The perfect MC - XS-Almost

[xs650-4-me]

My 1st thread

Have/had a lot of MCs in my 6 decades...

Have a 77 XS650. Almost the perfect bike...thought I'd improve on it on this cold winter day...in order somewhat...

- wider ratio gearbox, for one reason so it would cruise at 60-70 with less rpm. Stock the gears are too close together. Good for racing maybe (I used to race MX).
- more cc, maybe a 750 or 850 (Norton Commando style)
- with more cc, a longer stroke not a larger bore, so it'll pull the tall gears at lower rpm. Undersquare engines pull better. Oversquare engines rev. I won't buy a big-bore kit as they are not the power I'm looking for. One day, when I have more play money, I'll stroke a 650.
- 1 carb instead of 2. Cars have 8 cyl (or 12) and they have 1 carb, and the Triumph Tiger has 1 carb, why do we need 2 ? We don't. The Tiger has what, maybe 2% less top end ? Who cares.
- no electric start. If you can't kick it over, you shouldn't be riding it I have always believed.
- a shaft drive version, or shaft drive standard, as long as it wouldn't add too much weight or price.
- oh yea, 2-way directionals, that double as marker lights, just like an older car. This way the directionals will be on all the time, at lower intensity. They come on with the headlight obviously.
- a charging system like the Kawasaki H1/H2, which means it'll still run with a stone-dead battery.

 

[JRay77]

I still have a lot to learn in the mechanics of these XS650. What I've done and seen: Far as the charging system, I've seen Morris Magnetos put on these. I have yet to do this as they are very expensive. I run PMA systems. I piece them together off of eBay. I have ran capacitors. Caps are very sensitive to vibration even rubber/spring mounted. So lately I've been running antigravity batteries. These require the right reg/rec as to not get over voltage. As far as wiring, charging, and electrical in general, I just start over. Usually what I get is in such bad shape, sitting outside or in a barn. These situations have lead me into going PMA, new reg/rec, fuse box, led lights and turn signals. Antigravity batteries. Kickstart only. I agree with you, if you can't kick one over....haha! Carbs, BS38. You couldn't sell me 34's. I have yet to single carb. I'm looking into it. I want to at least try solid intakes. Get away from the rubber boots.

 

[TwoManyXS1Bs]

Welcome to the forum, xs650-4-me.

I see you have a couple other threads started, regarding engine upgrades.

Although the old marketing brochures claim that the XS650 has a wide-ratio tranny, it really is indeed a narrow ratio. The earliest 70-71 XS1s had a taller 1st gear, making those the narrowest ratio. The original performance charts show that this ratio range is optimum for no-loss gearshifts.


In 1972, the 1st gear ratio was lowered, widening the range, but increasing the 1st-to-2nd torque gap.

An aftermarket overdrive 5th gear is available, widening the range a bit more. A forum search on "OD 5th" will yield info.

Some info on high ratio primary gears:

http://www.xs650.com/threads/is-there-any-interest-in-high-ratio-primary-gears.20073/

In my opinion, this engine is pretty good as a 650cc, but it really wants to be a 750cc. A recent thread shows larger versions.

http://www.xs650.com/threads/840-bore-kit.53491/

270YAM's 950cc Sidecarcross rephased stroker engine build.

http://www.xs650.com/threads/270°-953cc-sidecarcross-engine-build.21710/

Here's a long thread on resurrecting a 1000+cc stroker:

http://www.xs650.com/threads/1010cc-cafe-racer.32481/

More can be found by doing a forum search on "stroker" and "sidecar engine".

Edit: Good to have, Craig Week's XS650/750 Engine Modification Guide.

http://www.650performance.com

 

[xs650-4-me]

I'm not looking for a racer, just something a little more in line with a Norton/Triumph 750 or 850.
Commando 850 - 77 x 89
Tri 750 - 76 x 82
XS650 - 75 x 74

Thx XS is a good all-around engine design, but I'd rather it be geared a little taller/wider. By gearing it taller, it will be a little wider too so my 1st project might be a simple bigger countershaft sprocket. 1-2 more teeth I'm thinking.

If my Dad was younger (or us all we might attempt a 750 stroker kit that we could sell. He used to race Supermodifieds and is a great machinist. He used to make his own pistons too though not if he didn't have to.

 

[TwoManyXS1Bs]

17 tooth drive sprocket is stock. Biggest you can fit in there is an 18 tooth, but it's close to the clutch pushrod and shifter shaft. Not too much of a problem on a hardtail, but a swingarm suspension allows dynamic chain slack, and risks chewing into things...

 

[650Skull]

Got any pics of your 77D..........We love pics...........

 

[xs650-4-me]

No pics. It's failry/very new looking, had a Windjammer on it when I bought it, off now, too heavy, will eventually sell it. No directionals currently. Rootbeer color. I ride my 72 more although I prefer the 77's ride, more cushy seat.

 

[5twins]

For an "almost perfect" bike, you sure want to change lots of stuff, lol. To me, the 650 is what it is - a nice old mid-sized motorcycle. You can certainly improve it, make it run, ride, and handle better, but it will never match modern bikes or be a "superbike".

I think this bike benefits greatly from a small gearing change, but just a small one. We're talking like 1 or 2 teeth smaller on the rear sprocket. As mentioned, it's not a good idea to mess with the stock front sized sprocket due to possible clearance issues. I think just one tooth smaller on the rear (34T stock to a 33T) is perfect with an 18" rear wheel. This is how the European models were geared and I think it's a darn near perfect match to the engine's power characteristics. With only about 50 HP on tap, if you go crazy on a sprocket size change, say 3 or 4 teeth, you kill the bike's "fun factor". It will be a real slug off the line and it won't pull 5th gear to redline.

The single carb thing doesn't work too well on the 650. For it to work best, you want equal length intake tracts, and with the frame backbone tube in the way, you can't do that. You have to angle the carb off to the side and one intake runner ends up longer than the other. Besides, your '77 model has what many consider to be one of the best 650 carb sets on it. It has about the largest needle jet ever installed on any 650 and that gives great midrange power.

I quite like the stock charging system. Cleaned up and with a few low cost mods, it works very well. It is a 3 phase alternator similar to what's used on most cars. Because of that, we're able to use good, low cost auto voltage regulators. These greatly stabilize the voltage output compared to the old stock mechanical regulator. Combine that with a more modern rectifier and you're good to go. And all this can be done for about $30 to $40 or less.

Stall the bike at an intersection a few times and you will miss that electric start, lol.

 

[xs650-4-me]

I have no interest in redlining anything, especially a XS650. I spend most of my time under 50mph; I just want to do it at less rpm in general...less time in 5th gear in other words.