Clutch slip cure
Wayne Kennedy was having some clutch slip problems on his staggered crank XS650 and this is what he did to cure it:- I put new genuine clutch plates in the 650 but when I was doing so I measured some other steel plates I had and was surprised that there was two different thicknesses between them. One set was about 1.35mm and the other 1.6mm. (no they weren't worn) The early 6 plate had thicker steels, as I had put in a later 7 plate to try and stop slipping with the torque. I put the thicker steels in which saved me shimming up the springs, and also left out the rubber rings between the plates. Low and behold, no clutch slip and it is easier to get neutral when the motor is hot. A quick solution to anyone that has a hotter motor and having clutch slip.
Dave Bath also suggests it's a good idea to bevel the edges of the clutch friction plate fingers with a file (just enough to take the sharp edge off ) to reduce to possibility of these catching on irregularities in the slots of the clutch basket which is one of the causes of clutch drag. I've just done it to my new clutch and it seems to work. (Terry Gliddon)
Tony Warner also informs me that the XS650 has two different length clutch actuating arms situated inside the left engine cover, where the clutch cable attaches, so if you have a heavy clutch you may benefit from using the longer arm from an XS1 if you can find one.
While you are in there it is advisable to check the back of the clutch basket to see if you have any broken springs.
Clutch Shock Absorber Spring Refit
Mikuni VM36 Jetting
I am in the process of adding a few extra ponies to my XS 650C,
kit, carbs, head, cam and pipe. Getting info on "correct"
VM36 jetting for a kitted engine took a little time....but here
is what I managed to get from Halco (UK) and the States (Bob
Bertaut). It might limit the amount of trial and error....though
some members may well have all this baseline info at their
fingertips. The HALCO pre-jetting is on the richer side and the
Bertaut is leaner. Both specifications fitted with free-flowing
filters (K&N or Unifilters). I'll will keep
you posted on the final jetting for my bike.
Main jet: 220
Pilot jet: 25
Spray tube(needle jet) 159-Q-2
Needle type: 6DH3
Air jet: 2.00
BOB BERTAUT (VM36 CARB KIT)
Main jet: 190
Pilot jet: 22.5
Spray tube(needle jet) 159-P6
Needle type: 6DP1
Air jet: None, removed.
Tuning for Speed - Phil Irving
Four-Stroke Performance Tuning - A. Graham
things first, methanol is extremely poisonous and can cause blindness and
insanity. It is absorbed through the skin or its
vapours inhaled, and once it is in your body,
it stays there.
methanol will have an 8% to 17% power increase over petrol.
burns slower than petrol so ignition can be advanced 6-15 degrees to allow for
running temperature is much cooler than petrol. This means that the air inducted
for combustion is cooler and so it is denser and so supplies more oxygen.
Because of the greater oxygen, the jet size is 2.2 times larger than those used
for petrol. The slides are cut away to allow greater air intake.
needs less oxygen to burn :-
Optimum fuel /air mix for petrol is 1:12.5
Optimum fuel /air mix for methanol is 1:5.5
is anhydrous in that it absorbs water from the atmosphere. If fuel is left in
the system, the water it absorbs will corrode up the works.
ratios can be ran at 14:1 as detonation is virtually non-existent with methanol.
doesn’t mix too easily with petrol because of its tendency to absorb water,
but 3-4% acetone can be used to help it blend.
mix of 60% methanol, 20% benzole, 20% avgas, is a
good substitute to 100% methanol as it uses less fuel and so requires a jet size
midway between petrol and alcohol. It still retains the anti-detonation and
cooling properties of methanol.
is a danger of a washing effect of the bore wall with a rich methanol mix. The
addition of caster based oil will alleviate this problem. Valve guide oil seals
can be removed on the exhaust valves to also help with this problem.
you are looking at a pure methanol fuel, try 97.5% methanol, 2% acetone, .5% Castrol
fuel is expensive and is not as easy as petrol to obtain, but, if you choose
this path, it would appear that you gain extra horsepower and the motor becomes
more forgiving with regard to detonation and overheating. I expect that this
could be a fair trade off for the risks involved in running an
high compression ratio.
I recommend EBC pads and a 13mm master cylinder
for the early 2 piston calipers. The late ones benefit from Ferodo Platinum and
a 11mm master. Ferodo replacement shoes( FSB 735) are a good upgrade for rear
shoes. Check the disc brake tips at my website.
XS1 front brakes have too light a link rod. Replace with Norton Manx ($50), or add a LH jam nut($1). Arm indexing also an issue here, as some off the arms are made wrong, apparently a carry over from the TD1. With the link rod disconnected, the centers between the actuating cam shafts and the link pin centers should be the same. Relining with the 2520V street compound is a big improvement, usually dropping racers lap times 6-8 seconds a lap.
Michael "Mercury" Morse
15069 Lupine Lane
Sonora, CA 95370
ph/fax (209) 533-4346
34mm Round slide Mikuni Jetting.
Some of the members have asked recently where to start with Mikuni jetting and I contacted the vertical twin discussion group for some input on this subject. Here are some of the responses:-
Mains: 180 to 190 is most probable.
Pilots: 20 to 25.
Needle jets: P5 or P6 both work well.
Needles: 6F9; start tuning
in the middle notch.
Slides: the generic 2.5 works fine.
Air jets: remove.
Needle Jet: P6
Jet Needle: 6F9
That is at 1000 ft elev. depending on your exhaust should be very close.
2.5 slides, 27.5 to 32.5
pilots, P-5 or P-6 needle jets, 6F9 needles, 180 mains, air correction jets
removed (standards are 2.0). Usual disclaimers "Works great on mine, but no
guarantees for OZ" - doesn't the air spin counter clockwise in the carb
throats down under? Finally got the high ratio primary gears completed, but
have not got the engine back together and in the project bike yet.
Alternative location for Vacuum Barbs For Tuning
Who told you that Göran, I couldn't have
written it any better myself.
Monday, 24 September 2012