2003 Honda CR 250

brooklynevans
Edited Date/Time 11/10/2018 10:56am
Been reading majority of the 2 stroke build threads for a few months now, however this is my first time posting a build.
Picked up this bike today, looks relatively ‘tidy’ from a distance, but needs a lot of work. Will probably be in quite a tight budget, so no Ti bolts or factory parts unfortunately.

This is as soon as I got the bike home (dog had to get in the picture)



Just to show how neglected this bike is; so many rusted parts


Started stripping the bike down almost immediately. Didn’t get too far


Any advice on mods or things to look out for would be much appreciated??
|
Kx125rider 7/29/2018 6:25pm
7/29/2018 6:25pm
They had problems with the airbox leaking and I think a lot of guys add an extra base gasket but I like the all red look good luck with it
1
Matt Fisher 7/29/2018 6:37pm
7/29/2018 6:37pm
Imo, the two best mods are
1) properly sealing the airbox to airboot junction https://www.mxbonz.com/cnc_airbox_fix.htm
2) fixing the terrible squish clearance from the factory. Cheapest way to do so is run a 05+ base gasket. That also lowers the cylinder a touch so it helps boost low-end power a smidge. An even better way is to have the head modified or have the base of the cylinder machined. Any of these options will increase power, make it easier to jet, and decrease the likelihood of detonation.
1
brooklynevans 7/30/2018 11:12am
7/30/2018 11:12am
Matt Fisher wrote:
Imo, the two best mods are 1) properly sealing the airbox to airboot junction https://www.mxbonz.com/cnc_airbox_fix.htm 2) fixing the terrible squish clearance from the factory. Cheapest way...
Imo, the two best mods are
1) properly sealing the airbox to airboot junction https://www.mxbonz.com/cnc_airbox_fix.htm
2) fixing the terrible squish clearance from the factory. Cheapest way to do so is run a 05+ base gasket. That also lowers the cylinder a touch so it helps boost low-end power a smidge. An even better way is to have the head modified or have the base of the cylinder machined. Any of these options will increase power, make it easier to jet, and decrease the likelihood of detonation.
Thank you very much for the info Matt. Don’t think MxBonz sealer kits are sold in UK but I will try to find something to fix it.
I’ll probably go with the 05+ base gasket initially then, and perhaps look into head work at a later date.

The Shop

See All »
brooklynevans 7/31/2018 12:55pm
7/31/2018 12:55pm
Got a small amount of time on the bike tonight. Not many more parts to go and it should be ready to start the clean up.

One problem I came across was a seized screw in the throttle housing which has also rounded off. I’ve tried WD 40 and all sizes of screwdrivers, but cannot get it out. Think I may have to resort to drilling it out..
rollin64caddy 7/31/2018 1:30pm
7/31/2018 1:30pm
id try an impact driver before trying to drill it out. the guy doing the TM build right now did a cr like yours a while back. I'm sure there is a ton of info you could use if you need help or ideas.
brooklynevans 8/1/2018 1:02pm
8/1/2018 1:02pm
rollin64caddy wrote:
id try an impact driver before trying to drill it out. the guy doing the TM build right now did a cr like yours a while...
id try an impact driver before trying to drill it out. the guy doing the TM build right now did a cr like yours a while back. I'm sure there is a ton of info you could use if you need help or ideas.
I’ve read blackdiamonds thread before, best bike on here I’d say. Read basically every other cr 250 build as well, but on some of the early ones I cannot seem to load the pictures up??
brooklynevans 8/2/2018 12:43pm
8/2/2018 12:43pm Edited Date/Time 8/2/2018 12:44pm
Got the frame and swing arm cleaned up today. Used turtle wax wheel cleaner with green scour/scotch brite pad (just what is sold locally and cheap).

Before:




After:



Some pretty bad gouges on the swing arm. Not entirely sure what to do about them as they’re deep.
brooklynevans 8/4/2018 9:28am
8/4/2018 9:28am
Parts I have cleaned up so far. Used a blow torch to get the airbox back to black.


Almost finished removing the casting marks from the dog bone, took me over 3 hours. Never before have I appreciated the effort it takes for this process using sand paper!

deccr250
Profile picture for user deccr250
Posts
449
Joined
2/25/2018
Location
GB
deccr250 8/4/2018 12:09pm
8/4/2018 12:09pm
Keep up the good work bud, it’s looking good. Recently built a 2002 CR250 so any questions you have, I’ll do my best to answer Smile
brooklynevans 8/5/2018 3:28am
8/5/2018 3:28am Edited Date/Time 8/5/2018 3:29am
deccr250 wrote:
Keep up the good work bud, it’s looking good. Recently built a 2002 CR250 so any questions you have, I’ll do my best to answer Smile
Thanks, that would be great. I’ll drop you a message if I’m stuck on anything. It won’t be anywhere near as nice as yours, but just trying to do my best with minimal parts on a small budget
brooklynevans 8/5/2018 9:52am
8/5/2018 9:52am
Took the cylinder head off and there’s quite a few marks where previous pistons must have detonated. I’ve had this on another used bike I bought and local dealer said to sand it down slightly.
Bike runs great, has a new piston, but would just like some advice as to what everyone else would do?

Got the dog bone cleaned up bit better as well.

deccr250
Profile picture for user deccr250
Posts
449
Joined
2/25/2018
Location
GB
deccr250 8/5/2018 1:53pm
8/5/2018 1:53pm
brooklynevans wrote:
Took the cylinder head off and there’s quite a few marks where previous pistons must have detonated. I’ve had this on another used bike I bought...
Took the cylinder head off and there’s quite a few marks where previous pistons must have detonated. I’ve had this on another used bike I bought and local dealer said to sand it down slightly.
Bike runs great, has a new piston, but would just like some advice as to what everyone else would do?

Got the dog bone cleaned up bit better as well.

How deep are the marks on the cylinder head?? When I rebuilt mine it had a few small marks on the cylinder head in the same place as yours. I spent a bit of time cleaning it up and it came up near new. If they aren’t too deep then I’d have a go at cleaning it up and see how you get on.
Have you got round to checking the power valve unit over yet? You must’ve had the power valve cover off as you’ve removed the head but I’m wondering if you’ve had a chance to look at it closer? The reason I ask is because when I started stripping my ‘02 CR build down, the power valve was rusted up and filthy and the cable was ridiculously slack which is a common thing for these bikes when they haven’t been maintained correctly Smile
brooklynevans 8/6/2018 1:51am
8/6/2018 1:51am
brooklynevans wrote:
Took the cylinder head off and there’s quite a few marks where previous pistons must have detonated. I’ve had this on another used bike I bought...
Took the cylinder head off and there’s quite a few marks where previous pistons must have detonated. I’ve had this on another used bike I bought and local dealer said to sand it down slightly.
Bike runs great, has a new piston, but would just like some advice as to what everyone else would do?

Got the dog bone cleaned up bit better as well.

deccr250 wrote:
How deep are the marks on the cylinder head?? When I rebuilt mine it had a few small marks on the cylinder head in the same...
How deep are the marks on the cylinder head?? When I rebuilt mine it had a few small marks on the cylinder head in the same place as yours. I spent a bit of time cleaning it up and it came up near new. If they aren’t too deep then I’d have a go at cleaning it up and see how you get on.
Have you got round to checking the power valve unit over yet? You must’ve had the power valve cover off as you’ve removed the head but I’m wondering if you’ve had a chance to look at it closer? The reason I ask is because when I started stripping my ‘02 CR build down, the power valve was rusted up and filthy and the cable was ridiculously slack which is a common thing for these bikes when they haven’t been maintained correctly Smile
Did you use some fine sandpaper to clean it up? Marks aren’t too deep, so I’ll give it a go without taking much material off.

Yes I’ve had a look at the powervalve mechanism. It looked pretty clean and the one cable looked new. I haven’t had a look at the butterfly valves in the cylinder yet, but will get round to cleaning it soon. Thanks for the help
deccr250
Profile picture for user deccr250
Posts
449
Joined
2/25/2018
Location
GB
deccr250 8/6/2018 6:39am
8/6/2018 6:39am
brooklynevans wrote:
Did you use some fine sandpaper to clean it up? Marks aren’t too deep, so I’ll give it a go without taking much material off. Yes...
Did you use some fine sandpaper to clean it up? Marks aren’t too deep, so I’ll give it a go without taking much material off.

Yes I’ve had a look at the powervalve mechanism. It looked pretty clean and the one cable looked new. I haven’t had a look at the butterfly valves in the cylinder yet, but will get round to cleaning it soon. Thanks for the help
One cable on the power valves is always prone to snapping, which would explain why one looks new. Probably been replaced at some point!
With the marks on the cylinder head I just used a scotchbrite pad and WD40 to clean it up and then used very fine sandpaper to take the fine marks off.
Tip...get the fine sandpaper and rub it against itself to make it even finer as you only want to use a very fine sandpaper to rub it down Smile
brooklynevans 8/6/2018 9:32am
8/6/2018 9:32am
brooklynevans wrote:
Did you use some fine sandpaper to clean it up? Marks aren’t too deep, so I’ll give it a go without taking much material off. Yes...
Did you use some fine sandpaper to clean it up? Marks aren’t too deep, so I’ll give it a go without taking much material off.

Yes I’ve had a look at the powervalve mechanism. It looked pretty clean and the one cable looked new. I haven’t had a look at the butterfly valves in the cylinder yet, but will get round to cleaning it soon. Thanks for the help
deccr250 wrote:
One cable on the power valves is always prone to snapping, which would explain why one looks new. Probably been replaced at some point! With the...
One cable on the power valves is always prone to snapping, which would explain why one looks new. Probably been replaced at some point!
With the marks on the cylinder head I just used a scotchbrite pad and WD40 to clean it up and then used very fine sandpaper to take the fine marks off.
Tip...get the fine sandpaper and rub it against itself to make it even finer as you only want to use a very fine sandpaper to rub it down Smile
Thanks very much for the help. I’ll give it a go now

Pit Row

See All »
deccr250
Profile picture for user deccr250
Posts
449
Joined
2/25/2018
Location
GB
deccr250 8/6/2018 10:21am
8/6/2018 10:21am
brooklynevans wrote:
Thanks very much for the help. I’ll give it a go now
No worries, let me know how you get on
brooklynevans 8/6/2018 1:24pm
8/6/2018 1:24pm
brooklynevans wrote:
Thanks very much for the help. I’ll give it a go now
deccr250 wrote:
No worries, let me know how you get on
Cleaned the head up a bit, but the marks around the edge of the insert are quite deep. Tried a bit of sand paper but didn’t want to take too much material off.

Also wondering if you’d be able to tell me how you remove the pin which holds the power valve in place. Doesn’t want to come out. Haven’t yet resorted to pliers as don’t want to damage thread.
deccr250
Profile picture for user deccr250
Posts
449
Joined
2/25/2018
Location
GB
deccr250 8/6/2018 1:56pm
8/6/2018 1:56pm Edited Date/Time 8/6/2018 1:57pm
brooklynevans wrote:
Cleaned the head up a bit, but the marks around the edge of the insert are quite deep. Tried a bit of sand paper but didn’t...
Cleaned the head up a bit, but the marks around the edge of the insert are quite deep. Tried a bit of sand paper but didn’t want to take too much material off.

Also wondering if you’d be able to tell me how you remove the pin which holds the power valve in place. Doesn’t want to come out. Haven’t yet resorted to pliers as don’t want to damage thread.
The power valve rod you’re referring to will be stuck in place because of the carbon that’s built up around it. If you have all the power valve mechanism off, then refit the small nut that holds the butterfly on but put a small washer behind the nut so you won’t damage it..then put a pair of pliers behind the nut and pull! It will come, it’s just stuck in there because of the carbon build up. If you can get someone to hold the pliers whilst you pull the cylinder head itself (if that makes sense) then that should get it out quicker and easier. Let me know how it goes Smile
1
captmoto
Profile picture for user captmoto
Posts
5377
Joined
4/22/2009
Location
Rancho Cucamonga, CA US
captmoto 8/6/2018 8:28pm
8/6/2018 8:28pm
Get ahold of Phil Denton Engineering. He's on board here and somewhere in GB. He might be able to fix and mod your head. If it can't be fixed obviously replace.
If you are cleaning up your cylinder you want to use a scotchbrite pad and your WD40, not sandpaper. It will work and is less aggressive than sand paper. Then use hot soapy water and wash and rinse until a paper towel comes out as clean as it goes in.
2
Matt Fisher 8/7/2018 10:54am
8/7/2018 10:54am
captmoto wrote:
Get ahold of Phil Denton Engineering. He's on board here and somewhere in GB. He might be able to fix and mod your head. If it...
Get ahold of Phil Denton Engineering. He's on board here and somewhere in GB. He might be able to fix and mod your head. If it can't be fixed obviously replace.
If you are cleaning up your cylinder you want to use a scotchbrite pad and your WD40, not sandpaper. It will work and is less aggressive than sand paper. Then use hot soapy water and wash and rinse until a paper towel comes out as clean as it goes in.
Agreed. No way I'd run that head without having it machined first. The problem with just sanding it down is you'll decrease the compression while making the squish problem worse. If the dents are too deep, then the head is either welded then machined or simply replaced.
1
brooklynevans 8/10/2018 1:28pm
8/10/2018 1:28pm
Cheers for the advice. I’ll see if I can find someone to skim the head for a reasonable price. Found new ones in USA for $85, so may just enquire to see if they will post to UK.
brooklynevans 8/10/2018 1:33pm
8/10/2018 1:33pm
Searched for some screws for the front master cylinder as the ones currently on the bike are clearly not made to be on there (not a countersink bolt). Found a pack of 20 ti countersink bolts for the same price as 2 stainless steel bolts. Thought this was quite interesting. Linked them below, they’re from US as well which is convenient for most vital members
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2F…
brooklynevans 8/21/2018 12:33pm
8/21/2018 12:33pm Edited Date/Time 8/21/2018 12:34pm
Cylinder and exhaust flange were covered in oil and dirt. Got them cleaned up a bit tonight, but will give it a better scrub soon.





Still failing to get the powervalve out. Cannot get the rod which holds the valves in place to free up at all.
H4L
Profile picture for user H4L
Posts
2559
Joined
3/18/2016
Location
CA US
H4L 8/21/2018 8:45pm
8/21/2018 8:45pm
Have you tried spraying PB blaster & letting it soak - penetrate overnight ? If it's really bad you might need to repeat the process the following day.
deccr250
Profile picture for user deccr250
Posts
449
Joined
2/25/2018
Location
GB
deccr250 8/22/2018 9:35am
8/22/2018 9:35am Edited Date/Time 8/22/2018 9:35am
brooklynevans wrote:
Cylinder and exhaust flange were covered in oil and dirt. Got them cleaned up a bit tonight, but will give it a better scrub soon. [img]https://p.vitalmx.com/photos/forums/2018/08/21/281940/s1200_4BE7BEA4_3006_4457_ADAC_DF555F49F75E.jpg[/img]...
Cylinder and exhaust flange were covered in oil and dirt. Got them cleaned up a bit tonight, but will give it a better scrub soon.





Still failing to get the powervalve out. Cannot get the rod which holds the valves in place to free up at all.
They can be really tough to get out mate, spray some sort of contact cleaner in there and let it soak for a few hours. Putting some grips on there and giving it a pull won’t harm it as long as you take extra care that you aren’t levering against the head itself excessively. Put a folded towel against the head to protect it if you’re levering against it. It will come Smile
brooklynevans 8/22/2018 12:38pm
8/22/2018 12:38pm
I’ve sprayed loads of WD40 in there, and tried levering a bit with the spanner behind a nut but didn’t want to damage cylinder. I’ll try some more WD40 and mole grips with a rag behind it. Thanks for the advice
brooklynevans 8/23/2018 1:12pm
8/23/2018 1:12pm
brooklynevans wrote:
Cylinder and exhaust flange were covered in oil and dirt. Got them cleaned up a bit tonight, but will give it a better scrub soon. [img]https://p.vitalmx.com/photos/forums/2018/08/21/281940/s1200_4BE7BEA4_3006_4457_ADAC_DF555F49F75E.jpg[/img]...
Cylinder and exhaust flange were covered in oil and dirt. Got them cleaned up a bit tonight, but will give it a better scrub soon.





Still failing to get the powervalve out. Cannot get the rod which holds the valves in place to free up at all.
deccr250 wrote:
They can be really tough to get out mate, spray some sort of contact cleaner in there and let it soak for a few hours. Putting...
They can be really tough to get out mate, spray some sort of contact cleaner in there and let it soak for a few hours. Putting some grips on there and giving it a pull won’t harm it as long as you take extra care that you aren’t levering against the head itself excessively. Put a folded towel against the head to protect it if you’re levering against it. It will come Smile
Managed to get the powervalve apart tonight. Used a mole grips with rag underneath and it come out without too much effort so thank you for the advice!

Valves themselves looked like they’d never been cleaned. I spent around an hour cleaning them with green scotchbrite and WD40

Comparison of ‘cleaned’ vs dirty valve


Cleaned off all the carbon I could with the basic equipment I had to hand


Should have gaskets by the weekend so hopefully get the engine back together soon

Post a reply to: 2003 Honda CR 250