Welded Camshaft?

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

Anybody ever cut and welded a stock cam for a rephase?

tracker79 · Posted: August 25, 2007, 1:29 pm Post subject: Re: Welded Camshaft?

I haven't heard of anyone doing it on 650's. In go kart racing it's a real common pratice, one of my best running engines had a reground stock cam.

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

No, I don't mean welded and reground, I mean cut, rotated 41.5 degrees, and then welded back together again.

XSKID · Posted: August 26, 2007, 2:37 am Post subject: Re: Welded Camshaft?

My brother applied the concept a few years ago that your talking of, it will fatigue the camshaft to cut and weld it, thus, it will break pretty quick. Maybie finding a cam maker and see if they could make one?

XSKID

xsjohn · Posted: August 26, 2007, 8:30 am Post subject: Re: Welded Camshaft?

XSKID......Welcome back.....getting a little boring around here without you.........

John

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

I'm skeptical about doing welding it... I think I'll wait and get a cam from Megacycle. Thanks for the input.

Finn51 · Full Member Joined: Apr 25, 2007 Posts: 59

Check out Colt cams, he has done rephrased cams with out welding, and does a good job. www.coltcams.com. John

xs1961 · Posted: August 26, 2007, 7:07 pm Post subject: Re: Welded Camshaft?

Yep,Ive done it...make sure you sleeve it before welding..mines naver broken..
As far as I can tell Megacycles 'rephased' cams are welded too...just a bit neater than mine..

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

xs1961,

How many miles do you have on it since it was welded?
Do you run it to the redline very often?

I was planning on sleeving it if I cut and weld it. I think it would be the best way to hold in in place while it's welded.

xsjohn · Posted: August 26, 2007, 9:00 pm Post subject: Re: Welded Camshaft?

If you run these to the redline or too high you may have more than a cam to worry about......

John

xs1961 · Posted: August 27, 2007, 3:49 pm Post subject: Re: Welded Camshaft?

Red line !
Red line an XS ? oh noooo...Never do that...Listen to John on that one !
ine did 6,000 miles + without probs.
The sleeve remains inside,made sure the internal diameter allowed a Boyer crossover rod to run through unhindered though.

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

My current engine (that ate a tranny dog) has about 40,000 on it and routinely gets run to the redline. Crank, etc. still in good shape.

mo650chopper · Posted: August 27, 2007, 5:35 pm Post subject: Re: Welded Camshaft?

It's the small end of the rods that will kill a high reving XS

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

What is the problem with the small end of the rods? Is the plain bearing the weakness? I wonder why Yamaha stopped using needle bearings in the small end. Seems to me that would be more tolerant of oiling issues.

grizld1 · Posted: August 29, 2007, 11:34 pm Post subject: Re: Welded Camshaft?

The small end of the rod is prone to stretching. The needle bearing wristpin didn't survive the power pulses of a 4-stroke engine very well, used only first year. Yamaha then went to the 22 mm plain bearing wristpin. The 447 engine (1974 and after) used a 20 mm wristpin, leaving more meat in the rod, and a detuned cam. Good aftermarket rods are more resistant to stretching than OEM. Mike's heavy duty rods (his standard rod, with beef-up big end bearings) are recommended by Michael Morse of 650 Central for competition use--great value for the money (Michael also offers a piston modification that moves more oil to the wristpin). Wiseco has our application in their Hot Rods series, and Wiseco tapered wristpins cut weight and stress the rods less. Crank Works, in Tempe, AZ (www.crankworks.com) produces a custom rod at a very reasonable price, and will also fit bronze bushings to the small ends of rods.

The other weakness that shows up past redline is flywheel separation, so if you're gonna wind 'er up tight, weld the crank pins.

Bottom line--factory redline can be exceeded safely, but only if you build for it.

xsjohn · Posted: August 29, 2007, 11:50 pm Post subject: Re: Welded Camshaft?

Sounds like an old plunker like me has a better chance of making the distance with his tall gears and mature use of this little engine than those who want to make a monster out of a toad.......no offense intended just trying to justify my old age and slap you dign bats for spending instead of preventing........guess I spent to many years going fast and in circles and want to chill......no not that chilled as in dead......but getting closer every time I get on this thing......Which has been about 200 miles a day this summer............people are asking do you have a life....I have to say no--I ride..........

John

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

The thing is, to get good performance out of even a stock 650, you have to run up it to or near the red line. According to the specs, a stock 650 puts out maximum torque at 6000 RPM and maximum HP at 7000 RPM.

In the beginning of shop manual there is a graph that can be used to pick the shift RPM for optimal acceleration between all of the gears. For the first to second shift, which has the biggest change in ratio the optimal shift point if more than 8000 RPM!

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

xs1961,

How did you modify the cam? Do you know what the cam is made of?

y idea is to V groove and then cut it. Then bore the hole in the cam bigger and make a bushing to put it back together and true it up. After that, fill the V groove with weld. I am concerned with maintaining the trueness of the shaft with the heat of welding.

xs1961 · Posted: September 7, 2007, 3:33 pm Post subject: Re: Welded Camshaft?

Youve described how I/we did it exactly....Took my mate 3 attempts to weld it straight though! Embarassed

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

Do you know what the cam is made of? Does it weld easily?
How do you like the rephased engine?

xs1961 · Posted: September 8, 2007, 6:28 am Post subject: Re: Welded Camshaft?

No Idea what type of metal its made of ,cast somethingorother,any half competent welder shouldnt have a problem matching it...
I sold the bike to friend of a friend...didnt get on with it..nothing 'wrong' with it it just wasnt an XS anymore , no grunt/torque, too revvy but a definite crowd-puller!
I did the same to an old 1970 Laverda SF750 some years ago...should've learnt my lesson Embarassed

I think the amount of time & effort spent - especially on the bloody ignition set-up Rolling Eyes

- killed it for me really !

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

xs1961,

What other modifications were made to rephased XS? Maybe the loss of torque was due to something else? I have read on the web where others claim an increase in torque.

y biggest reservation to doing a rephase (other than the work and the expense) is that it will alter the sound and character of the bike. I wonder how much the vibration could be reduced by balancing instead...

xs1961 · Posted: September 9, 2007, 12:09 pm Post subject: Re: Welded Camshaft?

Ive read that too,I wonder if some peoples idea of torque differs from others?
With a 're-phased' engine I found the 'flywheel- effect' lessened(what little there is on an Xs compared to big British bike engines) maybe they are thinking that because the re-phase revs a little easier it must be producing more power !? Re-phased it felt more like a Honda 450 'Black Bomber' than a good ol 650 ! Rolling Eyes

Nothing wrong with finished job ,I often get so pissed-off with bikes after Ive spent a lot of time/money on them that I sell 'em...
Actually..I quite miss the old girl....Might see if he'll sell it back to me... Embarassed

xsjohn · Posted: September 9, 2007, 12:21 pm Post subject: Re: Welded Camshaft?

Still think it has something to do with one cylinder compressing while the other is on the power stroke........could be wrong.........

John

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