86r with 87 crank????? how????

[the nether lich]

what all do i need to put a crank for a 87-89 in my 86?

[jar 250r]

a crank, split your case, install

[kristynluann89]

This questions gets asked all the time, one of the professionals on here needs to do a really good write up and have it stickied.

[mennis1971]

Whatever year crank you run, then you need to run that same year of piston basically. There are exceptions to this rule such as spacer plate motors, but that is the general rule.

[C-Leigh Racing]

Just like mennis said, just match up the crank/rod/piston together & it will work.
All year ATC/TRX cylinders, 85/89, how the castings are machined measure the same, so just a mater of having the right piston on the proper lenght rod & bolt the top end on.
Neil

[acecarlos]

85R-86R with 87, 88 or 89 Long Rod crank: 85/86 cylinder, + 85/86 Piston Kit to 69.50MM, + 3/16" Spacer Plate with 2 Base Gaskets

85R-89R with 85-86 Short Rod crank: 85/89 cylinder, + 85/86 Piston Kit to 69.50MM

87R-89R with 87, 88 or 89 Long Rod crank: 85-89 cylinder, + 85-86 Piston Kit to 69.50MM, + 3/16" Spacer Plate with 2 Base Gaskets

85R-89R with 87, 88 or 89 Long Rod crank: 87-89 cylinder, + 87/89 Piston Kit to 68MM

85R-89R with 85-86 Short Rod crank: 87/89 cylinder, + 87/89 Piston Kit to 68MM

Carlos.

[the nether lich]

Ok i think i have it figured out thanks carlos! So i have a 86 case im putting a 87 crank in it with a 86 68mm piston and the 86 jug and the spacer plate. if im right that will make it a 276 right?

[jdh250r]

No the stroke is the same... the rod length is THE only difference in cranks 85/86 vs. 87/88/89. It's +5mm longer on the 87 and later. so your engine size at 68mm will be [pi/4]x[(6.8cm)^2]x[7.2cm]=261.481cc's (i converted all mm into cm)

[acecarlos]

No the stroke is the same... the rod length is THE only difference in cranks 85/86 vs. 87/88/89. It's +5mm longer on the 87 and later. so your engine size at 68mm will be [pi/4]x[(6.8cm)^2]x[7.2cm]=261.481cc's (i converted all mm into cm)

Future Engineer

Carlos.

[C-Leigh Racing]

Future Engineer

Carlos.

Yep, big ol swish right over my head.
Being simple sure is easy.
Neil