Rephasing the crank

robertpokerplayer · Posted: March 15, 2005, 11:05 pm Post subject: Rephasing the crank

I have been looking into rephasing my crank. Have looked at a few sites and was wondering if anyone here has done this. If so could you please go into what it took to do and was it worth it? I have found a spare motor for $150 that I would be doing this to and at the same time bumping it up to 840cc. I will try and fing the sites I have got some of the info from, it is always nice to talk to someone that has done something like this.

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

Poker

I'm rephasing my motor and what needs to be done is to notch the crank cam chain gear ( you rotate the right crank halfs 3 splines forward and press the crank halfs back together on a 20 ton press or more,it's simple Wink

The camshaft right side will need to be modified by cutting the right lope section for the intake & exhaust and move it 41.5 degress forward and welded back together. When timing timing the ignition firing point for the right piston on compression stroke,you'll need to use a degree wheel to relocate firing order to 83 degrees to right ...Jack

Wulf · Posted: March 16, 2005, 6:11 pm Post subject: Re: Rephasing the crank

What exactly does rephasing do for the engine/power? Are there aftermarket cranks and cams made for this mod?
Wulf

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

In the XS 650 stock form ,both pistons come up at the same fot the intake and exhaust cycle and this is where the vibes come in a XS ,to much mass revolving at one time and nothing cancelling the other side out to reduce vibrations , plus they're mass perduced ,so not much effort when into reducing vibrations from the factory.

you use the original crank assembly for this operation and the cams can be modified by MegaCylce or Web Cams for about 300 to 350.00 "That Huurts". The ignition is another mod you can perform with the stock point set up or go NewTronics as I did.

The added benifits are less vibrations but have it balanced anyway, differant power band ,less wintage in the sump area and pressure build up, more torque and power (But some will despute this claim) but from the people I've spoken to about this topic, say there's a big advantage to be had. But whats impressive is that improved exhaust note "Bad Bad Sound"

Wulf · Posted: March 16, 2005, 8:40 pm Post subject: Re: Rephasing the crank

Thank you for an excellent explanation. That was pretty much what I figured it would be, but you clarified it well. Would the stock tci ingition work on this type of setup? Now that I've finally gotten my finances straightened out, a few hours of sidework would pay for the mods. I'm going to try to find another 650 down the road after I get Wilderbeast up and going to do some serious experimentation with. Thanks for the input. Ride safe.
Wulf

robertpokerplayer · Posted: March 17, 2005, 10:19 am Post subject: Re: Rephasing the crank

Thanks Jack!

Barrett · Posted: January 22, 2007, 11:08 pm Post subject: Re: Rephasing the crank

In the old days they called this conversion a "twingle"
Later model parallel twin have chnaged the phasing to make the engines smoother, or make more torque etc. They sound sorta' like across between H-D and Ducati depending on cam, compression, and exhaust...
I have also seen some re-cut/custom pins that the flywheels press onto.

kingwj · Posted: January 23, 2007, 9:07 am Post subject: Re: Rephasing the crank

Jack, any comments on the Newtronics? I am considering losing my points and putting one in.

RainLand · Posted: January 23, 2007, 10:05 am Post subject: Re: Rephasing the crank

Falicon's will do this crank work for you. I started to do it, then just decided
to do a 750 thumper motor instead. The Aussies have a multiple-page
explanation of how to time valves and ignition somewhere on their site,
I think.

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

How much does Fallicon charge to have a crank balanced and welded?

yamaman · Posted: January 23, 2007, 10:52 am Post subject: Re: Rephasing the crank

This is ! aussie site with the info
www.xs650.org.au/Racers.htm

www.users.bigpond.net.au/dave650/

is another

yamaman · Posted: January 23, 2007, 11:00 am Post subject: Re: Rephasing the crank

My road bike is a TRX 850- 270* crank. Its very smooth, and with the pipes, it sounds horn! Very Happy

On a ride day at our local track, a Ducati 916 (they were new then) owner said my bike sounded more like a Duke than his with termi pipes!!!!!!!
I dont reckon it's at all like a harley, except it frightens folks when you crank it up Very Happy

Tomterrific · Posted: January 24, 2007, 9:36 am Post subject: Re: Rephasing the crank

A twingle is a 360° twin cylinder engine that fires both pistons at the same time. This type of engine was found during the 60s and 70s on dirt bikes and flat trackers that used a powerful twin two-stroke. The powerful twins lost traction on dirt due to the even firing of their 180° crank so a few owners would split the crank and rephase to 360° so both cylinders would fire at the same time. This gave enough time between firing impulses for the tire to regain traction. I owned a Big Bear Scrambler with a twingled engine. Whew, was that engine rough. I can say with full confidence that there will never be a twingled 650.

Tom Graham

Cooltouch · Posted: January 24, 2007, 10:31 am Post subject: Re: Rephasing the crank

Tomterrific wrote:

I can say with full confidence that there will never be a twingled 650.

Actually, John Zelna (Uncle Johnny to those on the Yam650 list) built an XS650 twingle several years back and raced it in vintage flat track events. As I dimly recall, it was quite a monster performer, and did well in the events in which it was entered.

Best,

ichael

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

Sounds grand, where do I start?

Tomterrific · Posted: January 24, 2007, 10:47 am Post subject: Re: Rephasing the crank

Yes, well, that is Uncle Jonnny! :^) I guess I was thinking more along the lines of normal people, street bike engines and twingles.

A 650 twingle will be easy, just cut the cam and turn one side 180° and reweld. Or send it out to a cam grinder. There will be no crankshaft changes. A late TCI motor needs no extra modification but a points motor needs a dual fire coil hooked to one point.

Tom

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

Sounds like a torque monster.....where do I begin?

What Happened to 650rider.com?

Yamaha xs650