Recently I started to notice vibration in the engine.
Was barely noticeable at first, but now it feels like riding a 250cc twin.
Engine vibrations become evident at 6k RPM and amplify with RPM increase. This happens while stopped and on the freeway while riding. If I pull the clutch at high speed, the engine goes to idle and the ride is perfectly smooth. There is also an overall loss in power.
So I tried some test - 8k -10k rpm about 80mph I turned off the ignition via killswitch - vibrations were still there as the engine was gear braking. So I'm a little stumped.
If the ignition was somehow involved - in the above test it should have smoothed out. Would it be the same for carbs?
Bike has 61k miles, and there is a small leak from somewhere in the chain sprocket area (1-2 drops a week). Clutch is brand new.
Any ideas would be appreciated.
update:
Air filter is K&N serviced 10k miles ago - just a little dirty. No oil on it.
Did a compression test - 115 115 120 115 - all within spec.
Check plugs for clean firing, see pics below. Were very slightly oil wet when I pulled them originally.
Oil was clean and clear - no metal flakes. I even fished around the pan with a magnet.
The only thing that was wrong is the fuel filter - had not been changed in years and it literally fell apart in my hands, I'm surprised any fuel was flowing though it at all.
So now I'm stumped. Plugs okay, compression there, no signs of canibalism.
Sounds like you are losing a cylinder or two at higher engine speeds. There are many possible causes for this: it could be ignition, fuel, water leak into a cylinder, valve float or a host of other things. I would suggest removing the spark plugs and looking at their tip color. They should all be roughly the same light tan color. The color of your plugs will tell you a lot about what is going on inside the engine. Also perform a compression check on all four cylinders. Results should all be within 10% of each other. The results of these tests will give some valuable troubleshooting information. It is better to get this information before you begin removing or replacing components.
[image: View Post]samaki, on 10 June 2010 - 08:33 PM, said:
Sounds like you are losing a cylinder or two at higher engine speeds. There are many possible causes for this: it could be ignition, fuel, water leak into a cylinder, valve float or a host of other things. I would suggest removing the spark plugs and looking at their tip color. They should all be roughly the same light tan color. The color of your plugs will tell you a lot about what is going on inside the engine. Also perform a compression check on all four cylinders. Results should all be within 10% of each other. The results of these tests will give some valuable troubleshooting information. It is better to get this information before you begin removing or replacing components.
Based on that observation I would suggest that you run your finger around the inside of the outlet on your exhaust muffler. Your finger should come away clean or with a small amount of brow n powder on it. If there is an oily residue you will know that your engine is burning oil. If there is a dark powdery residue it means your engine is running too rich. Either of these could be the source of,or a contirbutor to, your problem. A properly jetted engine that is not using oil should have a clean exhaust outlet.
[image: View Post]samaki, on 14 June 2010 - 09:40 PM, said:
Based on that observation I would suggest that you run your finger around the inside of the outlet on your exhaust muffler.
Exhaust had a little bit of black powder, but no oil.
Drained the oil and it was super clean. I even fished around with a strong magnet in the drain pan and it came up clean. Collected some samples to send to the lab. Compression test tomorrow.
Right now I'm thinking carbs or valves.
What air filter do you have in the bike and what condition is it in? If it is foam, when did you last clean it and what did you oil it with? Is the air box interior dry and clean?
When you lay the four plugs together are their colors identical? Can you post a photo of the firing end of one of the plugs? That might help.
Air filter is K&N serviced 10k miles ago - just a little dirty. No oil on it.
Did a compression test - 115 115 120 115 - all within spec.
Check plugs for clean firing, see pics below. Were very slightly oil wet when I pulled them originally.
Oil was clean and clear - no metal flakes. I even fished around the pan with a magnet.
The only thing that was wrong is the fuel filter - had not been changed in years and it literally fell apart in my hands, I'm surprised any fuel was flowing though it at all.
So now I'm stumped. Plugs okay, compression there, no signs of canibalism.
Borrowed a gauge-type carb sync tool. The readings were all pretty close, but now I think I'm going to build a manometer, as the gauges measure the vaccum in 10's of inHG. And the allowed difference is 20mmHg. (20mmHG = 0.8inHG)
[image: View Post]ke5aux, on 22 June 2010 - 10:02 AM, said:
Borrowed a gauge-type carb sync tool. The readings were all pretty close, but now I think I'm going to build a manometer, as the gauges measure the vaccum in 10's of inHG. And the allowed difference is 20mmHg. (20mmHG = 0.8inHG)
Pull your carbs off and check inside the bowls for pieces of your fuel filter; also pull the carb tops and *carefully* pull the diapragms/slides out so you can check there for pieces of the secondary air filter, which is inside that small black box attached to the right side of your airbox.
[image: View Post]SEBSPEED, on 22 June 2010 - 10:13 AM, said:
[image: View Post]ke5aux, on 22 June 2010 - 10:02 AM, said:
Borrowed a gauge-type carb sync tool. The readings were all pretty close, but now I think I'm going to build a manometer, as the gauges measure the vaccum in 10's of inHG. And the allowed difference is 20mmHg. (20mmHG = 0.8inHG)
Pull your carbs off and check inside the bowls for pieces of your fuel filter; also pull the carb tops and *carefully* pull the diapragms/slides out so you can check there for pieces of the secondary air filter, which is inside that small black box attached to the right side of your airbox.
Will do.
Also, can a bad exhaust can cause vibrations? The one i have now has fallen appart inside, and has been jb-welded together by yours truly on multiple occasions.