzzi]

interesting challenge
there are almost too many ways to build a hot mid size sohc motor, the final configuration will require a lot of thought and planning. I find that my racer builds are as dependent on logistics/time available as they are on technology or $$$.

Gets even more complex as you have zero experience and LSR is even more of a niche than road racing or drag racing.

so i tend to agree with whoever suggested you jump onto "run what ya brought" class and start your learning curve form there.

And as much as you love your kimtabs, leave those to your street bike to pose with.

[B.O.X.N.I.F.E.]

Considering the time constraints and requirements to pass tech and run in a class, I think "what ya brung" is probably what I'll be running in. I have run out there before in a similar capacity, I beat up on 90mph on my 550 when I went out there and ticked just over 110mph on my buddies hot '05 Bonneville. The "what ya brung" experience wont be totally foreign. The goal is a legit 120, but something like 110 - 115 is more likely.

I definitely agree, the time you allow yourself to build dictates the build almost more so than what is possible given any amount of time.

[754]

 The 2 sideplates hold the bearings and center the wheel Radially.
 That is to say a small lip on the innerside of the bearing plates, must fit very precisely, into the bore of the wheel... keeps it all straight. Nice weight on that pair !!!

[turboguzzi]

I definitely agree, the time you allow yourself to build dictates the build almost more so than what is possible given any amount of time.

if its any help, then consider that my racer builds (including complete tear down + fabrication/tuning/etc. + re-assembly ) have taken around 300 to 500 hours.

[bwaller]

I definitely agree, the time you allow yourself to build dictates the build almost more so than what is possible given any amount of time.

if its any help, then consider that my racer builds (including complete tear down + fabrication/tuning/etc. + re-assembly ) have taken around 300 to 500 hours.

[/b]

Then there is thinking about it when you go to bed, dreaming about it, plus all the day dreaming. 

[Old Scrambler]

Plus several on the time and dreaming!!!  Glad to see you on this thread!  If Sam can build a dragster to go slow, I think a few of us could have some fun at Bonneville with sohc bikes at somewhat higher speeds. 

I started to build my Triumph Cub with a machine-shop friend and bike enthuziast about 8 months ago.  The motor was first. Now the chasis build after many hours of consideration for each feature.  I'll post some pics when I figure it out and a few more welds are completed.

Advice.......no front brake.......drum on rear with no drag.  Lower the frame but try to get taller wheels.........most likely will need to extend the swingarm.  Read the rule book for BUB and then read it again. Get your shoulders and head as low as possible........use clip-ons with downward angle to get narrow...........as you build torque and compression the horsepower will take care of itself. Look for narrow fenders to match tire width. Get an electronic tach with memory.

[MRieck]

Plus several on the time and dreaming!!!  Glad to see you on this thread! If Sam can build a dragster to go slow, I think a few of us could have some fun at Bonneville with sohc bikes at somewhat higher speeds. 

I started to build my Triumph Cub with a machine-shop friend and bike enthuziast about 8 months ago.  The motor was first. Now the chasis build after many hours of consideration for each feature.  I'll post some pics when I figure it out and a few more welds are completed.

Advice.......no front brake.......drum on rear with no drag.  Lower the frame but try to get taller wheels.........most likely will need to extend the swingarm.  Read the rule book for BUB and then read it again. Get your shoulders and head as low as possible........use clip-ons with downward angle to get narrow...........as you build torque and compression the horsepower will take care of itself. Look for narrow fenders to match tire width. Get an electronic tach with memory.

Thanks....you are a real inspiration Old Scrambler. I'll be happy to ship all the stuff to you next time. Obviously you know how to make it quick and fast.

[Old Scrambler]

Ooooooooops............I didn't quite mean it that way...............I've read every word of that novel. Its a very fast motor just hobbled by the short track!  Looking at the rpms from the dyno, it would likely top 160 mph with the right sprockets.  BTW, I would not begin to do my own motor building............I let that up to the experts. I just read and try to learn...........then go riding!  My Bonneville Cub is the 1st total bike build where I have touched all of the parts. One cylinder may lead to more in the future.

[B.O.X.N.I.F.E.]

The 2 sideplates hold the bearings and center the wheel Radially.
 That is to say a small lip on the innerside of the bearing plates, must fit very precisely, into the bore of the wheel... keeps it all straight. Nice weight on that pair !!!

Ah, see thats why you're the man with the tools, let me know if you'll have some time to work on it and what you would need from me.

they're featherweights, couldn't believe it when I got the box

[754]

 If need be we can get the front on for Bub.
 You should check for cracks and paint them, the salt is bad for them.
 Your front hub area, get a straightedge across the side and see if the distance to rim edge is same both sides, then there is no offset.
 Stock hub appears to have a mm or two offset on one I looked at today.also 82mm wide which would mean stock disc may have too much offset on the carrier, when mounted to your forks.
 The inner size 59.5mm is very close to 2. 343 which is a 32nds size.. it should be checked with a micrometer.

 Not sure why TG, suggests you should  use the racing wheel on the street, rather than the track...??

[turboguzzi]

"Not sure why TG, suggests you should  use the racing wheel on the street, rather than the track...??"

because you should build the wheels according to tire/rim size that works best on the salt flats.

[B.O.X.N.I.F.E.]

If need be we can get the front on for Bub.
 You should check for cracks and paint them, the salt is bad for them.
 Your front hub area, get a straightedge across the side and see if the distance to rim edge is same both sides, then there is no offset.
 Stock hub appears to have a mm or two offset on one I looked at today.also 82mm wide which would mean stock disc may have too much offset on the carrier, when mounted to your forks.
 The inner size 59.5mm is very close to 2. 343 which is a 32nds size.. it should be checked with a micrometer.

 Not sure why TG, suggests you should  use the racing wheel on the street, rather than the track...??

Double checked everything
Hub: 86mm
Hub to rim side a: 7.5mm
Hub to rim side b: 9mm (hub center beveled around thru hole on this side)
Thru hole: 2.34 inches (my caliper only goes 2 decimal places)

I guess that 7.5 & 9mm confirms an offset. Not looking good for that stock disc.

I'll look into xraying the wheel, just ordered a can of Gibbs brand for coating. Check it out here if you're not familiar, used it on my 3100 Chevy build to keep bare parts from oxidizing and it was excellent. Also a fantastic penetrant.

http://www.roadsters.com/gibbs/

Bare mag, coated in Gibbs. Love the dark coloring.

[TwoTired]

You might be able to adapt one of these?