Author Topic: Classic Bonneville Racer  (Read 46316 times)

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Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #525 on: October 22, 2018, 11:16:46 am »
Generally 35-mph for bikes and other vehicles on the salt............except on a RUN ;D ;D ;D ;D ;D ;D
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
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Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #526 on: June 06, 2019, 07:59:09 pm »
Time to add a few things to this thread............For 2019 a few things are being changed on the Chassis and several things in the bottom-end and the tranny.

Chassis: Changing from a 19" to 18" front wheel with slightly lower profile to lower the bike about 1" with very similar trail, added stream-lining to the front fender behind the forks, at the front of the motor below the head, and near my legs. The seat-pad will be modified, the handlebars will be slightly shorter, and the non-streamlined seat will be improved with a longer tail.

Motor: Lightened and balanced crank, new bearing shells all around, new HD primary and cam-chains, new tensioners, and a new copper head-gasket. The tranny will get both 5th-gears exchanged for F2 units which will reduce the overdrive ratio. I am tempted to install a complete F2 clutch/primary and secondary shaft plus the shifter drum and forks..........but reluctant because my current clutch is very reliable......and guidance???

I hope to get the motor together in the few weeks and have the bike assembled to show at the AMA VMD in July. I was thinking a sound-demo would be nice ;)
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
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Offline bwaller

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Re: Classic Bonneville Racer
« Reply #527 on: June 07, 2019, 04:48:47 am »
It's always tempting not to fix what isn't broken, but in the name of improvement.  ;D

Just give yourself plenty of time to test in case you need to "back track" to original!

Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #528 on: June 07, 2019, 06:52:26 am »
Thanks, Brent, for the encouragement. The testing is the problem........other than the dyno, I don't have any 'roads' to test on.

I have been using Brad Penn 20-50w oil..........but tempted to go to a 5-50w synthetic with zinc-additive for the clutch........that also needs to be tested. ::) ::)

All of this is to get a timing slip with a 150+mph reading ;D ;D
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
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Offline Tintop

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Re: Classic Bonneville Racer
« Reply #529 on: June 07, 2019, 07:57:48 am »
Using the different oil will help.  The FF racers would qualify with a 5W oil, then change for the race.  It did make difference for the fast guys in qualifying.
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Classic Bonneville Racer
« Reply #530 on: June 07, 2019, 09:00:39 am »
+1  ;) after break in of the rings.

Make a couple passes with the dino oil, I'll pick up yer time slip then change and see the difference.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #531 on: June 07, 2019, 11:11:09 am »
OK guys..........synthetic with zinc will be 'tried' ;) ;) ;)

Upon teardown we found a ring impression about 2-inches long in the liner near the bottom of the stroke on #1 which I attribute to salt in the fuel and from sitting for 2-years between events. Another set of cylinders were bored to 62mm and will have a fresh hone for the 'used' rings and pistons. No evidence of rust or scoring was found on the ring or in the piston-lands. I have observed a small amount of salt in the #1 carb and believe it enters through the tank vent despite the filter. That will be changed for this year.
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
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Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #532 on: June 21, 2019, 07:14:32 am »
Overall Ratio............In an effort to reduce the spread between 4th and 5th, I am ready to install an F2 tranny into a K case. This requires exchanging the 48t gear-wheel on the output shaft for the 43t unit on the F2. That calculated differential is a positive 0.003 because the drive-gear in the tranny is 56t on the K vs 50t on the F2...........hardly a consideration, but must be done to get the gears to work. The spread between 4th and 5th actually increases by 6.5% :( :(........but because 4th is lower I think the overall will be lower......and that may slightly reduce power loss in the tranny ;D

The K tranny is the same as F2 from 1st to 3rd..........then K 4th is 31/34 vs F2 30/34.........and 5th is K 33/31 vs 33/32.

I need someone to confirm the calculated overall ratio from crank to the output shaft............and then the final drive using a 16/42 set of sprockets and show me the difference between the K and F2........... I know its lower but unsure by how much ;) ;) ;)
« Last Edit: June 26, 2019, 03:35:37 pm by Old Scrambler »
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Classic Bonneville Racer
« Reply #533 on: June 21, 2019, 11:50:17 am »
Salt air condensing salt out as it dries?
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #534 on: June 22, 2019, 06:47:38 am »
Jerry...........that's salt WATER drying to form a crust ;D

Decided to stick to the original plan of exchanging the 5th gears from the F2 onto the K tranny.........along with the exchange of the lay-shaft/output shaft gears which are the same diameter in both trannies. The result is a rounded 30% reduction to the spread between 4th & 5th which hopefully allows me to enter 5th-gear at the peak of the torque curve. Motor assembly begins on Monday evening........noise is expected by Friday.
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
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Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #535 on: June 28, 2019, 08:42:15 am »
The tranny works as expected...............only changed the 5th gears. Other things have gotten in the way so the motor will not be finished in time for the VMD event. My K3 will make it. Hope to see some of you in Ohio. I will be at the VJMC booth in the swap-meet area on Saturday from 9-11 AM...........
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
'77 750F2 Cafe Project
2000 Aprilia Pegaso

Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #536 on: July 20, 2019, 12:22:57 pm »
Lesson Learned.........We measured the CB900C rods at 1mm longer than CB750 OEM when we first assembled the motor. Now thinking that maybe the rods had stretched......we installed an alternate set of CB900C rods.........only to find that the units with sprayers but retaining the 15mm pin are indeed 1.3mm longer than the CB750 units:o :o.......Soooooo.....we will double-gasket the cylinder-base to retain the original clearances within 2 or 3 thousands of an inch..........only a small delay but time is ticking ;)
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
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Offline Sam Green Racing

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Re: Classic Bonneville Racer
« Reply #537 on: July 24, 2019, 04:15:44 am »
Lesson Learned.........We measured the CB900C rods at 1mm longer than CB750 OEM when we first assembled the motor. Now thinking that maybe the rods had stretched......we installed an alternate set of CB900C rods.........only to find that the units with sprayers but retaining the 15mm pin are indeed 1.3mm longer than the CB750 units:o :o.......Soooooo.....we will double-gasket the cylinder-base to retain the original clearances within 2 or 3 thousands of an inch..........only a small delay but time is ticking ;)

Dennis, sorry for coming in 4 days late but I don't recall you mentioning the CB900 rods before unless I missed it.
I used the same trick, double up on the base gasket to get the clearance needed on my little 154cc Honda twin LSB.
I opened it up to take CB175 pistons which would give me more cubic capacity plus a much higher compression ratio.
I knew I would run into problems with the valve clearance so drilled through a used piston I had to see how much I could take off.
The answer was not enough. I took off as much as I thought safe but it was still not enough.
Enter the double up of the base gasket and it was perfect.
A trip to the dyno told me I was making great power low down but at the expense of a big loss of revs at the top end where needed.
I was at a loss for what to do next. The motor was on the bench and I checked the tappet clearance and chain tension, all OK.
Standing back from the motor that was set on TDC, I noticed that the cam timing mark was a tooth out, quick double check and I was right. Another check on the chain tension and tappets which proved correct, I had messed up.
A quick slotting of the cam sprocket and I was in business.
You might have already taken this into account but don't make my mistake mate, it's a long way to Bonneville. Good luck.

Sam. ;)
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Offline johno

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Re: Classic Bonneville Racer
« Reply #538 on: August 01, 2019, 11:48:49 pm »
Hi Dennis,
Nice to see your hard at it.
Re the gearing discussion the best gear ratio chart in the world is on our home page near the top, SOHC / 4 technical documents and manuals, click on it, then click on 750K or 750 F, the first section is Service manuals, ignore that,  the second section is General Technical info with the 3rd line down titled CB750 Gearing chart. Click on that baby and bam u got what u need baby. ;D

I didn't run your info through it as I don't know your tire circumference etc but for me I ran Bridgestone 18 " Batlax BT45R 120/90 65V with those numbers when I changed the 5th gear from K to F it made the following differences.   All at 9,000. RPM, All numbers M.P.H
17:41   K 158  F  153
18:41   K 167  F  162
17:42   K 154  F  149
18:42   K 163  F  158
17:43   K 150  F  146
18:43   K 159  F  154

That will give you an idea of changing the 5 th gear from K to F
cheers Johno



 
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Offline bear

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Re: Classic Bonneville Racer
« Reply #539 on: August 02, 2019, 01:41:27 am »
Johno's back! ;D
The older I get the faster I was.

Offline MRieck

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Re: Classic Bonneville Racer
« Reply #540 on: August 02, 2019, 06:06:53 am »
Lesson Learned.........We measured the CB900C rods at 1mm longer than CB750 OEM when we first assembled the motor. Now thinking that maybe the rods had stretched......we installed an alternate set of CB900C rods.........only to find that the units with sprayers but retaining the 15mm pin are indeed 1.3mm longer than the CB750 units:o :o.......Soooooo.....we will double-gasket the cylinder-base to retain the original clearances within 2 or 3 thousands of an inch..........only a small delay but time is ticking ;)
Just seeing this now Dennis. In the future....how about a custom copper base gasket or an aluminum spacer from Cometic? You could probably sandwich either with 2 thin steel/viton pieces as well. I plan on doing this for a stroker engine.  https://www.cometic.com/p-35446-custom-gaskets.html
Owner of the "Million Dollar CB"

Offline MRieck

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Re: Classic Bonneville Racer
« Reply #541 on: August 02, 2019, 06:07:24 am »
Johno's back! ;D
Yes....very nice to see.
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Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #542 on: August 03, 2019, 02:38:34 pm »
Thanks Sam, Johno, and Mike for the advice..............its all good ;D

Upon further inspection..........what we thought was piston interference as we turned the motor by hand was really an intermittent rubbing of the clutch face-plate against the inside of the 'threaded-nipple' for the outer clutch cover. I now have an F2 clutch pack which is a bit thicker. All is well after a little filling of that nipple.  With all other systems checked over, the motor started instantly with a small amount of idle adjustment. Even the tach works ;)

Three heat-sessions and all is still good..........Now working on minor upgrades to the streamlining. We have installed header-pipe ID reducers as an experiment. If no improvement, they are easily removed. This coming Wednesday is planned to be a 'track-day' at Road America. We will only be running the bike on the perimeter access roadways........not on the actual track. We want to put a few hours on the motor to seat the rings into the fresh bores. This should also tell us if the clutch is working. Then an oil change to HONDA Professional 10-30w synthetic.

The lightened crank, small exhaust ID, fresh bore and lighter oil are hoped to provide an extra HP or 3..........and allow the F2 top-gear to have more power at the top of the rpm range...........starting sprockets will be 16 x 42.
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
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Offline bwaller

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Re: Classic Bonneville Racer
« Reply #543 on: August 03, 2019, 02:48:19 pm »
Sounds good Dennis. This is interesting work which hopefully helps you move forward.

Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #544 on: August 03, 2019, 03:19:42 pm »
Thanks, Brent..................Mike; I used the thin metal base-gasket on this motor assembly. We paid special attention to 'shaping' the copper head-gasket by over-laying the used gasket and marking the areas where the valves and pistons had interference-fits. We then scribed the new gasket by machining each hole with a stationary rotary sander.

Johno............Great to hear from you ;D Three weeks from today is Tech on the salt...........I will have to be ready with my current team of helpers but sadly will not have my motor-builder/fabricator/race-coach with me. Dave has other plans and thinks I can handle things without him. Jerry..........are you ready? Frank from MN will be with me and my daughter with boy-friend will be on-hand for 2 days.
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
'77 750F2 Cafe Project
2000 Aprilia Pegaso

Offline RAF122S

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Re: Classic Bonneville Racer
« Reply #545 on: August 03, 2019, 04:20:23 pm »
David stuck in the curvy back roads of "Upper East" TN

Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #546 on: August 03, 2019, 04:49:38 pm »
Its sad to see that a fool's play has to draw attention to the salt conditions at Bonneville..........and notice that the BMST was not mentioned or included as an event. I saw the diagonal mark in the salt after it was graded smooth for our event. Many others drive on the salt........including motorcyclists.........without regard to the national monument status. 
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
'77 750F2 Cafe Project
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Offline 754

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Re: Classic Bonneville Racer
« Reply #547 on: August 03, 2019, 05:29:31 pm »
Gotta break past that 150 mph.. This year. .
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Offline Old Scrambler

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Re: Classic Bonneville Racer
« Reply #548 on: August 03, 2019, 05:46:59 pm »
That's the goal, Frank. I think 152+ would be the fastest CB750 at Bonneville not including big-bores or blowers.
Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
'77 750F2 Cafe Project
2000 Aprilia Pegaso

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Classic Bonneville Racer
« Reply #549 on: August 03, 2019, 07:34:01 pm »
Hot damn baby.... we're on again. Coming to you from Cali, Colombia. Be home on the 8th. Hoping that will give me enough rest period  ;D ;) Trying to talk my new roomie into coming along. Professional photographer. That never hurts to have pro team pics.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

 

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