Topic: CB750 AHRMA Sportsman 750 Racer

[slikwilli420]

i would not like to try and put a lot of power through that !

Why is that?

[simon#42]

because it does not look very strong , dont worry though you are not putting a lot of power through it .

[slikwilli420]

Plenty of road racers running hubs just like this making lots more power than me. Far stronger than an old cush drive hub as well.

[754]

That's a thick flange hub, some are half the thickness. If you are slipping the clutch vs dumping it, it should be ok..
 Note ..as with all lightweight race parts frequent inspections are necessary..

[754]

MAD MEL was running dirt track wheels on his turbo Honda and Suzuki.    Both were in a 69 CB 750 frame.

[scottly]

Interestingly, the spokes have not had issue as far as coming loose, though every time the rear comes off, I remove the sprocket and re-tighten the bearing adapter bolts. On my hub, there are 8 bolts, 4 sit in counterbores and 4 are the "pins" that the sprocket rides on. I find that at least half of them have loosened to some extent after a race weekend, despite having lock washers on them.

What type of lock washers? I've found the typical split washers aren't worth a damn, especially with Allen head bolts seating on aluminum. I've had better results with blue locktight and hardened flat washers, with a close fitting ID for the Allen heads. (I have resorted to reaming the washers to size. )

Should have said lock nuts. They are nyloc nuts that were provided by the hub manufacturer.

If the bolts are loosening up, it's probably due to the heads deforming the aluminum, due to the very small area of contact, rather than any locking mechanism. The solution, at least for the drive pins, might be to make "Tee" nuts, with a bigger, thicker base, counter-sunk into the hub, with the bolt inserted from the other side, or custom bolts with a similar head.

[NitroHunter]

MAD MEL was running dirt track wheels on his turbo Honda and Suzuki.    Both were in a 69 CB 750 frame.

I'd forgotten all about that guy. Thanks for the memory. 

[754]

Look up Mad Mel Honda or Suzuki online, a few pics..
 He made double the power we have..

[gschuld]

https://www.rbracing-rsr.com/madmel.htm

Mel has nice taste.😁. Oh, wait a minute, I was supposed to look at the bike.🤔

George

[slikwilli420]

Interestingly, the spokes have not had issue as far as coming loose, though every time the rear comes off, I remove the sprocket and re-tighten the bearing adapter bolts. On my hub, there are 8 bolts, 4 sit in counterbores and 4 are the "pins" that the sprocket rides on. I find that at least half of them have loosened to some extent after a race weekend, despite having lock washers on them.

What type of lock washers? I've found the typical split washers aren't worth a damn, especially with Allen head bolts seating on aluminum. I've had better results with blue locktight and hardened flat washers, with a close fitting ID for the Allen heads. (I have resorted to reaming the washers to size. )

Should have said lock nuts. They are nyloc nuts that were provided by the hub manufacturer.

If the bolts are loosening up, it's probably due to the heads deforming the aluminum, due to the very small area of contact, rather than any locking mechanism. The solution, at least for the drive pins, might be to make "Tee" nuts, with a bigger, thicker base, counter-sunk into the hub, with the bolt inserted from the other side, or custom bolts with a similar head.

Im liking that idea and will need to come up with something like that for sure. Having to get back on those after each race is just another thing and if they loosen too much I may have a bigger problem to deal with.

[slikwilli420]

Couple things from the weekend. I showed my bike at the Garage Brewed Moto Show in Cincinnati in the race class. I didnt win anything but had a good time and some great beer in the process.









I was also following the activities down under at the PI Classic and noticed a few shots of the frame of a CB750 race bike down there that I found quite intriguing.





There is a lot going on around the neck but I like the thought and it seems like it would add some much needed rigidity. I think with my Superbike build that may be something to pursue, and potentially on my Sportsman bike as well.

[Tintop]

That is similar to how Denis @ CMR braces the headstock.  Not sure were the pictures are (which page), but check out how he revised that area on Brent's bike.

[calj737]

Who’s that skinny fella standing next to your bike? 

[slikwilli420]

Who’s that skinny fella standing next to your bike? 

Just stop it Cal. Still lots of work to do. 2019 has started slower than anticipated.

[gschuld]

That is similar to how Denis @ CMR braces the headstock.  Not sure were the pictures are (which page), but check out how he revised that area on Brent's bike.

Brent’s bike has had a substantial amount of the factory frame replaced.  Dennis Curtis went to the limits of the class rules about what had to stay stock frame wise for his VRRA rules.  Way beyond bracing😎

George

[slikwilli420]

After some parts swapping, my cycle x 4 plate clutch system is in and the clutch cable was shortened 5 inches and rerouted. oil change to Motul 5100 forthcoming to complete that upgrade.

New brakes in and ready to rock with fresh race pads. The lever feels so much firmer with the AP unit vs the Grimeca.



More thing on the punch list before first race which is now Roebling Road in Georgia... in 11 days. Things in my schedule changed for the year so had to add a race earlier than expected. Better get moving!

[slikwilli420]

Bike is all set for 2019! Roebling Road is in 4 days. My wife and I are driving from Michigan starting Thursday morning, with an overnight stop in Charlotte, NC then onto the track in Savannah, GA. Too hard to put 14 hours in one day so it will be a little bit vacation as well as some racing. I will practice Friday afternoon, then racing Sat/Sun, then back to the frozen North.

The bike is all set and ready to go with no time to spare. I will fire it this afternoon to bring it out of hibernation and get the new Motul 5100 moving through the system. I have double checked every wire and bolt on the bike and every system looks like a go.

I have a number of changes I am going to make to the bike for this year, after Roebling and NOLA (early March), including a new seat, adding a dash mounted oil pressure gauge, front fender, and a few more refinements. I am also planning on starting to build a new fuel tank. Im going with aluminum and will gas weld it together in my shop. After all the back and forth on my oil tank, I want to try to get my in-house aluminum welding up to speed. It may take longer than going to the welder but it keeps my ability to change things on the fly very much in tact. I have a design that will echo the tank on Brent's racer, as its fairly simple from a shape standpoint, and will hopefully be more ergonomic than my current tank, which I find limits my movement on the bike.

4 days...

[Ramrod_Racing]

See you there!

[slikwilli420]

See you there!

Awesome!!

[slikwilli420]

Threw the bike on the rollers last night to fire it before loading in the trailer, and its making the most awful grinding noise from the trans. Sounds like a can full of rocks. It seems that when I let the clutch out on the rollers to engage the engine, it grinds as if the gears arent meshing all the way and simply spinning past each other. Either way, to make Roebling Road this weekend I need a small miracle. Thank God I have extra trans parts I can swap in. Wish me luck.

[754]

 Change back to the old clutch.
 I think you had said you tried a 4 plate..

[bwaller]

Agreed Frank, first thing to check.

[slikwilli420]

That is definitely step one after work today. I did find that my clutch pack height was too tall, making the pressure plate rub the clutch basket rivets and after I took out one steel (extra steel for early vs late inner hubs) I had eliminated the spacing issue, but the grinding persisted. Im going back to my original clutch from last season to see. Im having visions of it being trans related where something is broken off in the gear set keeping them from engaging. I can swap the clutch back to the original quickly and get on the rollers, but if thats not it, then the engine is coming out.

[Rocketman]

Fingers crossed.....

[dragracer]

I see that Roebling is a non-spectator track. So much for showing up in support of a fellow racer. Shame,  you would be only 2 hours from me down Interstate 95.