chattering engine

[baker]

I have 08' EC 300 with only about 10-15 hours on it. I drowned it at the last race and pulled the cylinder off to check everything out and flush. Everything looked good 175 compression .585mm ring gap. I started the bike and there is horrible chatter when at idle. Soon as you give it gas it goes away. Riding, the chatter stays same tone when you let off but soon as gas the noise goes away.

Checked all mounts, play in crank/piston, clutch plates...

Any ideas??

 

[GMP]

Power valve. Perhaps something did not go back together right? Also clutch hub dampers, but this less likely. Simple things first.

 

[baker]

power valve is working. pulled up manually on right side to open, i hear a change in the muffler but chatter never changes tone. checked slack in clutch basket too, very little play left to right , a 1/16th or so

 

[GMP]

power valve is working. pulled up manually on right side to open

Thats a sure way to dislodge a ball in the governer, and cause it to not return to the idle stop completely, which would make it rattle.

 

[baker]

i didn't do that until i had the rattle. Could this have happened otherwise? How can I check?

 

[baker]

when in the woods water logged, we filled cylinder up with gas, turned bike upside down and spun wheel in gear to flush out. Could this somehow done what you are talking about.
Rode the bike about 2 hours. It runs great, with no performance problems. Just this nerve racking chatter/rattle at low rpm. My friend said it sounds like somebody put a bolt in the pipe rattling around

 

[GMP]

It won't happen by itself, but if you pulled on the PV rod enough to remove it from the plate when you pulled the top end that could do it, it has happened to a couple members here. Remove the right PV cover and run the bike, it should move stop to stop. Hold it against the idle stop and see if the noise changes.

Did you take the PV apart?

I generally don't have a lot of faith in bikes holding up after drowning if they were restarted. Most need a lower end soon after. What was this situation like? Is there a vibration along with the noise? Does it start OK and not backfire?

 

[baker]

Thanks for your help. I was pretty reckless with the powervalve when taking apart. I can see it moving up and down when i run it and I made sure all parts of the power valve were intact. I will try pushing it against the stop. When I had the cylinder off I checked for slack in the bottom and top bearings and seemed ok. The bike starts and runs as normal. It does backfire sometimes when it doesn't start but usually starts in a kick or two.

We flushed the cylinder with gas 3 times in the woods, then got the bike running and rode it back to the truck. That should have dried up water before it sat. I did notice changes in the tone of engine as I was riding it back to the truck (probably water in exhaust) but it then cleared up.

 

[GMP]

Its not the water as much as the silt that is carried in by it that settles in the lower end. I would not be surprised if you need mains and/or a rod kit soon. If your deep in the woods you do what you have to do though.

BTW, did you know the bike has a crankcase drain? No need to go upside down.

A bad main bearing will usually "roar" and get worse with speed, bad rod bearing will "knock".

If it wasn't rattling when you shut it off at your truck, its probably something you did during teardown and re-assembly. Keep looking for simple stuff like hardware and parts touching. If its in the motor for sure get or make a stethescope from tubing and nail it down.

Did you mess with the ignition at all?

 

[widebear]

Somewhat off topic here.That silt is a killer allright.I once watered out twice on the same lap on my wr 200 the most brutal hare scrambel ever, put on by our club no less, we decided to go ahead with the race depite a week of torrencial rain.I had to do the last 4k with about 80 pounds compression, first gear, full throttle fanning the clutch like a mad man, all this in a two foot deep rut. I finished but the engine was complete toast, cyliner ,rod ,everything ,as was yours truely.It took five days for the water to recede enough from one crossing till we could recover a guys rm 250, another friend just about drowned when he was swept downstream with his bike behind and above him pushing him under.At post race we could'nt account for one rider , he was found two hours later by a search party, away from his bike ,despondent eating wild berries.

 

[2 strokes 4 life]

That sounds like one heck of a race. Strange things happen when your survival mode kicks in. What race was this?

 

[widebear]

gritty ginch. McNutt Mtn, I believe it was sept 95 or 96

 

[baker]

I tried pushing the pv arm to the stop and it was actually already there at idle. I used a screwdriver and i could feel the knock strongly in the arm. My buddy used a stethescope earlier and said he believed the noise was coming from the powervalve. Is there any possibility something is wrong with the pv. I never disassembled it when I removed the cylinder, just sprayed lots of cleaner and worked it back and forth. I took it somewhat apart after this problem and everything seemed ok (compared to pv assembly pic on this website)

 

[GMP]

Did the bike rattle after the ride back to the truck before you shut it down?

I had a '00 XC250 that developed a noisy PV and it was the right side bearing, but this does not happen overnight.

Back to basics though, could it be the pipe vibrating on the spigot/spigot bolt heads? If the o-rings are bad this can happen, especially if the pipe is tweaked. Look closely at this when running the bike.

 

[baker]

Also, not to leave out any details I used the .5 base gasket, stock there were 3. Never had any trouble with this before on other brands

I just disassembled the entire pv and everything looked good.
Guess if no more suggestions I will replace piston, rings, gaskets and top bearing

 

[baker]

the o-rings are not torn but they may not be full thickness. I tried pressing on the pipe with my boots and noise never changed tone. I dont remember the bike making the noise on way back to truck. I pay more attention after engine work though

 

[widebear]

Dont want to be negative here but to me that sounds like a big end bearing gone bad . Did you feel for slop in the rod when you had the jug off?

 

[baker]

no felt really tite.

 

[baker]

thanks for the help- Update, it was the piston skirt worn. The rings and compression were in specs but piston slap was cause of the noise. New piston= quiet motor!!

 

[rpduc]

New piston= quiet motor!!

Oh-oh... that's what I'm afraid of on mine. I've been watching this thread in hopes that it was something piddly.

I imagine I can scrounge it up somewhere but if anyone knows off hand what "in-spec" measurements are for the piston that would be convenient. I have no idea how many hours are on this one since I bought the bike used.

Thanks for the follow up baker.