Top and bottom end rebuild

[Hondacrrider]

Well, I have a new top and bottom end kit on order, and should be here shortly, I was just wondering if you guys had any step by step tutorials you guys could give me, or any tips on how to do a bottom end? Also, the kit comes with a hot rods crank and bearings, Athena complete engine gasket kit, and a wiseco top end, not a bad price, it was only 440 dollars, including shipping to get it to Canada. If you need a package like this, I suggest motosport. Also, how much are mechanics charging in the US to put in a new bottom bearing(in the crank) and rebuild the top end, the local guy in town says that it would cost me 1100-1700 dollars, which I find crazy, so I plan on doing it myself, and get a new crank at the same time, for less. Any tips would be appreciated.

[riffraff]

I take it you have a Honda CR, so my first question is what kind of manual do you have for it?

[Hondacrrider]

I have a 2001 Honda cr 125, and I only have the bike manual, the one that comes with the bike.

[opfermanmotors]

Smack out the bearings with a hammer and a socket.  Press in the bearings using a press on the outter race or put the cases in the oven and the bearings will drop in, Honda does not reccomend using a propane torch because their cases are weaker than european bikes (Maico reccomends using a propane torch and for good reason those cases are hard as hell).  I used a propane torch anyway, worked fine since its low heat just dont over do it or you can warp the cases.  Some people also put the bearings in the freezer.  One thing tho, if your cases are hot try to greese the bearings or keep moving them, don't want to get a flat spot.  Overall, its pretty easy to rebuild a bottom and top end.

You can see me doing my CR500 here, for entertainment purposes only its not a tutorial.

http://www.maicowerk.com/Honda/1986CR500R/FullRebuild/

[JohnN]

Our very own dogger315 has a complete step by step rebuild artcle in 9 parts on rebuilding a CR250 Honda. I would start there.

http://twostrokemotocross.com/category/tech/

[admiral]

I have a 2001 Honda cr 125, and I only have the bike manual, the one that comes with the bike.

the genuine Honda service manual is a great investment. if you were any closer i would have you bring it by the shop and we would get it together in a few hours.

[Coop]

the genuine Honda service manual is a great investment.

+1, I always recommend when someone buys a bike investing in a service manual, it's the best money you'll spend if you work on your own bikes. Rebuilds are easy, but you won't really be able to separate the crank and replace the lower rod bearings on your own without the proper equipment. Crank bearings and seals in the case, top end (piston, rings, etc) all easy peasy. Rebuilding the crank is better left to a pro if you've never done it before because it needs to be perfect.

[riffraff]

Yep, I always get me a manual for any bike I get

[SachsGS]

I find "Preparation and procedure" essential to any engine overhaul. Make sure everything is spotless and clean, engine,work area, tools and even your hands. Protect all gasket mating surfaces and lubricate everything on reassembly. Keep an eye on small details when putting the engine back together, for example, you may have to shift the position of a seal slightly if it has worn a groove in the shaft. Basically just take your time and do the job right.

I once had a XR200 come in and the guy said it shifted "funny" after he had overhauled it. I pulled the Honda apart and the owner had forgotten to reinstall transmission bearings on one side of the engine! Believe it or not the XR ran! Another time a Yamaha Enduro came in with some strange banging and crashing coming from the trans.I pulled the engine apart and discovered a 1/2" dia. ball bearing loose in the transmission. I asked the owner about this and he said that after he overhauled the engine he found the ballbearing lying on the bench so he "just threw it in"!

[Hondacrrider]

Well, luckily, this kit has the crank coming preassembled, which I am very thankful for, but, do you guys think i will gain any horsepower from this?

[Chokey]

Well, luckily, this kit has the crank coming preassembled, which I am very thankful for, but, do you guys think i will gain any horsepower from this?

From the crank? No. From a fresh top-end? Absolutely. Replacing a worn out top-end wil bring back the power that you don't realize you've lost because it happens so gradually.

Be sure to service the power valve assembly. I also replace my reeds and repack my silencer at rebuild time, and give it a new plug as well.

[evo550]

Smack out the bearings with a hammer and a socket.  Press in the bearings using a press on the outter race or put the cases in the oven and the bearings will drop in, Honda does not reccomend using a propane torch because their cases are weaker than european bikes (Maico reccomends using a propane torch and for good reason those cases are hard as hell).  I used a propane torch anyway, worked fine since its low heat just dont over do it or you can warp the cases.  Some people also put the bearings in the freezer.  One thing tho, if your cases are hot try to greese the bearings or keep moving them, don't want to get a flat spot.  Overall, its pretty easy to rebuild a bottom and top end.

You can see me doing my CR500 here, for entertainment purposes only its not a tutorial.

http://www.maicowerk.com/Honda/1986CR500R/FullRebuild/

Heat is a popular option to the cases, but if your not comfortable with fire, you can also put the bearings in the freezer for an hour to achieve the same results.

[opfermanmotors]

Harbor Frieght sells presses for like $130.

1984 KTM 495 Rebuild Part 1: Bearings

[G-MONEY]

Thier is another way to deal with bearings and I'm suprised no one has mentioned this in the past. I think 2t institute probably knows this trick. What we are talking about is something called thermal differential it is the swing in the temp range to fit things  together  that have an iterference fit. That means the space between the bearing and hole in this case measures around a human hair cut into 1/4ths yes a very small difference.
So creating a temp difference between the hole and the bearing needs to be around 200 degrees f. heat exspands cold shrinks.Ok hear it is dry ice and lacqure thinner or acetone will get you well bellow minus 150 degrees.So drop the bearing in the mix for a few minutes pull it out it out with kitchen thongs and it will drop right ih the hole. I find this easier than dealing with really hot case halfs. Again bearings at minus 150 case halfs at 70 degrees gives you a temp swing of 220 degrees. 

[2T Institute]

Thier is another way to deal with bearings and I'm suprised no one has mentioned this in the past. I think 2t institute probably knows this trick. What we are talking about is something called thermal differential it is the swing in the temp range to fit things  together  that have an iterference fit. That means the space between the bearing and hole in this case measures around a human hair cut into 1/4ths yes a very small difference.
So creating a temp difference between the hole and the bearing needs to be around 200 degrees f. heat exspands cold shrinks.Ok hear it is dry ice and lacqure thinner or acetone will get you well bellow minus 150 degrees.So drop the bearing in the mix for a few minutes pull it out it out with kitchen thongs and it will drop right ih the hole. I find this easier than dealing with really hot case halfs. Again bearings at minus 150 case halfs at 70 degrees gives you a temp swing of 220 degrees. 

100% correct. Pressing in bearings without heat/freezing wil eventualy lead to the bearing bore being enlarged, the heat/freeze trick makes the press redundant