Topic: CB750F private test session results.Video added

[PeWe]

Engine data?
Displacement?
I think you wrote RC327 cam before.

[gschuld]

I’ll let Frankie give more details.

But from what I recall:

F2/3 cases and bottom end/non lightened crank
CycleX steel rods with ARP bolts (won from a previous Man Cup prize)
Used but not worn out 70s...Edit: NOS MTC 12.5:1 72mm K pistons (heavy but tough)
1026cc
Older big bore sleeve K cylinder
k head, locally ported with new SS valves/springs 33.5/28 I assume.
Used RC 327 cam
Good condition OEM rockers
RS34s(?)
Chrome cam cover(offers 2 tenths reduction per 1/4 mile run😎)
Lightened starter hub(removed all charging rotor weight, for electric start only)
Modified GS Dyna pickup(?)
Schnitz Top Gas 2000 ignition/nitrous controller http://schnitzracing.com/manuals/top-eliminator-manual.pdf
Vance and Hines pro pipe, sidewinder designed for the DOHC cb750/900.

It’s a very old school well proven in battle layout.   CycleX steel rods are not especially light, but likely quite strong. The RC “Super Rod” big bolt factory based steel rods are around the same weight, lighter actually (which Frankie has been using with great success in his Red bike for YEARS)

Based on MPH and known dyno readings from similar motors, Frankie is likely around 110RWHP.

It’s not to say that a far more expensive engine with lighter more up to date parts and a 40 year newer cam design wouldn’t offer the potential for a few more ponies, or perhaps greater life expectancy.

But in power achieved per dollar spent, Frankie is a master.😎

George

[dragracer]

Your memory is correct George.  That about sums up the engine specs. The only difference is the pistons were actually new MTC (NOS). It was the last set they had on the shelf.  Heavy as George described but for bracket racing, they work just fine. The crank was supplied by Cyclex and is balanced but not lightened.  I'm just not a fan of lightened cranks in a dragbike engine.

[dragracer]

Frankie,

You are, or at least should be, an inspiration to everyone here.  Your success in cost conscious yet high quality reliable race engines should be a good example for anyone to consider. It’s hard not to appreciate your knowledge on chassis mods(maybe looking past some of the welds😄), wiring, nitrous systems, carb systems, chassis tuning, etc

You’ve shown that you can make respectable big bore power levels, make them reliable, and do it without needing to sell a kidney.  I’m glad to help wherever I can.😉

George

George. I've tried to show you can build a quick SOHC without spending your last dime. I took my time and bought as many used parts as i could. I picked up pieces and parts here and there over time as long as they were cheap. This allowed me to save money to buy necessary new parts when the time called for them.

Yes, this project got somewhat off key when i decided not to use that stock Katana arm and installed  a reasonably price, used chromemoly Busa arm instead. I searched until i found  a good deal. Or when i made a decision to use the lightweight PM wheels i had on hand instead of a set of stock easy available Katana or GSXR rims. Yes, i used the new Cycle Ex super rods instead of the used RC heavy duty rods i had laying around, no i didn't use the stock crank from the F3 bottom end but got a balanced, unlightened Cycle Ex crank because i decided to add nitrous. I could have saved money if i hadn't done those upgrades. In the end, would the original plan have netted a mid to low 10 second bike? Uhhh, i think it would still be close.

Could someone reading through the entire build thread recreate a similar bike? I hope so, as that's why i took the time to show almost everything i did in the process. It didn't matter if it was a failure or success, if it was a proud moment or an embarrassing mistake, i shared the steps.  I had a basic formula that didn't include using billet parts or an exotic cylinder head and it works for me. 

As to my welds. I tried to tell you all on the front end I was not a trained or experienced welder, hahaha. All i can say is i feel i achieved full penetration and think the end results are safe for my application.  Lucky for me,  the powder coating hid the flaws in the end.  I did end up getting a nice gas mig welder as a christmas present from the wife. Hopefully the next project will have nice, clean welds that will meet everyones approval .

I think wère going testing again in a few weeks. The battery went dead in the gopro last time or i would have recorded all 3 of the runs. It will be charged next time so i can capture more action.

Thanks again for the encouragement and feedback from the forum.  i need to chase down the source of that odd noise Scottly picked up in the video. I initially concluded it was wind but i am now second guessing myself. Better safe than sorry.

[scottly]

Pop the tappet covers off and see how wet things are.

[dragracer]

Pop the tappet covers off and see how wet things are.

I do plan to check under the tappet covers.  I want to look over the rest of the bike first to be certain nothing is rubbing or loose.  Could be a bad bearing in the wheel, or transmission.  Anything is possible.  If all checks out there, the tappets will come off. To be safe, I'll probably pull the valve cover and the cam for inspection of the journals and towers. I can pressurize the engine with my oil pre-lube rig to make certain all of the passages in the head are open. I'd hate to wipe out the cam and ruin the head due to oil starvation.  Ask Billy about how that works. He trashed a nice RC 327 cam and a RC Cobra head at a Man Cip race about 4-5 years ago. He was heartbroken after tearing up that Cobra motor.

I probably won't get a chance to look at this until next week.  I'll be spending time with family members over the weekend.  I'll report back what I find.

[scottly]

Do you have a frame kit installed? If not, I'll give you a racer's discount.
I trashed a 413 Mopar on my third pass at the strip due to oil starvation: the squeaking sound when the engine was started before the forth pass was the clue.

[dragracer]

Yes sir. I installed a frame kit during the build.  I appreciate the offer nevertheless.  I'll let you all know what I find. I'll remain optimistic for now that there's no internal problem. I'm going to err on the side of caution and do a once over though.

[dusterdude]

Keep on truckin frank

Sent from my LM-X420 using Tapatalk

[dragracer]

Keep on truckin frank

Sent from my LM-X420 using Tapatalk

Thanks Mark. I'm trying to sort this bike out. 

Hope to see you at the XDA, VMP race in Augusta. It could be our first major event of the season but only if we feel comfortable with containment of the virus. As of now, the numbers don't make me very optimistic about the overall health status of this country.

[seanbarney41]

Pretty sure the sound in the video is from wind and not the engine...but safe is always better than sorry.  Thanks for sharing, frank!

[dusterdude]

Keep on truckin frank

Sent from my LM-X420 using Tapatalk

Thanks Mark. I'm trying to sort this bike out. 

Hope to see you at the XDA, VMP race in Augusta. It could be our first major event of the season but only if we feel comfortable with containment of the virus. As of now, the numbers don't make me very optimistic about the overall health status of this country.

Lets hope it happens

Sent from my LM-X420 using Tapatalk

[754]

So have you used Nitrous , or not yet.

[dragracer]

So have you used Nitrous , or not yet.

No. I haven't sprayed it. I'm trying to be certain I have all the gremlins out first and get the best all motor ET from the bike before i drop the bottle in.

[PeWe]

How much nitro is the normal dose?
I used model engine fuel in a moped once, tricky to switch off when it revved a lot at idle. Even without the spark plug HT lead I had off in my attempts to kill it.
15-20% nitro, some castor oil and mostly methanol.

[Sam Green Racing]

How much nitro is the normal dose?
I used model engine fuel in a moped once, tricky to switch off when it revved a lot at idle. Even without the spark plug HT lead I had off in my attempts to kill it.
15-20% nitro, some castor oil and mostly methanol.

PeWe, Nitrous is not the same as Nitro.

[PeWe]

How much nitro is the normal dose?
I used model engine fuel in a moped once, tricky to switch off when it revved a lot at idle. Even without the spark plug HT lead I had off in my attempts to kill it.
15-20% nitro, some castor oil and mostly methanol.

PeWe, Nitrous is not the same as Nitro.

Aha!
N₂O, like doctors use when having fun!

[dragracer]

How much nitro is the normal dose?
I used model engine fuel in a moped once, tricky to switch off when it revved a lot at idle. Even without the spark plug HT lead I had off in my attempts to kill it.
15-20% nitro, some castor oil and mostly methanol.

Pe We, nitrous oxide is what I've set this bike up to use as a power adder. And yes,its the very same gas that's utilized in the doctors office to put a patient into lalala land. Lol. I have fairly large jets installed right now but have no intentions of ever using 100% of the rated horsepower jetting. The ignition controller on the bike is capable of progressively bringing the nitrous in based on user programmed settings. I can control the starting percentage and then ramp up to my final desired percentage based on the amount of time I input. I can also delay the beginning startup if I don't want to spray right at the drop of the clutch. I also will program a timing retard setting in the box so I can stay ahead of detonation as the percentage of nitrous increases down track.

[dragracer]

So here's my initial nitrous tune up::
* set the nitrous start percentage at 20%
*set the final nitrous percentage at 50%
* set my nitrous ramp timer at 7 seconds to go from 20-50%.
*set the initial timing retard at 2 degrees
*set my ramp retard at 6 degrees to bring my total retard to 8 degrees.
*set the total timing ramp timer at 7 seconds.
* set my nitrous start delay at 1.5 seconds into the run, the bike will leave the line on raw horsepower and not begin to spray until after i pass the 60' mark.


If you blow up the picture of the bike in the post above this one, you can see the features of the Schnitz Top Eliminator ignition controller.  This box has features i will never use for this particular bike. Its an all in one box to control every function a racer would need except data logging but there is an output to connect to one.

This soft tuneup should take the bike into the 9.60-9.70 ET zone easily.  I'd expect to see a  135-140mph pass also.

[754]

 So you expect around 10.0 to 10.20 on motor alone ?
 And how much more on Nitrous ?
Bad thing here, I have most of what you have in the motor , except electronic stuff, and different carbs that can be 34mm, the bad part have  not been able  to scratch together a bearing set, and freshen a head,, and take a 970 to 1000cc.  Aaargghhh.
 I want it for street.. and a few strip runs

[PeWe]

Very interesting details!
I had no idea about the programmed delivery of the nitrous (N₂O) gas.

I thought it was a button to press as long as more power was required.

[scottly]

I thought it was a button to press as long as more power was required.

Forty or so years ago it was exactly that, Per. The nitrous adds oxygen, so additional gasoline must also be added. A lean fart can destroy pistons in an instant.  

[dragracer]

So you expect around 10.0 to 10.20 on motor alone ?
 And how much more on Nitrous ?
Bad thing here, I have most of what you have in the motor , except electronic stuff, and different carbs that can be 34mm, the bad part have  not been able  to scratch together a bearing set, and freshen a head,, and take a 970 to 1000cc.  Aaargghhh.
 I want it for street.. and a few strip runs

Frank. I feel that 10.20s is very attainable. The best pass at Rockingham was a 10.35 with a 1.45 sixty foot time.  The passes i had the prior time out were 1.40 and 1.41 sixty foot times. I feel confident i can get into the high 1.30's on the short times and it should give me low to mid 10 .20s in the 1/4 mile. With only 6 total passes, i'm still trying to learn how to ride the bike. That is;, what exactly does the bike want from me in order to perform at its best?? I've got to test the limits at a track with idea traction conditions to see precisely how much i can lower the 60' times without adjusting the shock. Once  I get a consistent baseline,  I'll determine from video footage what specific adjustments need to be made.  I set up an onboard camera system to monitor the travel and rebound of the suspension.  I didn't use it the last time out because I didn't have an SD card installed.  I also have a gopro camera mount on the swingarm that I'll aim at the shock. I'll use my helmet mounted camera again also but be certain its pointed more at the handle bar controls so I can actually replay what I'm doing with the throttle and clutch. It'll also pick up if I'm Hitting my shift points when the light comes on. All these little things will paint a complete picture of the bike's moves along with the riders activities. 

[dragracer]

Very interesting details!
I had no idea about the programmed delivery of the nitrous (N₂O) gas.

I thought it was a button to press as long as more power was required.

Its possible to set up a simple press of the button system as long as you aren't to aggressive with nitrous jetting. A 40 hp shot would probably be the max I'd run without a way to retard timing. In the old days. Lol. They would simply retard the static timing and spray nitrous at 100% of whatever the jet size might be. Now there are all kinds of standalone nitrous progressive controllers and all in one boxes like the one on my bike that do multiple functions like ignition control/booster,  progressive nitrous control, timing control, rev limiting, autoshifting, shift light activation and a host of other Features. My box activates the nitrous through a toggle switch that powers the solenoids and fuel pump.  Once I release the clutch, the voltage travels through a wide open throttle switch,  to an activation terminal on the ignition controller. Unless all conditions are met, the nitrous system will not activate.  In other words, if I'm in the middle of a nitrous pass and need to abort, I can roll out of the throttle which cuts off the WOT switch and kills voltage to the activation terminal on the box, or pull the clutch in which drops the voltage through the WOT switch. If that fails, i have a few other toggle switches that can break power to the system. All else fails, i can pull the tether kill and shut the whole bike down.

Pete, the nitrous system on the bike is considered a wet system . That is, the system not only introduces nitrous oxide into the engine through a fogger nozzle,  but fuel is also introduced into the engine via its own orifice on the nozzle.  If you go back and look at any of the pictures of the engine on the bije, you see two black nylon lines running to each inlet boot and they're connected to the nozzle which is screwed into the boot. The outlet if the nozzle is positioned so the fuel and nitrous are directed at the intake valve. The more oxygen you introduce into the engine via nitrous oxide, the more fuel you can also throw at it so you achieve additional combustion/cylinder pressure. Its extremely important to be mindful of retarding the timing at this point or you will reach the potential for detonation as all of the fuel and oxygen builds up in the cylinder just before TDC. In the past, lots of engines were grenaded before they realized the correlation between burnt spark plug tips,  melted pistons, correct jet sizing and timing retard. The adage used to be: pill it til you kill it and then back down one jet size. Now they let the progressive controllers, ignition timing devices and data loggers for AFR and other sensors dictate the proper and safe tune up.

[754]

 The last few times I was at the drags I seevracers purging on the line , do you and why?
 I assume it prevents damage, but uses a bit of nitrous..
 How many seconds of nitrous in your tank ?