Author Topic: Cobra motor disassembly and rebuild  (Read 107719 times)

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Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #475 on: July 11, 2016, 07:55:02 AM »
Frank got two batteries I think, and Bill with a big cut on his head and special pistons he might need two and your right leg will take a beating self starting a ST/ET  SOHC 750. Looks to me like the Blinkster [ BLINKSTAR ] will be the new number for SEL ................. 10 flat.

Pops, my F model is kick start only. You might be thinking about my Crazy 8’s KZ. It’s a 1325, 13.5:1 engine so I had to have 24 volts to crank it up.

In respect to my F model, it’s somewhat crossbred in the fact that the pistons are for a K model but the head is an F2 head with the larger combustion chamber. In essence, the pistons do not fill the chamber like Bill’s 1080 since he has a matched K head and piston set. Think of it as putting a J model head on top of a set of  KZ pistons. The J model head has a large combustion chamber, but even high compression KZ pistons won’t fill the chamber enough to get the compression up. Even by milling the head to get to closer to the KZ pistons, it won’t help to optimize the better flowing head until you get the right pistons to match the chamber. That’s the scenario I’m working from on my current package. Bottom line, Bill’s matched parts should net much more compression and a lot more horsepower and torque than my engine. As a result, his engine should be capable of 10.0’s. The dilemma is, the total package including bike has to be set up correctly to put that power down on the drag strip. In addition, the rider has to be able to fully utilize the overall package to produce a low ten second time slip. I don’t feel this engine will get into the 9’s without being placed into a properly set up wheelie bar bike chassis- unless you put a 120lb experienced rider in the seat.

Offline POPS 911

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Re: Cobra motor disassembly and rebuild
« Reply #476 on: July 11, 2016, 10:21:00 AM »
Tuning lesson this past weekend : Racer has a 1150 base Suzuki motor, lockup and a air trans brake = run 9.40...... I st. pass he went nowhere and pulled thru the lights on the 2 step and I asked did you touch anything since last race ?????? Yes in his hopes to go faster he add a spring to the clutch and with a 7000 chip in the two step it pulled thru the line lock. My fix to him why 7000 chip for two step = seems high, put in a 5500 chip two step and a 10,000 rpm auto shift up from 9500 and he ran 9.16 and the best 1.2 60ft time he ever had in 1320 and this guy is a wrench spinner. Lesson learned in drag racing motorcycles is balance....... he complained about MPH NOT AS HIGH and I ask him do the pay for MPH or WIN TICKETS !!!!!

Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #477 on: July 11, 2016, 12:55:45 PM »
Tuning lesson this past weekend : Racer has a 1150 base Suzuki motor, lockup and a air trans brake = run 9.40...... I st. pass he went nowhere and pulled thru the lights on the 2 step and I asked did you touch anything since last race ?????? Yes in his hopes to go faster he add a spring to the clutch and with a 7000 chip in the two step it pulled thru the line lock. My fix to him why 7000 chip for two step = seems high, put in a 5500 chip two step and a 10,000 rpm auto shift up from 9500 and he ran 9.16 and the best 1.2 60ft time he ever had in 1320 and this guy is a wrench spinner. Lesson learned in drag racing motorcycles is balance....... he complained about MPH NOT AS HIGH and I ask him do the pay for MPH or WIN TICKETS !!!!!

No doubt that proper tuning is important on a bar bike. Leaving harder doesn't always net the best results as I learned a long time ago.   

So true about the MPH. I see so many people get caught up in that number its crazy. When I see high mph, it usually indicates a crappy short time. That's why when my mph increased this season I paid close attention to my time slips and sure enough, my 60' and 660' times dropped off.

Offline POPS 911

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Re: Cobra motor disassembly and rebuild
« Reply #478 on: July 13, 2016, 04:07:27 PM »
Bill: How did the dyno pulls go this past Friday with [ PACE or RC COBRA head ] ? Their is a guy who has a HARLEY shop near my home with a DYNO he has not used in the past so I will stop by his shop and ask if he wants to pass it on for a fair price [ I mean a low price ] could be a tool for you to learn to run and tune your many race bikes.  In the PRO-STAR days MSP brought their own dyno in the big double stack trailer and made cash dollars night and day. I would like to see your Yellow turbo Hondamatic SOHC750 make passes in 2016.......

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Cobra motor disassembly and rebuild
« Reply #479 on: July 13, 2016, 06:01:22 PM »
BAMMMMMM. Exactly the addition Billy needs!!
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: Cobra motor disassembly and rebuild
« Reply #480 on: July 13, 2016, 06:31:10 PM »
POP'S, sounds good, waiting for a dyno date this week.Let me know on your buddies dyno, thanks,  Bill
BentON Racing Website
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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See our latest build 'Captain Marvel' CLICK HERE

Offline Medyo Bastos

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Re: Cobra motor disassembly and rebuild
« Reply #481 on: July 13, 2016, 07:42:50 PM »
yeah, you can keep it at my place  ;D

Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #482 on: July 13, 2016, 08:47:48 PM »
BBQ is on me at interstate one night that weekend ;D

Dammit! Up to my nose in gators.  ;D  ;)  8)
Looking like I'm gonna miss that BBQ I was counting on.  :-\  :(  >:(

Offline Medyo Bastos

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Re: Cobra motor disassembly and rebuild
« Reply #483 on: July 14, 2016, 03:04:07 PM »
BBQ is on me at interstate one night that weekend ;D

Dammit! Up to my nose in gators.  ;D  ;)  8)
Looking like I'm gonna miss that BBQ I was counting on.  :-\  :(  >:(

we'll send you a doggie bag  8)

Offline kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #484 on: July 14, 2016, 07:05:38 PM »
.....
we'll send you a doggie bag  8)

Hey thanks! You got my address!  ;D  ;)  8)


Offline POPS 911

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Re: Cobra motor disassembly and rebuild
« Reply #485 on: July 16, 2016, 09:58:26 AM »
Bill: Remember to leak down that motor after the dyno pulls, you do not want to find a problem when you get to Memphis........ your parts will be home in Georgia.

Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #486 on: July 16, 2016, 01:05:45 PM »
Yep, I will. See ya next week, Bill Working on z back up ride, making it a real drag bike also,  well, my opinion, lol, Bill
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
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See our latest build 'Captain Marvel' CLICK HERE

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Cobra motor disassembly and rebuild
« Reply #487 on: July 16, 2016, 02:42:47 PM »
Well that LIGHTWEIGHT tach should drop you at LEAST a tenth!!
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #488 on: July 19, 2016, 12:04:12 PM »
Are we ready Bill??

I've still got to finish the maintenance to my Honda then work on 2 other bikes. If I don't get my bike straightened out, can I borrow Purple Rain??

Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #489 on: July 19, 2016, 02:31:14 PM »
Haha, of course you can. Of course I gotta finish it too! Lol.
« Last Edit: July 19, 2016, 03:00:37 PM by Bill/BentON Racing »
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
______________________________________
See our latest build 'Captain Marvel' CLICK HERE

Offline dragracer

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Re: Cobra motor disassembly and rebuild
« Reply #490 on: July 22, 2016, 05:01:47 AM »
Hmmm, can we assume that you never made it to the dyno?? Or are you withholding other news???

See you this evening. Getting a late start after a long night of tying up loose ends that are still somewhat unraveled. Thrashing will be going on in my pit area tonight.

Offline Bill/BentON Racing

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Re: Cobra motor disassembly and rebuild
« Reply #491 on: July 22, 2016, 10:18:05 AM »
No practice.  No dyno!  But we think we ready.  3 hrs sleep over last 2 nights.  Lol. Trailer took a lot,damn was it hot! Just saw Ratbike Mike at the gas station.  Wilbur's there by now,  K. More later, woke up yesterday morning to my 14 year old cat had passed overnight. Oh well, let's go racing. Bill
BentON Racing Website
OEM Parts | Service | Custom Builds
BentON Racing Facebook
Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
______________________________________
See our latest build 'Captain Marvel' CLICK HERE

Offline Sam Green Racing

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Re: Cobra motor disassembly and rebuild
« Reply #492 on: July 23, 2016, 09:39:57 AM »
Live from Memphis via the UK.  Looks Like Bill ran a quick time but no details available in trials, looks like he missed 1st round.
Frank pulled a red in first round and broke out anyway, Trey also pulled a red.
All should be out in the next round.

Sam. listening live on facebook.
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 kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #493 on: July 23, 2016, 10:12:07 AM »
.....
Sam. listening live on facebook.

Thanks much for the updates Sam.
Where are you getting this on FaceBook?

Offline Sam Green Racing

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Re: Cobra motor disassembly and rebuild
« Reply #494 on: July 23, 2016, 10:14:22 AM »
I'll share it to your status.
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 Sam Green Racing

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Re: Cobra motor disassembly and rebuild
« Reply #495 on: July 23, 2016, 10:16:08 AM »
Done Keith, should be on your page.
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 kmb69

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Re: Cobra motor disassembly and rebuild
« Reply #496 on: July 23, 2016, 10:22:21 AM »
Got it. Thank you Sam.

Offline madmtnmotors

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Re: Cobra motor disassembly and rebuild
« Reply #497 on: July 23, 2016, 10:31:28 AM »
Somehow I managed a first round bye. Not sure how, must have been a random draw. Tried to trade it for a round two bye but that was not an option, dammit!
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline madmtnmotors

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Re: Cobra motor disassembly and rebuild
« Reply #498 on: July 23, 2016, 10:36:08 AM »
Maybe they felt sorry for me after the tie down strap broke on the way up...
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Cobra motor disassembly and rebuild
« Reply #499 on: July 23, 2016, 10:44:37 AM »
Ouch!
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)