86 250r with 85 ATC 250r engine

[klotzkid1992]

Well ive been working on this for 3 years. Toook it out riding maybe 3 times. Sold my yfzs im all in on the R's. Time to clean this thing up and set it up.


I need this 250r to bang rocks and roots. Fly up sandpits. And pull on the 450s on the fire roads. Occasional motocross.(have a lonestar R for moto)

86 frame.
85atc 250r motor.
Honda 450r A arms & swingarm
+2 axle.
No shocks lol

Tune in if you wanna see this northern Wisconsin R come alive.

[klotzkid1992]

First time ive been into this motor since purchase 3 years ago. I want to make this more along the lines of a "sleeper " motor.

Checked compression cold, kicked about 185 cold. I believe it's bored .02 over (haven't measured bore yet to confirm this.) New crank recently. V force 3 reeds. Brand new updated clutch.

What kind of port job this look like?

Should I hone this cylinder? Looks really smooth yet.

What's the piston telling you guys? Looks like some carbon buildup? Could be due to the squish clearance being .096"? There was a .045" head gasket on motor. Plan on Ordering the .010 steel head gasket and a new wiesco piston. Instal those. check squish clearance again. Don't know how critical that spec really is.. I've read to get that spec around .045 using the solder method to check it? if i need to mill my stock head the aditional .010 or so i can do that.

Planning to put cr ignition and new exhaust on this R.

[klotzkid1992]

Pulled the head & cylinder for the first time since I bought the quad.

I am going to do all machining myself.

I inspected the cylinder for taper,roundness, & size. To my surprise it is bored .100 over.Bore probes at 68.532mm (2.6981"). (Taper and roundness were both under .001" (Honda spec). I am going to run a wiesco brush hone in it, clean and fine sand any port burs. I will go with the lighter cast pro x piston and change it every 30 hours of riding. I plan on drilling 2 small diamiter holes on center of the front of the piston right behind the exaust bridge for more oil lubrication (if they aren't already there)

I'm hoping the piston diamiter will allow for a .0025" clearance to the cylinder. My 85ATC manual says .006" piston to cylinder clearance is the service limit. I will see when the piston arives. If its pushing .004" i think I will order the 69mm piston and machine the O.D. (outside diamiter) down to obtain a .0025 clearance to my bore size.

I'm sticking with the stock head. I'm going to machine the squish area widening that to match bore. While holding the same angle that is on the stock atc250r head. I don't know this angle yet but I think it's around 10° but I will check this with my lathe compond.

[klotzkid1992]

I'm making a tourqe plate fixture to bore R cylinders.

Base plate is almost done. Need to put 4 metric studs in it and dowel pin holes.

Still need to make head plate. I am going to make the head plate out of .750" thick aluminum. This should work well being the measurement from the 6 spotfaces on top of the head to the head gasket face is .700"

[2ndmoto]

Nice. I haven't seen people using torque plates in awhile. I know it is a must on big bores