Cam disaster: now need OEM cam tuning help
 

Well, one of my Yoshimura Stage 1 exhaust cams is snapped in two... I had the bike on the dyno a while back for some jetting fine-tuning and the chap inadvertantly ran it up to 11,000 rpm (HRC ignition, with apparently no rev limit). Anyhow, after said run, power dropped SIGNIFICANTLY and bike ran like crap (for reason stated above).

So, I am now having to go back to stock cams (looked into some Moris but they are $$$$$$). I have a set of almost new stock cams that will be going in and was wondering if anyone has some set-up tips or settings that would help me get the most out of these. The stock lobe center settings are 102.5 and 107.5 degrees (intake and exhaust, respectively) which generates 35 degrees of overlap. I am led to believe that I should shoot for more overlap to help bleed off cylinder pressure (have JE pistons and 0.015" decked heads). Other factors to consider are port work, long billet velocity stacks and a full Akrapovic exhaust.

I was wondering about trying something like 101/106 (which would bump overlap up to 38 degrees, for more pressure bleed off and better breathing in upper mid-range). I ride exclusively on the street and am looking to optimize (lower and upper) mid-range power.

Anyone?

cheers

I'll ask the obvious dumb question: doesn't the dyno op have liability to compensate for the replacements/repairs?

Never, car, bike or truck.. never seen a Dyno operator held responsible for damage done during a pull.. Every one I've used, and that is dozens.. has a form for the customer to fill out giving consent or like, and may include a place for you to write in the max RPM YOU want the engine taken too. I suppose if you had such a form, and the upper RPM limit was supposed to be, say 9k, and the dyno logs provided post run said they spun it to 11k.. The operator (shop) might have some culpability in damages.

But I am not a lawyer, and that is what it would take I bet to get a shop to cover damages.

Wish I had cam timing info to help ya, but I don't for this bike... Your assumptions look good, but like you, id just had to try it, and see how it runs to build my own data pool.

Good luck

WTF..........i'd wanna choke that sumbitch. If someone's gonna waste my motor, I wanna be the one havin all the fun, really.

"Yeah we'll just take her up til she blows. Who knows, maybe we can get her up to 14 grand? Gotta get those critical stats."

Agree with Cranken, he needs to pay and loose his job if he doesn't know max rpms of what he's winding up.

Good you have the financial resources to withstand the devastation, but i would never let that one near my throttle again.

I won`t say I am happy with the outcome (ie. broken cam), far from it. The dyno operator in question is very comptent (likely the best in Eastern Canada from what I have seen and read) and has run my bike on the this dyno many times. It was the first run after the installation of the HRC ignition which, I was led to believe, was supposed to have a cut-off at 10,450 (which is obviously not the case, not for this particular box anyhow). It was a case of human error. I could potentially make a stink about it but everyone makes mistakes (thankfully most are less $$$ than this one) and the said shop is the only one my bike has seen in the 11 years I have owned it (they always do top-notch work and typically go well beyond the call of duty for me, having solved a few nagging issues for me that I am certain no other dealer (the "parts changers" of the world) would have bothered to do). So, I have decided not to pursue the matter in terms of recourse (not an easy thing for me as I am not the most forgiving person by nature) and will instead focus on getting the bike running again.

so. back to cam timing solutions.......

Seems to me that 101-106 is the cam timing posted on here by someone running all exhaust cams, something I plan on trying. Apparently the exhaust cams more lift than the intakes.

I thought the crank would break before the cams at high rpm? Have you tried web cams? I wish i could give insight on overlap but ive never messed with it on the vtr...

I think an email to someone like Rodger Ditchfield is about the only way difinitive info is going to be had on cam timing... Otherwise... set it, double check piston to valve clearance and make some dyno runs

Already done, I am waiting for a reply (he is away from his shop until tomorrow). I just thought I would ask around in case someone had a secret/special set-up to share.....

I take it that it broke in such a way that the broken piece was still being driven enough that it didn't didn't stall the the cam with a valve depressed and cause a collision?

Bummer about the mishap, and glad you are trying to find a different solution. Afraid I don't have any solutions for timing on a VTR though. Did you slot your OE sprockets, or are they from the Yosh sticks?

I have Falicon adjustable sprockets so altering the lobe center tuning will not be a problem..

Hard to tell exactly what happened but the tech seems to think the retainers fell off or let go. Anyhow, I dropped off my old cams (have two complete sets, dropped off the one that is almost new, came with the heads I had bought for porting, supposed to have only 700 miles on them, look brand new) yesterday and the tech informed me that he had found a piece of metal (from cam) in the head (thankfully it didn`t migrate to the sump) so it could have been much worse. It`s not a free ride now but the parts I have to replace are basically only valves and retainers,.... so no permanent damage to any critical parts...... massive *whew*!!!!!!

Why not have the cams measured, and then send off to webcams for making relacements? It won't be Yoshi cams per se, but equal spec...

I may get around to doing just that (or a custom grind; was thinking of possibly mating the Yoshi Stg 1`s superior lift with the Moriwaki Stg 1`s longer duration to see how it would pan out). However, in the short term, I want to get the bike back on the road. Depending on how it runs, I may just leave it with the stock cams.

Cam timing is a no $$ cost deal, with stockish lift cams..... changing a deg or two is just a cost in time....

So install, get and confirm a base line, and then move um a deg or so in the direction you want and see where it goes.

well mik. It's maybe laudable that you don't feel the need to get some kind of justice from the aberrant enginator, but it might be beneficial for the next victim to at least make him aware of the rpm debacle.

By the way, how many rpms are we going for on the rebuild? just kiddin :D

Just to point out something... mikstr did give them a bike with no rev-limiter and asked to test the hp/torque limits of the motor. Not saying I've compiled an opinion beyond that, but that's probably not an issue that they have too often... I'm sure the guys aren't going to forget the broken cam.

Hope you get your cams like you want them after the disaster. Perhaps Rodger will have some insight for ya!

I hope you had a good talk with them on what happened. You'd think if they were any kind of decent shop they'd at least give some sort of solution.

Many times on the dyno when they are testing the limits they'll run the rpm up against the rev limiter. He could have simply been doing this but it kept going. In wich case the lack of a rev limiter would be the culprit. Real sorry to hear of your misshap. Have you happened to place a call to Yosh to see what they will do about their cam breaking?

Mik wrote the guy "inadvertantly" ran it up to 11 grand and stated, "apparently no rev limiter", and said it, "ran like crap", after the run. "Inadvertantly" leads me to believe that the guy running the dyno accidentally exceeded a known rpm limit, which should be a critical part of the pre-run discussion. "Apparently no rev limiter" suggests that neither mik nor the enginator understood what was in his rebuild. And "ran like crap after the run" to me may mean that he finished the dyno run, rode it on the street and discovered the power loss after the fact. Don't know?

You're right, I'm sure the guys aren't going to forget a broken cam(if it was evident immediately or if they were told later by mik after he rode it home....not sure), but "inadvertantly" and "apparently no rev limiter" and most likely no pre-agreement relative to max rpms sounds like there could be some culpability in terms of the enginator IMO.

Regardless, it seems that the mistakes should be clearly defined so that this doesn't happen to others in the future, kinda like when you analyze a crash in an effort to avoid repetition.

Mik seems to be standing by the enginator and his credentials so it's a moot point anyway. I'll bet when he gets his next monster engine together, he's not gonna take it in for a dyno run and say, "Yo Jake, I got another one fer ya, see what you can get out of her for me will ya?". :popcorn:

Well, all your different theories aside... If anyone of you have run a bike on a dyno before, you would know how friggin fast you gain revs vs how fast you can take in the information you need... So if he was shooting to hit the revlimiter in the ECU, having been told to get the data for tuning, and that it had a revlimiter at a fixed rpm, then from 10450 to 11000 or just above is a split second, nothing more... So, by the time he realized the bike hadn't cut out on it's own, it would probably already have been too late, and the damage would have been done... And you would probably find that the bike was running poorly already on "cool down" on the dyno, so no riding around on the street needed... With an experienced guy, he'd know the symptoms, and know roughly what went wrong, and shut things down then and there and talk to the customer...

If a guy did that with me, I'd be alright with that too... I'd be bummed, and I would probably expect the shop to help make things right, ie cut me a deal on installing the replacement parts or something, which I suspect might be the case here... But, no I wouldn't expect them to replace anything out of their pocket, or make a stink if not... It's the rules of dyno work... You know that going in...

You're correct tweety........ I don't know shit about the nature of dynos and these are theories because of that and the fact that all the info is based on mik's description of what transpired.

That said, It seems to me that with the money and labor invested, esp in the case of a single person's bike(this isn't Honda or Yamaha's race bike), there would be caution to stay well below the danger zone for just the hair trigger reasons you stated. That said, mik was negligent for not knowing that a rev limiter was in place and he's gonna eat the damage so all is fair sort of.

It also seems to me rev limits and limiter would be critical information to be resolved well before the the bike ever got near the dyno. If i were operating the dyno and had somebody's blood and sweat in my hands, I would be diligent to err well on the side of caution unless the owner said to give her hell.

My thinking is along the same lines as Markus (Tweety). If I thought it was negligence, I would be on him like a hound on a steak.

The two guys that own the shop in question (including the one chap who does all the dyno runs) have become friends over the years and I know that the mistake was practically unavoidable (the standard practice being to run a bike up to the cut-off then ease off). I only wish I had known the HRC box had no cut-off (or one that lies above 11K)......

They have givne me stellar service over the years and I will continue to do business with them. Mistakes happen, such is life......

I would think the bike would live after a very brief moment at 11000rpm? As stated earlier, dyno runs wind the motor up fairly quickly (if this dyno was an inertia dyno that is). These dynos don't place excessive load on the engine for extended periods of time (like you would find on the road, or even a dyno with a highly resisitive load cell) and you've only exceeded factory limits by 1200rpm.

I would place the blame on the camshaft, not the dyno tuner. If the camshaft was weak enough (or over hardened) to crack during a brief 11K run, I would venture to guess it would eventually break when you're slammin gears trying to squeeze ever last turn out of the motor.

1200? How did you get that number? The factory (hard) limit is actually 10300 rpm, so it's "only" 700 or so over, but the difference is that a big twin will disintegrate pretty fast if you overrev it... I have seen it happen on a number of ducati's... And yeah, the camshaft should really have survived it, which plays a part in the fact that I wouldn't hold it against the dyno operator...

I wasn't aware the hawk revved that high. My tach needle bounces at 9800rpm.

You don't have the HRC Ignition Module which apparently has no rev limiter

I'm aware of this...

I love how its "only" an extra 700 rpm... lets not forget thats an extre 11.6 and change full revolutions per second thats alot when you think of how much is going on in those spins... good luck mik you have one of my favorite vtrs... that thing is a piece of art... (not to say others arent or put anyone down) if it were 1200 thats 20 revs a second... for a total of 183 and change revs per second... thats an incredible amount of motion especially for a twin... could have been alot worse at least it didnt shoot a rod through the cases...

Isn't the redline on these bikes 9,500? It's right on the tach - why would dude rev the thing to 11 grand?!

The VTR's tach is nowhere near accurate.

I'm sure the tech was expecting a rev limiter. Hard to blame him.

I would guess that Roger will have a Kent Cam regrind to suggest.

You must have put is good valve springs, to keep from bouncing the valve off the piston and ingesting a valve. It's also a good thing you lightened up the rotating assembly, so the crank survived. It might be a good idea to tear down and inspect.

I wouldn't retard the intake cam. Just advance the exhaust cam a few degrees.