Who's done a top end rebuild?

[pace]

Also this may be a really dumb question but, do you need to take the engine out to do the topend?

Nope.

 

[yamasaki]

i'm doing my top-end for the first time on my 97 yz250.

http://dirtrider.net/forums3/showthread.php?t=118527

so far, so good. i'm just waiting on parts now for the reassembly.

that's a good question about the misalignment of the power valve. i'm curious, besides the timing on the exhaust port being off (bike wont run as hard), are there any "catastrophic" issues in not linking up the PV correctly?

 

[James980]

What happens when you forget to aligne the power valve linkage properly?

The powervalve won't work.

But there's a trick to it that I discovered on my second or third set of rings on my 2000 CR250 that makes it real easy on that bike.

Leave the powervalve cover off and start dropping the cylinder down on the piston. When you have an inch or so to go before the cylinder is fully seated, losen the nut on the shaft of the actuator arm and pull out the cotter pin. The arm will slide partially down out of the cylinder and you can line it up on the pin sticking up out of the bottom end. Then, just fully seat the cylinder, make sure the powervalve linkage is in the right position (fully closed), torque the nut and put the cotter pin back in.

Simple as pie!

 

[Porstala F9]

Not on mine yet. I've helped friends do it though, doesen't seem to bad. I enjoy working on engines.

 

[kshackleton]

i did my first top end 2 weeks ago and it is really easy. i thought it was going to be hard but it was a peice of cake. i think the harest thing is tourquing the bolts back but ft lbs torque confuses me.

Ft-lbs is confusing?

it is simply the force at the end of a lever. If your ratchet handle is exactly 1 foot long and you pull on it with exactly 50 lbs force.....guess what....that's 50 ft-lbs of torque [rotational force].

Force [in lbs] x length of lever [in feet]

Smaller forces measure the torque where the lever is measured in inches....not feet. 1 ft-lb = 12 in-lbs.

 

[Mike_socal]

Now that's a good tip! I'm going to do that next time around.

The powervalve won't work.

But there's a trick to it that I discovered on my second or third set of rings on my 2000 CR250 that makes it real easy on that bike.

Leave the powervalve cover off and start dropping the cylinder down on the piston. When you have an inch or so to go before the cylinder is fully seated, losen the nut on the shaft of the actuator arm and pull out the cotter pin. The arm will slide partially down out of the cylinder and you can line it up on the pin sticking up out of the bottom end. Then, just fully seat the cylinder, make sure the powervalve linkage is in the right position (fully closed), torque the nut and put the cotter pin back in.

Simple as pie!

 

[seehollanot]

i just got done putting a new top end in my yz125. its pretty simple. i'd recommend for you to buy the manual and starting with that. it took me approx. 1 month to do it because i was waiting for parts half the time and i have no experience with dirt bikes( 2 strokes) prior to this one. this is my first off road bike and definitely won't be my last.

 

[Scottp5]

Check your compression. Should be between 150psi - 200psi !!!

 

[bike_rider250]

could anyone tell me what the measurment wear limit is for a wiseco piston? i have a kx 250, I emailed wiseco but i have yet to get any response, also did a search but couldn't fined any thing for a 250 just a 125

 

[MX Junkie]

just a question about the forged pistons; when I did a topend after I bough my bike used the piston skirt was cracked so maybe a forged piston will give me a little more peace of mind. I remember hearing that with a certain kind of piston you have to make sure you warm up your bike really well becase these kind of pistons expand very quickly. Is this talking about forged pistons?

Yes, cracked piston skirts are caused because of too much clearence between the piston & the cylinder.

 

[maximumbob]

Are there other bikes like the '00 rm250 where you have to do the topend every 8-10 hours? I mean that would be like riding all day one sunday right?

 

[rockers109]

I have a 00 rm250. I change the piston ring at about 15 hrs even though my compression is still good,before there is any damage to the cylinder. Then change the piston, ring and top end bearing at 30 hrs. The reason behind changing your top end not only for peak performance but also to prevent damage to the cylinder and crank. All 2 smokes need top ends frequently. $ strokes are not that different you can't ride every weekend for the entire year with out doing a top end and still have top performance.

 

[maximumbob]

Thanks for the reply that just seemed really often to do it and that guy had the horror story about letting it go to 30 hours. So you would replace the ring after a couple weekends of riding both days? I mean I know these things are high maintenance but those number seem almost unreal to me.

 

[MOTOX888]

Do you need to hone the cylinder?

 

[rockers109]

Yes, hone the cylinder with a ball hone. 240 grit aluminum oxide ball hone that's about 10% smaller than the cylinder. That's what Eric recommends, that's what I use. If you don't the rings don't seal well and you'll be doing another top end very soon. That's the mistake most make. Can't just slap the piston in and go. Buy one of Eric's books it has great info. Hey Bike_Rider250 the wear limit is .004 time to replace it. That's the maximum wear. But I'd replace it.

 

[CRryde]

200 hours!!! SWEET!!!

I won't be racing but I won't be putting around either. I'll be riding once a week (2x's if I'm lucky)

So once a year should be fine.

How do I no I need to get one done before I blow my engine?

take your kickstarter and push down with hand, and if you
can push it down pritty easy then its about time. if it's not so
easy but not to hard then i would pull the head to make sure
everything is fine. always check your piston it could have
cracks. you never know untill you look, rings could be fine
so you mite have good compresion but the piston could be bad
so just keep up with it. it's super easy with right tools should
take 45 min. to pull apart and put back together.

 

[SoFlo]

I just did one recently, not really too big of a deal at all. I started by making sure the bike was very clean. Then drain the coolant, pop off the pipe and take the carb off. Then I took off the head brakets and head off. After that, cylinder pops off. I had to disconnect 2 coolant lines and the powervalve linkage thing. Then off comes the cylinder. I took apart the powervalve and cleaned it, not too hard with the manual at my side, after the first time it's cake.
Then I took the piston, oiled it up, and put it in the cylinder. Then with the help of my dad, we held the cylinder up while we got the wrist pin through. I did it this way to make sure that the rings were in the grooves right. With the Wiseco I was using, the rings spin around the piston really easy.
So once everything was on right, put the c clips in, lower it, connect the powervalve, radiator houses, new gaskets, torque to specks, fill it up with coolant, and that's preety much it right there.
The only special tool that I needed was a torque wrench (not really special) and the Motion Pro torque wrench adapter thing. It's just a 14mm wrench with a box cut in it, to mount on the torque wrench. For my skill level, I'd say this was 6 out of 10 of how hard it was.

 

[nick545]

I'm 14 years old. I got a 86 kx 80 (really old). I did the top end last week and with the rapair manual I found it very easy.

 

[Lokair]

I just ordered my first Top end for my 1997 YZ 250, I am a capable auto mechanic, is there any thing I need to know special for my 2 stroke. I ordered a wiesco piston and ring set pro light standard with the wrist pin and cir clips, Along with a gasket kit. Any thing else I might need? I have all my Torque wrenches and such, will I need one of my Ring Compressors, any special assembly lube, or a special hone(I have a set of Ball Hones)?
Lok

 

[BDAY]

i just use some premix oil as assembly lube, you might have trouble with the cylinder to base bolts.

 

[cjonesy22002]

i tore apart my KDX and put it back together without a KDX manual. (bought a KX125 manual by accident) i've replaced the clutch and clutch side seal, replaced carb, and rear tire. my theory is to cuss kick and wrench until it runs, give it hell until it doesn't, then repeat. so far it's been mostly cuss kick and wrench with just enough run to make it worth it.

i'll be needed a new piston and a replate soon. trying to avoid it.

 

[dirtman2527]

Quick Tip,
Use an old rag or paper towles to cover your lower end to prevent the wrist clips from falling into your motor. I have seen it done and it sucks trying to get them out!

 

[J1mMy]

i done my first topend when i was 14,im only 16 now but have done my topends plus alot of my mates :)

Oh and 1 tip always start on clean motor.

 

[*KISSofDEATH*]

Top ends aren't too hard. it's worth the money that you save by not taking it to the shop
good luck :cool:

 

[rm_racer]

With the Wiseco I was using, the rings spin around the piston really easy.

I know its a little late, but I dont think the Circlips are supposed to be easy to turn. The clips have not been easy to turn in any of the 4 top ends I have done (2 dirtbikes, 2 sleds), I just tryed turning them in two of the old pistons I have and they were really pretty hard to move (Weisco). I just put them in with the open part facing down.

Anyway, I can put a top end togeather in 20 mins with the engine in the bike. That doesnt include the time to take it apart. I find the hardest part is getting the cylinder linded up, over the rings, and the power valve rod in the hole.