98 xp ltd cylinder gone 947

[caper]

Hi i lost a cylinder and havent taken it apart yet compression 160 and 30 on other .. I dont quite get what people are saying about blocking the holes off for the needle bearing when take piston off so they dont fall down to the crank. What best procedure to do so not to screw it up. As you can tell i never had one apart.. I am assuming take rave out then pull pistons.

Also the filters for the carbs where are they and i am assuming the grey lines starved the cylinder why it blew .

 

[nswillin]

Hey Caper. I just rebuilt the same engine. Those needle bearings are very important to catch. I stuffed rags down in between the rods and bottom end of engine. As I pulled the piston off, slowly, I caught them with a magnet bowl. Just take your time and do it really slow. I pulled the entire engine out to rebuild topend, a lot easier to work on. Looking back I'm really glad I did. My cylinder blew b/c of a hole in the hose going from the crank to the rave valve solenoid. I would not have seen that if I had not pulled the engine. Also I found a huge hole in the fuel line that feeds the pump. So..... make sure you go through everything so you know why the cylinder was blown before you spend all the time and money fixing it.:cheers:

 

[caper]

So in the end what did you spend on parts .. I take it you got a new head and top end kit.. I will take a look at those hoses not sure where rave solenoid is .. One of my hoses to rave was off

 

[nswillin]

Yeah prob not good that hose is off. I think all together I spent about $500. I ordered the topend kit from SBT that had .5mm oversize pistons. Bought new wrist pin bearings and exhaust gasket kit. I had my cylinders bored and matched to the pistons at a machine shop. If your gonna do this you really need to get a shop manual from here. I also had to rework the rave valves also b/c the oversize pistons.

 

[caper]

Well i started taking it apart the top of of one piston was like new could read the number off of it and the other kinda pitted. I will replace all the fuel line hoses and take carbs apart for a good cleaning. The only thing i wonder about is the cylinder itself. Once you have the head off those studs remaining do you unscrew them out to pull the cylinder off the piston or does it just come off after carbs and exhaust is removed. Those little bearing is my worry .

 

[nswillin]

The manual will tell you step by step on how to take everything out and put it back together again, torque specs, which bolts to take off first, everything.

Those studs have to be removed to get the cylinders out. Take two of the nuts you took off of the head and tighten them on to the stud and then unscrew the stud. As long as you go slow and be careful and get plenty of rags stuffed in there and use the magnet bowl those bearings will not get lost. You cannot reuse them though but don't lose them in the engine.

 

[caper]

Okay what manual did you use there seems to be a few available.

 

[nswillin]

Join as a premium member. Go to "manuals", and download the one for your year.

 

[KTMatt]

I also found that out the hard way also. needle pin bearings everywhere! for my second piston I used a 14mm socket to push the wrist pin out. I let the socket stay in the rod with the needle bearings and the zip tied both sides of the socket to the rod for safe keeping. worked good when I put the pistons back on set another 14mm in the other side and slid all the pins in around it. Then install piston, pushing the socket out of the way with the wrist pin.

Matt from Mass

 

[nswillin]

Thats a pretty good idea KT. If you buy new wristpin bearings they are now "caged" so no risk in getting them everywhere.

 

[caper]

Okay maybe i got this is the needle bearing in the rod that goes to the piston and you used a 14 mm socket .. So after i take the jugs or cylinder off all is left is the piston on the rods.. Then put rags all in holes and use the magnet to catch all the balll bearing or i got this screwed up ..

I took the engine out today and one of the rods from the rave was broken off. It's kinda funny the piston that is shot is on the other side of the rave shaft that was broken .

 

[nswillin]

Yes, the wrist pin bearing are in the rod, there is a wrist pin that slides through them and through the piston, also there will be a washer on each side. There are no "ball" bearings. I did not use a socket, I used a piston pin puller tool. Just be careful with the rags and magnet and go slow. Order new wrist pin bearings that are fully caged in case you ever have to take it off again, you wont have the risk of dropping one.

 

[caper]

How is your machine working now i saw that your compression reading were around 130 each . Thanks for help by the way .

How did you decide which size pistons to use. .The walls on mine are pretty good a small flat spot nothing major. You might make a mechanic out of me yet . lol