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Attempting a full rebuild on my 250

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I've decided to do a full rebuild on the my 03 CR 250R. What are some good links that people would recommend/videos for walkthroughs? There is one on that is on youtube that is, ok. Doesn't mention anything about the crank (I think it is end play?) and how to check that. 

 

Ill keep the post updated as I work my way through the rebuild, assuming I have time. Im only home on the weekends so it should make things... interesting. 

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Also, anything else I should be on the lookout for other then the crank tolerances? 

 

Thanks! 

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there's this great video called the service manual. walks you through everything : P

..then you can supplement certain things on youtube.

 

So you want to rebuild everything, or just the engine i don't get it. Suspension, Link bearings. Steering... yeah there isn't really much more to a dirt bike.

 

as for checking the cranks, the manual will tell you what and how to check... but i think what you're talking about is crank runout.

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Sorry, that was about as clear as mud. I meant the engine. Top to bottom. Sent the jug off to be sleeved. Bottom end already arrived and ordered case splitter and flywheel puller today. Didn't get the tool used to press the crank back in, what is that thing called exactly? 

 

As for the service manuals... haha. There is some truth to that. Some are well written, some are not. 

 

Yes, I believe crank run out is what I need to check for. I was told 18 thousands is a good standard. I am going to have to look into finding out how to check mine once I start getting things back together. 

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oem service manuel.Do not waste your money on others.Ebay great resource for used manuels

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If you dont have a copy of the service manual, you really need to get one just to have the torque specs, bearing depths, and assembly/disassembly procedures.

 

If you go to google.com and type in 2003 Cr250 service manual, there will be a link that pops up that was on ThumperTalk a while back- The thread was "Smoke'em while ya got'em 2003 Cr250 service manual" 

 

You can click that and go to the posters mediafire account and download a very good copy of the manual complete with PDF bookmarks. 

 

American Honda sells their manuals directly through a company called Helm. www.helminc.com  You can buy the manual there for 49.95.

 

Ebay is also a great place to find the manual, either new or used.

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Sorry, that was about as clear as mud. I meant the engine. Top to bottom. Sent the jug off to be sleeved. Bottom end already arrived and ordered case splitter and flywheel puller today. Didn't get the tool used to press the crank back in, what is that thing called exactly? 

 

As for the service manuals... haha. There is some truth to that. Some are well written, some are not. 

 

Yes, I believe crank run out is what I need to check for. I was told 18 thousands is a good standard. I am going to have to look into finding out how to check mine once I start getting things back together. 

If you had posted before before you sent the cylinder out to be sleeved you would have heard a collective NO. Replating fully restores your cylinder to factory specs. Sleeveing is vintage technology in a modern design. It would not have cost you much more if any to re-plate. About being able to bore? You are at the mercy of the sleever to buy pistons.

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Yes, I believe crank run out is what I need to check for. I was told 18 thousands is a good standard. I am going to have to look into finding out how to check mine once I start getting things back together. 

Just a heads up OEM spec for crank runout is about .0015" which is 1.5 Thousandths. If your crank is running out 18 thousandths, you're going to have some major vibration coming from your bottom end...

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Oh boy who said re-sleeve?!?!!

 

dude. no. get your jug back and spend another $70 to get it re-plated -.-

 

think about heat conduction. Aluminum transfers heat about 4x better than steel.. plus by sleeving you have an imperfect contact between two materials (steel sleeve and aluminum), that also expand at different rates (AL about twice more than steel) so probably 5x worse heat transfer.  Basically you will knock (pre-ignition from a hot combustion chamber) and overheat forever (because you can't get the heat out to the coolant/radiators). Yeah and the re-plate (nickel chromium carbide) is harder than hardened steel sleeve... if a good hardened one is even used.

 

 

Yes, I believe crank run out is what I need to check for. I was told 18 thousands is a good standard. I am going to have to look into finding out how to check mine once I start getting things back together. 

You need blocks and a dial at a minimum to check. both of which are expensive. go to a shop for that. I have that stuff at work for example (we design engines here) so i get use a lathe for this kind of stuff.

 

Also don't believe anything, verify it with the manual man... and its a honda manual, trust all of us. its well written. has exactly what you need. step by step. Most things that you see and read online are mediocre at best. As you say, some things are well written, then 98% of everything else is not and that is if you are lucky to find some model specific info.

 

Anyways, anyone can butcher a rebuild. Take our advice and build your engine like a hombre with dos grande hairy cojones. This is not legos though given the simplicity of a 2-stroke i'm sure it'll last a bit if thrown together... but as i said you'll be wrenching after every ride, running hot (a bitch with jetting), so running like doo doo, over heating, noises yada yada yada. i'm out.

 

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Oh boy who said re-sleeve?!?!!

 

dude. no. get your jug back and spend another $70 to get it re-plated -.-

 

think about heat conduction. Aluminum transfers heat about 4x better than steel.. plus by sleeving you have an imperfect contact between two materials (steel sleeve and aluminum), that also expand at different rates (AL about twice more than steel) so probably 5x worse heat transfer.  Basically you will knock (pre-ignition from a hot combustion chamber) and overheat forever (because you can't get the heat out to the coolant/radiators). Yeah and the re-plate (nickel chromium carbide) is harder than hardened steel sleeve... if a good hardened one is even used.

 

You need blocks and a dial at a minimum to check. both of which are expensive. go to a shop for that. I have that stuff at work for example (we design engines here) so i get use a lathe for this kind of stuff.

 

Also don't believe anything, verify it with the manual man... and its a honda manual, trust all of us. its well written. has exactly what you need. step by step. Most things that you see and read online are mediocre at best. As you say, some things are well written, then 98% of everything else is not and that is if you are lucky to find some model specific info.

 

Anyways, anyone can butcher a rebuild. Take our advice and build your engine like a hombre with dos grande hairy cojones. This is not legos though given the simplicity of a 2-stroke i'm sure it'll last a bit if thrown together... but as i said you'll be wrenching after every ride, running hot (a bitch with jetting), so running like doo doo, over heating, noises yada yada yada. i'm out.

 

no body use chrome on modern dirt bikes. you maybe meabt. nickel silicon carbide. NiKaSil

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Oh boy who said re-sleeve?!?!!

 

dude. no. get your jug back and spend another $70 to get it re-plated -.-

 

think about heat conduction. Aluminum transfers heat about 4x better than steel.. plus by sleeving you have an imperfect contact between two materials (steel sleeve and aluminum), that also expand at different rates (AL about twice more than steel) so probably 5x worse heat transfer.  Basically you will knock (pre-ignition from a hot combustion chamber) and overheat forever (because you can't get the heat out to the coolant/radiators). Yeah and the re-plate (nickel chromium carbide) is harder than hardened steel sleeve... if a good hardened one is even used.

 

You need blocks and a dial at a minimum to check. both of which are expensive. go to a shop for that. I have that stuff at work for example (we design engines here) so i get use a lathe for this kind of stuff.

 

Also don't believe anything, verify it with the manual man... and its a honda manual, trust all of us. its well written. has exactly what you need. step by step. Most things that you see and read online are mediocre at best. As you say, some things are well written, then 98% of everything else is not and that is if you are lucky to find some model specific info.

 

Anyways, anyone can butcher a rebuild. Take our advice and build your engine like a hombre with dos grande hairy cojones. This is not legos though given the simplicity of a 2-stroke i'm sure it'll last a bit if thrown together... but as i said you'll be wrenching after every ride, running hot (a bitch with jetting), so running like doo doo, over heating, noises yada yada yada. i'm out.

 

 

 

 

 

ok just for the sake of argument and with all due respect I must say that I have to disagree about the sleave thing. I bought my 01 with a sleaved cylinder{didn't know it when I bought it} I don't have any of the above issues...over heating or jetting issues,i live in southern AZ and have ridden in a few 100 + degree days and haven't over heated my bike once,also rebuilt the top end with a stock piston and rings as my sleave is in perfect spec for an A cylinder...all that being said im not stoked about the sleave and will be buying a new stock cylinder when I get a chance...just sayin

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I will be moving to AZ soon, so I take some comfort in knowing that somebody else has a sleeved bike running in those temps down there once it is rebuilt. 

 

Got the case split. Now, just need to remove the bearings and pick up some other things to move forward. I travel for work so I won't have a chance to really put in any wrench time until next Saturday. : (

 

As for the sleeve/plating, Ill call in the morning and see if they have already ordered the piston and started the sleeve process. If so, guess Ill have to wait till next time to do the nikasil plating. 

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Ok shave some surface off the bottom of the cylinder..epoxy you're transfer port ..resurface you're dome to compensate for cyl drop..buy bearings gaskets ect on eBay always save at least 5-10$ on most of all purchases ...ohh and make sure you have all ...aaalllll case bolts before using case splitter I've seen a perfectly good case ruined by some guy who didnt double check....

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If you are going to redo the crank, use an 05-07 stock crank. It doesn't have the tin cans on it. 

Edited by SMarquez

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