depends on yr, weight and gear ratio. I had a 94 and it was bout 80+, but hard to gauge when trail riding.
No. The 83 has a single front downtube and the 86 has a double downtube.
1982-87 yz 490 - ngk br8es - 0.024 " , 1988-90 yz490 - 0.032 "
Yes it will. The 1984 yz490 and the 1985 yz490 are identical bikes other than the front disc brakes.
6.9:1
55
55 hp
60+
about125mph
That would be a negative.The 490 which is probably a 1982 model as 1981 was a 465 were all side exhaust ports .The 82 yz 250 was a centre port with a twin tube frame. Also the expansion chamber on a 250 needs to be much larger than on a 490.You can get a new pipe from DG in usa or watch ebay. Good luck.
60-75 mph
Faster than you are in bed.
about 98 to 104