2009 XR650L Bad valve seal symptoms?

[ejs989]

Guys,

 

It's been a while since I've posted.  I moved to houston and riding sucks here so the BRP has been parked majority of summer due to excessive heat outside.  I have ridden it occasionally.

 

So, I went to start the bike a couple weekends ago around Thanksgiving and when it hit the starter, I noticed a couple compression strokes and then a pop.  Though it was a backfire, so I tried to restart.  No luck.  I happened to look down and noticed the slightest bit of separation in where the carburetor fits into the black "engine intake boot", not the soft rubber boot from the air box.  I figured i just forgot to tighten the hose clamp down when I had changed the oil and cleaned the carb the weekend before.

 

So, today, I reseated the carburetor properly.  I had a hard time starting once again, but I got her to turn over and idle for about 5 minutes.  I noticed that the idle RPM was really low, so I initially thought that I had maybe twisted the idle screw when reinstalling the carburetor after it had been cleaned a couple weeks before.  So I readjusted the idle screw to "audible" range where the bike normally runs.  After I adjusted the idle screw, I bumped the throttle just a hair and "POP", the bike went dead.  I immediately went to the carb again since I heard the same symptom, and once again, the carb has slightly been pushed out of the hard black engine intake boot.  I noticed a bit of white smoke coming from the boot around the carb/engine boot junction as well.

 

Does this sound like my valve seals are blown out?  I'm not an expert mechanic.  I've never adjusted the valve clearance since I've had the bike (i know, i know).  I've been the only owner, and I have about 3400 miles on the bike.

 

Any thoughts?

[brianhare]

valve seals will not cause a backfire,,valve seals  will cause smoke at start up........

 

You have an engine firing while an intake valve is still open causing pressure to push the carb off it`s boot..

 

check your valve adjustments,,an over tight intake valve can cause this among other things...

 

B

[garthr]

valve seals will not cause a backfire,,valve seals  will cause smoke at start up........

 

You have an engine firing while an intake valve is still open causing pressure to push the carb off it`s boot..

 

check your valve adjustments,,an over tight intake valve can cause this among other things...

 

B

you coughed off the carb due to backfire. in valve to tight or sticking open.

[ejs989]

valve seals will not cause a backfire,,valve seals  will cause smoke at start up........

 

You have an engine firing while an intake valve is still open causing pressure to push the carb off it`s boot..

 

check your valve adjustments,,an over tight intake valve can cause this among other things...

 

B

What are the other things...I'll go ahead and set the valves to the correct measurements.  Just seems odd that i've seen this happen literally overnight.  I went from riding the bike, to changing the oil/cleaning carb, to try to start up again and it blew the carb off.

 

Any other things i should be looking for?

[brianhare]

So was it running good before you worked on it.....or you pulled the carb because it was running bad????????

 

backfires can be caused by a jump timing chain.....but not at that mileage..

 

the main causes on these bikes at your low mileage  is valves being to tight.......followed next by the CDI...

 

I`ve repaired quite a few CDI`s that would start the bike after backfiring and missfiring for a few seconds..most would just let an occasional pop throughthe intake or exhaust and not start the bike though..

 

but i bet on a tight intake valve..

 

B

Edited December 14, 2014 by brianhare

[ejs989]

Bike was running fine before the carb was removed for cleaning.  I have actually never had this symptom on the bike before.

 

I've got the feeler gauges and everything i need to set valve clearances.  I guess i'll just man up and do it and see if that helps.

 

If it doesn't help, then i've heard of the CDI issues, but i'd have to dig in more to that.

 

If it makes a difference, that bike has seen maybe 25 miles of dirt, and the rest is pavement...so the engine has really not been "exercised" a lot per say.

[brianhare]

the first valve adjustment is the most important one,,,they go out of adjustment fast on a fresh engine..it`s not hard to do either..

 

my first bike took to backfiring on decel badly after 2k.....i learned quickly after paying a couple hundred bucks for the dealer to do it..that i could do it myself.

 

B

[Onederer]

It could be a bad ignition coil too. I've seen coils just drop dead from heat / old age and they'll sometimes fail when the engine is shut off and the problem only shows next time someone tries to start it. A bad coil can cause intake and exhaust backfires.

 

A far as valves go, when the engine seemed to run fine before last time when it was shut off but now won't start, or backfires, that's almost always jumped timing. Just about anything with a cam chain / belt is more susceptible to jump time from a faulty tensioner or worn parts during engine shut-down because of the jerking motion and rotating mass, not rotating, on the last couple crank revolutions before it stops. It won't happen to a Ford or Chevy inline six though, no chain or belt, they have gear driven cams. There have been a few gear (bevel) driven cam motorcycles; very few.

 

The auto cam chain tensioner on the XR650L / XR600R engines is just a sprag clutch and they are know to wear the shaft to the point the clutch rollers won't hold well. Combine that with a worn chain and there is a situation for jumped valve timing. Some people have just pulled the tensioner shaft and hit it with some fine grit sandpaper and had it working again.