racerdave
^ Gone not forgotten ^
I get a video does not exist screen from the link
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Maybe this is better:
Is there any power increase with the rephase or does it just sound quicker? I'm just about to rebuild my engine and not sure if there is any power increase with the rephase or not, I've already got a few mods to the engine, 750cc, ported head and large cam, had my terminal speed at 115 in 4th over the 1/4 mile once, now looking to improve on this.
racerdave
^ Gone not forgotten ^
That is pretty good performance IMO. what was your et?
650performance
XS650 Addict
No, it won't add power or torque. However it will change how the engine feels because vibration will occur at different rpms when compared to the stock setup. 115 is pretty good. As a yardstick, 70 rear wheel horsepower will generate about 120 - 121 in the quarter with a bike that has been lightened considerably.
Rephasing is a power distribution thing that better utilizes torque to assist in pulling the other reciprocating piston through it's cycle as opposed to pushing two heavy mass pistons through it's cycle. Don't know who ported your head but porting the exhaust can get tricky as reducing it's resistance is #1 and getting the flow through the turn without creating turbulent resistance is a real key element is unleashing it's true potential . But for valve choices that I've found to help the XS head is cutting down virago valves to XS stock head dimensions,thick valve margins help to reduce resistance and you want to cut the exhaust valve thick margin with a slight radius or cut the bottom face of the E/V on a radius all contributing to a flow increase and resistance deduction or buy the xs performance head along with the matching pistons. If you want want some top end pull,long rod it and rework the intakes for maximum port velocity allowing the L/Rs to pull it up top.
Another area where power can be unleashed is through the exhaust system,stepped headers work great while offering somewhat of a reversion step in reducing the wave kickback and a solid megaphone system that's functional at speeding up the exhaust pulse through the outlet to enhance the the pulling effect at the E/P
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When I went through at 115 it was quite slow, 13 seconds as I'd just changed the carbs and it took me by surprise and left a tyre mark 100 yards down the track, best time is 12.2, normally go through around 12.6.
member3480
RICH
Ok going to throw my two cents in here. I have been building race and stock motors for over 35 yrs. So if you want to increase some horse power it just depends how fast you want to go and how much money you got to spend. Its a running JOKE in our shop because someone always comes in NEVER FAILS and says I want my bike to run in the 8"s and I always say give me $10.000 now and I will get back to you.
HORSEPOWER is NOT CHEAP..... If you want some extra power on your stock XS650 I would say to start with head and cam and get it to flow good. Ignitions is a big key to get the max spark. Then a good big bore kit will round out the motor. Plus some good carbs. Now the bad news you just spent close to $2000.00 in parts with no labor. I have done a couple XS650 motors with the 750 kit-cam-carbs-ignition and yes you can tell the difference. The end horsepower is much more but never put one on Dyno.
I would say start with head and there is plenty of HP in there not used. On some bikes just degree in the cams with slotted gears and there is a increase. The only problem unless you want to make it a all out Drag Bike you can only go so far then the daily rider becomes the daily fixer.
If you ever want to pick my brain you can contact me at DADDYGCYCLES@YAHOO.COM
Rich
HORSEPOWER is NOT CHEAP..... If you want some extra power on your stock XS650 I would say to start with head and cam and get it to flow good. Ignitions is a big key to get the max spark. Then a good big bore kit will round out the motor. Plus some good carbs. Now the bad news you just spent close to $2000.00 in parts with no labor. I have done a couple XS650 motors with the 750 kit-cam-carbs-ignition and yes you can tell the difference. The end horsepower is much more but never put one on Dyno.
I would say start with head and there is plenty of HP in there not used. On some bikes just degree in the cams with slotted gears and there is a increase. The only problem unless you want to make it a all out Drag Bike you can only go so far then the daily rider becomes the daily fixer.
If you ever want to pick my brain you can contact me at DADDYGCYCLES@YAHOO.COM
Rich
So would these valves work? http://www.ebay.co.uk/itm/YAMAHA-XS...rcycles_Parts_Accessories&hash=item35d56662e9 would kibblewhite valves be better than xv valves? seen them on offer on one site, or there's a guy in the UK that adapts xv valves
Jay,those ebay valves look really cheap with no thought put into them for flow. I've used K/W valves in my BMW,so again they're ok but won't have the thicker margin nor will the k/W have the tulip shape of the intake and especially not the exhaust. IMO the XV's are the better choice when cut down or if the intakes port volumes are reduced to maximize port velocity then installing a 2mm oversized intake valve would be beneficial in opening up the seat and bowl pocket area without fear of port velocity dropping off when the valve breaks from the seat. Don't get in a rush just yet as I'll try and post a shot of the Xv E/V cut down in comparison to a stock valve,it'll probably be this coming week.
