Topic: CB750 AHRMA Superbike Heavyweight Racer

[slikwilli420]

Good info on the DOHC vs SOHC in terms of cost/performance.

Id like to find a fork that is pretty plentiful and really liking the early GSXR/Katana forks from the late 80's and early 90's as they are 41mm, plentiful, affordable, and have fork brace mounts cast into the top. I should be able to make a plate and dimension and mount a fender underneath to stay within the rules.

Are there any particular GSXR/Katana forks/years that are most desirable? Most I have found after a quick ebay search look nearly identical. Would be nice to find ones similar length to GL1000 forks as that's what is on my other bike and I was able to get rake/trail geometry nearly perfect on that.

[simon#42]

as lap times between your class and this new class are very similar is there much point in building a new bike for it ?  the new bike is not going to be much better than the one you have
why not spend some of the cash on the bike you have and race it in both classes
is there not a class for bikes with proper racing frames etc that you could build a bike for as well ?
it would be nice to have two bikes that are different

[754]

 I have 41 mm Sv forks. Don't know an thing about them but they were raced, so there should be goodies.
 2 axle sizes on fat end  found out the hard way..

You can always get a faster out of the box bike to start with.

 But, and I bet many agree on here, the big fun is in how much you yourself improve the bike you have.
Our sohc 750 is a bit of an underdog, but you can double the hp, and triple the fun.. try that with the others..

[slikwilli420]

as lap times between your class and this new class are very similar is there much point in building a new bike for it ?  the new bike is not going to be much better than the one you have
why not spend some of the cash on the bike you have and race it in both classes
is there not a class for bikes with proper racing frames etc that you could build a bike for as well ?
it would be nice to have two bikes that are different

Current bike meets almost none of the rules for the Superbike class. I would need to swap in a different tank, seat, add side covers, etc, etc to make it legal.

These will be quite different in look and function but still both be SOHC Honda's at heart. Very few things applied to the old one will be applied here.

As for a fairing bike, I could build one for Formula, but so few guys race that class any more that I don't see much point. Maybe some day, but not right now. Formula bikes are essentially my current bike with a second disc brake and a fairing, which is the idea. Sportsman is the ground to get fast and then Formula is the highest level in that lineage.

[kmb69]

.....
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.
.....

Maybe, but they don't necessarily have to be so thin.
And I was thinking of using 7075 or even better, Tennalum 7068. The 7068 is "2.5 times stronger than 6061, and 35% stronger than 7075" and "33% better strength-to-weight performance than 7075, and 28% better performance than 6Al-4V Grade 5 Titanium" according to Kaiser. Yep, 3-4 times the price of 6061 but you only need 4. 

Very familiar with Mike's blocks (6061) since I have 4 of them including one that he had custom manufactured to my specs. 

.....
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.

It probably is, but as mentioned previously, the cost to compete with a DOHC is astronomical! The weight, the stock head won't breath, cam chain control, needs gear drive conversion for no primary maintenance, reverse oiling for the tranny, dry sump oil system, cost of cams and twice as many valves. You got to spin them high for power and the oil pumps begin to cavitate around 10,500 rpm's. Honda recognized this issue and had to dry sump their factory racers. I know because I'm building a dragbike engine using the best available components today including some of Brent's and it is costing cubic dollars. Some similar issues with the SOHC but a lot bigger variety and cheaper solutions for the SOHC.

[scottly]

Maybe, but they don't necessarily have to be so thin.
And I was thinking of using 7075 or even better, Tennalum 7068. The 7068 is "2.5 times stronger than 6061, and 35% stronger than 7075" and "33% better strength-to-weight performance than 7075, and 28% better performance than 6Al-4V Grade 5 Titanium" according to Kaiser. Yep, 3-4 times the price of 6061 but you only need 4. 

Aluminum is 1/3rd the weight of iron/steel, so if the alloy sleeves are 3 times the thickness, it's a push as far as weight, but waay more expensive. Also, 7068 gets weaker with exposure to elevated temperatures, as low as 250*F, IIRC.

[kmb69]

.....
Aluminum is 1/3rd the weight of iron/steel, so if the alloy sleeves are 3 times the thickness, it's a push as far as weight, but waay more expensive. Also, 7068 gets weaker with exposure to elevated temperatures, as low as 250*F, IIRC.

You are correct about the lower temperature degradation on the 7068. I missed that. Not to mention, I could not find the 7068 bar in a large enough diameter.
But 7075 appears to hold up pretty well to 200°C/392°F. Shouldn't need to go 3 times thickness IMHO.
Not sure what alloy(s) are being using for casting a lot of the newer plated aluminum cylinder engines but it's pretty common these days in water cooled applications.
Nikasil plating the iron sleeves should work well also but I have no personal experience yet. I am planning to try it on a really high compression motor.
Most iron sleeves are relatively low grade stuff. Another possibility might be to use thinner high strength material that might not be suitable for ring sealing unless plated.
Just thinking out loud I guess. Also, the engines I'm working on right now are for drag racing and don't have to stand the time duration of a road racer.

[slikwilli420]

The guys at Millennium are the gurus when it comes to sleeves. They said they will plate iron but with its oil absorption properties they don't guarantee the plating where they will on aluminium. I would spec sleeves the same thickness of the ones in the 915 kit but in plated aluminum. The cooling provided by aluminum sleeves would be worth it with the bigger bore in my opinion. I thought about exploring it for the sportsman racer as well but that one runs so well right now it wouldn't be until a rebuild was needed. The XA ring pack Wiseco uses is compatible with plating and basically never wears out. Cost to get into but one done pays off with more power via better cooling and extended component life. Definitely on the plan for this one. I talked to Kenny yesterday and his juices are flowing on this one now. Going to be a giant killer.

[simon#42]

i would use iron liners for strength and stability , i would only get them plated if i intended to do a couple of hundred thousand miles on them .
i did test some tests with iron and alloy liners about 35 years ago and the heat transfer is not much better . the main difference was the time needed
to warm the steel linered cylinders . with a larger bore i doubt a standard honda cylinder would have the strength to support alloy liners

[slikwilli420]

Plenty of modern bikes running plated aluminum cylinders. Heat transfer has to be better than iron based on the science of thermodynamics. Also ring seal is better and maintained longer than with non plated cylinders.

[bwaller]

Modern engines are more like Mike's billet cylinder with no replaceable sleeve.

I've had nikasyl plated iron for several seasons now.

[simon#42]

yes modern cylinder block design is different which is why i said i did not think alloy liners would work well in a standard honda block
an alloy liner really needs to be supported equally around its circumference and length to prevent distortion , unless you intend to fit
8mm thick liners . also ring seal will be no better , you will need to run a soft ring in order to get it to bed in which causes other problems .

[scottly]

Plenty of modern bikes running plated aluminum cylinders. Heat transfer has to be better than iron based on the science of thermodynamics.

Two stroke MX bikes were running plated aluminum cylinders as far back as 1975. The aluminum was thick enough to provide the structure, and the plating provided the hard load bearing surface. A pressed-in sleeve, regardless of the material, will have poorer heat transfer, due to microscopic voids at the junction which prevent transfer by conduction.

[kmb69]

The guys at Millennium are the gurus when it comes to sleeves.
.....

I'm with you Matt. I would put Millennium's knowledge and expertise above all the "expert naysayers" on this forum! 

Come on guys, "no", "can't", and "won't" seldom make any innovative progress. I'm placing my bet on Matt making it work!

[kmb69]

.....
I've had nikasyl plated iron for several seasons now.

Have you had to replace any rings? Anything special about the rings?

[simon#42]

.....
I've had nikasyl plated iron for several seasons now.

Have you had to replace any rings? Anything special about the rings?

d

Ring millennium and ask them

[bwaller]

I talked to several people about replacing iron sleeves with alloy but in my case it was clearly outside the rules. That's why I mentioned I used plated iron.

Wiseco supplied the rings knowing it was a Nikasyl bore. I replaced rings this spring. Didn't do a leak down last fall and the bores looked really good. I believe with Nik, rings should be sacrificed more frequently.

[slikwilli420]

Talked to millennium at Road America a few weeks back. The XA ring pack from Wiseco is a perfect match for the plated bore. More or less the bore never wears out so rings would be the item to replace. Not sure about replacement interval though. There are no rules against using aluminum sleeves either so I'd go right for that as they guarantee that with to a certain extent where they will not guarantee iron. I also want the reduced weight and added cooling of aluminum. This is a well proven modification and with the high compression and bigger bore should be a bit of added insurance.

[MRieck]

Talked to millennium at Road America a few weeks back. The XA ring pack from Wiseco is a perfect match for the plated bore. More or less the bore never wears out so rings would be the item to replace. Not sure about replacement interval though. There are no rules against using aluminum sleeves either so I'd go right for that as they guarantee that with to a certain extent where they will not guarantee iron. I also want the reduced weight and added cooling of aluminum. This is a well proven modification and with the high compression and bigger bore should be a bit of added insurance.

The Nikasil is very hard....need diamond hones. I remember Moto Guzzi using it many, many years ago....I thought is was BS but I was wrong.

[kmb69]

.....
Wiseco supplied the rings knowing it was a Nikasyl bore. I replaced rings this spring. Didn't do a leak down last fall and the bores looked really good. I believe with Nik, rings should be sacrificed more frequently.

Thanks Brent. Always good to get factual feedback from those with real time experience.
Just curious, did you notice any degradation of power with the old rings and/or improvement with the replacement rings?

[bwaller]

Keith, he didn't complain of any power loss. However the last couple races at Barber I noticed some smoke on decel, that was the key for me. It has never shown any previously. I should have done a leakdown but had already decided there was a need to address this.

Mike & I talked at length before using Nikasyl, it is hard and this winter I found the bores had virtually no wear. As a result these thin XA rings are understandably sacrificial. As a result and depending on the race season, which for us this is max 6 event weekends, I'll replace every year.

As an aside, I had lengthwise marks in each bore which turned out to be minimally thicker sections of plating in the sleeve. Checking with a very accurate gauge proved this. I doubt it caused seating issues to measure but was still evident.   

[slikwilli420]

Alright, we are off and running... well maybe walking.

I picked up a very choice set of GSX600F Katana forks from a '94 model. They are 41mm, have replaceable bushings, and full compliment of Race Tech parts available. They are also the exact same length as the GL forks on my other bike, so should be able to use same offset. Not that its a big deal since I am making my own trees, but still nice. I am going to replicate the AHM superbike trees that Freddie Spencer had on his bikes in 81/82. They are basic but a nice nod to the OG of Honda superbikes.

I am also going to replicate the fender mount used once I find out what I can get away with regarding fenders. I have seen some bikes in class using stock fenders, stock cut down fenders, and more modern fenders. I guess anything that constitutes a fender is good.

I am waiting for the Spondon replica calipers by MotogpWerks to be finished then will be picking up two of those honeys for the front end. I also have the task of making the bearing adapters for the front and rear wheels which I need to design carefully. I will also need to get gauges going. Rules say OEM gauges (gutted or operational) are required. I will be going with a gutted speedo and replaceing the guts of the tach with a digital tach from Speedhut as a member did here:

http://forums.sohc4.net/index.php/topic,95342.0.html

I also have a very nice adjustable ratio AP Racing master to use up front.

Still up front but not on the front end is the oil cooler mount. I have to retain a headlight bucket but it does not need to use stock headlight ears so I can move it wherever.

It will look like this more or less:


I will need to keep the oil cooler height smaller since I need room for the headlight bucket/number plate.

Here is how Brent Hyde mounted his:


Again, not perfect since there is no headlight bucket but I will make it work.

[slikwilli420]

Time for a rant/update.

I have started tearing the front forks down for a full rebuild which is interesting since I have never done forks with replaceable bushings before. The GSX600F Katana forks have both internal and external bushings that can (and will) be replaced. They also have a 3-setting damping knob on the fork caps, which was removed to make way for the Race Tech parts. Im upgrading to at 20mm hollow axle from a CBR600 just like the other bike, but one fork leg is smaller so needs to be bored out, then off to vapor blast, or maybe satin black gunkote, still deciding.

Now for a rant. I do love Race Tech, good service, great parts, but the pricing that can be found across the internet is a bit frustrating. While I like the best deal like anyone else, I do also like to go right to the source to get parts, especially if I will need service as well. Well this time, I knew what I needed from Race Tech, but happened to be looking at other pieces for the forks on Amazon and noticed they were selling the same parts for a drastically lower price through Amazon vs their website. Im talking $170 vs $122 for emulators, and $130 vs $97 for fork springs. I was pretty blown away at the price difference of the same part by the same vendor, just through different outlets. Moral of the story, shop around before assuming the price is as good as it gets. Rant over.

The hub adapters for the front wheel bearings and rotors are back from waterjet and I will document how I turn those into something useful from their current form. I was going to use the aftermarket rotors I were told were Z-Mark but I also have a set of what I believe are Kosman rotor centers that are the same bolt pattern that I am going to try and use instead. I found a place that will make rotors to my specs from iron for about $100 each. This will allow me to go up to 13" rather than 12". I figure I will get a bit better braking with this setup so if I am going custom, why not.

[MRieck]

Matt....the oil cooler looks good. The only comment I have is can you use rubber bushings etc at the mounting points? I have had the Earl's units crack from vibration.
I also noticed the primary tubes on Hyde's bike. Looks like a variation of Micron's "Serpent" pipes from the late 90's.

[slikwilli420]

Matt....the oil cooler looks good. The only comment I have is can you use rubber bushings etc at the mounting points? I have had the Earl's units crack from vibration.
I also noticed the primary tubes on Hyde's bike. Looks like a variation of Micron's "Serpent" pipes from the late 90's.

It will definitely be rubber mounted somehow. I won't use earls coolers based on reports of cracking. I use Setrab coolers. Competitively priced and made in Sweden. The stepped header on Brent's bike is awesome. Moto gp werks makes them like that for the 550 but won't be doing them for the 750 which is a huge bummer.