Damage from loose cam chain?

br1ckd · June 5th, 2015, 03:23 PM

Last weekend my 07 EX250 started making a lot of noise. I figured out the cam chain was really loose and I was able to tighten it by resetting the CCT. I also checked the cam timing and it looks like it didn't jump a tooth. It's still making some noise around 5k rpm, though, and I'm having trouble starting it and it won't idle (the RPMs slowly drop until it shuts off). I just did a compression test and only got about 90psi in each cylinder, but when I put some oil in the cylinder I got about 140psi. This probably isn't related, but I adjusted the valves a couple weeks ago and did a bench sync on the carbs (I tried to do a dynamic sync but wasn't very careful and had to do a bench sync just to get the bike to start again, and never got around to doing a dynamic sync again).

Here's a video of the sound it was making before I cleaned and reset the CCT: https://drive.google.com/file/d/0B2n...ew?usp=sharing

Here's a video of how it sounds now: https://drive.google.com/file/d/0B2n...ew?usp=sharing

Edit: When I did the compression test I let it crank 4-5 times, and had a spark plug in the other cylinder (disconnected from the coil).

CZroe · June 7th, 2015, 10:08 AM

Second link appears to be just a picture. My J-bike makes a sound like this until I reset the tensioner but it keeps coming back. I'm pretty sure I need a new tensioner.

Motofool · June 7th, 2015, 02:44 PM

Welcome, br1ckd !!!

I see that you have three different issues ............ or just one producing three related symptoms:

1) Noisy cam chain.

2) Difficult start / excessively low idle.

3) Low compression results.

Did all those manifested at once?
Have you been feeling reduced power?
Did you fully open the throttle for the compression tests?

br1ckd · June 7th, 2015, 04:11 PM

Quote:

Originally Posted by CZroe

Second link appears to be just a picture. My J-bike makes a sound like this until I reset the tensioner but it keeps coming back. I'm pretty sure I need a new tensioner.

Thanks for pointing that out, I fixed the link. My bike had almost no power when the chain got really loose, so you might want to fix that sooner than later.

Quote:

Originally Posted by Motofool

Welcome, br1ckd !!!

I see that you have three different issues ............ or just one producing three related symptoms:

1) Noisy cam chain.

2) Difficult start / excessively low idle.

3) Low compression results.

Did all those manifested at once?
Have you been feeling reduced power?
Did you fully open the throttle for the compression tests?

They all mostly manifested at once. The bike was running pretty well before this happened, except that the carbs weren't synced so it wasn't idling very well (the RPMs would jump around, from ~1k to ~3k). That idle problem started after I tried to sync the carbs after a valve adjustment. I wasn't very careful and made it bad enough that I had to do a bench sync, which got it running but not as well as before I messed with the carbs.

I had almost no power when the CCT was really loose. I've only ridden it up the street and didn't get the engine above ~6k RPM since I tightened the chain, so I'm not sure if it's got less power than before the chain got really loose.

I forgot to open the throttle when I did the test, I'll redo them with the throttle open.

br1ckd · June 9th, 2015, 08:40 PM

Quote:

Originally Posted by Motofool

Welcome, br1ckd !!!

I see that you have three different issues ............ or just one producing three related symptoms:

1) Noisy cam chain.

2) Difficult start / excessively low idle.

3) Low compression results.

Did all those manifested at once?
Have you been feeling reduced power?
Did you fully open the throttle for the compression tests?

I finally redid the compression test with the throttle open and got the same reading as before, 90psi after it cranks 4-5 times. The pressure didn't increase any faster than when I didn't have the throttle open.

Motofool · June 9th, 2015, 08:58 PM

Quote:

Originally Posted by br1ckd

I finally redid the compression test with the throttle open and got the same reading as before, 90psi after it cranks 4-5 times. The pressure didn't increase any faster than when I didn't have the throttle open.

That reading is too low to start the engine; however, the engine was starting correctly before the valve adjustment.

The compression test with oil indicates that the rings are worn; unless you have used too much oil and the chamber volume has been reduced much.

If that is the case, you have low compression with or without oil helping seal the rings.

If that is the case, the low compression reading may be due to a leaking valve.

This is how to test that:
http://www.dansmc.com/leakdown.htm

If positive, the leak may be due to the cams being out of synch with the piston due to a jumping cam chain.

The tensioner's spring is not strong enough to keep the chain with no slack during the four cycles, it needs the help of the the one-way ratcheting mechanism.
If the balls are not perfectly round, the mechanism may go back enough to induce slack:
http://faq.ninja250.org/wiki/Cam_cha...sioner_removal

Linkin · June 9th, 2015, 09:08 PM

Higher compression when you squirt oil into the cylinders means that you need new piston rings, or the piston ring end gap have all been lined up straight. Ideally all the end gaps should be 120 degrees apart from each other.

As for the cam chain and tensioner. Reset the tensioner and then reinstall it. Run the bike, then check how far the tensioner extended. If it extended all the way and the bike is noisy, you need a new cam chain.

While doing all this, you should check the valve clearances and change any shims that are out of spec.

June 5th, 2015, 03:23 PM	#1
br1ckd ninjette.org newbie Name: br1ckd Location: Hawaii Join Date: May 2015 Motorcycle(s): 07 EX250 Posts: 6	Damage from loose cam chain? Last weekend my 07 EX250 started making a lot of noise. I figured out the cam chain was really loose and I was able to tighten it by resetting the CCT. I also checked the cam timing and it looks like it didn't jump a tooth. It's still making some noise around 5k rpm, though, and I'm having trouble starting it and it won't idle (the RPMs slowly drop until it shuts off). I just did a compression test and only got about 90psi in each cylinder, but when I put some oil in the cylinder I got about 140psi. This probably isn't related, but I adjusted the valves a couple weeks ago and did a bench sync on the carbs (I tried to do a dynamic sync but wasn't very careful and had to do a bench sync just to get the bike to start again, and never got around to doing a dynamic sync again). Here's a video of the sound it was making before I cleaned and reset the CCT: https://drive.google.com/file/d/0B2n...ew?usp=sharing Here's a video of how it sounds now: https://drive.google.com/file/d/0B2n...ew?usp=sharing Edit: When I did the compression test I let it crank 4-5 times, and had a spark plug in the other cylinder (disconnected from the coil). Last futzed with by br1ckd; June 7th, 2015 at 04:03 PM. Reason: fixed video link

June 7th, 2015, 02:44 PM	#3
Motofool Daily Ninjette rider Name: Hernan Location: Florida Join Date: Mar 2011 Motorcycle(s): 2007 Ninja 250 Posts: A lot. MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16	Welcome, br1ckd !!! I see that you have three different issues ............ or just one producing three related symptoms: 1) Noisy cam chain. 2) Difficult start / excessively low idle. 3) Low compression results. Did all those manifested at once? Have you been feeling reduced power? Did you fully open the throttle for the compression tests? __________________________________________________ *Motofool* *.................................Never ride faster than your guardian angel can fly* "Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí

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June 7th, 2015, 10:08 AM	#2
CZroe CPT Falcon Name: J.Emmett Turner Location: Newnan, GA Join Date: Apr 2009 Motorcycle(s): '08 CP Blue EX250J, '97 unpainted EX250F, 2nd '97 unpainted EX250F (no engine), '07 black EX250F Posts: A lot.	Second link appears to be just a picture. My J-bike makes a sound like this until I reset the tensioner but it keeps coming back. I'm pretty sure I need a new tensioner.

June 9th, 2015, 09:08 PM	#7
Linkin Down Under Name: Linkin Location: Sydney, Australia Join Date: Jun 2014 Motorcycle(s): Kawasaki ZXR250C Ninja Posts: 296	Higher compression when you squirt oil into the cylinders means that you need new piston rings, or the piston ring end gap have all been lined up straight. Ideally all the end gaps should be 120 degrees apart from each other. As for the cam chain and tensioner. Reset the tensioner and then reinstall it. Run the bike, then check how far the tensioner extended. If it extended all the way and the bike is noisy, you need a new cam chain. While doing all this, you should check the valve clearances and change any shims that are out of spec.