Posted October 15, 2000 - 09:55 PM
i have considered for some time the craziness of the way yamaha could change a tooth on a racing engine & "it would suit both bikes".
yamaha of course, are very clever engineers & the only thing that let's any model down is the production cost or commonality of parts etc.
so i decided to check the cam timing & as i expected it is out from what i would consider the correct timing by a considerable margin-enough to invest $175 to bring you this news anyway!
HOW IT GOES
to me the YZ timing just lacks depth-or torque & if my calculations were right it was going to increase the torque. the yz timing spins across the revs so quick that you can't beat it. trouble is when you make it work or you're in a taller gear it struggles.
with the valve timing adjusted it revs but you never doubt that it'll pull-& hard too.
power wheelies in 2nd are no problem off the bottom & the wheel goes light in 3rd. roll on power in 4th is improved slightly as well. the only thing it hasn't cured AT PRESENT is that bloody dead spot off tickover!
the first thing i noticed was how softly, how quietly & surely it ticks over. you're never in doubt it will be running still when you're back from the loo!
lucky with the screws & jets?-maybe but i doubt it.
WHAT I DID
i checked the cam timing & full lift on the inlet was at 113dg atdc & on the exhaust it was 101dg btdc. by using variable timing camwheels (VTC) i was able to make this 108dg atdc on the inlet
110dg btdc on the exhaust.
SO WHY THE FREE POWER?
this is why i had a go at it. i knew in the back of my mind that the engine might have been compromised due to production costs.
the valve timing on the exhaust should be 1/3 of a tooth forward if you have yz timing & 2/3 of a tooth back if you have a wr.
the crux of it is that the enduro bloke at yamaha said that he needed a softer engine & the motox guy said i'll move by only 1/3 tooth & we'll both be happy. yippee! production costs kept down, commonality of parts etc.
HOW MUCH/WHO FROM?
$175 for a pair of well made camwheels
you could, now that you know the correct (or better) cam timing just have the wheels moved around on the cams.
you need lot's of time, patience & TLC.
instead of writing more now i'll wait for your questions. don't forget i'm 7 hours ahead of you though!!
[This message has been edited by Taffy (edited 10-15-2000).]
[This message has been edited by Taffy (edited 10-15-2000).]
[This message has been edited by Taffy (edited 10-16-2000).]
Posted October 15, 2000 - 11:59 AM
Nice work on the cam indexing. Was that 108deg btdc on the exhuast (says inlet) and 110deg atdc on the inlet (says exhaust)? Is there any aftermarket shop that just sells torque cams with a similar timing?
Could you post your setup - exhaust, intake, jetting (pilot,needle DXM#?, main), other mods. That dead spot doesn't need to be there, probably pilot screw and needle clip.
Posted October 15, 2000 - 01:03 PM
i've gone back in to the above & corrected it-all this atdc & btdc is harder here than when you do it.
you can't really buy this one jd, it takes lot's of TLC, time & patience & it can be free (if you know the engineer!). i think only the tiffossi are going to bother with this one.
as you know it's known as blueprinting & it's where the tuners & the buy-a-bit-&-bolt-it part the ways.
it's what the factory wanted but couldn't do due to mass production. i haven't explained the mechanics of how i did it yet but i will answer a whole bunch of questions when i get them.
the valve timing on the inlet & exhaust are as written
inlet is fully open at 108dg atdc (corrected)
exhaust is fully open at 110dg btdc(corrected)
bike set-up is embarrasingly rather standard still as follows;
standard euro exhaust
white bros air filter
std DXM needle on 4th clip (standard anyway)
45 pilot is now up to 48
168mj is now 170
screw is out until it ran sweet!!!!!
i hardly know the carb on this thing but that is about to change! you have been warned!!
it's 4 weeks to the 'john banks' & i've time to try things. but i have to say to you when i get out there i want to ride & not work. i gave up my youth to that f******* ducati & i'm not doing it again!
Posted October 15, 2000 - 02:08 PM
it's easier with the engine out than in, but both can be done. the difference is that by the the time you've pushed the wiring harness up & out the way 50 times there is a lot of muck on your cams.
i'll try & explain it all-jargon free (impossible i hear you say!)
remove the rocker cover & the flywheel cover.
remove the spark plug
put a tray under the flywheel cover as the bike will leak oil as you crank it over.
you need a bolt the same thread as your plug to go right down into the cylinder head. about 1 1/2" of thread will do. i then stuck it on a bench grinder down one side all the way up & onto the shank of the bolt.
it should look a little like the letter 'D' from the end. round nose the end with the benchgrinder so that when it taps the piston it doesn't leave a 'chip' in the surface.
the 'D' is to let air out as you turn over the crank. screw it in the head like a plug.
i have a stealy flywheel which has three spare holes in it. i drilled three holes in my 8-10" protractor so that it lined up the top dead centre (tdc) line roughly with that which is marked on the standard flywheel. the holes i drilled were big enough for me to move the protractor left or right a few degrees. so, 8mm holes, 6mm screws with little pinch nuts to tighten it all to the flywheel nice'n'tight.
you now need a strip of metal under that 6mm screw on left side near the bottom of the barrel. it should twist from horizontal to vertical & stop near the top & back of the protractor & act as an accurate marker to the protractor.
turn the crank over using a screw driver between the screws holding the protractor as a lever.
you'll hit the bolt & make a note of the degree's (dg) before & after tdc it touches. loosen the protractor & adjust it, re-pinch & try again until you end up with, for example 22dg before & 22dg after tdc. that means that you can now pull out the bolt & 0dg is when the strip of metal & the protractor zero line up.
you need to cut a strip of sheet steel about 15mm wide & 10-14" long. fold in middle, drill appropriately & bolt to dial guage which has an old rivet pin in the end.
fold metal to 45dg & twist etc until it holds the dial guage over the end of the cams & the guage can get the pin down onto the top of the tappet nearest to the right of the machine. undo the cam cap bolts & pinch clamp the metal strip underneath them in such a way that the pin is on the cam follower, is free to slide up & down & is fully crushing the dial guage up to it's near maximum reading.
check the cam timing by gently turning the engine. getting a loose & free reading from the dial guage is harder than you think but persevere(sp?).
the dial guage will whizz round until it gets to maximum lift, slow down, check the timing, roll back the engine, try again, try again. the dial guage won't move for 8/10dg sometimes. don't panic, take the middle of the figures!! if it comes shooting up to 119dg & goes back again at 107dg you know the answer is 113dg. easy!
write down your figures. now do the tdc test with the bolt in again. is tdc still the same? when i set mine it had somehow moved the protractor 1dg thus what should have been 109dg for both cams became the figures you see posted above.
now remember that at the worst at the moment you've scratched your piston otherwise you haven't changed a thing.
put the bike back together, report your figures here, or if your feeling brave go ahead with the timing change. the timing changes you'll make take the valves further from the piston making it SAFER.
all this stuff has been done by TY Davis (whoever he is-sorry!-etc since the day they got the bike). fAlconer carry this stuff in stock as part # SA-Y-400. I'M NOT THEIR FIRST CUSTOMER. like i've said time & again "what a shame we don't have a top GP mech on the site who would say that after 10 hours on the dyno the best cam figure is *** for tight & *** for open racing. oh well, we got each other!!! sounds like a song is coming on!
time for bed.
Posted October 16, 2000 - 10:18 AM
Posted October 16, 2000 - 01:27 PM
it seems a long time ago when he used to leave my WR for dead.
the first time i rode my bike as a WZ i couldn't keep up with another rider on a 250EXC in the first two gears across an open field.
i hope that at least one guy off the website will have a go at this mod. there are plenty of roadrace shops that will have a go at this work. they may even recommend pressurising the wheels to move them around. in which case your just paying for the labour.
i had no choice but to buy the camwheels. i didn't know for sure that it would work & i guessed i might try a couple of different settings before i struck lucky. you simply can't press a camwheel on & off half a dozen times to get it right without the wheel going a bit loose with dire consequences!
but moving it once to the correct timing is feasable.