Author Topic: Report from Bonneville Motorcycle Speed Trials  (Read 6639 times)

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Offline richmagee7

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Report from Bonneville Motorcycle Speed Trials
« on: September 09, 2017, 05:38:52 PM »
Hello all,
Made it out to the BMST 2017, my second year, we went in 2016 and had so much fun we had to return.

Conditions: Attendance was reported to be down a fair bit and they ran just one track, 10 miles long, less staff, etc.  It did make the return to pits much quicker.  They thought the single track might actually speed the runs along but I'm not so sure.  The salt was reported to be in much better shape than a couple weeks earlier for speed week, the salt certainly seemed to be thicker than last year.  But some also reported it being a bit choppy in places.  The weather was really hot, near 100 on Saturday and Sunday, though on Monday morning we had the most glorious cloud cover for a few hours, even a sprinkle of rain for a few minutes that caused no worries. Was a little breezy quite often, not sure if the streamliners ever got out there.

750s: Pretty sure I did not see another CB750 out there.  Last year of course, there was Dennis, the Canadian couple, the fellow from Minnesota with the supercharger, my stock 75, and at least one Japanese rider. 

Runs: Last year my stock 1975 bike was jumping out of fourth gear in the timed mile (I had never revved it that high before) and our fastest run was 102.9mph by shifting into fifth early and we set a record of 100.7 for Production-Production Classic 750cc.  I tore it down (10k original miles and it looked beautiful inside) and had CycleX massage the gears over the winter.  Last year I had also switched gearing from the stock 18/48 gears to 18/43.  Old Scrambler Dennis told me I needed to make sure I got it into the higher revs to get into the power band and also suggested I might even go the other direction on the gearing.  So this year after putting the bike back together, I went with 17/48 gearing to start and plans to go through the various combinations I could make with a 17, 18, 43, and 48.  I also changed jets from my stock 105s to 110s.  First run- couldn't remember when to shift, how to shift, searching around for smoother salt, ran 101.  That was above my record and allowed a return run, though my wife was surprised at my disappointment.  On the return, I decided I would only worry about watching the tach and shifting when it quit climbing.  Went straight to impound and my wife brought me a scrap of paper with 113.something scribbled on it.  I was stoked.  Sealed the motor and the next day we made a down run of 111 and a return of 113.  The new record should be 112.2 up from 100.7.  I was exhausted, still had to pull the engine out, drive back to Texas, and it was taking hours to make a down run so I didn't play with the gearing any further.

Thought I would skip next year since I don't have unlimited leave at work, but after seeing old friends, making new friends and experiencing the camaraderie out there, I think I have to go back in 2018.  Thanks again to Dennis Weinhold for the advice last year, and to Jerry RxMan for the interest and encouragement.  And this year, I also have to thank Tom Mellor who helped with a sticky throttle that didn't pass inspection initially, and his friend Bob Duncan who helped get past that one head bolt during teardown that made me think I was going to have to saw the thing in half.  And our friend Lynn Pfeiler once again. Bonneville is iconic, beautiful, surreal, going fast on the salt is exhilarating, but the people involved may be the best part of the entire experience.

Thanks to everyone on this forum also, I have only posted a few times, but have consulted it possibly hundreds of times, there is so much information.  Hope I didn't ramble too much.  Pics to come.

Offline 754

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #1 on: September 09, 2017, 05:49:23 PM »
Great report Thanks.
 DENNIS is starting to make his way south ....? Bet he wished he were there..
« Last Edit: September 09, 2017, 07:07:28 PM by 754 »
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Lost quite a few CB 750's along the way

Offline scottly

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #2 on: September 09, 2017, 07:02:57 PM »
Yes, great report, but pics would make it even better. ;D
What RPMs did you see at 111-113 MPH?
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #3 on: September 09, 2017, 10:46:41 PM »
Fantastic results Rich!! You had that thing tuned! Pretty damn good for a stock 75 K. Making me want to install the spare low mile stock F engine I have now that I have a trailer.  :D

What has to be stock and what can be altered on the bike and engine for that production class?
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline richmagee7

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #4 on: September 10, 2017, 12:39:22 PM »
Having trouble posting pics, maybe I'm trying to post too many.  Anyway, trying again.  Sorry I didn't take more pics of bikes but it seemed I was always on the salt waiting, or finally in impound tearing down.  I've only done two 750 engine removals and both were on the salt flats.  I'm getting faster, but I am thinking of a frame kit, exhausting in the heat.

Not sure how to label pics, so:  Bonneville sign with my wife- best pit crew EVER.  Funny looking car that passed me kinda quickly.  Heading toward the salt and getting excited.

Offline richmagee7

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #5 on: September 10, 2017, 12:42:47 PM »
More pics, Edwards Racing our neighbors in pits, Sandy Vetter with my bike -79 year old triple record holder, waiting with a couple Japanese run Harleys, the pits from 1.5 miles away

Offline Stev-o

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #6 on: September 10, 2017, 12:46:35 PM »
Great report.  Now wondering is the GT40 could do 215 on the salt?!
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Offline richmagee7

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #7 on: September 10, 2017, 12:50:30 PM »
Final pics - For Scottly -Gauges at end of first return run - timed mile (mile 6 to mile 5) was 113.3, my gps showed max of 116.5, speedo was bouncing around, tach was climbing slowly to 7800, wasn't going to go much further.  Time slips for record, in impound, finished in impound.

If interested, here is a link to youtube of a guy whose leathers show he gained a lot of weight.


Thanks for the interest.  I think the pending records have already been posted online by BMST.

Offline 754

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #8 on: September 10, 2017, 12:51:12 PM »
Bet the Japanese guys said, CB750  Horry #$%* !!
What rpm thru the traps. Stock compression ?
I see your RPM now.. I wonder how fourth would work , I have run at 9,000 in 4th.
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline Sam Green Racing

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #9 on: September 11, 2017, 04:13:24 AM »
Hello all,
Made it out to the BMST 2017, my second year, we went in 2016 and had so much fun we had to return.

Conditions: Attendance was reported to be down a fair bit and they ran just one track, 10 miles long, less staff, etc.  It did make the return to pits much quicker.  They thought the single track might actually speed the runs along but I'm not so sure.  The salt was reported to be in much better shape than a couple weeks earlier for speed week, the salt certainly seemed to be thicker than last year.  But some also reported it being a bit choppy in places.  The weather was really hot, near 100 on Saturday and Sunday, though on Monday morning we had the most glorious cloud cover for a few hours, even a sprinkle of rain for a few minutes that caused no worries. Was a little breezy quite often, not sure if the streamliners ever got out there.

750s: Pretty sure I did not see another CB750 out there.  Last year of course, there was Dennis, the Canadian couple, the fellow from Minnesota with the supercharger, my stock 75, and at least one Japanese rider. 

Runs: Last year my stock 1975 bike was jumping out of fourth gear in the timed mile (I had never revved it that high before) and our fastest run was 102.9mph by shifting into fifth early and we set a record of 100.7 for Production-Production Classic 750cc.  I tore it down (10k original miles and it looked beautiful inside) and had CycleX massage the gears over the winter.  Last year I had also switched gearing from the stock 18/48 gears to 18/43.  Old Scrambler Dennis told me I needed to make sure I got it into the higher revs to get into the power band and also suggested I might even go the other direction on the gearing.  So this year after putting the bike back together, I went with 17/48 gearing to start and plans to go through the various combinations I could make with a 17, 18, 43, and 48.  I also changed jets from my stock 105s to 110s.  First run- couldn't remember when to shift, how to shift, searching around for smoother salt, ran 101.  That was above my record and allowed a return run, though my wife was surprised at my disappointment.  On the return, I decided I would only worry about watching the tach and shifting when it quit climbing.  Went straight to impound and my wife brought me a scrap of paper with 113.something scribbled on it.  I was stoked.  Sealed the motor and the next day we made a down run of 111 and a return of 113.  The new record should be 112.2 up from 100.7.  I was exhausted, still had to pull the engine out, drive back to Texas, and it was taking hours to make a down run so I didn't play with the gearing any further.

Thought I would skip next year since I don't have unlimited leave at work, but after seeing old friends, making new friends and experiencing the camaraderie out there, I think I have to go back in 2018.  Thanks again to Dennis Weinhold for the advice last year, and to Jerry RxMan for the interest and encouragement.  And this year, I also have to thank Tom Mellor who helped with a sticky throttle that didn't pass inspection initially, and his friend Bob Duncan who helped get past that one head bolt during teardown that made me think I was going to have to saw the thing in half.  And our friend Lynn Pfeiler once again. Bonneville is iconic, beautiful, surreal, going fast on the salt is exhilarating, but the people involved may be the best part of the entire experience.

Thanks to everyone on this forum also, I have only posted a few times, but have consulted it possibly hundreds of times, there is so much information.  Hope I didn't ramble too much.  Pics to come.

Rich, why not take your bike to a dyno and get the jetting set up properly and then take it down the Texas mile (https://www.texasmile.net/) before going back to Bonneville next year.
I'm guessing San Antonio TX isn't much different to the elevation of Victoria TX at 95 feet but it's nowhere near the elevation of Bonneville at 4,219 feet, this will let you know how to jet for running at high altitude.
Just my thoughts mate and I hope this might help, a great report and better luck next time.

Regards Sam.
C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #10 on: September 11, 2017, 06:41:56 AM »
It sure sounds good. A cam would be interesting.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Bill/BentON Racing

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #11 on: September 11, 2017, 10:17:41 AM »
Congratulations,  nice job mate.
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Offline richmagee7

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #12 on: September 11, 2017, 03:12:28 PM »
Thanks for the comments and advice guys.

Sam, Victoria TX would be about 1400 miles closer, we'll see.  Can a dyno simulate the altitude change, or I guess a calculation?

754- Maybe I'm afraid to wind up the RPMs but it seemed to stop pulling hard at 7200 rpm so that is about where I was shifting.  Was in fifth just after the quarter mile.  Stock compression.

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #13 on: September 11, 2017, 03:24:34 PM »
Depends on where it makes its most power. Dennis started using 4th. Might need more cam for more HP at higher rpms and or a MIke Rieck head job. More rpms = more mph. Maybe one more tooth on the rear with the 17 tooth front. Maybe next size up main if it was playing out at 7200?
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Sam Green Racing

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #14 on: September 11, 2017, 05:10:05 PM »
Thanks for the comments and advice guys.

Sam, Victoria TX would be about 1400 miles closer, we'll see.  Can a dyno simulate the altitude change, or I guess a calculation?

754- Maybe I'm afraid to wind up the RPMs but it seemed to stop pulling hard at 7200 rpm so that is about where I was shifting.  Was in fifth just after the quarter mile.  Stock compression.

Rich, most dyno's will give a read out but I doubt it can simulate such a large change in altitude. I don't fully understand the readouts on my own dyno graphs but it gives the changes in temperature to relative air density which can greatly affect the performance of any bike running carburetor's.
On the drag strip, my bike would run 2 tenths of a second slower in the heat of day when the temperature went up to 90 to 100 degrees. It being a dial in ET bike, I just changed my dial in instead of jetting down.
Perhaps my team mate Jerry can explain better than me as he lives 2,000 feet higher than Bonneville than you and I, I don't know how he breaths, I would need oxygen at that altitude in the heat of day, hahaha.
 
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CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline scottly

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #15 on: September 11, 2017, 08:04:13 PM »
The dyno measures the actual horsepower, then applies a correction factor for barometric pressure, temperature, and humidity to estimate the HP under "standard" weather conditions. For example, my 836, tested at 4500", showed an actual HP of about 60, and a corrected (call it sea level) 70 HP. The dyno will not give any guidance as far as jetting for different elevations or weather conditions, other than data obtained at the time of the test.
Rich, for your LSR attempts, the key information you will get is the peak HP RPM: This is the point where your motor has the most HP, above the peak and below the peak the motor will make less HP, and it takes HP to push the bike through the air at 100+. 7800 RPM is probably very close to the peak for a stock 750? BTW, I have a dyno, so if you are inclined to detour to AZ next year, we can check the A/F at 4500'.   
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Offline Haybus

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #16 on: September 11, 2017, 08:15:35 PM »
The dyno measures the actual horsepower torque,

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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #17 on: September 11, 2017, 09:03:19 PM »
Rich,

Yeah, you need to set it up at the correct elevation for max power and final results, not at home elevation. Scott's offer is a great idea. At this point I believe it to be perfect tuning and perfect carburetion that will improve your results. At that point you get into air density differences. This is what minimal changes to big jets and gearing changes are for.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline scottly

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #18 on: September 11, 2017, 09:44:55 PM »
The dyno measures the actual horsepower torque,
An inertial dyno calculates HP based on how quickly the heavy drum is accelerated, and if an engine RPM input is provided, can also calculate torque. A "brake" type dyno measures torque, and calculates the HP using the torque and engine RPM. The inertial dyno is the most common.   
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Offline scottly

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #19 on: September 11, 2017, 10:03:43 PM »
On the subject of gearing: if you motor has it's HP peak at, for example, 8000 RPM, and you are turning 8500 through the speed traps, your gearing is too low. If you are turning 7500, the gearing is too high. Neither gearing puts the motor at it's peak output. Since Rich's bike seems to be close to the optimum RPM, it might be worth a try to run a rear sprocket with 1 less tooth? If the RPMs go down, the motor can't pull the taller gearing, but if it can, the bike will go a wee bit faster at the same RPM. There is no substitute for trial and error.  ;)
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Offline Sam Green Racing

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #20 on: September 12, 2017, 04:44:07 AM »
The dyno measures the actual horsepower, then applies a correction factor for barometric pressure, temperature, and humidity to estimate the HP under "standard" weather conditions. For example, my 836, tested at 4500", showed an actual HP of about 60, and a corrected (call it sea level) 70 HP. The dyno will not give any guidance as far as jetting for different elevations or weather conditions, other than data obtained at the time of the test.
Rich, for your LSR attempts, the key information you will get is the peak HP RPM: This is the point where your motor has the most HP, above the peak and below the peak the motor will make less HP, and it takes HP to push the bike through the air at 100+. 7800 RPM is probably very close to the peak for a stock 750? BTW, I have a dyno, so if you are inclined to detour to AZ next year, we can check the A/F at 4500'.   

Thank's scottly, that was the explanation I was looking for on the corrected factor. It might as well have been in Chinese with my messed up brain and it's not getting any better with age. haha.

Sam. ;)
C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline gschuld

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #21 on: September 12, 2017, 07:18:21 AM »
Richmagee7,

Congratulations on the new record.  Very cool. ;)

George

Offline richmagee7

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #22 on: September 12, 2017, 08:37:29 PM »
Thanks George

Thanks Scottly for the info and offer

Dang it, I just wanted to ride my old motorcycle and now you all are making me feel the need for more speed.

Offline 754

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #23 on: October 14, 2017, 10:11:39 AM »
 Here is one from near to me.
Ran at Speedweek, snagged a record at 89 mph
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My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline gschuld

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Re: Report from Bonneville Motorcycle Speed Trials
« Reply #24 on: October 14, 2017, 12:32:58 PM »
Nifty... decent amount of windage on that sidecar.  Based on the pegboard pics, I'm guessing the bike is a vintage Bonneville build of some sort?

Cb500, cool

George
« Last Edit: October 14, 2017, 12:37:16 PM by gschuld »