Shell #1 cam vs XS1 cam vs my cam

Rexxis

Almost there...
Messages
247
Reaction score
3
Points
16
Location
Oklahoma City
My bike is an '80, How much does my cam differ from a XS1 cam. Also, what is this shell cam thing I'm seeing here and there.

I'm asking bc I'm considering a rephase and I'd like a hotter cam to go along with it. I think I do anyway, I haven't ridden a 650 before and mine probably wont be ready till next spring.

Anyway, couldn't find much info on different cams for our bikes, I just want to know what options are out there and which cams are considered higher performance.

Thanks!
 
Shell cam is a grind designed by Sheldon "Shell" Thuet - famous XS650 flat track tuner/builder, http://www.motorcyclemuseum.org/halloffame/detail.aspx?RacerID=280
http://www.650motorcycles.com/AMAnomination.html sadly he recently passed away.

Megacycle do a cam, Punskalar & MrRiggs both rephase the xs 650 cams using your original core. MrRiggs has also just started offering a reground + rephased Shell#1 cam I beleive.

Depends what you are going to use the bike for, for a more streetable bike I would stick with either the stock or a mild cam grind.

Forgot to mention the XS1 cam is a "bigger" cam than the later models, to what extent I dont know. PM Punkskalar, I think he runs one (or did run one ) in his bike.
 
Last edited:
Bear a couple of things in mind, here. All aftermarket performance cams have fast ramps on the lobes, so heavier valve springs are a must; I had to learn the hard way that Minton's claim (in "Building a Better 650") that stock springs can be used with the Shell #1 is flat wrong. Second, you can't compare cam profiles without a dial indicator and degree wheel. Valve opening and closing specs are given at different specified valve lifts (just off/on the seat for OEM, .050" for Shell, .040" for other makers) and at different inspection valve lash settings (zero lash for aftermarket cams, .016" lash for OEM, IIRC).

Both the Shell #1 and the Megacycle 250-00 will give very nice performance down low. Avoid the Taiwanese XS Performance "billet" clone of the 250-00. I thought the bolt-on sprocket was a cool idea, and bought one. Unfortunately the design entails two heavy bosses for the bolts, positioned 180* apart on the camshaft--which is 360* apart at the crank. It'll have your motor shaking like a dog passing peach pits. My old Shell #1 comes out of mothballs and goes back in the motor this winter, with a set of RD springs.
 
So a shell #1 is just a regrind, not a cam you can just go out and pick up off the shelf..?

:thumbsup:Great information guys, I truly appreciate it.

I think I'm gonna stick w a stocker for now. We'll see how I like it after I've ran the bike. If I still want more then I only have to pull the head.
 
Only pull the rockerbox, not the head. Dont forget to pull thee rockerbox that means engine out of the frame...
 
You're not going to install performance valve springs to go with an aftermarket cam without pulling the head, guys. Also, it's pretty touchy trying to separate the head cover (rocker box) without breaking the seal on the head and base gaskets; those dowels don't let go easily, and the same fasteners hold everything from the case up. Sometimes you get lucky, but don't count on it.
 
I personally LOVE the XS1 camshafts myself... Old technology yes, but they work very well in the rephased engines.... I've used 5-6 of them in my own engine builds.

Listen to Grizld, he knows his stuff as well... You can't go wrong with any of the XS650 cams honestly, but some are in need of more mods ($$) than others...

Hugh - Hugh's HandBuilt
 
Good point grizld, I hadn't though abt possibly breaking the lower gasket seals when I remove the rockerbox.

Hugh, what would it take to receive an xs1 cam in exchange for my cam when Im ready to rephase?

Thanks guys
 
All series 256 engines (XS1, XS1B, XS2, and TX650) used the same camshaft. The early crank/cam sprocket combination was 17/34. If you install a 256 cam in a later engine (74-83), the sprocket must be pressed off and replaced with a 36 tooth sprocket to match the late 18 tooth crank sprocket, and you'll need to degree the new cam in. It isn't a drop-in job.
 
XS 1 VS. 1980 cam lift at valve .372 VS. .388 When YAMAHA changed valve lash settings from .006 to .002 intake and .012 to .006 ex, 1980 cam I.VO@ .002 95 deg.BTDC . I.V.O @ .006 50 deg.B.T.D.C I.VC @ .002 124 A.B.D.C THAT'S 91 deg. that the intake valve is hanging around on the dead slow opening and closing ramps a few thousands off the valve seat doing nothing but causing reversion and lost compression both cams have dead slow ramps it woud be interesting To see how the XS 1 cam cam stacks up useing the tight valve settings . valve lift info 0 lash Information given Was from Bob Bertaunt 650 motorccles.com Do it your self article 13 Worth reading :D
 
No pins and no key, Dave. What I do is to determine how many degrees the sprocket needs to move (if it's off 10* on the degree wheel, the cam sprocket needs to move 5*), compute the circumference of the camshaft boss, and divide it by 360 to find how much sprocket rotation, as measured where the corner of the boss meets the sprocket, is needed for 1*; if memory serves it's around .007", but I'd need to go to my notes to be sure. Multiply by the degrees of movement you need for the sprocket (half of the error measured at the degree wheel). Select a feeler gauge of the right width for the correction you need to make, set the gauge against the timing notch, and snap a mark into the sprocket with an automatic punch, so that you'll be where you need to be when the corner of the notch is moved to the mark. Keep things lined up while pressing the sprocket back on is tricky.

BTW, I didn't recall correctly re. inspection valve lash on OEM cams. It's .012" for all years.
 
There are some threads that explain it very well. A search for "rephasing" will get you there.
That's much easier than rewriting it all over again.
Leo
 
Punksalar or Riggs would have the best answer to this question but my understanding is lower vibrations, exhaust tone and maybe some performance increases?
 
Back
Top