2003 cr250r rc valve problem

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6/7/2019 7:55 AM
Edited Date/Time: 6/7/2019 7:56 AM

i have a 2003 cr250r that my son uses for mx. it has pc pipe and silencer, vforce reeds, pwk carb. the bike has always ran flawless. last sunday he was racing and it was muddy. it ran beautiful most of the day and in the last heat it developed a hesitation and skip in the mid rpms. i tore everything down, new air filter, cleaned carb which is brand new 2 months ago(only has about 5 rides on it), replaced reeds and gaskets, resealed air box, new fuel filter, new plug, and it still does it. jetting was always very good with this carb setup. i pulled the rc cover and the valve is full counter clockwise at idle , but the valve twitches at idle, and doesnt open consistantly at rpm. when the rpms come up the valve twitches more, every once and a while it will go full clock wise most of the time not. i pulled the cables and they move fine, the butterfly turn with very little effort. which way is open and closed on this.mine is ccw at idle the twitces clock wise. here a some videos of the valve

rc valve

rc valve 2

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6/7/2019 8:18 AM

That's a servo motor problem, leave the pv cover off, Honda built in an indicator upon intial start up, the pv servo motor will cycle once to prove it's in good working order, without any throttle input or increase in rev, it will go from closed to open to closed again, if It fires up and never returns to the resting or closed pisition, your servo motor needs to be replaced. It's seriously the biggest downfall of these engines, is fhe simple fact that Honda stoped making the servo motors, and I know this because literally ordered the last one from Honda Canada, I can't speak for the states, and the supply down there, but up here, there's no more available from Honda here, and gojng eBay, unless it's bnib never been used, it's a gamble on used ones as well because you don't know if the person selling it has properly tested it, or even know about testing their operation, it could work, it could not, its chance taken on these servo motors unfortunately.

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6/7/2019 9:38 AM

would this cause a skip or hesitation at mid throttle, ive read alot about broken wires going to cdi and some cases of a bad cdi which is also not available any more. so i have to look in to it some more. he loves this bike and we got some money in to it, cant belive we would have to junk a 2003 bike due to lack of parts. i see some used stuff on ebay but 400 for cdi and servo used seems very high priced.

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6/7/2019 10:20 AM

I know, it sucks, they are such beautiful bikes, and the engine is vastly superior to the old gen engines, but there is hope, and it comes in the form of the old gen engine lol. It may be a teeny step backwards power wise, but power delivery wise, a broader powerband with minimal tuning vs, what's needed to really make these case reed engines shine. And the swap doesn't really require much in the way of modifications, there's plenty of info on it out there and I believe even a airbox kit on eBay, as Iv looked into doing this swap and do intend to do the 97-01 engine swap into my recently acquired 05 crf450r. but finding a used 94-01 cr250 to just reap the engine from shouldn't be an issue either. But rule out all options though, make sure it isn't the servo motor and check your harness out, but if there are no faults in the harnes, then maybe try and find another ecu off an 03 and try it, if not least you have ruled out the other options, and have narrowed it down to the servo motor. But there is a solution!
No matter what, if he loves the frame enough, (NOTHING whips or handles like a honda) I loved mine, all three of them, and had planned to buy another one to do the old gen swap, but ended up thinking that taking half the strokes and 200cc's off a crf450r sounds like fun. So I switched tactics

Hopefully someone with some real knowledge on testing the ecu's as Iv never had to do anything like that before, will see this and give some more insight to the possible issue, but from my experience with these engines have been the servo motors life spans are comming to an end, lots of use or little use, they are all aging, and time takes its toll on electrical components, its next to impossible to stop copper cores from oxidizing over time

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6/7/2019 10:32 AM

thanks for all your insight, i see threads of people who have changed the motor inside the servo so i way try that. ill follow up how i make out

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6/7/2019 10:35 AM

Oh totally! Rewinding the core is an option for sure, I may be a high voltage electrician, but Iv never even attempted to rewire a copper winding, lol, and never even thought of that route either, sounds like you got it covered

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6/7/2019 11:16 AM

actually i just called bristol racing in syracuse ny and he says he has the servo motors brand new! so i just bought one from him. he said their race team used to race the cr250r for years. i asked about the cdi and he said they never go bad, he never replaced one, so i have some hope! i also got 2 new cables. so hopefully this will remedy my issue. thanks again

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6/7/2019 11:28 AM
Edited Date/Time: 6/7/2019 7:38 PM

Pretty sure you can hop on eBay and buy a mabuchi rs365sh electric motor and it should work. It's cool you got the whole assembly tho.

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6/7/2019 12:41 PM

Oooooooo-woooo! That's hot news!! I'm gonna have to keep that in mind that makes the reed case engine way more probable for an engine swap, that's the only downfall, cuz for years there was zero aftermarket support for the servo motors, that's seriously sweet news!

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6/7/2019 1:26 PM

i hope after all this it gets rid of the bog/ hesitation in the midrange

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6/7/2019 7:25 PM
Edited Date/Time: 6/7/2019 7:39 PM

15tc150 wrote:

Oooooooo-woooo! That's hot news!! I'm gonna have to keep that in mind that makes the reed case engine way more probable for an engine swap, that's the only downfall, cuz for years there was zero aftermarket support for the servo motors, that's seriously sweet news!

There are some threads about it, I think black diamonds CR250 thread was where I first saw it. You might need to head over to a hobby shop so they can press the little plastic gear on/off the shaft. I've got one and it looks like it would work no problem.

EDIT. It's called a mabuchi RS365sh

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6/8/2019 5:24 AM

Well, that's really neat to know! Cuz the Reed case engine is a bullet around a track, it's so deceptively fast, and with focus in the right areas, its one amazing engine.
There must have been a heck of a lot
More people doing this kinda stuff in the states, I know there was a business I think in Oregon, that offered a motor rewind service, but it was pretty expensive, and logistically, cheaper for me to just buy one from Honda. This was probably aboot 8 years ago though, and I definitely wasn't looking on here at that point lol. Ima look around a bit, this is a game changer

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6/15/2019 1:56 PM

Go on ebay and search for CRB600RR servo motor. They're readily available for under $20. Most of them have not been exposed to water or mud (read not much corrosion inside the case which is a problem on the CR250)
The CBR electric motor will fit in the CR250 case. Remove the CBR600 motor from the CBR case and install in the CR250 case..
You use the stock CR250 plastic gearing.
While you are swapping motors, be sure to seal the wire bundle where it enters the case with your choice of sealant. Add a little sealant to the case halves to supplement the sealing of the O-ring.
The CBR600RR servo uses the same Sumitomo connector that Honda specs for the CR250.
Problem solved.

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6/15/2019 4:59 PM

OP - Have a spare 02 CDI box with approx. 5 hrs. of run time if the RC motor isn't the issue. Let me know if you would be interested in it.

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Speak softly and carry a big stick.

6/15/2019 9:23 PM
Edited Date/Time: 6/16/2019 4:51 AM

Did you search for a broken wire going to the cdi? Mine did something very similar to what you are describing. Ended up being a broken wire. Fixed the wire and the problem went away.

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No brains, No headaches.

6/16/2019 8:14 AM

40 wrote:

Go on ebay and search for CRB600RR servo motor. They're readily available for under $20. Most of them have not been exposed to water or mud (read not much corrosion inside the case which is a problem on the CR250)
The CBR electric motor will fit in the CR250 case. Remove the CBR600 motor from the CBR case and install in the CR250 case..
You use the stock CR250 plastic gearing.
While you are swapping motors, be sure to seal the wire bundle where it enters the case with your choice of sealant. Add a little sealant to the case halves to supplement the sealing of the O-ring.
The CBR600RR servo uses the same Sumitomo connector that Honda specs for the CR250.
Problem solved.

That's pretty neat, never knew Honda did a servo motor butterfly valve in their exhaust piping, and super cool they reused the winding in other applications. All this Info is duely noted, as Iv stayed away from these bikes due to this issue, mechanical pv actuators don't fail, so to have something easily fixable, reaaaaaally makes me want to bring another cr250 home lol.

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6/16/2019 8:20 AM

Thanks for all the replies. I bought the new motor fro. Bristol but I found a broken wire to the motor so I'll keep the motor as a spare because it sounds like on day I will need it

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