Cam disaster: need OEM cam timing tips

[mik_str]

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 pretty dear....). 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

[tony.mon]

Feel for you, mate.....

I can't suggest very much more than you've got on the table already, except there's a company in the UK called Kent Cams who offer a set of "improved" cams for VTR's.
I haven't bothered with them much because although they can tell me what overlap, dwell angles and recommended lobe centre settings they don't have any dyno data, so although it should have improved things it's a stab in the dark, rather than measured and specified.
But you might be able to get them to put you in touch with someone who's used their cams, and maybe done a before and after dyno set?

With the settings your'e suggesting you're adjusting both cams; I wondered if leaving the exhaust side where it is and changing the intake lobe centre to get the overlap you want is an option?
But it seems to me that the intake (airbox cough) misfires are a result of early opening of the inlets, so maybe a better approach might be to leave the inlet timing alone and delay the exhaust closing....

A few people have suggested fitting two sets of either inlet or exhaust cams; I can't remember which- that might help a little but I don't think you'll get the same effects as your old (sadly no longer with us) Yoshi cams.

Will Yoshi sell you just the one? They might be interested to see and inspect the failed one.......

As a further option, you could get a set of std cams machined, as I have done. Taking the base circle down 1mm gives an additional 1mm lift, assuming that the tip of the cam lobe is pretty much left alone. You can also fatten the lobe so a gain on cam profile is also achieved, and this will boost the midrange as you require, rather than merely a steep ramp and high lift, which aids top ends peak hp.
You'll need thicker shims all round (I am using thicknesses around 2.7/2. but although that means the shims are slightly heavier, I don';t think the extra weight will be noticeable, unless you're planning on keeping your new 11K rev ceiling, of course.....

I believe that some companies also offer a build-up and re machine service, which means you could get the Yoshi profiles copies, and dial them in.

What the hell, why not go pneumatic?

[mik_str]

Thanks Tony.

At this point, I think I will stick with the set of (almost new - 700 miles - came with the set of heads I had bought to have ported) stock cams and have them re-timed. A chap on the Superhawk forum is running 101/106 and is reporting good results so I may go with that (unless Roger gives me another suggestion, of course).

I may go for some custom cams later (when the funds allow) but for now my goal is to get the bike back on the road.

cheers

[VTRDark]

Sorry to hear the news Mik that's rather unfortunate. I'm surprised the cam broke. . I think Tony's got a point about contacting Yoshi regarding it.
As your most probably aware from the Hawk site it's the standard exhaust cam some have used as an inlet. I know a lot of dyno places make one sign a disclaimer before a run but I hope the dyno place have got some kind of insurance and can maybe cover some of your costs. At least it did not happen in the middle of Summer which would have prevented you riding. Winter is around the corner so your bike will be off the road anyway. What a pain in the back end though.

(:-})

[benny hedges]

funny you should say that mik..... well, not really funny but -
on the sp facebook page there have been two owners so far recently who have snapped camshafts.
as in the gear shearing off the billet.

has it done any further damage?

[mik_str]

No, essentially limited to cam and the exhaust valve. The tech told me, after the teardown, that 5 of the retainers (the stepped washers that fit over the springs) are in need of replacement. Thankfully, the pistons and heads are ok so no major component damage.... It still won't be cheap to fix, but it could have been MUCH worse......

[sirch345]

Sorry to hear about this Micky, how gutting
Concentrate on the positive side of it could have been much worse, and the fact that it's not going to take a lot to get her back on the road again,

Chris.

[mik_str]

Thanks Chris