How to replace pistons on 800cfi and run in Wossner drop in piston kit?
- Thread starter Xileh
- Start date
S
Piston replacement
How mechanically inclined are you? It is actually very simple, but the first time is always the worst. I take the hood off to do this.
1. Drain coolant
2. Remove pipe and can
3. Remove y-pipe and ves valves
4. Remove thermostat housing from head/head cover
5. Remove head and head cover and unhook wires and sensors
6. Remove cylinder/cylinders
7. Remove C-clips from the sides of wrist pins and remove the wrist pins. When the wrist pin is removed, the piston should now be free and in your hand.
Wrist pins don't always come easy. Get creative or look for a special tool. You will need to hone the cylinder to break the "glaze". You will also need to check the piston-to-cyclinder clearance. I don't know what this spec is. Check ring gap clearance too. I don't know this spec either, as I have not had to replace pistons on my CFI's yet. Two stroke pistons have "locator pins" in the ring groves. A two stroke ring does NOT rotate around the piston like the rings in our pickup engines. Ring ends butt up to these pins when reassembling. Individual cylinders are easier to reassemble than mono blocks. I rotate the crank to get the piston to as close to tdc as possible.
Reassembly is pretty much reverse order. You will see where you need to replace gaskets. When installing head o-rings, place them in a container of cool or cold water. You want to try to avoid touching these with your fingers before you get them into the water(I read someplace that the oil from our fingers helped to make the o-rings deteriorate faster). Be careful not pinch them when you put the head back on. Use 2-stroke oil to lube things up as you go back together. I just collapse the rings with my fingers as I slide the cylinder down onto the pistons. I believe cylinder torque is 35 lb/ft and head is 25. I use a little bit of pipe thread sealant under the head bolts.
Not super hard to do. I think you can surf the forum to find the two clearance specs. It is late here, so I hope I didn't leave anything out. I am sure that someone will fill in that gap if I did. Maybe YouTube will have a clip of how to do this. They seem to have everything else. Keep asking and we'll keep helping! Good luck!!!
How mechanically inclined are you? It is actually very simple, but the first time is always the worst. I take the hood off to do this.
1. Drain coolant
2. Remove pipe and can
3. Remove y-pipe and ves valves
4. Remove thermostat housing from head/head cover
5. Remove head and head cover and unhook wires and sensors
6. Remove cylinder/cylinders
7. Remove C-clips from the sides of wrist pins and remove the wrist pins. When the wrist pin is removed, the piston should now be free and in your hand.
Wrist pins don't always come easy. Get creative or look for a special tool. You will need to hone the cylinder to break the "glaze". You will also need to check the piston-to-cyclinder clearance. I don't know what this spec is. Check ring gap clearance too. I don't know this spec either, as I have not had to replace pistons on my CFI's yet. Two stroke pistons have "locator pins" in the ring groves. A two stroke ring does NOT rotate around the piston like the rings in our pickup engines. Ring ends butt up to these pins when reassembling. Individual cylinders are easier to reassemble than mono blocks. I rotate the crank to get the piston to as close to tdc as possible.
Reassembly is pretty much reverse order. You will see where you need to replace gaskets. When installing head o-rings, place them in a container of cool or cold water. You want to try to avoid touching these with your fingers before you get them into the water(I read someplace that the oil from our fingers helped to make the o-rings deteriorate faster). Be careful not pinch them when you put the head back on. Use 2-stroke oil to lube things up as you go back together. I just collapse the rings with my fingers as I slide the cylinder down onto the pistons. I believe cylinder torque is 35 lb/ft and head is 25. I use a little bit of pipe thread sealant under the head bolts.
Not super hard to do. I think you can surf the forum to find the two clearance specs. It is late here, so I hope I didn't leave anything out. I am sure that someone will fill in that gap if I did. Maybe YouTube will have a clip of how to do this. They seem to have everything else. Keep asking and we'll keep helping! Good luck!!!
Thank you for a very good write up
I have worked much with car engines (tuned much old audis) so I know quite much about mechanics. I have also changed pistons on a old Indy Trail 488 air cooled. But never on a liquid cooled engine with EFI/CFI
Hmm,I need to hone the cylinders, even if they are nicasil coated? Can I do this myself? Remember I did this on the trail on my own with a drill and hone tool.
The rest seems very easy to do. I have ordered the piston-kit,and a complete gasket kit for the engine.
I think the ring cap and piston clearance is written on the wössner page. They got less piston to cylinder clearance than the stock pistons I know.
S
From what I have read, you can hone it at home. I have not had to do my 700s yet as they both have less than 2000 miles. Check here in the IQ section and check in the PRO section for threads on if you really NEED to hone or not.
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