Honda 250 2-stroke mystery problem, need help!

7eleven
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3/25/2013 9:22am Edited Date/Time 4/13/2017 8:23pm
I have an 03' 250 and after I replaced a top-end last week, I started have this reoccurring problem.
It runs great for about 10 minutes, then it loses about 30% power all of a sudden. keeps running, just no revs. It turns into a moped...
What i've done so far: pulled cylinder to check piston, ok. checked reeds, changed fuel, cleaned carb.
If bike sits for a minute it goes back to running fine.
When it happened in my 2nd moto this weekend, I kept on truckin with it, like the first moto. I had a pretty big get-off in the 2nd moto and when I picked the bike back up and started it, it was back to running normal for the rest of the moto. WTF!!!

I'm lost, it may be the Devil....
711
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JB 19
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3/25/2013 9:26am
Stuck power valve?
7eleven
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3/25/2013 9:32am
JB 19 wrote:
Stuck power valve?
Have you seen a power valve do this? I don't know these Honda power valves at all. I gave it to PC and they cleaned it and put it back together, so I assumed it was right. The bike runs like a champ when it normal, and it's not heat related. I know this now after I crashed it, started it and then it ran fine again.
JB 19
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3/25/2013 9:40am Edited Date/Time 3/25/2013 10:08am
The RC valve has been known to do weird stuff if the cables are not adjusted right. I have rode an 01 that had a stuck power valve and it felt like a 175.
BD233
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3/25/2013 9:44am
Yup, it's electronic...sound like your servo motor is going out.

The Shop

PC
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3/25/2013 9:45am
JB 19 wrote:
The RC valve has been known to do weird stuff if the cables are not adjusted right. I have rode an 01 that had a stuck...
The RC valve has been known to do weird stuff if the cables are not adjusted right. I have rode an 01 that had a stuck power valve and it felt like a 175.
Werd to that. My buddies 02' CR250R ran like a 175 until the PV cables were adjusted properly.

Strange that it runs good for 10 minutes and then shits the bed though. Maybe something electrical/heat related!?!?
Runs good til it gets hot and then cant deliver enough juice.
CamP
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3/25/2013 9:56am
check the cables for proper tension. If that is okay, remove the RC cover plate when it is exhibiting the symptoms and watch the powervalve when revving the engine. If it isn't opening all the way, the servo is probably going out.

Here is a cheap servo replacement. http://www.ebay.com/itm/Mabuchi-RS-365-SH-Motor-6-to-20-VDC-Appliance-Motor-/280736861168?pt=LH_DefaultDomain_0&hash=item415d388bf0
BD233
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3/25/2013 9:58am
When my 2002 CR250 servo was going out it felt like i was riding a 250-125-250-250-250-125-250, etc....it kept cutting out/losing power. Changed the servo motor, all 250 again. >>>>>
daveoevo
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3/25/2013 10:12am
CamP wrote:
check the cables for proper tension. If that is okay, remove the RC cover plate when it is exhibiting the symptoms and watch the powervalve when...
check the cables for proper tension. If that is okay, remove the RC cover plate when it is exhibiting the symptoms and watch the powervalve when revving the engine. If it isn't opening all the way, the servo is probably going out.

Here is a cheap servo replacement. http://www.ebay.com/itm/Mabuchi-RS-365-SH-Motor-6-to-20-VDC-Appliance-Motor-/280736861168?pt=LH_DefaultDomain_0&hash=item415d388bf0
Yep pop one of those in and it will run like a champ. Had that problem with mine and honda parts are mega expensive but it is just a 12v motor.
7eleven
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3/25/2013 10:38am
Awesome! Thanks for the feedback, I get the smelly little $10 part that cost me $400 this past weekend.
1st $650

2nd $260.....grrrrr.
I had that race in the bag.
7eleven
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4/2/2013 2:24pm
Well, I changed the servo motor on friday and unfortunately this wasn't the problem. The little bastard buzzkilled my first moto on saturday at halfway again, then went back to running right for the rest of my moto's.
I took the day off work this thursday and I'm bringing a 2nd bike to my practice session, I'm just going to start changing electrical parts one by one. I'm starting with the kill switch...
As soon as I find the problem, I'll post it up!

Braap, Braap, Braaaaap!
4/2/2013 2:29pm
id bet its not the kill switch but nothing wrong with starting small
4/2/2013 3:54pm
Put a fresh plug in it, take it out and run it hard. When it starts to run really bad, immediately cut it off and pull the plug out and look at it.

If its not getting a strong spark, and the problem is electrical, i'd think the plug would look dark and wet. If the problem is some sort of funky air leak that only happens when the bike is red hot, then itll be pretty white.
lamy962
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4/2/2013 3:55pm
I'm sure you did while changing the servo motor but like a bunch of the other dudes said, but make sure to adjust those power valve cables. I had the same bike (02) and while I didn't have quite the dramatic random change in power, once I adjusted those cables it ran like new. Also it won' t fix that problem but when I threw a FMF SST pipe on it, it really helped get some more giddy up! And I hope you bought an OEM servo and not that one from eBay, I highly doubt that $7.50 little thing is the same as the $200+ Honda piece...
4/2/2013 4:01pm
lamy962 wrote:
I'm sure you did while changing the servo motor but like a bunch of the other dudes said, but make sure to adjust those power valve...
I'm sure you did while changing the servo motor but like a bunch of the other dudes said, but make sure to adjust those power valve cables. I had the same bike (02) and while I didn't have quite the dramatic random change in power, once I adjusted those cables it ran like new. Also it won' t fix that problem but when I threw a FMF SST pipe on it, it really helped get some more giddy up! And I hope you bought an OEM servo and not that one from eBay, I highly doubt that $7.50 little thing is the same as the $200+ Honda piece...
You are right. It is not the same. Its much better. The Mabuchi 365SH shortcan motor is a much better constructed Japanese unit, whereas Honda decided to use a junk chinese motor on the 02+ CRs

I reccomnned switching to the Mabuchi motor, and sealing the servo housing with a little silicone to every CR owner.

and cable tension. some will try to tell you that a little slack in the cable will soften the hit, but all you are doing there is not letting your powervalve fully function in it's range of motion. you don't want it like a banjo string, but damned close.
ToolMaker
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4/2/2013 4:07pm
I don't know if this is relevant but I had a motor one time that when the stator got warm it got funky,
I was always told they either work or don't work, no in between, but it was not the case with mine.
TM
Shawn142
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4/2/2013 4:11pm
I hate to be the bad apple but this does not sound like a power valve issue. You wouldn't lose that much hp and it wouldn't do it all of a sudden. It would be consistent from when the bike started to when it died.
JW381
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4/2/2013 4:18pm
Put a fresh plug in it, take it out and run it hard. When it starts to run really bad, immediately cut it off and pull...
Put a fresh plug in it, take it out and run it hard. When it starts to run really bad, immediately cut it off and pull the plug out and look at it.

If its not getting a strong spark, and the problem is electrical, i'd think the plug would look dark and wet. If the problem is some sort of funky air leak that only happens when the bike is red hot, then itll be pretty white.
Weird, can you elaborate on this? As you saw in my thread in pro shop, I was having a similar issue, and my plug was dark and wet. I know you said it was the jetting, and I think that was part of the issue, but I was only running one richer on the main jet than when I previously rode it a while before, so I felt like it was maybe something else. My problem was more consistent, I'd say, but I had never considered a weak spark. I'll replace that servo motor just for the heck of it.
4/2/2013 4:22pm
pull the plug out and check the spark with the lights off. if the spark is bright blue, you are good. if it is yellow or orange, you have an issue.
JW381
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4/2/2013 4:24pm
pull the plug out and check the spark with the lights off. if the spark is bright blue, you are good. if it is yellow or...
pull the plug out and check the spark with the lights off. if the spark is bright blue, you are good. if it is yellow or orange, you have an issue.
Thanks for this, easy way to check too. Any guess on where to start if it's yellow or orange? I have brand new plugs, so I'll throw one in and check the color. I'll also bring someone else along for verification, as I'm color blind, and afraid of the dark.
malachi177
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4/2/2013 4:29pm
ToolMaker wrote:
I don't know if this is relevant but I had a motor one time that when the stator got warm it got funky, I was always...
I don't know if this is relevant but I had a motor one time that when the stator got warm it got funky,
I was always told they either work or don't work, no in between, but it was not the case with mine.
TM
I've have this problem^^^ with my 08 RM125 right now. Weird how it starts fine but once warm it starts running really strange and will idle down crazy low without stallingBlink My friend (mechanic) and I thought it was the stator. I decided to take it to the Suzuki dealer and have them check everything just to make sure. They said everything electronic tested out and it's your CDI. So I got a new CDI put it in and nope not the CDI. Of course Suzuki now says there's no returns on electricalEvilEvil I have an Electrosport aftermarket stator coming in the mail.

Good luck 7 eleven!!
JW381
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4/2/2013 4:33pm
ToolMaker wrote:
I don't know if this is relevant but I had a motor one time that when the stator got warm it got funky, I was always...
I don't know if this is relevant but I had a motor one time that when the stator got warm it got funky,
I was always told they either work or don't work, no in between, but it was not the case with mine.
TM
malachi177 wrote:
I've have this problem^^^ with my 08 RM125 right now. Weird how it starts fine but once warm it starts running really strange and will idle...
I've have this problem^^^ with my 08 RM125 right now. Weird how it starts fine but once warm it starts running really strange and will idle down crazy low without stallingBlink My friend (mechanic) and I thought it was the stator. I decided to take it to the Suzuki dealer and have them check everything just to make sure. They said everything electronic tested out and it's your CDI. So I got a new CDI put it in and nope not the CDI. Of course Suzuki now says there's no returns on electricalEvilEvil I have an Electrosport aftermarket stator coming in the mail.

Good luck 7 eleven!!
Sometimes I question why I got back into the world's most expensive hobby, working 25-30 hours a week while going to skewl. So expensive, but what can you expect considering the abuse we put these bikes thru?
4/2/2013 4:43pm
Did you check if you left a plastic bag on the air filter from the last time you cleaned it? I did that once and I am taking that mistake to my grave aside from posting it here.
7eleven
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4/2/2013 4:45pm
I am 99% sure this is electrical. After it turned to moped mode last saturday in the 1st moto, it ran like a champ in the next 3 moto's. These are 20 minute moto's, so if it was mechanical I truly doubt it would run fine the rest of the day.

Like I said earlier, I crashed it late moto pretty hard, picked it up and bump started it and she was back to ripping mode! so there's the only when it's hot factor out the window...

I hate raceday testing!
7eleven
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4/2/2013 4:50pm
Did you check if you left a plastic bag on the air filter from the last time you cleaned it? I did that once and I...
Did you check if you left a plastic bag on the air filter from the last time you cleaned it? I did that once and I am taking that mistake to my grave aside from posting it here.
haha, we've all done it i'm sure.
MR. X
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4/2/2013 5:00pm
Is the vent line on the gas cap plugged ?
wacker
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4/2/2013 5:12pm
I had a 2003 CR 250 that acted similar. I also thought it was possessed by the devil and sold it. Wish I had more help for you but I don't like demon bikes.

Don't think this would necessarily cause the same symptoms, but after it was gone and talking to many people we figured it was probably the stator side main seal. Honda had a huge mess of a problem with those and I even saw off the showroom bikes dripping oil.
mxtweeker
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4/2/2013 5:56pm
wacker wrote:
I had a 2003 CR 250 that acted similar. I also thought it was possessed by the devil and sold it. Wish I had more help...
I had a 2003 CR 250 that acted similar. I also thought it was possessed by the devil and sold it. Wish I had more help for you but I don't like demon bikes.

Don't think this would necessarily cause the same symptoms, but after it was gone and talking to many people we figured it was probably the stator side main seal. Honda had a huge mess of a problem with those and I even saw off the showroom bikes dripping oil.
Probably the bike 7-11 bought..
malachi177
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4/2/2013 5:57pm Edited Date/Time 4/2/2013 6:00pm
if your spark is weak, start with the thing that is attached to the plug....
No shit Sherlock....I mean Jefferson :-) First thing I did was check the kill switch, second was a new plug cap because it had a higher resistance then it was supposed to...made no difference. Gone through everything. We think it's the pulsar coil on the stator.

Electrical issues are brutal, more frustrating then anything else.
JW381
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4/2/2013 6:58pm
if your spark is weak, start with the thing that is attached to the plug....
malachi177 wrote:
No shit Sherlock....I mean Jefferson :-) First thing I did was check the kill switch, second was a new plug cap because it had a higher...
No shit Sherlock....I mean Jefferson :-) First thing I did was check the kill switch, second was a new plug cap because it had a higher resistance then it was supposed to...made no difference. Gone through everything. We think it's the pulsar coil on the stator.

Electrical issues are brutal, more frustrating then anything else.
Now I am so confused.. my 04 has never been very hard to start, 3-4 kicks at most on a cold start. Just checked my spark after reading what Sherlock said, and I cannot get any spark at all? I have the cap on, I've put the plug end on many different surfaces, move the kickstarter, no spark? How is this possible when the bike runs and starts (although not perfectly, routinely)?

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