help in building my yz 490 up

[amcfeek]

ok my neighbor had a few of yz490's back when i couldnt afford one ..
now i kinda can squeek one in on a budget so i bought some parts and 2 basket cases .
i would like help on annybody's input on porting this monster probably just open the exhaust up to one that i have / alreaddy ported .radius the ports ,and drill out the boost ports from reed cage to transfer ports keeping them small 8mm
polish everything up and kick my nads off to get her started.

what i have so far is this
2 basket cases . 84 and 85 1 will be donor for the missing bolts . 1 is too far gone

ok bought 1 good bottom end complete cdi wireing etc with a new rod in it
this is the it490 5 speed version . its a 83 ish.
2 84 jugs #40t 1 thats 3rd over 1 is .060 thats good with fresh wiseco piston kit
1 head for the 40t 7 bolt heads .
1 complete 84 bottom end that needs a rod kit its loose and bearings are noisy .
came from basket case when piston chernobled
1 rod kit from ebay 60$ with shipping
1 good 82 yz 490 jug that is only .10 over wont work with the 84 frame was going on my 82 it 250 that is a complete bike still std bore, till i got the basket cases and 1 good 83 yz 490 jug thas a fresh 80 but cracked external trans port
i have enough to make 1 motor fom the yz top end on the it bottom end .
i probabbly have 400 bucks into all of this i am shure you would shell out the 4 bills for all of this

i also will chop up a ktm roller for the front forks inverted marzochi 's
only thing i am shy is the exhaust for this i do have 2 yz250's 90'sish and a fmf unknown bike on the way . if worse comes to worse i have a mig welder and its winter out if you fill a piece of pipe with water you can bend it without crimping it.
that is if its pennsylvania and the pipe is outside and its winter . i watched a how things are made and they made trumbone parts this way .. heck a piece of flat steel plate 3 small wheels with no tires burn a slice so the one wheel can bend the pipe looped through all 3 , add an air shock , or a hydraulic lifgate pump to the center wheel thay rides in the slot and i think i can bend my exhaust myself ..
ok now shoot me

[JordanM]

yz 490? Thats a friggin monster..

[honda86]

how did the 490s do running with the old KX and CR 500s?

[amcfeek]

well in about 86 from what i know the championship went to yamaha , with a very unpleased works rider that chased it all year on his cr500 . and the 490 was suposed to be pretty close to stock . speacial porting and exhaust .. but no fancy works backing.
some of the things i will try as these 490 were miserable to start .
clean the plug and add a primer from a snowmobile maybe a help for me .
i know enough to wind em up and clean the plug before you hit the kill .

[MX86]

my dad has a polished and ported 84 yz490, it has a 5 speed out of a 87 yz490, had the head milled to run 110 race fuel he's running 15-46 gearing, and a compleate pro circuit exhaust.

as far as yz490 vs CR and KX 5's if you drop the 5 speed in there there is no comparison between the 3. the yz will dominate

[rix005]

If your engine is hard to start or detonates under hard acceleration, try using 100 or 110 avgas, about 5 bucks a gallon at your local airport. If that is not an option add an additional base gasget to reduce compression, or have the head milled. Also a speed shop in Long Island showed me a compression release valve, like those found on 4 strokes, that had been installed in the head. He stated that it worked great,kiked over like a 125 till you let the lever go. hope this helps.

[amcfeek]

thanxz for thetip . i am 210 and a very stong right leg . normally if i dont break my boot i will snap off the kicker..
i have run av gas before my neighbors dad {ex neighbor} is a mechanic at the local airport .. so yeah nothing we aint gonna try , also the outlaw octain boost works . i used the outlaw and i blew the rivets loose on my it 250's silencer {old oval aluminum} ran like a raped ape with it..
also my one 60 over jug was alreaddy ported before i got it . i am not through cleaning up whast left or finish polishing up where he left off or gotten anny major work done to it . i did start on it . i almost have my yz/it400 jug close to finish .. i have like more then 20 cylinders here in my parlor i did count them in december .. {where i can keep a fucking eye on em and crack heads can't get at em}..
things is i have only so much skin on my hands ..
one thing i dont have for this project is an exhaust . if some one wants to donate to a worthy cause ... i will give you my addy..
but anny way i will probbly take a look at one of my yz490 side dump exhausts and copy it over using car exhaust pipe and an expansion chamber from a snowmobile and my mig welder i should do alright untill i can get into some money and buy a aftermaket like a dg ...

i alreaddy know jetting this is gonna be fun . i think i read on ebay soomebody suggested tiping the bike over for 20 seconds to raise the float level ebough to spill some gas up to prime the animal after she has been sitting
thanxz for anny help ...

[mgty3whlr]

I have an 87 YZ490... "f"-in animal !!! I don't ride it much ...but when I take it out... It's an adrenaline rush Big Time !! Yea, you're right...They are a bitch to start!

I have a tip to make it a whole bunch easier to start !

1: turn the fuel on...(DUH)
2: put the choke on.
3: put it in 1st gear.
4: rock the bike back and forth in gear..you'll feel the piston rock up and down in the cylinder.
5: Rock the bike back and forth about a dozen times..this will get the fuel into the cylinder.
6: put the bike in neutral
7: kick the bike over..guarenteed to start in 3 kicks !

Once I used this technique, the bike would start every time without kicking your A$$!

Try it, I guarantee you start it this way every time! TRUST ME !!

[drag lt guy]

talk it over with Flotek about adding sub exhaust ports to that beast.

[amcfeek]

i would talk to somebody about porting my jug but that would cost me money ... money the option some ppl have .....
i may be able to do that myself . but the jugs kinda thin the way it is . i am sooner to try the port on a dt360a . and sooner then thaton a dt400 jug that needs to be 80 over just to clean it up of a fubar . i also have a early 490 jug to waste time on that is a door stop . its cracked and needs a sleave some one pryed it off with the usual ammount of no brains cracking the transfer port area!
i need to buy a snake ..
i dont think some porters would give away trade secrets ... yoou need to buy their port work . i do have a esr cylinder here .. ktm 250 .. kinda leaned a bit from just looking at it ...