Piston/Cylinder Clearance Measurment Question

[ABMax24]

Whats the best way to measure the piston to cylinder clearance? I currently have the reeds off and am just wondering if measuring the cylinder skirt to piston is accurate, as i am getting between 6-7 thou on both cylinders.

If it is accurate at what point do you put in new pistons?

 

[Jeffpro800]

Whats the best way to measure the piston to cylinder clearance? I currently have the reeds off and am just wondering if measuring the cylinder skirt to piston is accurate, as i am getting between 6-7 thou on both cylinders.

If it is accurate at what point do you put in new pistons?

The sooner the better. After your cylinder skirt breaks off and your crank eats it, well then it's too late. When you have it apart inspect your cylinder skirts carefully for cracks. Some guys change out the stock pistons with 0 miles on them just to be sure. It's a known fact that these motors develop an excessive piston to cylinder clearance within a short amount of miles with the stock pistons.
Last season my 2011 800 dropped a cyl skirt with 1200 Kms on it, the compression was good and the motor ran great, simply put there is no way to tell untill it's too late if you don't tear it down and inspect it. Then again lots of guys have high mile motors with no issues. From my experience tho it's better safe than sorry.

 

[gedakbx]

Whats the best way to measure the piston to cylinder clearance? I currently have the reeds off and am just wondering if measuring the cylinder skirt to piston is accurate, as i am getting between 6-7 thou on both cylinders.

If it is accurate at what point do you put in new pistons?

how are you measuring that with a feeler gauge?

 

[ABMax24]

how are you measuring that with a feeler gauge?

Yes, feeler gauge between piston and base of skirt through the opening in the crankcase for the reeds.

 

[gedakbx]

I think I would pull it apart and measure it with Micrometers sounds like it is on the loose side already, could save you a lot of head ache down the road. I had a 700 come apart and ruin the cases, crank and cylinder and it gets exspensive fast to repair it.

 

[007sevens]

Pistons are not perfectly round and it matters where you measure and how you measure. Measuring with the rings on through the intake hole would be an unusual way of measuring and the measurement wouldn't be accurate. If you planning on an upgrade to better pistons, rip er down and giv er. But if your trying to figure out if your pistons are good for another year. Take it to your dealer and let them tell you. At least then you have a fighting chance.

Personally I would just replace the pistons.

 

[moyiesledhead]

Measure one inch from the bottom of the cylinder, and across the bottom of the piston skirt....on a cat anyway. Can't do it properly without taking it apart.

 

[Rhodesie]

Whats the best way to measure the piston to cylinder clearance? I currently have the reeds off and am just wondering if measuring the cylinder skirt to piston is accurate, as i am getting between 6-7 thou on both cylinders.

If it is accurate at what point do you put in new pistons?

how many miles? disassembled a 12 assault today that was starting to foul plugs and found flaking rings, collapsed .006", .011" clearance. you can shave with the top of the upper ring land on the intake side of the pto piston. 840 miles. surprized the mono wasn't cracked!

 

[ABMax24]

Pistons are not perfectly round and it matters where you measure and how you measure. Measuring with the rings on through the intake hole would be an unusual way of measuring and the measurement wouldn't be accurate. If you planning on an upgrade to better pistons, rip er down and giv er. But if your trying to figure out if your pistons are good for another year. Take it to your dealer and let them tell you. At least then you have a fighting chance.

Personally I would just replace the pistons.

I was hoping to get another year out of the motor. Currently I've got it all tore apart so I can put in my turbo, but when I pulled out the reeds it felt like there was a fair bit of movement with the piston which brought me to my above post. But obviously if the motor isn't going to make the year or is going to end up costing me more later then I will fix it now and be done with it.

how many miles? disassembled a 12 assault today that was starting to foul plugs and found flaking rings, collapsed .006", .011" clearance. you can shave with the top of the upper ring land on the intake side of the pto piston. 840 miles. surprized the mono wasn't cracked!

I have 1254kms (~779miles) and 46 hours on the motor.

Now comes the million dollar question, do I put stock pistons back in or go with something else? Will new stock ones only last 1200kms again?

 

[Rhodesie]

stock are garbage as you can tell. every time I check the pistons they always have excessive rock. this seems to be happening in as little as 5-600 miles in a few cases. I have checked my wife's 13 with 1200 miles and I can't believe the movement in the pistons. I have been replacing the stockers with wossners from rk tek for a couple of seasons now if the owner agrees to it and have had 0 probs. they just don't change shape. The stockers just collapse and then eventually break off the cylinder skirt and mass mayhem. the silly thing is the oem's are more money than any good aftermarket.

 

[ABMax24]

stock are garbage as you can tell. every time I check the pistons they always have excessive rock. this seems to be happening in as little as 5-600 miles in a few cases. I have checked my wife's 13 with 1200 miles and I can't believe the movement in the pistons. I have been replacing the stockers with wossners from rk tek for a couple of seasons now if the owner agrees to it and have had 0 probs. they just don't change shape. The stockers just collapse and then eventually break off the cylinder skirt and mass mayhem. the silly thing is the oem's are more money than any good aftermarket.

Do the RK Tek's change compression? I thought I heard that they bump up the compression, which is the opposite of what I would like to happen now with boost.

Also where would be the best place to order a set of the RK Tek's or Woessner designed pistons?

 

[Rhodesie]

the direct replacement pistons from rk are made to directly replace oem's. they hold cylinder pressure better because they hold there form and the rings don't flake. if you are around that Edmonton area or passing through, get a hold of chrisco on here as he carries rk's products. if you are around the south east I can get you a set also.

 

[dragonweld28]

IMO... get the taller piston with the cylinder spacer.... MNTK and Bikeman offer these kits. Both are good. MNTK uses wiesco pistons and Bikeman uses wossner pistons.Again, Both are good, but i would go with the wossner piston.