How many times have YOU replaced your top end?

  • To Many to count...

    Votes: 123 22.7%
  • 5 - 10 Times

    Votes: 69 12.7%
  • Less than 5

    Votes: 98 18.0%
  • Once

    Votes: 86 15.8%
  • Never

    Votes: 102 18.8%
  • I have but I recommend letting the shop do it

    Votes: 3 0.6%
  • I have and I don't think it's too dificult for the do it yourselfer.

    Votes: 62 11.4%

  • Total voters
    543

Frontside720

Member
Aug 12, 2004
64
0
I'm looking at picking up a 2000 CR250 and I know with the 2 smokers come the maintenance.

I'm not a mechanic but I like to think of myself as capable. I replaced my full system on my R1 and I'm not afraid to give things a try.

I have some questions...

1. How hard is it to replace a top end?
2. Is it as simple as follow the instructions in the manual?
3. Do I need any special tools?
4. How will I know that I need a new top end? Bike wont start?

After searching the site there's many different suggestions on how often but it seems to be that every 10-12 hours you need to replace the rings and every 20-25hrs the pistons. Is this a safe estimate?
 

crazyYammi

Member
Aug 31, 2004
89
0
top ends are pretty easy to do..
what kind of riding are you doing? Unless you are a pro the topend will last you much longer than 20 hours... i do mine at 200 hours and the rings and piston are still within design specs.
Whoever told you 2strokes require alot of maintinence is FOS.
 

Frontside720

Member
Aug 12, 2004
64
0
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?
 

kuchera89

Member
Jul 9, 2004
55
0
i have put some hours on my 125 and it still wheelies up,
i would use wiseco, they have forged pistons which i hear wont shatter like others.
i bought my bike used in july of 04, i high rev it alot around the track every couple weeks and i still havent replaced anything in the engine. 2-strokes are only high mantainants when you crash, but so is everthing else :nod:
 

Studboy

Thinks he can ride
Dec 2, 2001
1,818
0
I put a topend in some sort of motor usually on a weekly basis. I have done four in the last two weeks.
 

kxmike

Member
Feb 2, 2005
65
0
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.
 

g_man80

Member
Nov 30, 2004
44
0
I just did one in my '00 cr250 last weekend. Not bad at all. It's pretty strait forward. Definitely pick up a torque wrench and an adapter for the cylinder base nuts. Motion Pro makes one. Otherwise the torque wrench won't fit on the nuts. It basically just offsets the wrench.

If you take apart the power valve assembly it gets a little more complicated, but it's not necessary.

And if you are just a casual weekend rider it sould last some time. I rode all last summer (each Sunday pretty much) and just decided to do it this spring. I don't even know how long the previous owner had it in.
 

Revver

Member
Feb 1, 2005
15
0
I recently did my very first top end job on a 01 cr250 and it was not hard at all in terms of sheer difficulty, but I did hit a few snags where patience was a virtue. Some tips: Working the jug off can take a little elbow grease, mine was very stubborn and took some time, but with a lot of taps of a rubber mallet, a buddy and I were able to work it off. Again be patient and avoid forcing anything. The cylinder only uses two dowel pins, I thought there were supposed to be four, needless to say i caused myself undue frustration trying to make four dowel pins work. Do not twist the cylinder when sliding it over the piston and rings, it can be easy to snag a port. Make sure you line up the power valve shaft on the bottom of the cylinder with the actuator on the cases when you slide the cylinder back on. Other than that it is as straight forward as can be. I highly recommend getting the service manual. And the guys on this board will be more than willing to offer good advice if you run into any issues. As far as taking apart the power valve, it is easy if you follow the service manual, and now that I have done it once I could do it again in my sleep. You will want to have access to a good torque wrench for when you're putting everything back together. Now order those parts and go for it! :cool:
 
Last edited:

The_STiLe

Member
May 9, 2005
58
0
also i think i should add if you clean your sir filter reguarly, i mean after every ride, use a good quality oil, keep your fuel tank clean than this will greatly improve the length of the life of your piston. also i wiseco pistons are forged and are very hard this can cause the bore to show wear and tear quiker than cast pistons. thought u mite like to know, otherwise il shutup :)
 

Frontside720

Member
Aug 12, 2004
64
0
Great posts everyone!!

I'm still waiting to find out if the trade is going to go through. Either way, if I end up keeping my kdx I will be doing the top end on it.

1) How will I know the top end needs to be done? (bike not starting?)
 

mobrown

Member
Jan 26, 2004
198
0
Piece of cake...

Top ends are easy if you have the right tools. You need metric wrences, soft blow mallet (rubber or plastic), razor blades and solvent (for removing gasket material), torque wrench and the Motion Pro torque adaper is a must!

Oh yea I forgot about the most important things... a manual and PATIENCE :)
 

Papakeith

COTT Champ Emeritus
Damn Yankees
Aug 31, 2000
6,695
50
RI
ummm, The makeup of the piston shouldn't affect the cylinder wall. The Rings contact the wall of the cylinder. If the piston forged or otherwise is hitting the cylinder walls there is a problem.
 

crazyYammi

Member
Aug 31, 2004
89
0
The only sure way to know if you need a topend is to take the head off and measure the end gap on the rings, and inspect the piston.
Some people say you can use compression testing, but by then it is too late and you have started eating up the bore in your cylindar.
I do desert racing and ride pretty hard and still got 200 hours. I would bet that most people could go at least a year without checking.
 

WillyM

Member
May 18, 2004
84
0
Get a compression tester , how I tell is when you do a fresh top end get a base line after brake in, then as you wear it in the compression will go up peak then go down and hold for a while then start down again which it is then time to replace.
If you get this bike do a top end as soon as you get it that way you know how many hours are on it and you can look at the bore and tell how well it was taken care of .
Wisco pistons are ok but I use stock ones and replace them often like 3 times a year but I race ,and I pin it and use the clutch.
Nothing worse than a broken piston in your case.
 

muddy226

Sponsoring Member
Sep 14, 2003
271
0
I think it also depends on the bike. I got fed up with changing pistons on my 2000RM250 at the recommended interval of 8-10hrs and finding them come out well within spec and looking good for at least the same again, so I left it for about 30 hrs. Big mistake. The first of many re-plates. The piston had got a bit slappy and taken some plating off the intake bridges, and the resulting problems weren't cured until Aptec gussetted the back of the bridges and relieved the front, having said that most bikes don't have this particular design fault. Also, when the 30 hr ( ART ) piston came out it was very close to losing its skirt. Since then I've stuck with Wiseco.
 

moabdaze

Member
Aug 12, 2004
31
0
Wiseco or Vertex, something forged, are the best way to go IMO. Also take the previous advice and get the Motion Pro Adapter. Best money I ever spent.
 

Kyleb15

Member
Oct 8, 2004
116
0
Hey crazyyammi you must be crazy! 200 hrs! Due that is way long. Let me get it straight though, you are riding a Yz 250, right? Dude at 200 hrs you are just flirting with disaster. I can't belive no one has said anything! But, please correct me if I am missing anything. The best advise is to check the piston every once in a while or do a compression test.
 

NWetRider

Member
Sep 24, 2004
72
0
for that engine, as others have said, you need the motion pro adaptor to torque the head. Really the only common mistake people make is to not get the foot of the power valve linkage aligned properly. The left side of the cylinder can be hard to get off - resist the urge to stick a screwdriver in there and pry. I would suggest a rubber mallet and patience. With these tools and a manual it's and easy job.
 

mxmatthew

Member
Apr 7, 2003
276
0
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?
 

ellandoh

dismount art student
~SPONSOR~
Mi. Trail Riders
Aug 29, 2004
2,958
0
mxmatthew said:
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 from what i hear they r the ones a little more finicky for warm up
 

jack10525

Member
Jun 21, 2005
10
0
Anybody got pics of this procedure? Yeah I've seen the link on this site. Also this may be a really dumb question but, do you need to take the engine out to do the topend?
 

Broken Spoke

Member
Mar 1, 2004
62
0
I made the mistake of not doing a top-end on my bike as soon as I bought it used in January. I thought I would make it through the summer. Now my bike is in the shed with the bottom end locked up from the peices of piston skirt that flew in there. I could have done a top-end a lot cheaper and faster than it is going to be now.
 
Top Bottom