1982-87 yz 490 - ngk br8es - 0.024 " , 1988-90 yz490 - 0.032 "
55 hp
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.
20.5 oz
i have ran 6ounces of 2 cycle oil to 1 gallon of gas
Step 1 Drain it Step 2 fill with 2 stroke oil
The prime factorization for 490 is 7x7x5x2= 490, or 7 to the power of 2 x 5x2
490 = 490
main jet#370 pilot jet#50 throttle valve#2.0 needle jet Q-2 hope this helps you.
490
25% of 490= 25% * 490= 0.25 * 490= 122.5
90% of 490 = 90% * 490 = 0.9 * 490 = 441