Big-bang Camshafts

spook · Post by **spook** » Mon May 30, 2011 9:56 pm

I'm thinking about having some kit type profile, big-bang camshafts made to try in a FZ-FZR race engine.

Any thoughts?

Big Jon · Post by **Big Jon** » Mon May 30, 2011 10:26 pm

Yup, I get thoughts occasionally. Voices too sometimes.

McFizzer · Post by **McFizzer** » Mon May 30, 2011 10:30 pm

Megacycle? What are your plans for springs? I've head racers keeping oem springs and different valves.

Are you going to degree them and how much lift are you looking for?

spook · Post by **spook** » Mon May 30, 2011 10:34 pm

Big Jon wrote:Yup, I get thoughts occasionally. Voices too sometimes.

Don't let my avatar teeth put you off Big Jon... I'm serious!

I have a supplier who will make new camshafts from billet. This also allows for larger journals to be used on the cams and subsequent line boring of old cam cases.

spook · Post by **spook** » Mon May 30, 2011 11:01 pm

Oem springs are okay by all accounts, some shim them. APE make stainless valves which are a good replacement for the soft oem inlets, exhaust are generally fine.

Kit cams and the like generally only increase the lift a small amount, the kit manual recommends opening the valve clearances on race engines for the purpose of valve/valve seat cooling, so in reality lift doesn't change much at all. The profile and duration is the thing that changes the most.

I'm talking about firing order changes... Ie both cylinders firing at the same time in close proximity to each other.

I'm interested to as whether the stresses on the engines drive train would destroy the engine? And other thoughts if anyone has them

Big Jon · Post by **Big Jon** » Mon May 30, 2011 11:20 pm

I believe you're serious, don't pay too close attention to me, I'm just tired.
Big bang type firing would require some seriously strong crank would it not? More than cam work I would think that here would lie your biggest engineering challenge. Proper balance is always good but the nice even firing our cranks run currently is pretty easy on a crank, I'm not sure lumping pulses together is.

I'm not sure the drivetrain would be as effected, I mean, they make Harley transmissions last forever and the engines deliver an "earth shattering kaboom" once every couple days to keep forward momentum to acceptable levels and other than separating the tranny from the engine completely I don't think they're cushioned.

Post by **Hooligan** » Tue May 31, 2011 2:19 pm

hey spook, i have talked with a few tuners here in regards to cam profiles and most agreed that when running kit type cam specs there were serious problems with the oem valve springs. something about a mix of harmonic problems and the inability to really control the valve when run hard. they all said the same thing: mild cam(s) with stock springs, not much of a problem; crazy cam(s) with stock springs, big problem unless you want to do a complete valve job each season. they all said try to find the kit springs and not the ones sold by megacycle.

not sure if it helps hearing this at all, just figure i would share what i have been told. course, i'm not an engine builder or pro tuner so it might not be worth jack shit.

oh yeah, this was for the yzf750 motor.

spook · Post by **spook** » Tue May 31, 2011 7:53 pm

Hmmm, thanks that's interesting Hooli.

When I was talking to Z on here when he was selling those megacycle cams, he said he uses new oem springs shimmed one millimetre with washers, and I remember Ozzy FZR talking about shimming springs with in a few thou of coil bound. I've got no doubt that lumpier profiles would probably decrease maintenance intervals ie: cause more wear. To date I have not used anything other than oem cams.

Anyone have thoughts?

hotcam · Post by **hotcam** » Wed Jun 01, 2011 3:22 am

I know that Yamaha had a heck of a lot of strength added to the R1 crank when they went to the big bang, that's one reason the new bike was heavier than the old one. But the other thing is a big bang crank needs more flywheel weight / inertia, and uses it to soak up the power pulses some.
That's one reason Harley cranks and engines survive, the crank and flywheels is about as heavy as my sister!

But they're building engines to survive the 100,000km mark and well beyond. A few years of racetrack use might be completely different requirements... I say follow your dream, everything else you've built so far has turned out great!

Post by **Hooligan** » Wed Jun 01, 2011 1:34 pm

spook, i'll see if i can dig up the name of the manufacturer that created yamaha's yzf750 kit springs/valves/pistons/rings. i think i might still have the email from another forum with that info.

we have a member here with some really great experience building motors for the 750, his name is mike walsh. he pops in every now and then. he might have some useful info as well.

kiwi60 · Post by **kiwi60** » Wed Jun 01, 2011 8:42 pm

Duke22 was thinking of building a big bang motor a while back, and the thing that put him off was something to do with the cam chain snapping (if I remember rightly), not sure what the R1 uses, but something might be able to be adapted to work on the FZR.

spook · Post by **spook** » Wed Jun 01, 2011 9:31 pm

Hooligan wrote:spook, i'll see if i can dig up the name of the manufacturer that created yamaha's yzf750 kit springs/valves/pistons/rings. i think i might still have the email from another forum with that info.

we have a member here with some really great experience building motors for the 750, his name is mike walsh. he pops in every now and then. he might have some useful info as well.

That would be great. I would love to hear from Mike or anyone else with tuning experience.

I know there are 6 sets (big bang camshafts) out in race circles already. They are in dirt outfits. I need to track down the guy using them, I think he bought a T-ace engine off me a couple of years ago.

Logic would say, if the concept was problematic, they would have stop ordering at one set. These obviously are new light weight cams made from billet. Another benefit is the journals can be made oversize, so cam cases that are worn can be re-used.

Phil Taiton (Suzuki Racing Team) ordered a set for one of his bikes (I would guess for testing), so there is interest in the concept.

Down side of using this set-up is that you are opening two sets of valves at one time, so extra stress as mentioned on cam chain and cam casings. I cant see having two cylinders firing at once would stress the crank, it would-should balance it??

I know that motorGP teams have tried the concept, and motors self destruct due to the extra stress of turning doubled loads. Pneumatic valves are an answer in the GP machines, but a FZR doesn't rotate at 19K rpm either.

While the concept is interesting it could be a very expensive project. As you can imagine these cams are not cheap

Money would be probably be best spent developing a high rwhp screamer and traction control

YEC_YZF750SP · Post by **YEC_YZF750SP** » Wed Jun 22, 2011 2:25 pm

Hooligan wrote:spook, i'll see if i can dig up the name of the manufacturer that created yamaha's yzf750 kit springs/valves/pistons/rings. i think i might still have the email from another forum with that info.

we have a member here with some really great experience building motors for the 750, his name is mike walsh. he pops in every now and then. he might have some useful info as well.

Any luck with the info Jason?

Post by **Hooligan** » Thu Jun 23, 2011 10:51 am

the only info i could find was the name of a company that MIGHT have created the original two ring kit piston. they are called IZUMI and were supposedly used by the v&h team here in the states. i found them on the web in taiwan, but i am not sure if they're the one. i'll keep looking for the info on the valve springs.

YEC_YZF750SP · Post by **YEC_YZF750SP** » Thu Jun 23, 2011 2:24 pm

Hooligan wrote:the only info i could find was the name of a company that MIGHT have created the original two ring kit piston. they are called IZUMI and were supposedly used by the v&h team here in the states. i found them on the web in taiwan, but i am not sure if they're the one. i'll keep looking for the info on the valve springs.

Thanks for looking Jason!

Post by **Hooligan** » Thu Jun 23, 2011 9:01 pm

no problem, i'll see what else i can find.

spook · Post by **spook** » Fri Jun 24, 2011 3:35 am

Hooli, the piston brand was Izumi, I've got a feeling they may have made the oem pistons for at least the OW anyway.

I've got a set of kit 1mm over 2 ring izumi's that I found for the 88 FZR750. Check out how deep the valve pockets are

spook · Post by **spook** » Wed Aug 24, 2011 9:13 pm

I've looked at all of the yzf kit brochures, and it is interesting to note that none of the years include valve springs.

So you would have to think that the factory thought the oem springs were up to the job, at least with the kit profiles, which once you have taken into account the increased clearance that is run as per specs have about the same lift, with increased duration.

Post by **Hooligan** » Thu Aug 25, 2011 2:26 pm

are you sure you have seen all the kit brochures? the only kit manuals i have been able to get a hold of to review have been for the "c" level customer parts. the "a" level stuff was the super-secret factory only parts that were supposedly only available to certain people and deep pocket teams.

julian has an "a" level part in the factory braced frame he beat me to on the net. the bastard.

spook · Post by **spook** » Thu Aug 25, 2011 7:35 pm

These ones?

YEC_YZF750SP wrote:
OK guys, here they are

93 YEC KIT Parts

94 YEC KIT Parts

95 YEC KIT Parts

97 YEC KIT Parts

Also:

I just picked up a kitted head and cam-case + cams for one of these... 93 I think as it has big fat inlet and exhaust lobes

When it turns up I will check the springs