No. The 83 has a single front downtube and the 86 has a double downtube.
about 80mph
60-65
The YZ series was built to race motocross and top speed was not a major factor. Handling and acceleration were key. The top speed of any motorcycle can be adjusted by changing sprocket sizes.
115-120 km
I have a 2001 Yz 125 stock Gearing, Fmf Pipes. 60-65Mph
1982-87 yz 490 - ngk br8es - 0.024 " , 1988-90 yz490 - 0.032 "
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.
25 mph
Yes it will. The 1984 yz490 and the 1985 yz490 are identical bikes other than the front disc brakes.
55
6.9:1