Who's done a top end rebuild?

[Frontside720]

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]

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]

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]

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]

I put a topend in some sort of motor usually on a weekly basis. I have done four in the last two weeks.

 

[kxmike]

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]

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]

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:

 

[The_STiLe]

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]

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]

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]

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]

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]

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.

 

[zookieman]

torque wrench and the Motion Pro torque adaper is a must!


You can also use a crows foot from sears.

http://www.sears.com/sr/javasr/sear...&keyword=crowfoot&displayTarget=searchresults

 

[muddy226]

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]

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.

 

[PhastPhart]

My rule of thumb for the last 20 years is as soon as it takes 3 kicks to start, it's time for a top end. Works for me.

 

[Kyleb15]

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]

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]

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]

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

 

[Melenko]

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

 

[jack10525]

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]

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.