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Author Topic: CR250R Idle pulsing?? (+top end)  (Read 6505 times)

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Offline Taco

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CR250R Idle pulsing?? (+top end)
« on: May 23, 2011, 11:18:42 AM »
So I have a 1993 CR250R and went riding yesterday, start of the day the bike did great, idled perfectly. However, After some hours and the engine got warmed up, the idle started acting funny. I'm not sure how to describe it but it pulsates. It wasn't a steady rpm idle, it would rise up, and low, rise up and low and so on. I tried lower and rising the idle but it kept pulsating. it got rather annoying when riding since the pulsing actually pulled the bike a bit. Any ideas? I'll post a video today if possible. I tried to look up videos and I couldn't find anything.

The only way I can describe is that a nice idle would be a constant "vrrooooooooooooooom" and my idle is something like "VROOoommm VROOoommmm VROOOommmm"  
« Last Edit: June 09, 2011, 06:21:20 PM by Taco »
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Offline MyckMcClung

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Re: CR250R Idle pulsing??
« Reply #1 on: May 23, 2011, 11:58:13 AM »
float level is low, trash in the filter,water in the bowl, choke not closing all the way. air leak somewhere in the intake, could be a number of things
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If a pair of 2" brass balls isn't working, I doubt that the 3" model will make much difference.

Offline yo_marc

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Re: CR250R Idle pulsing??
« Reply #2 on: May 24, 2011, 09:14:59 AM »
I agree -- My first through was 'lean condition' coming from somewhere.   The pilot circuit, carb boot, countershaft side crankcase seal, air screw worked loose, etc....

I hear a very worn top end will simulate a lean condition too. I personally dont know where in the RPM range that would show up.   Perhaps you might want to check the compression just for the sake of it.
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Offline MyckMcClung

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Re: CR250R Idle pulsing??
« Reply #3 on: May 24, 2011, 03:03:12 PM »
Yeah I forgot to mention worn rings will do that too. pinched vent hose too
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If a pair of 2" brass balls isn't working, I doubt that the 3" model will make much difference.

Offline SachsGS

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Re: CR250R Idle pulsing??
« Reply #4 on: May 24, 2011, 04:32:42 PM »
I'd check your crankshaft seals and cylinder base gasket. ;D

Sometimes Bing equipped bikes will do this - worn carb slide.
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Offline Taco

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Re: CR250R Idle pulsing??
« Reply #5 on: May 24, 2011, 10:00:58 PM »
Alright, my filter is brand new and clean. Getting the carb cleaned tomorrow.  What PSI should my compression be?
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Offline eprovenzano

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Re: CR250R Idle pulsing??
« Reply #6 on: May 27, 2011, 04:41:31 PM »
I have. KTM which is the jetting very sensitive. I have to adjust for temps all the time.   Try the simple things 1st, let's adjust your air mixture screw.  Start by counting the number of turns until it bottoms out (so you can return it to it's current setting if hue adjustment does not work)  return the screw to where it was and then turn it out an additional 1/2 turn. Continue to adjust until your idle is smooth.
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Offline Taco

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Re: CR250R Idle pulsing??
« Reply #7 on: May 28, 2011, 05:20:32 PM »
I've decided to simply buy a whole new top end while I'm at it. I've ordered Wiseco piston kit along with a gasket and bearing and other small misc things. I'm not riding this weekend so it gives me time to work on it. While I wait for that I'm installing new forks. Are wiseco pistons good? I've seen a lot of Wiseco and Namura pistons, and a few PRO X ones too. My friend recommended Wiseco.
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Offline Taco

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Re: CR250R Idle pulsing??
« Reply #8 on: May 28, 2011, 05:26:12 PM »


Here's a pic when cleaning the engine, before taking the top end apart.
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Offline TotalNZ

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Re: CR250R Idle pulsing??
« Reply #9 on: May 28, 2011, 05:41:27 PM »
Quote from: Taco on May 28, 2011, 05:20:32 PM
I've decided to simply buy a whole new top end while I'm at it. I've ordered Wiseco piston kit along with a gasket and bearing and other small misc things. I'm not riding this weekend so it gives me time to work on it. While I wait for that I'm installing new forks. Are wiseco pistons good? I've seen a lot of Wiseco and Namura pistons, and a few PRO X ones too. My friend recommended Wiseco.
I use wiseco ultralites in my CR and highly recommend them.
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Offline MyckMcClung

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Re: CR250R Idle pulsing??
« Reply #10 on: May 29, 2011, 05:48:22 AM »
Wiseco, did you leak test it before you tore it down? Those crank seals could be going too.
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If a pair of 2" brass balls isn't working, I doubt that the 3" model will make much difference.

Offline Taco

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Re: CR250R Idle pulsing??
« Reply #11 on: May 31, 2011, 08:48:53 PM »
No I didn't leak test it. Where exactly are the crank seals?
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Offline MyckMcClung

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Re: CR250R Idle pulsing??
« Reply #12 on: June 01, 2011, 07:51:51 AM »
on the crank, duh :P
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If a pair of 2" brass balls isn't working, I doubt that the 3" model will make much difference.

Offline Taco

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Re: CR250R Idle pulsing??
« Reply #13 on: June 01, 2011, 05:12:57 PM »
Haha yeah, duh. I'll check for leaks when the top end is done. I had a bit of lack of luck today since the forks I bought didn't fit my tree. Anyway, I've been reading my service manual alot and one of the things I noticed is that the clips look difficult to take out, is it? And should I take out my power valve cover?
« Last Edit: June 01, 2011, 05:32:49 PM by Taco »
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Offline Taco

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Re: CR250R Idle pulsing??
« Reply #14 on: June 09, 2011, 06:20:27 PM »
So I finished installing the top end today. When I pump the kick start it's very tough and firm. No leaks as far as I can tell as of now. My friend noted me on something though, I never filed the piston rings, I wasn't even aware of such practice. Should I take the jug out and do them? I'd think they would come ready for installation since it all came together.
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