Topic: CB750A Street ET bracket drag bike. A year to build it.

[Jim F]

I am not going to spill the beans so you
Will have to wait for bill
But we are getting close

Jim

[Bill/BentON Racing]

Jon's right,dyno,graphs,charts,info etc.But first a little story to set the record straight........Them carbs (the CV ones) well no wonder they had us ALL scratching our heads!When we had problems ,it didn't add up,Jon sending carbs not ready or right? Well we all thought they were ready to go on,I put them on,my fault as builder,final assembly,I should have known better!Well,so on they went,ya'll heard how it ran,so off they came,well I found some interesting things! Carb sync on 3&4 the same,but off by 1/8 INCH to 1&2!!! Oh and trash blocking #3 choke pick up completely(blk silicone).same stuff wrapped around pilot,burred up main jet holder,metal shavings,Jon your friend who borrowed your carbs for that one weekend didn't tell you all he did,all this and broke off # 62 drill inside # 1,no wonder,Jims drill took a sudden TURN!No wonder we were lean,ran like sh*t,some buddy he turned out to be!
After cleaning,carbs were all good,well #2,3 and 4!I discovered the blockage when cleaning,carb sync not visual as carbs came with manifolds on and we were told easier to mount that way. Jon,hanging not good enough,shoot the Bast*rd!So now with Big Jim's help we'll get those right,in the meantime off we went to Brian's place,Dyno Heaven:


Now,you got something to look at.

The culprit!

Not what you want!

This one about made me sick!#4 is as bad,camera just wouldn't pick it up.

Jon,your buddy liked blk silicone!

was blocking #3 choke feed!

Clean pilots?.......

Burred up main jet holder.
Just give Big Jim his address!

It's worth it,now POST! ....80.52 RWHP,almost 50 ft/lbs torque,Bill a happy camper! 8)Thanks,Mike Rieck and Jon Weeks,Jim,Frank,Brian and yeah Sam Green for getting us started,now get back over soon!Keith ,what's up and a special thanks for being there for Samauto's first runs!I'm tired,but I can pull and jet 29's with my eyes closed! ,lol,Bill....Sam,you still up?

[Bill/BentON Racing]

More pics,cause well you know!

more like it.

yes,we"ll take it.

I love it!

This we got to fix! parts on the way! Thanks,Bill

[Jim F]

Here is the little bugger that had all of us scratching our heads.
Its a .062 drill bit that was broken off down in the air passage
No it wasn't machine chips or casting slag or something gone wrong in the machining process
I don't like to embarrass people that are trying the best to help.
and even if there not trying to help I don't like to embarrass people

I dont think John has much hair left on his head nor do we trying the figure this one out

it is what it is and all well be good soon enough

Jim

[jweeks]

The rich spot in the midrange will be corrected. That should nearly eliminate the horsepower dip between 5+6k. The flat power band showing until you chopped the throttle (10k) will allow you to rev this motor a little higher. The shift can go 10,500 with at least 10,200 rpm at the finish line if you want all that you can get out of this combination.

Jim, you are as always a gentleman. You also have a good memory. It doesn't matter what my "friend" did. I didn't go through the carbs before bringing them down for Sam. That was my fault. Assuming - well we all know the saying. I'm lost for what the drill was for. It doesn't make any sense. Not much of anything else does either. I don't use silicone on carbs, never have, never will. The stuff gets into passages and orifices, etc causing general mayhem. I've already apologized to Sam off line. He would have been better off letting me buy back the carbs. Mike, your motor deserved better!

My generosity does come back to bite me at times. Like most people here, I was just trying to help get a combination working well. When you lend something out, you expect it back in the same condition that it was given out. I am the tech inspector at my local drag strip.  One racer will have to know the fine print this year....

For everyone who has wondered about getting the bike to launch harder, take a look at the torque that we are playing with below 3 grand. This is more than we had with the CV carbs. Eventually the 34mm CV's should be better for top end and no worse for the launch when sorted. The bike will load to 3,000 rpm on the starting line now. The same reworked converter on my 1180cc motor would load the motor to 4,200 rpm with a different brand 34mm CV carbs. Yes, that motor made significantly more torque in the 3-4k range than this 836 can dream of. 6mm increase in crank stroke helps a lot with torque! Higher compression than what Sam's pistons are advertised at also helps the torque.

The situation now is to get the 29's some fatter needles to lean out the midrange. The CV's will need dyno time when they are put back together. Once the carbs are near the right A/F, we still can use some more torque between 3k and 3,500. The more we have, the harder the bike will launch. The harder the launch, the quicker the bike goes. You don't get low 12's/high 11's without getting all that there is available with tuning. Total ignition timing may still give us some changes to the powerband. Yes, the oxygenated race gas should give another 4-5%. If you really want the most that the bike can give you, use the gas.

When the carbs are done, and we know how much timing it likes, Bill should go to the track. Seeing what we get for 60' times will tell us what the dyno plots show for the lower rpms vs torque. If we don't like the 60' times, we'll have to figure out where to get more torque in that 3-4k range. The bike should be able to go in the 1.9's for 60' times at a minimum.

I've got a 811 motor going together in the next few weeks. I'll post my timeslips to show that it is possible to get 60' times where I'm claiming. I'll be playing with less horsepower, but it will be maximized for good launches. If you read back enough, I cautioned Sam about power wheelies as he's going down the track. As the midrange improves, that's the fringe "benefit".  The rear brake also becomes more of a challenge with the harder launches. This isn't the last tweak to be done. It's a long process to get everything available.

Sam, I must be back. Multiple paragraphs again...



                                                                                  JW

[scottly]

Thanks for the update, guys. Looking forward to the next dyno test with the CV carbs!

[dragracer]

Bravo gentlemen. It was nice to see the positive results of all the hard work.

Welcome back Mike and Jon.

[Grnrngr]

And totally cool to see the details of repairing that carb. Micro laser welding....wow....
Thanks a bunch, guys, you're awesome, and it's a priviledge to watch your progress. Best of luck at the track!! And we'll be here watching...

[Bill/BentON Racing]

K.    Team Sam Green will get it DONE!!!
I've got to go unload,long day yesterday,but worth it! ,Bill

[Tintop]

Great update guys, thanks.  Can't believe all the issues with the CV's, but some masterful work seems to have sorted those out.  Special thanks to JW for the educational post.  Starting to get a feel for what it takes to make a great drag motor.

[mick7504]

That is great news.
As an observer, you've been tested and come out on top.
It's a credit to you all, and a fine example of what is acheivable with perseverance and a willingness not to be beaten.
Take this example to the track with a fierce desire, punch the air and wave the winners flag with pride.
We're all waiting.
 

[dragracer]

Bill/Jim,

Test time, test time!!!

There is an all bike race on saturday at Jefferson-Pageland Dragway here in SC. The same guys who put on the race in Union are doing this one. ET brackets and 5.60 index along with test and tune. I know its a bit far but what the heck, dragracers will travel for some fun. This event is normally packed with spectators. They even have a car and bike show. The racing a great and the track personnel are really nice people. The usual crowd that you guys know will be there as well. I know you said you would try local testing first but give it some thought especially since it sounds like the bike is now running better.

Again, congratulation to you fellas on getting both the smoothbores and the CV's sorted out.Can't wait to see some real time dragstrip results.

 

[Bill/BentON Racing]

Frank,don't think we'll make this weekend,want to go back to dyno this Sat.!
Got to fix that midrange! We'll get it,and then hit the track.Where? Want to make the Rock May20-22nd if at all possible.Bill
Sam,where you at?

[Sam Green Racing]

I'm here Billy, was mad busy yesterday and have been tied up all morning at work

When you get the fueling something like right, do your best to get some miles on the motor without keep changing things, try to change gear at 9,800rpm and note what the revs drop back to, It'll help for sorting the gearing and getting the shift minder dialed in.

Onlookers, thanks for the kind words and encouragement.

Sam.

[Sam Green Racing]

I am happy to see that power is holding to 10,000.

That cam sure is strong up at the top Mike, sadley It's killing the bottom end, your thoughts on going back down to the 65 at a later date ?

Sam.

[Bill/BentON Racing]

Sam,z answer is NOOOOOOOOOOOOOOOO!
We don't need it!
We need proper A/F
We will get it
Brian,dyno operator and owner and builder of R6's that produce 131 or 134 RWHP(his 2mm over motor 143RWHP,55 ft/lbs torque said.....
Leave  that motor alone,I agree,I KNOW Mike agrees!
Already better than we've been.
Consistentcy will come.
Dyno time and persistence will win.
It will repeat,it's closer to ATM now than ever
Z motor is CONSISTENT
Z ignition,Dyna 2000,Taylor Pro wires and Dyna 2.2 coils are CONSISTENT
A/F will be CONSISTENT,then it'll repeat
Worry about geting back over,it'll be ready!


NOW,another subject,if it was a strong car motor we'd tell the converter guys what we wanted........Jon,I have 2 stock converters....I know this nice chap that welds a little now and then(Big Jim).what do you think?Feasible? Jim's willing! ,Bill

[jweeks]

Sam,
     The 2 more tooth rear sprocket should be already at or on the bike. It will help with the improvements that we are looking for in the first 60'. Anything that will help make the bike more consistent now should be considered. Yes, you can shift it where ever you like. I gave the best estimate for lowest ET. The goal should be to have some consistency while you are breaking in the motor. Since the motor seems to only get mileage a quarter mile at a time, Bill needs a carrot to keep making passes.  It may not be as big of a problem after the dyno passes are made, but it will help the bike now and after it has bedded in. Give it some thought?

                                                                              JW

[Bill/BentON Racing]

Sam......I thought you said 10,800rpms,......it's got Carrillo's!.....OK 10,500? Z rabbit is hungry! ...Big Jim has new chain,I have z sprocket,who's got the workshop manual? ;)OK,it will be on ,probably pull wheel in a few minutes.Can Samauto pull off a second win? Bike Of The Month? Ya'll vote,you too! ,Bill

I couldn't help it!

[Sam Green Racing]

 down to the 65 at a later date ?

Sam.

I did say at a later date William.
I was thinking more along the lines, if when it loosens up and the fueling is corrected, what happens if we still don't find enough torque to spin the converter fast enough to launch the bike quite a bit faster ?
The 125-65 cam has hell of a lot more grunt low down but the power will drop at the top end as will the revs (8,900rpm)
Personally, I like that big rush at the top but it looks embarrasing slow off the line but I can live with it.
Get chaseing that carrot.  nice one Jon.

Sam.

[Jim F]

Who has my #50 drill bit
dang it
Its not in an air passage I promise

I am going to replace all of the air jets and get rid of the epoxy. Will have them in today and will start to polish

Jim.

Bad spelling on my part John

also one of the jet holes is too big for the dyna jets. I am going to weld the diameter and re-machine it.

[jweeks]

Jim,
     "if the air jets"?  Making new air jet inlets?  I can lend you a #50, but the post office wants a couple of days....

                                             JW

[Bill/BentON Racing]

Jim,I've got you covered.#50 let me know.No news on jets,did see one size smaller needle jet.stock 0-6, 0-4 was available back then.1980 Action Fours catalog.Bill

[bwaller]

Bill, I was told a 0.4 needle jet was not available before June & with the situation in Japan that might even be pushed back. I understand there may still be 10 different needles but one leaner that might help is 5DP39. I have an old jet needle chart that's barely legible and it shows the 5DL31 as being a rich one. That was the needle most used on the street I believe.

[Bill/BentON Racing]

Brent,good info,OK you guys,someones got em,let us know!
Sam......nitrous and another brake! ;)Bill

[Jim F]

going to sneak over to northern tool (MSC is too far) and get a # drill set
thanks
Bill I called livengood yesterday and they will call me when everything is in
chain is here
see you soon
J