cylinder compression testing

OldTimer · September 25th, 2012, 03:53 PM

Just resurrected a 250 after 4 years of sitting. Checked the cylinder compression and only got 120psi in each cylinder. My old Harley which has 100,000 miles on it and is 8.5:1 compression ratio has 160 psi in each cylinder. The ninja 250 is supposed to have around 12:1 compression ratio but I'm only getting 120 psi. Has anyone on this forum done a compression test? What were your results. My bike runs, starts fine, idles fine, revs fine.

alex.s · September 25th, 2012, 04:37 PM

what problem are you trying to diagnose?

csmith12 · September 25th, 2012, 04:51 PM

Isn't spec 139psi - 218psi? If so, he is low.

csmith12 · September 25th, 2012, 04:53 PM

@Racer x Is 120psi a problem?

Racer x · September 25th, 2012, 05:15 PM

The engine will not run with that number. I had an engine with 120 and I think less. It had been sitting forever. I pulled the cylinder and removed the rings. They had gotten stuck from rust and gunk. After cleaning and putting it back together it ran great, Bottom end knocked but it ran great.
Check your valve adjustment first. But if that OK then its maybe rings if crud in the valves,

alex.s · September 25th, 2012, 05:17 PM

any chance the compression tester is incorrect?

OldTimer · September 25th, 2012, 06:25 PM

Thanks for confirming what I thought. Although the bike starts and idles fine and revs up, I feel that it should have more power. Its a dog. My son had a 2005 ex250 and it was a little rocketship. I adjusted the valves to spec, not hard to do on this bike but a bit time consuming compared to my 2005 1000cc Kawasaki Concours. I just put in a new 6 speed gear set. The positive neutral finder on the old transmission was only allowing it to get 1st and neutral. It would hang up and not let the forks slide on the shift drum past neutral. It shifts great now but I thought the bike should be faster than it is. It is not burning oil and both cylinders are registering within a couple of psi to each other. The compression tester is new, about 6 months old. I just used it on my dune buggy and found a leak in #3 cylinder so I think the compression tester is fine. I will concur with RacerX's diagnosis. This motor was sitting for 4 years. All I did was split the cases and change out the transmission. I did not open the top end except for the valve cover to check/adjust the valve lash. When I got the motor, the pipes and carbs were off and the ports were open to the air. Here in the Florida humidity, that's a bad thing. I will pull the head and cylinders and check the rings and valve seats for crud. Thanks for the help!

September 25th, 2012, 03:53 PM	#1
OldTimer ninjette.org member Name: Nick Location: Florida Join Date: Sep 2012 Motorcycle(s): Hayabusa, Vespa 200GT, Harley Electraglide, Ninja 250 Posts: 20	cylinder compression testing Just resurrected a 250 after 4 years of sitting. Checked the cylinder compression and only got 120psi in each cylinder. My old Harley which has 100,000 miles on it and is 8.5:1 compression ratio has 160 psi in each cylinder. The ninja 250 is supposed to have around 12:1 compression ratio but I'm only getting 120 psi. Has anyone on this forum done a compression test? What were your results. My bike runs, starts fine, idles fine, revs fine.

September 25th, 2012, 04:37 PM	#2
alex.s wat Name: wat Location: tustin/long beach Join Date: Sep 2009 Motorcycle(s): wat Posts: Too much. Blog Entries: 5 MOTM - Oct '12, Feb '14	what problem are you trying to diagnose? __________________________________________________

September 25th, 2012, 04:53 PM	#4
csmith12 The Corner Whisperer Name: Chris (aka Reactor) Location: Northern KY Join Date: May 2011 Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track) Posts: Too much. MOTY 2015, MOTM - Nov '12, Nov '13	@Racer x Is 120psi a problem? __________________________________________________ Goal: Shake A Million Hands \| Look through the corners \| Track Day Prep \| Closest track? \| The Mid-Ohio School

September 25th, 2012, 05:15 PM	#5
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	The engine will not run with that number. I had an engine with 120 and I think less. It had been sitting forever. I pulled the cylinder and removed the rings. They had gotten stuck from rust and gunk. After cleaning and putting it back together it ran great, Bottom end knocked but it ran great. Check your valve adjustment first. But if that OK then its maybe rings if crud in the valves, __________________________________________________ Top speed 123.369mph. Ohio mile Worlds fastest 250 ninja

September 25th, 2012, 05:17 PM	#6
alex.s wat Name: wat Location: tustin/long beach Join Date: Sep 2009 Motorcycle(s): wat Posts: Too much. Blog Entries: 5 MOTM - Oct '12, Feb '14	any chance the compression tester is incorrect? __________________________________________________

September 25th, 2012, 04:51 PM	#3
csmith12 The Corner Whisperer Name: Chris (aka Reactor) Location: Northern KY Join Date: May 2011 Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track) Posts: Too much. MOTY 2015, MOTM - Nov '12, Nov '13	Isn't spec 139psi - 218psi? If so, he is low. __________________________________________________ Goal: Shake A Million Hands \| Look through the corners \| Track Day Prep \| Closest track? \| The Mid-Ohio School

September 25th, 2012, 06:25 PM	#7
OldTimer ninjette.org member Name: Nick Location: Florida Join Date: Sep 2012 Motorcycle(s): Hayabusa, Vespa 200GT, Harley Electraglide, Ninja 250 Posts: 20	Thanks for confirming what I thought. Although the bike starts and idles fine and revs up, I feel that it should have more power. Its a dog. My son had a 2005 ex250 and it was a little rocketship. I adjusted the valves to spec, not hard to do on this bike but a bit time consuming compared to my 2005 1000cc Kawasaki Concours. I just put in a new 6 speed gear set. The positive neutral finder on the old transmission was only allowing it to get 1st and neutral. It would hang up and not let the forks slide on the shift drum past neutral. It shifts great now but I thought the bike should be faster than it is. It is not burning oil and both cylinders are registering within a couple of psi to each other. The compression tester is new, about 6 months old. I just used it on my dune buggy and found a leak in #3 cylinder so I think the compression tester is fine. I will concur with RacerX's diagnosis. This motor was sitting for 4 years. All I did was split the cases and change out the transmission. I did not open the top end except for the valve cover to check/adjust the valve lash. When I got the motor, the pipes and carbs were off and the ports were open to the air. Here in the Florida humidity, that's a bad thing. I will pull the head and cylinders and check the rings and valve seats for crud. Thanks for the help!

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