Sand_man

Member
Jun 30, 2006
145
0
i just bought a piston kit for my bike, ive never done the top end before. how often do i need to replace the top end? and do i need to replace everything, like the piston itself and the rings etc, or do i just need to replace the rings? also, is the cover to the top end tourqed on, will i have to tourqe it on everytime? thanks for the help!
 

-Mark-

Member
Dec 31, 2005
8
0
rebuild every 10 hours riding time, some people rebuild every 15-20hours riding time.. less if your riding it very muddy, wet, dusty conditions.. but 10 hours riding time is recommended by most mechanics from honda etc.
 

Sand_man

Member
Jun 30, 2006
145
0
damn i ride like 4 hrs a day wtf! hahha, that sux! do i have to replace the piston, and the rings, and the gasket everytime?
 

rerfurt

Member
Jul 7, 2005
50
0
I replace parts when they are worn beyond spec. - but pistons and rings can develop fatique, thus I will replace them at least every 30 hours (I use cast pistons) - I feal reasonably safe doing it this way, but thats just me.

Gaskets and little end bearings can to some extend be reused (if you are cheap) and they are not broken or worn down.
 

Sand_man

Member
Jun 30, 2006
145
0
my dad said on cars you need to tourqe down the bolts, is this true with dirt bikes too?
-Thanks!
 

Kevin003

Member
Jul 5, 2005
237
0
I don't do any racing, (but still ride hard )and have about 96hrs on my RM125. It still starts first kick so i don't think ill replace anything for a while. Maybe when it starts to start 2nd kick ill re-ring it but thats probably it for a while.

Basicly if you don't race every week theres no need to replace them every 20hrs like many people will claim. Just make sure you TORQUE THE HEAD BOLTS!!!!!!
Other wise you can warp your head from the bolts not evenly being torqued.
 

crrod

Member
Aug 14, 2006
87
0
Don't forget to torque the cylinder nuts as well. I have a 1999 CR125 that hasn't been in to. The compression is down to 120 PSI, it still starts first kick most times, and it runs like a striped assed ape:) I ordered a wiseco top end kit for it along with a set of Boyesen Corbon fiber reeds that utilize the factory reed cage. I'll be doing the top end sooner than planned, mainly due to the bike being 7 years old and on the original top end.
 

crrod

Member
Aug 14, 2006
87
0
Compression tester, pull the spark plug, install compression tester, connect plug wire to plug and gournd plug anywhere to engine, shut off fuel, hold down the kill button, hold the throttle wide open and hick away. The compression tester will read the highest PSI registered from the cylinder and retain it until pressure is relieved. Testers run about 30 buks at Wal-Mart. I found a friend that had one and borrowed it.
 

dudenasty

Member
Oct 15, 2006
5
0
hundreds of hours on my kdx200

IT STILL HAS TONES OF POWER with hundreds of hours on my kdx200 it's a 91 i don't no if it's ever been rebuilt but i'v put a lot of riding time on it 3 seasons i've put it through a lot of deep mud infact yesterday my buddy blew his moter(ktm125sx) going through the mud and his bike is higher than mine i ride really hard and my bike does'nt start first kick when cold but it always starts and it never fouls plugs and i can putt really slow on it without pulling clutch and reving and it iddles realy good (it wont stall) unlike all my freinds with there race bikes(always fouling plugs and rebuilding top ends) thear always hounding me to rebuild mine and i tell them wen it fouls a plug or dies i'll rebuild it....I HAVE BEEN USING THE SAME SPARK PLUG FOR THREE SEASONS mabey it's just luck or mabey it leves something to say for the kdx200 endoro engine if I had to rebuil my engine every 10 to 30 hours i would'nt want even ride the thing............ps can anye one tell me what the compression psi. should be on the ktm125sx????????? I think it has no compression left i hav'nt tested it yet but i will....i dont think it died just from the water it was'nt running right it kept dying out....
 
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