[Zach_Godel]

I was riding home several weeks ago and the bike had been sounding odd. I thought it was the packing coming out of my aftermarket exhaust, or the pernicious exhaust leak that I had been dealing with, only worse. The day that the bike died I noticed that I lost most of my top end power and under load it was making a loud noise that, as mentioned before, sounded like an unpacked aftermarket muffler. As I got closer to home I noticed that I was slowly losing speed and power with the same throttle position. I thought my battery wasn't charging, but then thought maybe there was a new problem with my electrical system. I tried to take her past 5,500 RPM to see if I could pull her out of her funk and right around 6,000 RPM I heard a couple sputter sounds and then the bike died. The battery hadn't enough voltage to run the starter, which made me think it just was not charging. I charged the bike and started it the next day and heard a wretched thud or clunking noise from the right cylinder. At that point I thought that perhaps the cam chain, which had reached its service limit, had not been tight enough, and had allowed a valve to be open when it ought not to be. After a compression test revealed 80 PSI on the right cylinder I thought this was clearly what happened. Unfortunately, after pulling the head and inspecting every valve on the right side, I was dismayed to discover they were all in fine condition. I now have no idea what would make a sputter sound, cause the bike to die and lose charge in the battery, make a clunking noise, and cause low compression on the cylinder. The pistons look fine, the cylinder walls look fine, there is no slop in the rocker arms or pistons, the push rods are fine and everything seems to move freely. Any ideas?

 

[Zach_Godel]

No ideas what makes a thunking noise like a bent valve smacking around inside the right cylinder, but is not at all a bent valve?

 

[kingston73]

Not really sure what to tell you, but if you've already pulled the head and didn't find anything you might need to drop the engine and open it up. Hopefully somebody else will be able to give you a less drastic idea of a fix first.

 

[Reg in Bristol]

Heres a horrible idea

When I snapped a crankpin, the engine lost power and would run

but sounded awful.

It started the next day but despite my hoping a good nights rest

would cure it, ( yeah I know, but I was in denial)

it was the same.

the rotor had thrashed about inside and chewed up the magnets and stator.

Oh, and snapped cam chain guides and stuff too



Hopefully thats not the case with yours.

 

[nolavox]

Heres a horrible idea

When I snapped a crankpin, the engine lost power and would run

but sounded awful.

It started the next day but despite my hoping a good nights rest

would cure it, ( yeah I know, but I was in denial)

it was the same.

the rotor had thrashed about inside and chewed up the magnets and stator.

Oh, and snapped cam chain guides and stuff too



Hopefully thats not the case with yours.

Mine did that same sort of crap with a collapsed air boot and a clogged breather filter...

@{z}Hopefully yours was 180 out and cold when you made your compression test

 

[Zach_Godel]

Alright, I replaced my cam chain and cleaned and inspected the heads and valves. the heads and valves appeared to be fine, and the new cam chain looked great. Before putting everything together I oiled everything down and put a drill on the bolt at the end of the crank just to spin the engine quickly for about 5 seconds and I listened to the transmission, connecting rods, and camshaft. I heard no unusual noises. I put everything back together and started the bike and heard the noise again. I am baffled. The valves were more or less adjusted before the incident and the noise, and I just readjusted the valves before installing the engine; I concede that there is a possibility that I adjusted the valves poorly, but I doubt it.

Watch the video and tell me what you think. It really sounds like it is something in the right head, but unless the issue lies in something that cannot be visibly inspected, then I have already eliminated that option.

Help?



My link

 

[Sam I Am]

Video?

 

[Zach_Godel]

I am a noob. I added the link.

 

[Linny]

I lost a compression ring in a cylinder of my CB and it acted similar to your bike except the battery issue. When it lost power and died with a terrible sound I suspect the broken bits of the ring found their way through the exhaust valve as they were not present upon pulling the head. I didn't know what was wrong until I looked at the piston and found most of one of the rings missing. Somehow it didn't muck up the sleeve a quick hone,, new rings, and I was back in business.



If you still have low compression and feel your valves are set ok and look fine the rings would be a sensible next thought.

 

[Zach_Godel]

That is interesting. I have not yet done a compression check, but I had best do one!

 

[achille]

Valve spring?

 

[Linny]

That is a hell of a sound. I would take another good long look at them tappets and be certain they are set proper on the compression stroke.

 

[Shep]

When you replaced the Cam chain did you use Thread-lock on the two small 10mm bolts that hold the top driven gear that holds the cam-chain?

 

[Zach_Godel]

Shep, I did not use thread lock on those bolts. The noise occurred before I swapped my cam chain though, if that is what you are implying. However, since I did not thread lock them, is it almost a guarantee that they well work loose?

 

[Zach_Godel]

Valve spring?

I did not do any tests on the springs when I had them out, but I did examine them all and I do not recall any showing obvious wear or damage. Would valve spring damage causing this kind of noise appear subtle or pronounced?

 

[Shep]

Shep, I did not use thread lock on those bolts. The noise occurred before I swapped my cam chain though, if that is what you are implying. However, since I did not thread lock them, is it almost a guarantee that they well work loose?

Yes.I've had to take an engine out because these bolts worked loose and caused tapping/knocking.I forgot to use thread-lock which is recommended in the manual and had done previously

I'm not saying this is the cause,just worthy of note.I now always use thread-lock on them as they are not deep bolts and only have a low torque.Same with my Water pump impeller nut and the Oil pump chain small gear bolt.

 

[Zach_Godel]

Good to know Shep, I may be taking this engine out again for anyway....



Compression showed 90 PSI left and 80 PSI right

 

[Shep]

Good to know Shep, I may be taking this engine out again for anyway....



Compression showed 90 PSI left and 80 PSI right

When doing a compression test use the Kill switch and hold the throttle open several times to get the pressure up.Jump with a car battery(Correct way round) if the battery is a bit underpowered for the test.

 

[bandit]

Compression showed 90 PSI left and 80 PSI right

those values are too close to be wrong

 

[Zach_Godel]

When doing a compression test use the Kill switch and hold the throttle open several times to get the pressure up.Jump with a car battery(Correct way round) if the battery is a bit underpowered for the test.

I do compression checks so infrequently that I forgot all the things I needed to do. I did everything but hold open the throttle. 120 PSI left, 100 PSI right.