What does a stock xs650 do in the quarter?

plattey

plattey

XS650 Addict
Messages
230
Reaction score
3
Points
16
Location
Chisago City, MN
The car club that I am active in went to TriStates raceway this past weekend and I ran the old xs there. I have done the following to the engine:

stock xs650 pistons and rings
mild port n polish
vm34's
torque cones made from stock xs pipes
1 3/4" wrapped street pipes from hoosracing (end just after footpegs)
0.017" copper headgasket
no basegasket
NGK iridium plugs
performance coil from mikes'
re-timed cam back to stock timing

best time vm34 jetting:
190 main jet
17.5 pilot jet
159-p6 emulsion tube
6d-p1 needle clip in middle slot
2.5 cutaway slide

17/34 gearing
shifting around 7k~7.5k rpm (still wanted to pull strong past that pt but heard nasty tinking from the valves, thinking the valves and pistons were getting too closely aquainted :laugh:)
in 4th gear through the traps
the scale at the track said: 610lbs with me on it and 430lbs for just the bike
Best run of the day was:

R/T 0.414
60' 1.986
330' 5.473
1/8 8.452
mph@ 1/8=81.41
1000' 11.076
1/4 13.331 @ 99.32mph

How does this compare to a stock bike?
 
There's a magazine review of a stock XS from the era when these were new that lists the 1/4 at 13.9 sec but last time this came up some of the guys here felt that was awful fast and must have been done by a very experienced rider. You beat that by a good half second so I'd say you done good.
 
The magazine article was from 1979 Cycle World . It compared the XS650 to Sportsters , Triumph Bonnevil 750 , the Kawasaki kz 750 twin , and BMW , + a bunch of other bikes .

The XS was faster than all of the twins in the test, was slower than the inline fours but could lean over much farther than any of them in the corners . You should be able to find that article if you google it .
 
GreasyC said:
There's a magazine review of a stock XS from the era when these were new that lists the 1/4 at 13.9 sec but last time this came up some of the guys here felt that was awful fast and must have been done by a very experienced rider. You beat that by a good half second so I'd say you done good.
Click to expand...

Most magazine reviews were done at a rolling start witch makes it faster.:bike:
 
plattey said:
The car club that I am active in went to TriStates raceway this past weekend and I ran the old xs there. I have done the following to the engine:

stock xs650 pistons and rings
mild port n polish
vm34's
torque cones made from stock xs pipes
1 3/4" wrapped street pipes from hoosracing (end just after footpegs)
0.017" copper headgasket
no basegasket
NGK iridium plugs
performance coil from mikes'
re-timed cam back to stock timing

best time vm34 jetting:
190 main jet
17.5 pilot jet
159-p6 emulsion tube
6d-p1 needle clip in middle slot
2.5 cutaway slide

17/34 gearing
shifting around 7k~7.5k rpm (still wanted to pull strong past that pt but heard nasty tinking from the valves, thinking the valves and pistons were getting too closely aquainted :laugh:)
in 4th gear through the traps
the scale at the track said: 610lbs with me on it and 430lbs for just the bike
Best run of the day was:

R/T 0.414
60' 1.986
330' 5.473
1/8 8.452
mph@ 1/8=81.41
1000' 11.076
1/4 13.331 @ 99.32mph

How does this compare to a stock bike?
Click to expand...

Nice to see this info. I just started a thread hoping to find out more. I ran this past weekend and had a best of

8.55 @ 79.0 mph. My R.T. was a 0.231 which was the worse of the day but I was trying to be safe. 60 ft was 1.923. I lost against my 8.63 dial in and made the mistake of not looking over my shoulder. The other bike, a kawi H2 750 had missed 2nd gear and I could have coasted through 4th gear and won. My urge to go fast bit me and I lost but was happy too since the bike ran good.

My motor is a stock 650 bored 1st over. Vacuum 38mm carbs jetted up on the mains with open TT pipes and K&N filters. I am launching at around 3000 rpms and get a great hookup with the M&H racemaster slick. The main problem is with the vacuum carbs they shut down some as soon as the motor lugs down so it is slow to open up again as the rpms build. I shift around 7K and it pulls real good on the top. With VM carbs there should be lots of gain on the 60ft times, and overall. I have 18t and 42T gearing giving me about 7K + as I go across the line at the 1/8th. I took off the wheelie bars since I am only getting the tire up about 3 or 4 inches on the launch with me sitting foward on the seat and the 4" streched swingarm. The bike is set up to run and I am about 170 pounds. I have a few other built motors that will go in next. Just trying to get a base on a stock set up first. Then the 770 motor with extras goes in, plus wheelie bars.

21667_10151243359142351_279932798_n.jpg
 
Last edited:
Awesome pic! A nice pair of roundslides would suit you very nicely TwoJugs! Gonna try the Lectron carbs for the drag bike? Hugh's Handbuilt sells them I think. As for the bog, could you launch from a higher rpm and keep the front end down by modulating the clutch? Clutch won't be too happy but it might help keep the diaphragms from dropping too far. The whole day I was at the track, I was launching around 5-5.5k and using the clutch to control the front end from popping up. The next thing for this engine is a set of racing valve springs. Also, how much does your setup weight TwoJugs? My bike is a dd and it's down to 430 lbs wet (the bike's weigh in is near the end of the video I posted up).
 
Plattey, I have a set of stock 1978 xs650 pipes which I replaced with 1 3/4 pipes. Can you tell me how you adapted the stock torque cones to fit the 1 3/4 pipes?
Thanks
 
That was great without the help of any areodynamics such as a fairing or even a headlight. You may have hit 100 mph with a headlight plugging that hole.
 
Stock XS 650's ran in the low 14's. Not a rod, not a dog. They paled against 4 banger 650's at the drags but had better high gear roll on numbers, especially with a passenger. Dancing on the shifter wasn't necessary. Fuel mileage was also much better on the twins than on the 4's. That's what I remember and matches my own experiences.
 
As for making "torque cones" from the stock pipes, you cut somewhere at or before the stock headpipe's first major bend. Once you do that, you will see the two layers of the stock exhaust pipe. Locate at the head pipe flange, the weld that bonds the outer and inner exhaust pipes and carefully make a circumference cut about an 1/8th inch on the outlet side of the weld in order to separate the outer pipe from the inner. If you cut too deep and make a slice into the inner 1 3/8th pipe, you will need to weld the hole shut and grind the inside diameter smooth. Once the outer pipe is removed from the weld, make more cuts to the OUTER pipe in order to remove it from the rest of the headpipe assembly. Trim the inner pipe to fit the style pipes you have and there you have it :) I tried to keep the inner pipe long enough so that it reaches just before the first bend of the new pipes. That way exhaust gas velocity is high at the entrance of the first bend.
 
Back
Top