So. As you may know im building up A superhawk.

The bike I got was missing alot of parts, most of which ill fabricate myself.

Here is whats going on with the motor.

Port and polish. Ive already done this. Basically smoothed out exhaust ports and buffed them. Intake ports got a little port enlargement and some changes to the wall that separates the valves. Also port matching to the carbs.

question #1. Whats this CV slide drilling I keep hearing about? I cant find a thread devoted to it.


Ill be building my own full exhaust. Can anyone provide me with the ID or OD of some aftermarket pipes? I want to know IF 2" OD will be too large and slow down the pulse speed too much.

Question #2 aftermarket exhaust diameter

I may get some RC pistons, just to fool around with. Bore the cylinders the extra 2mm. Depends on the wristpin diameter and if the combustion chamber is similar. But that would be a while from now.


OK now to the airbox. I dont have one. Ill be making my own very soon. It will have alot less volume than stock. Thats because in doing an undertail radiator and I need all the room under the tank I can get. Building my own gastank also.

Question #3 Anyone have any good pictures of the stock velocity stacks on the bike? Anyone know the height of the rear velocity stack?

Question #4 What are common main jet sizes with airbox mods, head mods, and exhaust mods?


I realize im asking alot. Any good information will be helpful. So thanks in advance.

Ive spent the last 3 hours searching the forum, but im sure there is tons ive missed.

one last thing. Since the superhawk is the predecessor of the rc 51, Im sure lots of them were built and raced.

Anyone know any specifics of these motors?

Thanks again

 

Drilling the carb slides is part of the recommended procedure for installing the Dynojet kit, which includes shorter-lighter springs and is supposed to provide quicker throttle response.

 

Quote:

Originally Posted by Truckinduc

So. As you may know im building up A superhawk.

The bike I got was missing alot of parts, most of which ill fabricate myself.

Here is whats going on with the motor.

Port and polish. Ive already done this. Basically smoothed out exhaust ports and buffed them. Intake ports got a little port enlargement and some changes to the wall that separates the valves. Also port matching to the carbs.
Make sure that you grind the aluminum out of the carb boot, it is a major restriction.

question #1. Whats this CV slide drilling I keep hearing about? I cant find a thread devoted to it.
You got one answer here, but you will have MAJOR rejetting to do with what you have planned.

Ill be building my own full exhaust. Can anyone provide me with the ID or OD of some aftermarket pipes? I want to know IF 2" OD will be too large and slow down the pulse speed too much.
2" will be a problem. You will not have the velocity for proper scavenging. Run a torque step if 2" is your end goal for the primaries.
Question #2 aftermarket exhaust diameter

I may get some RC pistons, just to fool around with. Bore the cylinders the extra 2mm. Depends on the wristpin diameter and if the combustion chamber is similar. But that would be a while from now.
Don't F with the RC pistons, there isn't a whole lot exchangeable from bike to bike, and you will have to mess with dome height in relation to wrist pin as well as that diameter.

OK now to the airbox. I dont have one. Ill be making my own very soon. It will have alot less volume than stock. Thats because in doing an undertail radiator and I need all the room under the tank I can get. Building my own gastank also.
I wouldn't mess with the intake volume if possible, this could be catostrophic in performance.

Question #3 Anyone have any good pictures of the stock velocity stacks on the bike? Anyone know the height of the rear velocity stack?
Use the factory pieces, figure out a way.

Question #4 What are common main jet sizes with airbox mods, head mods, and exhaust mods?
This will be determined by individual setup.

I realize im asking alot. Any good information will be helpful. So thanks in advance.

Ive spent the last 3 hours searching the forum, but im sure there is tons ive missed.

one last thing. Since the superhawk is the predecessor of the rc 51, Im sure lots of them were built and raced.

Anyone know any specifics of these motors?

Thanks again

 

I'm not sure of the Moriwaki exhaust header ID. It is a bit larger than stock.

The other thing to look at with pistons is wrist pin height. I haven't heard of anyone installing RC51 pistons in a Super Hawk engine, so it is not likely to be a direct swap with stock rods. I have a good set of stock RC51 pistons, if you need them. I can measure the wrist pin heights for you. I have VTR pistons too.

If you can route the coolant hoses under the carbs, you'll have room for a bigger airbox. With the big gulps of a twin, more volume is more better. Maybe put a coolant ovrflow tank in front of the lower triple clamp, below the headlight to free the space under the carbs. Antoher possibility is to make intake ducts to pressurize the radiators in their stock location.

You'll pretty much be in uncharted territory with jetting. Perhaps someone can give you a reasonable starting point.

 

Thanks for your responses everyone.

1. I do not have the stock velocity stacks or airbox. The bike I have was a parts bike and was missing alot of parts. Thats why im looking for pictures and measurements. It didnt even come with carbs.

2. The RC pistons I was talking about were going to be given to me. If wristpin diameter was the same and wristpin height was very close I was going to have a friend machine up some Titanium wristpins. I doubt Ill do anything with the pistons.

3. The airbox Is something different all together. I plan on making aluminum velocity stacks slightly longer than stock. Ill be running a k&n panel filter. A scoop will protrude from between the right side of the head and the frame. Im not expecting high positive airbox pressure numbers, But anything is better than a vaccume.

I realize ill be trading a little low end power for a little top end power with this setup. Im hoping around 40 or 50 mph to be the point where the airbox goes from negative pressure to positive pressure. I dont know if anyone has ever experimented with ram air on a vtr. Thats why im looking for race bikes.

I also realize tuning is going to be a bitch, but hey thats half the fun.

 

do you have carbs, if not then you should be looking at fcr's and use a dual pull setup, its easy enough to tune and it will give you ALOT mor room as the carbs are much smaller. AS for the airbox, you could make the airbox sit on top of the fuel tank (buried between spars, lower center of gravity) and gain volume and access for your ram ducts.

 

Moriwaki had a ram-air box and ducting for the VTR. They are completely unobtainable, as far as I know.

With a carbureted bike, you need to supply the ram air pressure to the floats. That's probably a major reason for the location of the air intake on the stock system. You get pressurized air from the fairing ducts, and the carbs see the same pressure as the intake to the airbox.

 

I got a deal on some stock carbs. Unfortunatly a dont have a grand to drop on some FCR's or I would.

Honestly in a FI man and I hate CV carbs, though I like flat slides.

Hey RCVTR, can you explain this ram air setup A little more, or point me in the right direction?

 

question- why didn't the moriwaki race bike or bob h. use flatslides or did they experiment with them?

 

another question, Ive got a new set of Dynacoils, but they are 5 OHM. I dont want to burn up my CDI so I need some 3 OHM coils.

What do you guys think of these?

http://cgi.ebay.com/ebaymotors/3-OHM...1%7C240%3A1318

will they work with the VTR ignition? Im not sure if the ignition discharges every TDC or just the compression TDC.

 

I think they were able to make a flat torque curve right up to the point where the crankshaft broke, then backed off a few clicks.

there's nothing wrong with the Keihin carbs that I'm aware of.

 

For instance, the RC51 MAP (manifold absolute pressure) sensor is mounted near the entrance of the ram air intake, perpendicular to the airflow.

You would need to supply a similar pressure signal (actual air pressure, not an electrical signal) to the float bowl. There is a float vent on each carb, that vents to the atmosphere. If you feed pressurized air to the airbox and not the float bowl, you will not get the correct pressure differential to meter fuel and the engine will run lean at high speeds.

 

The reason that I am saying flatslides is because he needs extra room, which they would provide. As for the coils, don't go cheap on that stuff. If you want to be broken down and looking for a tow all the time, then thats your business. The electrical system is too important for cheap aftermarket coils.

This is a major undertaking, and sounds like it could be pretty cool when done. Figure on it taking twice as long and repairing or redesigning atleast half of what you make. The exhaust is Uber critical, so don't throw caution to the wind. I made some changes that really affected fueling. I changed to a dual undertail, and saw huge fueling changes that the jetting couldn't keep up with. I changed it again (outlet size) and corrected my fueling. I changed it again after a mishap and thought it was close, went into my carbs and saw an "obstruction" (the carb boot aluminum) and saw my jetting go from good to bad. I am now on the umpteenth iteration of jetting and think its just about perfect, and now I had an exaust mount crack, my undertail needs work, one of my tail light mounts has broke, and I need a serious undertail change to provide some real support for the electronics before that becomes a major issue. Obviously a labor of love, but just be careful on what you change. Exhaust could take your bike from being decent everywhere to a super hero somewhere and a pos everywhere else.

 

Well said!

 

Ive built about 6 full exhaust up to this point, im only 19, so we will see how it goes.

Im thinking stock primaries for about 14 inches then stepping up to 2 inch OD, im not sure of the ID of the tube. The 2 into 1 will be 2.25 OD and then split back into 2 separate pipes again. Outlets are 2 shorty moto gp style megaphones, approximately 8 inches that exit under the rearsets.

The 2 into 1 will house a perf core muffler that may provide a decibel or 2 of deadening.


Im thinking I may make the airbox tall and narrow to gain some volume, but still retain the ram air scoop.

 

Whats this "obstruction" in the carbs? Is it the boot between the carb and the head? If it is, I dont have those boots, I made my own. Ive port matched the head to the carb so its smooth all the way in.

 

thanks! so they did try them out, is that what they were using with the pressurized airbox or did they use the stockers. i'm seriously considering them if i can find some that'll work. i know the sv's and ducs see some good results with them but i haven't seen much data for them on the vtr or anyone that has actually used them(i've seen a few pics of them mounted but no info or results.) i figured if the mori bike and such used highly modified stockers vs. the flatslides then there might have been a reason or problem with them but wasn't really sure what was used.

(sorry for the threadjack truck)

 

The obstruction is just in the factory carb boots.

 

If you do anything but an X pipe for your tru-dual setup (meaning a 2-1.......-2) you will have some issues with jetting and you will lose torque in exchange for some power on top. that is the one thing that I wish that I could change. My "1" setup is about 10ish inches long and drastically changed the character of the bike.

Also, why are you running the primaries at 1.75" (OEM) for 14 inches? why not 10"? I ask because the stepped header setup works, but the spacing for those steps is critical for the rpms. If your pipe overall length is 28" for the primaries, this would make a nice division for different rpm torwue peaks, but what are they, and is the 28" mark just an "octave" of the 14"? If so, you would be better off running three sizes in the primary.
When I built a torque step header for a Honda F2 motor used in a race car, the initial primary size was smaller than any after market size. it stepped twice over 24" to create a flatter torque curve and it was also tri-y in construction.

Needless to say that a fabrication of this type takes some wave tuning that involves knowing the duration and lift of the cams, at the valve, for every 2 degrees of crank rotation, the size of the intake, the length of the intake, the volume of the intake bowl, the size of the valves, the bore and stroke, the rpms that it will run, the size of the exhaust, the length already in the head (your first primary section), and I can't remember what else.

I didn't go this involved on my bike and have suffered because of it. I am on my third pipe setup. Is it tuneable? yes. is it a pain? yes. Would I suggest doing this? No. Here is my reason. The cost of materials is expensive, you don't have an engineering degree ( and I don't for that matter), and the reward is small. If you were to buy a full system from manufacturer 'A', you will get a much better product that will last longer. They also know what jetting you should go to. These are my thoughts on this matter...

 

I think you may have misinterpreted.

I don't know what the Moriwaki bike in Japan used, but Bob used modified stock carburetors. I'm not sure of the extent of the modifications. They were "tuned" versions of the stock carbs.

He had a wrist pin failure from being overhardened that sawed an engine in half with the end of the con rod.

I don't know of a broken crank in one of his engines. That failure mode was identified on the dyno in Japan. The basic message was "don't use those cams".

 

A connecting rod failing and stabbing the crankcase will indefinitely cause a "crank failure". The crank breaking, with what most of us would be doing, is highly unlikely. The mori bikes were unlikely to be running 9500rpm. Kept in this range, the crank shouldn't fail. I also don't know of a way to exceed 10k, as that is where the rev limiter is at. To get to an ultimate power, you would have to go to :
HC piston, racing setup, one compression ring with a small skirt.
Forged Ti rods
Balanced assembly
Ti intake valves, stainless exhaust
1.5mm valve seats with 5 angle valve job
Cleaned combustion chamber
Full port and polish, flow balanced
Cams- race lift and duration. Could lighten inake cam because of Ti valves.
Valve springs, ti retainers
Micro ground gearing in trans, undercut gears
Lightened or smaller flywheel and stator
Bigger Carbs, FCR's
Ignition system (advance curve change as well as spark intensity)

And after all this work, you still need an exuast that flows big, and the money to constantly rebuild. Crank failures are just not going to be a problem for any of us humans with actual budget constraints.

 

Bob's engines had:
Custom JE pistons
Carillo rods
lightened, polished crank
HRC/Moriwaki OS steel valves
HRC valve springs and retainers
stage 3 cams, which required extensive head work for clearance.
Extensive head porting
HRC ignition - with no rev limiter
HRC kit transmission
Moriwaki Superbike (stage 3) exhaust system
I believe redline was ~11,500 RPM, but I may be thinking RC51.

And were built with extensive knowledge of building race engines. He was a teammate with Dan Kyle in the 80s and they got on the podium at Daytona with VFR750R (RC30). Dan did the engines, Bob did the chassis.

Yes, when the wrist pin broke, it destroyed the crank. It was not the root cause, however.

There is no reason to be concerned about breaking a crank with the stock redline or even quite a bit more. But it gets expensive fast.

The character of the engine is preserved with a stage 1 build, but just a bit more everywhere.

 

there is free HP in every system that is mass-produced. I think that is the place that everyone should start. The list you had there looks pretty similar to what I was thinking and posted. If you look at the list there are a few spots that one should chase first, and really the most effective for reliable off track use.

 

Can anyone PLEASE help me find pictures of the stock airbox and velocity stack setup? I cant find them on my own.

 

Ill also be machining out my can sprockets so a can degree my cams. Why not.

 

When you do it, remember that the cam sprockets are nitrided. This treatment doesn't go too deep, but the best way through it is to "peck and drill". It will take some pressure (more than you are used to) to get thru that hardening. I did this on an F2 engine.

 

Ron Ayres parts fiche

 

http://fiche.ronayers.com/Index.cfm/...up/AIR_CLEANER

 

http://www.orientexpress.com/product...tm_campaign=gb

best price I've found for a set of 4 adjustable cam sprockets...RC

 

The slotted cams are great, but if you want to save some money you can use the stock cam gears and place them in a three jaw on a rotary table for a vertical mill and get the same result for less. That is, if you have the access to one. If you do, a word of advice: the nitriding on the sprockets makes them extremely wear resistant, meaning that they don't machine easily. If you are going to do this, I wouldn't slot them. If you won't 1 degree increments, machine holes in that increment. This will leave a point that will make it easy to get the adjustment you want without lots of time.