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my xr died today...I think

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My 2001 XR250R has me worried.  It has about a millon hours on it with little compression but the old girl would still fire up and run all day long.  No oil smoke...ever.  I hardly ever ride it but today I started her up and rode around my house a few laps.  Thought I'd just let it sit and idle for a while and after about five minutes of idling the rpms climbed a bit.  Weird. I walked over to it and blipped the throttle a couple of times and it coughed and died.  I thought no big deal but after 20 kicks no go. Then I noticed the decomp on the head wasn't moving at all.  Can't feel any compression now eithier.  Oh, oh. Valves and decomp were adjusted less than 20 hours ago.  Maybe the engine got hot idling and the valve clearance went away but after sitting for a hour it still had the same problem. 

I'll prolly take a peek under the valve cover tomorrow but for now any guesses?????

Edited by WFO_Pete

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If you left fuel in the float bowl after the last time you rode it, the fuel has turned bad and the jets and for sure the fuel screw/screw passage are gummed up/occluded.

You need to pull the float bowl, both jets, fuel screw, it's spring,washer and oring and blow some cleaner thru them.

I'd do that before anything else.

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your stuck decomp explains the no compression i guess.

what year is it - is the decomp external cable or on the cam like my 400 was ?

if its on the cam, the decomp lobe can crack and break.

 

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38 minutes ago, FFMan said:

your stuck decomp explains the no compression i guess.

what year is it - is the decomp external cable or on the cam like my 400 was ?

if its on the cam, the decomp lobe can crack and break.

 

2001...cable. I'll pull Mr. Valve cover and check.

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Is it out of gas?

Did you leave the choke on while it was idling and foul the plug? 

Start with the simple stuff.

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21 minutes ago, Bad Moon said:

Is it out of gas?

Did you leave the choke on while it was idling and foul the plug? 

Start with the simple stuff.

I understand, has fuel and the choke was off.  At least the rocker arms are moving but I don't think the auto comp. release is.

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My suggestion to check the fuel was from my own experience...

Auto decomps have been known to stick. I've never experienced it but the previous owner of my bike did (he's a friend of mine). 

Something had to have changed suddenly for the bike to be running just fine one minute and then be impossible to start the next. 

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19 hours ago, Trailryder42 said:

What do you mean, you noticed the decomp on the head wasn't moving? It's not supposed to move unless you pull the manual decomp lever on the handlebars.

Sorry about the confusion.  I was thinking about a XR200 (the decomp works off the kicker).  I don't even use the decomp on my 250.  Checked the valve clearance and everything is good (even set on the loose side of the specs) at .004" intake and .005" ex.   If this is a stuck decompression issue does moving it by hand free it up or do you need to go inside for a closer look?

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2 hours ago, WFO_Pete said:

   If this is a stuck decompression issue does moving it by hand free it up or do you need to go inside for a closer look?

The manual and auto decomp are not connected to each other internally. The auto decomp is a separate cam on the right side of the camshaft, directly behind the chain sprocket flange. It's not unheard of for it to become sticky, but I'd certainly look at all other possibilities before that.

If it's a sticky auto decomp cam, a higher rpm and of a longer duration may free it up. Try push starting it or better yet, pull start it behind a vehicle.

Use the manual decomp method for roll starting. Connect the bike to a vehicle, set the engine up for a normal start (gas on, choke, etc.), shift into 2nd or 3rd, pull in and hold "both clutch and manual decomp", get rolling, release clutch "while continuing to hold decomp", as that gets the engine turning with no resistance from any compression. Pull it around like that for a little while. The auto decomp cam is centrifugal force operated, so a fast spinning cam is likely to free it up if it's sticking. After you've done that, while still rolling, release the manual decomp. It will be a smooth start, not that wheel locking up action like if you just dumped the clutch on a rolling start.

 

Edited by Trailryder42

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pull start is a good call - i had this om my 400 once. it refused to start, but once i got it running on a pull it was ok after that. 

 

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Make sure your fuel isn't old. When the bike has been sitting for a long time with fuel left in the bowl, always drain the bowl, open the petcock and flush it before ever trying to start it.

When the RPMs raised on you as it was idling, that could have been from the engine warming up or the air/fuel mix it was getting turning lean, as in starving for fuel.

Check for a rats nest in the airbox. Make sure the carb vent lines are not clogged up from the last time you rode it.

Change the spark plug.

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While I checked the valves I dumped the fuel tank contents and drained the carb.  Fresh fuel is inside now and a bump start hopefully tomorrow.  Hell I might even pull the plug first and see what that looks like.

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I put a new IMS shift lever on the XR and then I gave the old girl a bump start down my driveway this morning.  She fired right up.  Rode it around a good five minutes then shut it off.  When I went to restart it the compression had returned and it started right up.  Let it sit and idle for another five minutes then rode it around some more.  Shut it off again and let it get stone cold, sitting for six hours, then started it up again.  

So I guess it was the shift lever all along.

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