I've got what I know is at least a head gasket problem but figure as long as I'm there anyhow...... can I remove the cylinder and replace the base gasket while the engine stays in place? Will I be able to get the pistons back in? Just curious, it's 150 miles away and I like to go as prepared as I can. Thanks in advance.

 

I would question why you want to pull the jug JUST to replace the base gasket. Is it leaking oil badly?

If you pull the cylinder you are at least looking at new rings and deglazing the cylinder walls. I usually like to replace the piston also, as the piston ring groves also wear and carbon up. By the time you scrape the carbon out of the groves they are not the best any more. Not many do this, but to me, a new piston is cheap insurance for good ring seating.

If it has some miles on it you could be looking at having to go with a oversized piston and ring set, which means having to bore the cylinder, more money.

Good luck

 

Putting in new pistons is unnecessary in my opinion, unless the ring land has been beaten badly you can just clean them up and re-ring them. A quick hone job would be a good thing to do, to make sure the new rings seat. Not sure if the cylinder and head can be removed with the engine still in, I would think so, but it would also make the work a major PITA....

 

The thing is difficult to start (turns good, just about starts, fires, fires, fires, finally catches, I'm pretty sure it's just low compression due to the head gasket). I'm burning anti-freeze and there is definitely combustion chamber pressure leaking into the cooling system - a radiator hose popped loose! So I know I'm hurtin for certain on the headgasket, and I don't know about the condition of the head. I was cruising along, bringing up the rear, with no indication anything was wrong when the rider ahead of me stopped, so I stopped. Whooosh! A cloud of steam caught up to me. So I got towed back to the trailhead. The plastic 'tee' in the radiator hose had failed, and I lost most/all coolant, not sure for how long. Not good. I'm sure the gasket is gone, the head may be warped or cracked, and I have no clue about other possible damage, so I was going to buy a head gasket and base gasket to bring with just in case. I'm pretty sure I can do the head with the engine in (if someone knows I can't, please chime in). I was worried about getting the pistons back in, so maybe I'll just do the head gasket and see if the head is warped or not.

 

OK, an update. On another thread, you'll see I replaced the headgasket and made things better, but not OK. So, back to the drawing board.

But, I did want to update this thread just in case anyone ever has the same question.

You can indeed remove/replace the cylinders with the engine in place. The cylinders come off OK, you'll have the usual PITA cleaning the gasket surfaces. I made some plastic guides out of old milk jugs to put in place of the cylinder walls to serve as a guide for the pistons so I could jumper the solenoid (just connect for a fraction of a second) to turn the engne over and get the pistons up where I could work on them.

After cleaning everything and sticking the new base gasket to the cylinders with some grease, I couldn't come up with a way to get the pistons back in the cylinders, so I removed the internal snap rings that retain the wrist pins (not too hard - place a rag around the piston/rod to keep the snap ring from dropping into the crankcase, just in case) and pulled the wrist pins (used a 4" long 1/4x20 bolt with a washer as a little puller, worked good). Pay attention to piston orientation and which cylinder has which piston, Polaris wants them back the way they were. Also, avoid rotating the rings so that they stay in proper orientation to each other.

The pistons heads are now free and you can put them in the cylinders in a normal fashion, and reassemble. Lube everything up (you have been keeping things clean, I hope), don't be stingy! Put the cylinders in place and reinsert the wrist pins through the piston and connecting rod, and replace the 'C' ring (again, don't drop it!). Put the cylinders back in place - voila'!

You can indeed replace the base gasket while the crankcase is still in the frame.