Completely ruined our 98 EXC 380 ! a long story that I don't want to get into really ! Instead I'm just going to deal with it and attemp to repair it myself.
So I did a compression test and it came out low around 70-80 psi. Took the head, cylinger and piston out. scuffing marks all over and mostly 3 long ones about 1/4 of an inch wide. the rings are welded into the piston too !
What are my options? How much can this cylinder be bored over? because I found some Wiseco pistons that are .040 over, would this route work?
thanks for any info?
idiot friend rode without adding oil in gas !
Started by
sinful
, Jan 16 2012 10:43 AM
53 replies to this topic
Posted 16 January 2012 - 11:50 AM
The cyl is nikasil plated. You dont want to overbore it. The nikasil plating needs to be removed, the gouges can be repaired and then the cyl needs to be replated. There are a lot of good places that can repair and replate your cyl and make it like new. I've had the cyl in my 380 replated twice. I once ran it too far and the cyl was out of round. I can go about 120 hrs of riding time before its time to have it replated. I've run the oem pistons but within the last year they have skyrocketed in price. I prefer to use a piston that has a coating on it.
Hope its just the piston & cyl and no damage was done to the crank.
Hope its just the piston & cyl and no damage was done to the crank.
Posted 16 January 2012 - 11:57 AM
Cant say without seeing it, but sometimes, the piston just melts onto the Nikasil coating, it can be cleaned off with muriatic acid, its possible you may get away with a cleaning light hone and a new piston and rings, if not ya you need it re plated and a new piston.
Posted 16 January 2012 - 03:13 PM
I would try to clean up the jug and install a new piston and rings. The scarring on the jug doesn't look like it penetrates the nikasil. Nikasil is a heck of a lot harder than the metal in the piston and rings for a reason.
Posted 16 January 2012 - 04:27 PM
sorry I'm not sure where to get muriatic acid (havent heard of it either).
Edited by sinful, 16 January 2012 - 04:27 PM.
Posted 16 January 2012 - 04:42 PM
I would clean the cylinder ! I have cleaned them before that looked like yours and put a new piston and rings and bike ran just fine . you should be able to find muriatic acid at a lowes or home depot . it is used to clean concrete . it took me a few days to clean my cyclinder . The way i did it was , I used a small brush and wiped the acid all over the areas i needed to remove the allumiun "melted piston material " . Then after it sat awhile i would spray some wd40 on areas and sand with 1200 grit wet and dry . trying very hard to only sand the scarred material off . then muriatic acid let it sit and then sand . hope it helps .
Posted 17 January 2012 - 06:24 AM
excellent ! thanks for the info !
so the goal here is to just attempt to clean the the cylinder and buy a std size piston. any piston/ring recomendations?
so the goal here is to just attempt to clean the the cylinder and buy a std size piston. any piston/ring recomendations?
Edited by sinful, 17 January 2012 - 06:24 AM.
Posted 17 January 2012 - 12:12 PM
i have no idea. how do you diagnose it? i know the rod to crank doesnt have any upward and downward play. there is side to side play though (normal?)?
Posted 17 January 2012 - 12:17 PM
we did some cleaning on the cylinder but only managed to remove about 50 %. we are doing some more cleaning as we speak. although i think it might be pointless because it has a nick or small hole already. you can see it on one of the pictures ( 9 of 10 ). "unless the rings dont travel as far but i dont know that".
Posted 17 January 2012 - 12:42 PM
Man I would have this "friend" paying the $150 for the new piston at LEAST, and If I was the "friend" I would be offering to pay for at LEAST that! That's BS. Sounds like hopefully you'll be able to get away with the $150 route 
Sorry to hear that, this is why I'm OCD about anyone but me or people I respect mechanically touching my bike.
Sorry to hear that, this is why I'm OCD about anyone but me or people I respect mechanically touching my bike.
Posted 17 January 2012 - 12:52 PM
There is no way your crank bearing survived if the piston was that bad. Those bearings get dry quick and once they do, they overheat and get cracks in the casing that holds the bearing components. You might not notice it now, but its most likely damaged.
My suggestion:
- Re-nikisil the cylinder $225 (http://www.mt-llc.com/)
- New Piston/ring $150 (vertex)
- New upper rod bearing $12 (KTM OEM)
- New lower rod bearing and re-balance crank $165 + parts (Andrew can do this no problem http://www.cookseycrank.com/)
Send the new piston along with the damaged cylinder and they'll match it for ya.
Roughly $600 including shipping to do this job right.
Pretty much thats what you gotta do if you wanna be sure. I wouldn't trust those crank bearings at all.
My suggestion:
- Re-nikisil the cylinder $225 (http://www.mt-llc.com/)
- New Piston/ring $150 (vertex)
- New upper rod bearing $12 (KTM OEM)
- New lower rod bearing and re-balance crank $165 + parts (Andrew can do this no problem http://www.cookseycrank.com/)
Send the new piston along with the damaged cylinder and they'll match it for ya.
Roughly $600 including shipping to do this job right.
Pretty much thats what you gotta do if you wanna be sure. I wouldn't trust those crank bearings at all.
Posted 17 January 2012 - 08:41 PM
tye1138, you are scaring me, man ! please tell me what to look for overheated rod/rod bearings/crank. I'm would be more than happy to take things apart, take pics and post them.
Also for some reasson I always thought anything below the piston was being lubricated by the transmission oil on all 2 strokes?
Also for some reasson I always thought anything below the piston was being lubricated by the transmission oil on all 2 strokes?
Posted 17 January 2012 - 09:39 PM
here are some pictures of the cleaned cylinder. finally after many hours of cleaning !
