Author Topic: CB750 AHRMA Superbike Heavyweight Racer  (Read 27580 times)

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Offline slikwilli420

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CB750 AHRMA Superbike Heavyweight Racer
« on: July 12, 2018, 06:09:46 am »
Here we go again!

I have had this tingling after Road America that feels like a void in my time that needs to be filled. I want to get back to street riding, but really enjoyed building my race bike for the Sportsman 750 class. The race bike was built with a mission and purpose and while I do want to finish my other project, I really have fallen out of love with street riding since there really isnt a goal in mind. Ride somewhere, enjoy the scenery, go home. Same with shooting. I never plink or shoot alone, and found competition to be far more stimulating and rewarding. I think the same goes for motorcycling.

With that said, I have some sheckles stashed away that are not earmarked for my current bike, and am planning on selling my '09 Thruxton to fund my new build. I like going fast and I like Honda 750's so what to do? Build a Superbike Heavyweight! Here are the rules outlined from the rule book:

10.8 VINTAGE SUPERBIKE
MISSION STATEMENT: AHRMA’s mission is to recreate and preserve the look and feel of
this important era of U.S. roadracing and to showcase these unique machines. While Superbikes
were based on the same production bikes available in the showroom, period performance
parts are extremely rare or even unavailable; therefore, a limited amount of modern replacement
parts are allowed in the interest of safety, cost containment and competition.
10.8.1 These rules have been designed with the following intent:
a) All motorcycles competing in these classes shall be as visibly close to “production”
motorcycles as possible. All eligible motorcycles shall be based on street-legal
models which were available for sale in the United States and/or Canada.
b) Allow the tuner to have more influence over the performance of the motorcycle by
eliminating the need for special frames, suspension systems and “state of the art”
components to be developed or purchased.
c) To provide racing classes with equipment available through normal commercial
channels, and in adequate quantities.
d) Provide interest to aftermarket suppliers and sponsors.
e) Provide a very distinct look and appearance from the other motorcycles competing
in AHRMA events with strict bodywork requirements.
10.8.2 REQUIREMENTS AND MODIFICATIONS FOR VINTAGE SUPERBIKE
a) GENERAL
1) Model year cutoff is 1982, or like design (see definition in Section 2). Exception:
The model-year cutoff for Kawasaki GPz550 is 1981.
2) Engines and frames must be from the same model.
3) All street equipment must be removed (turn signals, centerstands and sidestands,
mirrors, horn, helmet lock, passenger pegs, etc.). Headlight shell must be
retained. Taillight and license plate bracket must be removed.
4) All motorcycles are to use three green number plates, 10x12-inches in size,
with white numerals not less than seven inches in height with a minimum of
one-inch stroke width. Standard block-type numerals, without serifs, must be
used. Visibility must not be blocked by rider’s foot or leg while racing. See section
9.5.
5) Competitors in the Vintage Superbike classes must comply with all applicable
parts of Sections 1 through 9 of the AHRMA Handbook.
b) ENGINE
1) All engines must use OEM crankcases, cylinders and heads from the period
1982 and earlier.
2) Allowed displacement may be arrived at in any manner (i.e., stroker and sleeve
kits are legal). Aftermarket “big block” kits are not allowed (see 1. above).
3) All round-slide carbs are allowed (Keihin CR, Dell’Orto, Mikuni “smooth
bore” and like design). Flat-slide carbs are not allowed. Pumper carbs may be used, but the pumper mechanism must be disabled. 1025cc four-cylinders may
use carburetors up to 29mm, or the stock constant-velocity carburetors that
were original equipment on that machine.
4) Any exhaust system design is allowed. However, all exhaust systems must be
equipped with an effective silencer. Open pipes and reverse cone megaphones
are not silencers. All exhaust systems must include sound-attenuation material
or devices. Modern canister-type silencers are not allowed. Period-style exhaust
systems are encouraged. See rule 9.3.h.
5) Liquid-cooled or two-stroke engines are prohibited.
c) CHASSIS AND FRAME
1) Frame must be a production model built no later than 1982 (or like design).
2) Frame modifications are allowed (bracing or gussets allowed, steering head
angle may be altered, shock location changed or altered, etc.), but welds and
modifications must be of the highest quality and are subject to scrutiny at tech
inspection.
3) Approved period aftermarket swingarms or accurate replicas are permitted.
Shock location may be changed and OEM swingarm may be reinforced, shortened
or lengthened.
4) Standard shock configuration must be used, but shock(s) may be repositioned.
Remote reservoir shocks are not allowed, although piggyback shocks are.
BMW models may replicate factory Superbikes of the period.
5) Front forks must be of OEM or aftermarket origin, with stanchions no larger
than 41mm in diameter. Anti-dive and external adjusters are allowed. Forks
must be conventional type (no upside-down units).
6) Handlebars must be fitted to the original mounts, and must not be below the top
of the fork crowns. No Clubman bars or clip-ons, except when used as original
equipment.
7) Any wheel diameter from 16-inch to 19-inch is allowed. Maximum rim width:
4.5-inch rear, 3.5-inch front. Wheels may be wire-spoked or mag-style in
either alloy or magnesium. Modern alloy mag-type wheels are permitted. Cut/
machined wheels (Performance Machine, etc.) are not permitted. However, As- tralite and Comstar wheels are allowed. If uncertain as to the legality of certain
wheels, please contact the Vintage Superbike Rules & Eligibility Committee
with questions before making a purchase.
8) Only single- or two-piston brake calipers are allowed. Front and rear discs,
floating or rigid mount of any material except carbon fiber, are allowed.
“Wave” or petal-type rotors are not allowed.
9) Only treaded modern racing compound tires are allowed. No slicks. Rain tires
are allowed and may be hand-cut. Tire warmers are permitted.
10) Airboxes and toolboxes may be removed or modified.
11) Fuel tank and bodywork must be as found on the same year and model of
the production motorcycle on which the racer is based. Motorcycle must have
original seat, which may be modified or recovered while retaining the stock
seat pan. Motorcycle must have the front and rear fenders, sidepanels and front
fairing as the original production model or accurate replicas. Fenders may be
trimmed to fit tires. No tail sections may be added unless OEM on that model.
12) Only fairings that were furnished as standard equipment on the street model
are allowed. Fairings must not extend below the fuel tank.
13) All motorcycles must use the OEM-appearing speedometer and tachometer
housing (if so equipped). Speedometer and tachometer instruments are optional.
10.8.3 CLASSES
a) HEAVYWEIGHT: Unlimited displacement twins and pushrod triples, and
displacement-limited fours and sixes (see chart).

The displacement limitation with a CB750 is 931, which seems a bit silly given the 1000cc limit for other bikes. Regardless of that, I have unrestricted intake, meaning I can run either Kehin or Mikuni round slides of any size.

Here is the master plan so far:

Frame
-Using my current race frame as I have one in the works for next year for my Sportsman bike (more to come on that later). This will also allow me to use shared parts like rearset brackets and such. There won't be much crossover but anything helps
-Going with an F model tank which I have a couple to choose from. They all need to be rehabbed in some way, but with a longer build time, I can take time to get it right
- F model seat, re-contoured saddle. I will need to find a donor that has a bad seat cover and maybe some bent trim, then I won't feel bad modifying it

Front end
-Up to 41mm forks so thinking early 90's CBR600F2, which are 41mm, right side up, and have nice brake mount points. I still need to make sure this is kosher as I need to run a stock-ish looking front fender. Im not sure if that means STOCK or just a fender that looks stock-ish. Whatever I choose will have full Race Tech internals
-Spondon or AP Racing 2 piston calipers, SS lines, and an adjustable ration AP master cylinder
-I have some cast iron rotors with Honda bolt pattern I was told were Z-Mark(??) but I have seen them on more than one period race bike, and should work just fine
-Wheels will be Astralites, 2.5" front and 3.5" rear, both 18" that I picked up from Frank in a partial trade
-Superbike bars on top of '81/82 AHM pattern triple trees (I really like the look and its a nod to early Honda superbikes)

Rear end
-Calfab swing arm - this is the one currently on my other racer, but will be getting a chromoly unit for that to say within the rules. As I get faster I will get scrutinized harder by everyone and need to keep things right and tight
-Similar brake setup as my other racer, with Brembo P32 caliper, SS line, and Brembo master, running on the same style rear set plate as the other bike
-Race Tech piggyback shocks

Engine
-890 12.5:1 pistons and new sleeves
-Big valve head reworked by Mike (I found a head at Mid Ohio last year that was heavily ported with bigger intakes that I will have Mike breathe on to make sure its all kosher and renew with current made springs and modern seat pressures)
-Big ass lumpy cam - I tried the CX10 from Kenny originally but there was piston/valve clearance issues that would require sinking the valves or more valve pocket work on the pistons than could be done on the custom 62mm units from my other bike
-Balanced and lightened crank with Kenny's rods
-Full-tilt trans, pro cut and ISF processed just like my other one
-Trimmed engine cases
-Power Arc or Dyna 2000 ignition running total loss off same battery style I use in my other bike so charger is compatible
-MessnerMoto cam tensioning system
-Etc, etc, etc, $, $, $, fun, fun, fun

That's all I can think of for now, but I plan on this being a slow burn, and hope to have it ready at least for a few races in 2020. I can scratch the itch with my Sportsman bike for now so there is no rush on this one. It nice to already have some parts so I can start building the front end minus triple trees at my leisure before the other bike even comes down for a new frame. At that time, it will also donate the swingarm. I can start to acquire parts over time such as major engine pieces (head, pistons, crank assembly) as well as the braking components.
« Last Edit: August 09, 2018, 03:54:45 am by slikwilli420 »
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline Rocketman

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #1 on: July 12, 2018, 07:37:08 am »
Nothing like jumping in the deep end of the pool with both feet!  I say GO for it!  Of course it is your money.   ;D

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #2 on: July 12, 2018, 10:05:53 am »
Why are you limiting yourself to 890? Carbs? Sounds good.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline slikwilli420

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #3 on: July 12, 2018, 10:15:37 am »
There isnt a 12:1 compression piston over 890 but under the class limit. I guess I could see about having some 915 slugs made in 12.5:1 for this project. Not like I have not done custom ones before, but guessing demand would be pretty low. Carbs are anything round slide under the sun. Of course I saw a very nice set of Mikuni 33's at Mid Ohio last weekend for $350 but at the time I had no use for them. So either those or some CR in 31-33mm.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline calj737

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #4 on: July 12, 2018, 11:19:25 am »
There isnt a 12:1 compression piston over 890 but under the class limit. I guess I could see about having some 915 slugs made in 12.5:1 for this project.
Sounds like a Mike Rieck billet block with Nikasil bores is right up your alley....!
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline slikwilli420

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #5 on: July 12, 2018, 12:42:59 pm »
There isnt a 12:1 compression piston over 890 but under the class limit. I guess I could see about having some 915 slugs made in 12.5:1 for this project.
Sounds like a Mike Rieck billet block with Nikasil bores is right up your alley....!

I wish. Already checked with Mike and all his have been bored for 1000cc+ pistons. He did say that I would get similar benefit by going with aluminum sleeves with Nikasil bores.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline kmb69

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #6 on: July 12, 2018, 01:28:56 pm »
.....
I wish. Already checked with Mike and all his have been bored for 1000cc+ pistons. He did say that I would get similar benefit by going with aluminum sleeves with Nikasil bores.

+1.
Little bit of weight savings there as well.


Offline Jerry Rxman Griffin aka MuthaF'er

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #7 on: July 12, 2018, 02:25:49 pm »
Yeah Leroy, but....

b) ENGINE
1) All engines must use OEM crankcases, cylinders and heads from the period
1982 and earlier.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline slikwilli420

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #8 on: July 12, 2018, 03:12:07 pm »
Yeah Leroy, but....

b) ENGINE
1) All engines must use OEM crankcases, cylinders and heads from the period
1982 and earlier.

Good call Jerry. Alloy sleeves may still happen though.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline kmb69

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #9 on: July 12, 2018, 04:40:55 pm »
Yeah Leroy, but....

b) ENGINE
1) All engines must use OEM crankcases, cylinders and heads from the period
1982 and earlier.

Yeah, but they mean you have to start with the original castings.
Spanky, you quit reading 1 rule too early!  :o

b) ENGINE
1) All engines must use OEM crankcases, cylinders and heads from the period
1982 and earlier.
2) Allowed displacement may be arrived at in any manner (i.e., stroker and sleeve
kits are legal). Aftermarket “big block” kits are not allowed (see 1. above).

"any manner" Doesn't restrict the kind of sleeve kit.
Pretty sure Matt can use alloy sleeves.  ;)

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #10 on: July 12, 2018, 06:20:14 pm »
My take is you must use a stock block ie "OEM cylinders" and not an aftermarket block such as Mikey's superblock. His 890 ambition would include a stock modified OEM block which should work just fine Leroy.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline seanbarney41

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #11 on: July 12, 2018, 06:26:22 pm »
Good luck and much encouragement!  ...seems like the popularity of this class in AHRMA has really dwindled in the last few years which is unfortunate, as it was my favorite class to watch! 
If it works good, it looks good...

Offline Tintop

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #12 on: July 12, 2018, 06:58:50 pm »
While I hate to rain on the parade, but the cut-off is 1982.  A Brent Hyde '82' CB750F (wet sump / wet clutch, pick your displacement) would blow the doors off a SOHC.  Think gear drive primary, proper cam chain control, super finishing, all allowed because it's internal.  Now all that looks like it will also be available for the SOHC, but rocker arms are going to have a hard time staying with shim under bucket in the RPM game.

All that said slikwilli420, if you build it with the gear drive and other newly engineered bits your going to scare a bunch of people. 8)
1977 CB550/4 Cafe - Speed Warrior / BOTM 03/11
1980 CB750F (project)
Whittaker GBF Vintage Racing Sidecar (XS750 power) - ITG / 151's / CMR Racing Products (SOLD)
1976 CB400 SS - stock / BOTM 04/11 (SOLD)
1973 CB750 K - basket case (SOLD)
77 CB550 Cafe build
550/750 Filter Thread
Sidecar Rebuild Thread

Offline seanbarney41

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #13 on: July 12, 2018, 07:16:27 pm »
Yeah, Kenny at Cyclex beat the pants off the dohc's  (and all the twins too for that matter) a few years ago.  It had some rather exotic cylinder head mods and a hired gun rider.  Still, pretty impressive when you consider a bone stock Suzuki GS1100e makes 100hp and handles too.   Matt will have a big challenge building a competitive engine.
If it works good, it looks good...

Offline slikwilli420

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #14 on: July 12, 2018, 07:37:13 pm »
Guys, read the rules. Brent Hyde's bike would not be legal on class since it is over displacement and carbs are WAY too big. His brakes are not legal either. Totally different class of bike. No one is building $100k bikes over here for this class either. The 1100 class bikes need to have displacement taken out and are restricted to smaller carbs than what I can run. Those bikes are also typically heavier and longer which test the limits of frame and suspension strength more than mine would. I plan to be under 400lb wet with this one which should be a fair bit lighter than other bikes in class. 100hp out of an 890 with high compression and a monster head should be possible. Yes, Kenny had a top rider and gobs of money and blew the doors off top guys in the class. Checking times at Road America where the big bikes should really shine and my times were only about 4 seconds off the lead times in that class. That's me, a new rider on a new bike pushing 760cc. In a year or two I'll be matching top guys on my class which are the times guys in heavyweight are running. Is this going to be challenge? Yes. Can it be done? You bet your ass.
« Last Edit: July 12, 2018, 07:38:51 pm by slikwilli420 »
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline gschuld

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #15 on: July 12, 2018, 08:14:59 pm »
Go for it Matt👍

George

Offline kmb69

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #16 on: July 12, 2018, 08:31:50 pm »
My take is you must use a stock block ie "OEM cylinders" and not an aftermarket block such as Mikey's superblock. His 890 ambition would include a stock modified OEM block which should work just fine Leroy.

I believe the question was related to alloy sleeves - not the block - which I read to be permissible within the engine size limits.  ;)
Spanky, if you're a little foggy on the topic, we're talking about replacing the iron sleeves in the "OEM block" with Nikasil plated aluminum versions.  ;)

Yeah, Kenny at Cyclex beat the pants off the dohc's  (and all the twins too for that matter) a few years ago.  It had some rather exotic cylinder head mods and a hired gun rider.  Still, pretty impressive when you consider a bone stock Suzuki GS1100e makes 100hp and handles too.   Matt will have a big challenge building a competitive engine.

+1. Kenny was blowing all of them away!

Guys, read the rules. .....

Just did. The SOHC 750 is unfairly limited versus the other bikes in that class IMHO. Same size limit as DOHC's? ???

.....
100hp out of an 890 with high compression and a monster head should be possible.
.....
Is this going to be challenge? Yes. Can it be done? You bet your ass.

I totally agree. And after observing your current build and your personal achievements, you can if anybody can!  ;)

Offline kmb69

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #17 on: July 12, 2018, 08:49:11 pm »
There isnt a 12:1 compression piston over 890 but under the class limit. I guess I could see about having some 915 slugs made in 12.5:1 for this project. Not like I have not done custom ones before, but guessing demand would be pretty low. Carbs are anything round slide under the sun. Of course I saw a very nice set of Mikuni 33's at Mid Ohio last weekend for $350 but at the time I had no use for them. So either those or some CR in 31-33mm.

I would sure consider having some 68.5mm, high compression pistons made resulting in 928.7cc - just under the limit.
It would also allow for some bigger valves in the head.  8)
 

Offline scottly

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #18 on: July 12, 2018, 09:33:41 pm »

I believe the question was related to alloy sleeves - not the block - which I read to be permissible within the engine size limits.  ;)
Spanky, if you're a little foggy on the topic, we're talking about replacing the iron sleeves in the "OEM block" with Nikasil plated aluminum versions.  ;)

Thin alloy sleeves pressed into a stock block will not be as stable as iron sleeves; they will distort with heat and pressure much more, which affects ring seal. Mike's billet block is an entirely different animal, as it has much thicker walls.
Since the cut-off is '82, I think the DOHC could be a viable weapon. The stock HP rating was 8 more than a SOHC, they had hi-vo primary and cam chains, superior to the SOHC chains, needle bearing swing-arms, etc.
Don't fix it if it ain't broke!
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Offline Tintop

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #19 on: July 13, 2018, 04:58:10 am »
Did read the rules, it's what I'm very good at seeming I've written many.  All the internal mods that Brent Hyde makes are legal, just put them in a smaller cc package.  And yes without his gear drive primary, and cam chain guide improvements the DOHC would not be a reliable package.
1977 CB550/4 Cafe - Speed Warrior / BOTM 03/11
1980 CB750F (project)
Whittaker GBF Vintage Racing Sidecar (XS750 power) - ITG / 151's / CMR Racing Products (SOLD)
1976 CB400 SS - stock / BOTM 04/11 (SOLD)
1973 CB750 K - basket case (SOLD)
77 CB550 Cafe build
550/750 Filter Thread
Sidecar Rebuild Thread

Offline bwaller

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #20 on: July 13, 2018, 05:26:42 am »
Brian is right, keep the engine exterior period looking and internally go nuts. Respect bore limitations of course and some will only allow nikasyl coated iron sleeves.

Every track is different, some will favor a smaller bike with less power but increased corner speed. Some are shoot-out horsepower tracks.

Then there is that absolute given... where the outcome can be 80% rider.

Offline slikwilli420

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #21 on: July 13, 2018, 06:03:30 am »
Keith - Yes, the SOHC is unfairly limited to 931, but I get unrestricted intake size, where the 1025 maxed guys have to run 29mm carbs. This should help to even the field a bit.

Scottly/Keith - I think if I went aluminum on sleeves, I would have the cylinder bored to accept larger sleeves, just as the 890 kit would call for, except they would be aluminum.

I don't want to go the DOHC route, because, frankly, Im not a huge fan, know nothing about them and like challenges. No one thought the single stick Honda could do anything in Sportsman either, but I plan to continue to change minds there as well.

Tintop, that is a good point on Brent Hyde's modifications, but the guys over on this side of the world who are doing those things still aren't on the podium very often. Id actually be most scared of a well set up GS, as the handling was already very good from factory and they can stand lots of mods and keep ticking.

I think the SOHC can make big reliable power and be a lighter package than many other bikes in the class. Things like a head with really big valves, getting close to 931cc, and a balanced rotating assembly will really make the difference. I had an issue with the CX10 cam last time with valve/piston clearances, but plan on using that cam this time, and knowing that, can have the head pistons set up differently to accommodate the higher lift.

Lap times for my class and VSH aren't very far apart and I think I can close that gap with more acquired skill and a well built bike. Time will tell.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline slikwilli420

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Re: CB750 AHRMA Superbike Heavyweight Racer - Front Forks?
« Reply #22 on: July 13, 2018, 06:06:06 am »
Going to start at the front on this one and work my way back. What does everyone like for 41mm forks? I was looking at the CB600F2 from '91-'94 as they are 41mm, right side up, have options for springs/valves from race tech, are fairly cheap/available and have conventional caliper mounts. I will need to mount something that passingly resembles a stock-ish fender to it, but thats the only restriction.

What else in the 41mm size is out there and meets the qualifications above?
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline livefast_dieold

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Re: CB750 AHRMA Superbike Heavyweight Racer
« Reply #23 on: July 13, 2018, 06:06:22 am »
My two cents (having actually competed against a CB750 DOHC with my 750 SOHC): a Honda DOHC needs way more investments and efforts to be competitive compared to a SOHC, and even if the engines are equally upgraded in terms of components and finishing, the extra weight of the engine & chassis is not compensated by the extra power generated by the engine.

Offline livefast_dieold

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Re: CB750 AHRMA Superbike Heavyweight Racer - Front Forks?
« Reply #24 on: July 13, 2018, 06:11:13 am »
What else in the 41mm size is out there and meets the qualifications above?

My Bimota YB9 has 41mm diameter regulars forks, made by Paioli