Hey guys,I just picked up a 2003 CR250 in what looks to be excellent shape.I was hoping someone could give me some insight on this machine,such as what the compression should be when doing a compression test(standard range)also are there any kinks in the bike that need to adressed?(This 03 is in mint condition COMPLETELY STOCK) It's been a while since I have had a CR250 and I am sure there are things that need to be addressed so I figure the best way is to ask.Thanks ahead of time.
2003 CR250 Compression
- Thread starter ALB
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SilverSurfer
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- Mar 28, 2006
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Compression should be >160. If it's <160 then you may need a top end rebuild. FYI, I just rebuilt my 1993 CR250 and the compression is 190. I expect it to settle somewhere around 170 and when it falls below 160 I will rebuild the top end.
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SilverSurfer
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- Mar 28, 2006
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76GMC1500 said:
< greater than
> less than
Oops. Fixed :)
You can calculate it...basically multiply 14.696 by your compression ratio. If you search compression, I went through the whole thing. Your calculation will come out about 5% low. I think this is because it leaves out the increase in temp that occurs during compression, but it'll get you close. Mine was 135 psi and has been since I bought my CR and my calculation was about 128 psi. Hope that helps.
- Thread starter
- #8
Guys I just investigated the airbox mod and found an MX Bonz for $39.99(which I bought) But by the replies that have been posted it seems there is quite a bit of difference in regard to how much compression the CR250 should have IE: 170lbs to 135lbs,this seems like a very big difference.Any input??? Thanks
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Don't forget to hold your throttle wide open while you do the compression test. Keeping it closed will cause your numbers to come out low. Kick it thorugh a until the pressure reaeches a max and stabilizes. Don't just kick it once.
150 psi is the typical compression pressure for fresh engines built to run on 87 octane. Engines running on premium typically have compression pressures from 175 to 195 psi. Porting or valve timing has a big effect on your compression pressures. The more radical your porting/timing, the lower your compression pressure will be.
The 1987 CR 250 I ride made 180 psi on a compression test.
150 psi is the typical compression pressure for fresh engines built to run on 87 octane. Engines running on premium typically have compression pressures from 175 to 195 psi. Porting or valve timing has a big effect on your compression pressures. The more radical your porting/timing, the lower your compression pressure will be.
The 1987 CR 250 I ride made 180 psi on a compression test.
kx125412 said:
Compression is based on your compression ratio. I'm not sure if the published compression ratio is "trapped compression ratio" which is the compression by volume when the exhaust port closes to TDC or regular ole compression ratio: BDC:TDC.
Here's the link where I went through the calculations:http://www.dirtrider.net/forums3/showthread.php?t=142480&page=2&pp=10&highlight=compression
rosscopeeko
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- Feb 25, 2005
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I bought the same bike as you in almost new condition last January. My airbox didn't leak, but as a precautionary measure i bought some Hondabond 4 and sealed the inner sections of the airbox where it joins the boot. I also just bought a James Dean jetting kit because my jetting was way off for the 1500ft elevation and hot temperature. I just geared mine to a 51 rear for woods riding but i think i went too low. I would like to have a 50 on the rear. I found the 48 rear just too tall. Watch your radiators also. Mine bent baddly when my bike fell over in the trailer on the way to a ride. I bought some Devol rad guards and also an Eline carbon pipe guard. I don't think there are any known quirks with this bike. It is very reliable and has excellent suspension and handling. A lot of people say it has a weak bottom end but i find it moves me just fine because i'm fairly light. If your bike is on it's stock tires and they aren't worn baddly i'm sure your compression is excellent. Check your airfilter and if it was maintained well you should be good to go. Another thing to look at for guaging riding time on the bike is to look at the magnesium cover and look to see if it's worn away in spots. My bike had 10 hours on it when i bought it and it was all there still, and was also on the stock tires which were still in good shape. The stock tires are Dunlop 755's. One other thing, buy the factory manual and strip down the bike and grease everything. Buy some Honda moly 60 for your rear linkage. Have fun with your cr.
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tony91
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- Jan 30, 2002
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john3_16 said:
After the first ride, I took a paper towel and wiped down the inside of the boot. As far as I could tell there was too much dust. After the MX Bonz kit, it was almost non-existent. I just got the 265 kit this year. I haven't noticed an increase.
darringer
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- Dec 2, 2001
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Yes, the higher the altitude, the lower the compression reading. I would imagine it not to be uncommon to lose up to 10% in the readings at high altitudes. I would still think the '03 would have 160-170psi at your altitude. Also, when checking compression hold the throttle wide open, do several hard kicks until the reading on the gauge stabilizes, and push the kill switch to protect the ignition. Also note, a warm engine will have higher readings. But in my experience it wasn't anything substantial, maybe a 5psi difference.
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