With my bike going to be out of commission for a while I figured it would be a good time to do some mods to it. I have read and seen pics of broken crankshafts and read that they are caused by Cams that have larger lobes. Is this true? Is there a place I can look for these issues? I know this bike will not put out the power of an RC-51 or a new Duc but I would like to find out what it can withstand while being reliable. Ill end up buying a separate engine for this whole thing so I don't ruin the #'s matching unit. On my list of ideas is:
1) Knife-edge and balance the crank
2) Hi-comp pistons and H-Beam con rods
3) Balance rotating assembly
4) port / flow bench heads
5) velocity stacks (Step-father has a cnc machine)
6) experiment with an open airbox design. (foam dome)
7) individual exhaust (2-into-2) no x-over and equal length.
8) Cams... not sure the grind yet but also not sure if the crank will hold up, OR if Knife-edging the crank will make it more prone to cracking anyway.

Again just doing this to a spare engine because I think it will be interesting to see what this power plant is capable of. Ideas, questions, let me know. Ill probably crack into it within the next 2 months or so since my wife is due mid July. One question I will answer already for you wondering 'Why?', the answer is because its my money, my time, my bike and I want to so kindly F*** off (respectfully) lol. All other questions will be answered to the best of my abilities.

 

Ignore the broken crank and camshaft thing, not an issue.

If you're leaving the motor in the frame do the following:
Lightened flywheel, exhaust, filter, adjustable needle, tps reset, 15/43 sprockets, voltage regulator, stick coils. Then enjoy it.

If you are pulling the motor and disassembling it do the following:

Ignore the broken crank/cam thing...not an issue.
Balance and resize the stock rods, use ARP bolts. Order 2 JE 11.5:1 99mm pistons and check piston to valve clearance.
Order and install RC51 lifters and springs
Slot your cam sprockets and retard the intake cam 2 degrees. Or get a regrind from Webcams.
If you want new rods...Pauter Rods in CA will make them for 500$ a pair. A bit less for aluminum rods.
Install an RC51 transmission.

I can confirm that you will enjoy the ergos of a VTR over an RC all day long and...you can definitely hang with an RC if you do some mods.

That pretty much covers it

AV

 

as already said the bottom end on these things is nothing to worry about. they will take upto 135 rear wheel horsepower for as long as you keep putting petrol into it.

 

+1, and then some more for sure. Did I mention the arp rod bolts. The v shares rod bolts with a busa. Go figure.

AV

 

We've had someone here break a crank, why ignore that?

 

Have we? I must ha e missed that...thought it was a myth or one of those..."at 11000 rpm my crank broke..." Things. Kind of like a yeah but we'd pretty much expect that to happen, but not typically. I mean, my current rotating assembly is only trued for straight with balanced rods and it seems redline no issue. Whose crank broke? I'd love to read about it.

Av

 

Apparently the search function still works...

I sent the pics of the broken crank over to the engineer that helps me out and here is his very brief answer:


A very brief (no charge) answer.

 

You can ignore it , because there were very odd circumstances involved.... Also,, After extensive Google-Fu, I can't find any other reports of failure... Pick just about any other bike and search..... So it is just a random bizarre thing...


.Also...... "My Vacuum Cryogenics REMOVES THESE VOIDS AND STRESS CRACKS..." ????? No.... It doesn't.... May cause them to be less of an issue by hardening the metal around them, But no amount of any kind of tempering will fix a crack, or fill a void...

 

Cryo does not harden....it decreases the tendency to fatigue by changing the properties of the metal. The austenitic/martensitic conversion through use of cryo is a well documented and researched topic and has been for decades. I know personally from having conducted literally 100k or more ultrasonic shear wave tests, and other non destructive tests, on aluminum, steel, and other materials that this true. Hardly debatable like it was in the early days.

AV

 

Hi Ace, hows things?
Can I ask you 4 questions please.

1-Can you give me the part number for the ARP conrod bolts?
2-The RC51 valve springs, did you use both the inner and outter springs?
​​​​3-Are the Kibble White valve springs any better, is it worth buying them?

4-JE 98mm forged pistons...(11:5:1 standard bore)...will they work with 39mm (1mm oversize) intake valves?
Or do they need to by fly cut for the larger intake valves?

Thanks.

 

It's been 5 years and 11 days since the last post by Ace. Seems unlikely you will get a response. Maybe you'll get lucky and someone else will chime in with that info.

 

Yo, I am here. So glad you're digging into this it's a very fun bike.

I do not have the ARP part numbers on hand, but I can look them up for you. Regardless, they were off the shelf Hayabusa bolts.

Valve springs...inner and outer. I cryo treated mine but that is a personal preference. I am sure the KW springs are up to the task, I used RC springs because I was able to get them off Ebay for cheap. Be sure to check them with a valve spring checker, or have someone do it for you, and verify they are good/even.

You did not ask but... please go buy a set of RC51 valve buckets off ebay. They are much lighter and a little shorter. Those buckets with better springs are what allow it to rev so freely and safely. You will love this mod, hands down one of the best.

JE Pistons... Yes, most definitely...but...You need to check your piston to valve clearance to be sure. Use modeling clay in the cylinder as it will also show you how much shrouding you have. You will have some shrouding in the valve pocket that you can easily fix with a dremel. One thing I did not do, because I didn't think of it yet, is check the valve shrouding to the cylinder bore. If you do a little digging, on the old GM 396's they had to clearance the bore a bit to help with valve shrouding. The V needs this too in order to produce optimal results. It is easy to do, even by hand, and if I were to turn back the clock I would do it. Also, back when I did flow testing on the heads, I found that one intake port outflows the other by a country mile. I believe Honda did this on purpose to create swirl. Considering this, I would only upsize the better flowing valve, which, IIRC, is the left when looking down the intake runner. Same applies to the exhaust valves. This method is known as "polyquad" and may have been invented by David Vizard. Doing this will give you a lighter valve train and less shrouding, possibly more power in certain areas of the power curve.

I hope this helps. I think about my old V pretty much every day and I'm glad you are wrenching on yours.

 

Hi, thankyou for replying to me, really appreciate it.

Yes, I have 8 RC51 valve buckets here, as I had read some of your posts in the past, about them being lighter.
Heads are being polished n ported, 39mm intake valves, and 4 Superhawk exhaust camshaft with slotted cam pulleys for degreeing when bullt.

So is it ok to use the RC51 inner/outer valve springs in the Superhawk heads aswell, yes??


If possible, would you be able to show me the ARP bolt part number ?
Or a link to the bolts for the ARP Hayabusa bolts?

Thanks.

 

Springs... yes, you can use the inner/outer RC51 springs. They are a drop in mod, no changes needed. If I remember correctly I was able to purchase used RC heads that were complete and that's how I got the springs and buckets cheap. It's also how I was able to figure out what cam profile they used and how they ported the heads.

Here is a link to the bolts, but you can find them elsewhere cheaper I am sure: https://www.vividracing.com/arp-bolt...OfOOkexay5Fsw3 But please measure your bolts first and tell me what they measure out at so I can be sure. Another option is to buy 1 busa bolt off ebay and compare. That's how I did it way back when.

AV

 

Thanks for that and the advice too, much appreciated.

1 more question for you.
JE 98mm forged pistons (standard size) and the 1mm oversize 39mm intake valves I have.
Will the 39mm intake valves work with the piston?
Or would I need to fly cut the piston?
Thanks.

 

Regardless of the bore you end up with you will not need to fly cut. You will need to clearance the valve pockets no matter how nice they look even on a brand new piston. They are very nice pieces from JE, but there is room for improvement. However, see if you can return the pistons you have. If so, exchange them for 99mm pistons. The reason I say this is because you need to bore and hone anyway in order to fit the piston to the jug. So far as I am aware, most people that are rebuilding, when they bother to do it right, find that the jugs are out of round and tapered beyond service limits. The last person I remember doing a rebuild without a rebore was having terrible blowby as a result and did not want to face facts....that you will very likely need to bore and hone....indeed they did and it was a real painful thing to watch. That being said, bore and hone is cheap to do, so you may as well go whole hog, including postage, whilst you are in there.

I also should point out that the rods are specific to front/rear. They are marked as such and the oil hole is in a different location. If you swap them, you will ruin the motor.

Also worth noting, resize your rods if you are using factory rods. The big end will be out of round a bit and correcting that makes for a very slick rotating assembly.

Also worth noting, a lightened flywheel is a thing of beauty on this bike. The RC flywheel is very light already but has crank signal triggers that need to be machined off. Machining the factory flywheel is also easy and cheap to do.

While you're in there... please get yourself a used RC transmission and swap that in. You will like the gear split much better, I think...and it's cheap.

Also, don't spend too much time on porting or polishing the head. There is not a terrible amount to be gained there (for sane amounts of money and drivability) beyond unshrouding the valves and correcting valve curtain and cross sectional areas. No need to polish IMHO. There is good value in thermal coating the piston tops, valve faces and combustion chambers as well as antifriction coating on the skirts and oil shedding coating on the rods.

Lastly, maybe...have your cams reground at WEB Cams, you will absolutely love how the power band is transformed. The VTR is like a tractor and makes very respectable torque. Therefore, you can sacrifice much of that down low power and it move it up top with minor reprofiling. It is of course preferable to get some Yoshi cams but good luck finding some. Kent cams in the UK seems to have a nice profile available but I can't speak for them directly.

Thanks for stirring up fond memories of a sweet machine...

 

Thanks for all that great info and advice.
Alot to think about, but alot that can be done to the Superhawk engine too,based on your advice..
Thanks again.