Top end repair?

[Nitro Blazer]

I had a rattle coming from my top end so I tore the top off my engine last night. The cylinder wall looks like glass and the piston looks ok. The wrist pin doesn't shake.

Would it be ok to just rering it and let er eat? Is there something else that could cause that rattle?

Theres also an X on the piston, does that have to do with the bore? I have another jug off a blown motor and the sleeve looks alot thicker, so I'm guessing this one is bored.

Thanks for any help...

 

[trailripper1500]

what condition r ur gaskets in? maybe the head itself is rattling.

 

[Nitro Blazer]

The head was on pretty tight and the gasket looked good. The noise was coming from the cylinder (I did the old screwdriver up to my ear trick all over the engine till I pinpointed it). I did notice some blackness below the piston rings. My Haynes manual says that's due to misfiring. I know the engine had a spark knock in the upper rpms often.

I'm worried about the crank now, right where the bottom rod bearing is looks heat tarnished on the shiny machined part (on the outer ends of the crank looking from the top. I don't know if this is normal or if that is telling me that my rod bearing got hot and is burnt. It wobbles back and forth a little but I'm not sure if that matters. It has no play up and down though. Plus I'm positve the sound was not coming from the bottom end.

The engine ran great and fired up on the first kick so I wouldn't think compression is an issue. I've heard the rings can wear and make it rattle.

I also checked the pin and it doesn't wobble in the rod or the piston.

I'm just having a hard time with this thing because it's my frst one and I don't know all the things to look for. I'm used to working on ford trucks and R/C cars.

 

[Nitro Blazer]

Anybody? I don't want to dump any money into this thing that don't have to.

 

[regal81455]

i know you said the wrist pin was solid but did you check to make sure all the needle bearings were still in the wrist pin bearing? my brothers bike blew it to smitherings and it made a similar noise till it wouldnt go anymore.

 

[rad-blaster230]

crank

The head was on pretty tight and the gasket looked good. The noise was coming from the cylinder (I did the old screwdriver up to my ear trick all over the engine till I pinpointed it). I did notice some blackness below the piston rings. My Haynes manual says that's due to misfiring. I know the engine had a spark knock in the upper rpms often.

I'm worried about the crank now, right where the bottom rod bearing is looks heat tarnished on the shiny machined part (on the outer ends of the crank looking from the top. I don't know if this is normal or if that is telling me that my rod bearing got hot and is burnt. It wobbles back and forth a little but I'm not sure if that matters. It has no play up and down though. Plus I'm positve the sound was not coming from the bottom end.

The engine ran great and fired up on the first kick so I wouldn't think compression is an issue. I've heard the rings can wear and make it rattle.

I also checked the pin and it doesn't wobble in the rod or the piston.

I'm just having a hard time with this thing because it's my frst one and I don't know all the things to look for. I'm used to working on ford trucks and R/C cars.

i would also double check the crank and see in the manual if it sapose to wabble like that. Also just to be safe i usualy put a new wrist pin in whe i have it apart anyways because they are so importaint and their only like $10
yah and new gaskets to

 

[Nitro Blazer]

Well, I went and bought a feeler gauge this weekend, checked the clearances in the haynes manual and I'm in the clear on the crank. It's way within the limits.

I checked the ring gap and side clearance which sucked ( I think the rings were my rattle ).

I don't think the piston/ cylinder clearance is bad and it doesn't seem to be out of round.

Is it possible I caught it just in time to getaway with only a re-ring?

I still want to take it to the shop and have it measured to be sure but all I can see is bad rings.

What would cause a high rpm top end knock? Not a consistent one just every now and then when you downshift. It also happens sometimes if I'm in like second or third sliding around a corner.

Thanks for the help so far.