How many hours till top end needed on 125?

[micah 23]

Could anyone tell me about how many hours of riding on a 125 before a new top end is needed? Also, how much in parts.. and is the labor easy enough that with a service manual one could do it themselves to save some money? Thanks

 

[marcusgunby]

Hard riding a piston will last only 10 hours-play riding upto 50 hours.Some bikes are alot harder than others to change(mainly the powervalve setup is the hard bit)With a manual most people can manage to change a top end-a digital camera is handy a you can take pics as you go in case you forget which part goes where.

 

[micah 23]

How much money is involved? I may have to go with a four stoke if I have to change it every 5 or 6 times out to the track.

Do most people change it that often? It seems like after a year they would have so much repair money into the bike to make it not worth it.

 

[Senior KX Rider]

You are looking at the wrong sport if you don't like to spend money. ;) 10 hours on a top end would be for someone that really thrashes a bike and demands peak performance. I run my 125 prolly closer to 40 hrs with no problems and my sons 125 30 hrs or more and he runs them hard

 

[Senior KX Rider]

If you are thinking you will go with a 250 4 stroke and save money......you may want to rethink your strategy. ;) You may go a little longer between teardowns but they demand attention and it costs a little more to tear into them

 

[micah 23]

How much money without and with labor would it cost to do a new top end?

I figure if your son goes about 30 hours and you do 40 with the amount of hours I ride a weekend I will have to do it every 2-3 months.

 

[bclapham]

a new top end kit costs $100 for a 125. i do a new ring ($15 + gasket) every 10 hours then a new piston kit every 20 hrs. You should learn to do it yourself, its not that hard.

if you want to look for a 4 stroke since they dont need maintainance, check out ebay- there are lots of yzf's on there being parted out since the owners were of the idea they were maintainance free...and then they blow up bad beyond the value of the bike.

three options 1. learn to maintain your bike. 2. buy and XR. 3 buy some golf clubs or a fishing rod!:)

 

[Senior KX Rider]

A two stroke top end is very easy and will cost you about a hundred bucks. Piston ring and gaskets. Takes about 2hours. I don't ride 4 strokes so I can't give you a cost difference but I would think your intervals would be similar on a yzf

 

[125 rider]

Shouldnt cost you more than $100 each rebuild, thats if you do the work yourself.

 

[125 rider]

you guys are fast :)

 

[Senior KX Rider]

I'm not :)

 

[jmics19067]

Usually takes me a week to do a top end;

Monday, clean bike tear it down and inspect andmeasure,
Tuesday order parts, clean and prep parts I am reusing, repack silencer
Wednesday walk around the bike a few dozen times making vroom vroom noises and day dreaming
Thursday make threats to UPS delivery guy
Friday recieve parts ,apologize to delivery guy, assemble, and first heat cycle,check leaks etc etc.

 

[RM_guy]

Originally posted by jmics19067
...Wednesday walk around the bike a few dozen times making vroom vroom noises and day dreaming...

:aj: :)

 

[SterlingYZ]

This is a good thread, and an honest one. Yes 10 hours if for is you are a HARD CORE racer, but even Class B and certainly C can race a FEW races without a new top end. Just keep an eye on it. I run mine prob closer to 40 hours before changes, and I run it pretty hard. I am going to the track (to compete) for the first time soon, and I will just make sure the bike (an myself) is ready, but I am not a Pro, so I won't be spending Pro money. Remember 80% rider, 20% bike. :)

 

[Jaybird]

I put more hours than most between complete top end change. A ring change every 10-15 hours allows this to happen, IMHO.

You guys getting by for a 100 bucks haven't rebuilt any KTM's lately. :)

 

[DirtRyder03]

Do you guys know if this is any different on a 250? do the top-ends last longer? shorter? thanks.....??

 

[bclapham]

much, much longer!:)

 

[Senior KX Rider]

thats right.

 

[Rcannon]

The 250 top ends should last quite a bit longer. I usually rebuild mine once per year (out of guilt).

Still, it is hard to judge this without seeing how someone rides their bike.

I saw a brand new RM 250 last weekend with low compression. The bike was shiny clean. Been ridden "twice" the owner said ..."and now the damn thing wont start..."

I looked at the airfilter. I think "twice" meant two very long days in a dust storm. The filter, despite being bone dry, was covered with 2 inches of dirt. The bike had sucked dirt and worn out the rings (at least).

 

[podia]

just curious, do ya 125 owner change ya piston ring twice before changing the piston? I mean the ratio is 2:1

Do ya measure the internal block ID and the piston OD before ya decide to change both the ring and piston at the same time? or remain at 2:1 sequence?

please advice, thanks.

 

[Jaybird]

podia,
If you are racing, you probably shouldn't go with more than one ring change in between complete top end replacement.
Do the whole thing in winter, then half way through season change out the ring. Repeat.
However, it is wise to check the parts when you do the mid-season change to make certain there is no bad wear.
Many things effect the need for top-end changes, ie...type of riding you do, ratio of oil/gas, jetting, overall engine and fuel tract maintenance, etc...

Two guys can ride the exact same hours and conditions, yet the guy who takes pristine care of his air filter will last far longer than the guy who doesn't.
Also many racers will have their jetting leaned out to the hilt....this is tough on a 125 and makes it imparative that you keep a good eye on your parts.

 

[MX2_motorex]

One thing I read in a MX magazine was 80s and 125s go through top ends like 3 year olds go through underwear, 250s go through top ends once a year and 500 hardly ever go through top ends. That 80 and 125 thing was cheesy I think I saw that in MXA

 

[99rmRACER]

when you do a top end change on a 125 is honing really necessary? also , do you have to disassemble clean and reassemble to powervalve everytime you replace top end? i am fairly new to this and do not really understand pwervalves. does anyone have a link to anywhere that explains them or has a diagram? (picking up the service manual this weekend so that should help).

 

[kawakx125]

what happens if you dont change your top end as often as you should.

 

[jmics19067]

It gets very expensive replacing all the parts that are damaged when a piston shatters