xr250 Bogs under load, or going up steep grades

[bwhollifield]

I was having some issues with it bogging going up steep hills. First, second didn't matter. If I was going slow, it was really bad. Fast... I would have enough momentum to top the hill. If I hit a ledge or bump to bring the front up it would bog as well. As if the gas would cut off.

 

So I'm thinking maybe lean due to the heat here in Alabama. Though it wasn't hard to start. I take the plug out and yes perfect chocolate brown. So I put it back in and now I can't get it to start at all. I replace the plug and set the gap at .033. And nothing. Both plugs would try to fire but back fire in the exhaust after about three or four kicks. Back fire only off choke.

So once I get this resolved I'm leaning toward main jet or float level. Idle was really low on cold start

 

Valve adjustment may need to be checked as well.

 

Am I heading in the right direction?

 

Thanks,

 

 

[Trailryder42]

Did you blow out the well that the plug sets down in before you removed it?

 

Is this bike new to you? Or has it just started doing this?

 

If you've never checked the valves, it would be a good idea to do so.

 

If the idle is really low, then turn it up a little.

 

Have you ever messed with fine tuning the fuel screw?

 

If you don't know that the float level is set correctly, then by all means, check it. Bogging on inclines and bumps suggests that it needs looked at. You won't see it in any shop manual, but when you set the float levels minimum drop spec, also set a max drop level to just 5mm more than the minimum spec. So if the minimum is 12.5mm, set max to 17.5mm. It's currently probably something like 25mm. That will help with bogging/cutting out on inclines and bumps.

 

When taking the float bowl off, pay attention to if the slosh baffle is sitting in the bottom of the bowl or still attached to the main jet tower.

[bwhollifield]

I have had this bike for a few months.  It has been a power house until the past couple of rides.  

 

I did have it washed down really good before I did any maintenance.  Though.... when I pulled the old plug out, it was a bit tight and rusted pretty good.  Now when I put it, or the new in, it feels like a possible cross thread.  I have not given it a good tightening past hand, but hand tight isn't as far as I wold think.  Two threads maybe.

 

Any good ideas on cleaning the spark threaded hole without removing the head or cylinder? 

 

 

[Trailryder42]

Before you ever remove a plug, you need to use a mirror and flashlight to look down in the well to be sure its clean of debris that can and will fall into the cylinder if you don't blow it out first. If that happens, all kinds of problems can crop up.

 

The threads in the head are probably full of galling from removing the old plug. If it feels like its cross threaded, don't force it. Put anti-seize on a new plug.

[BOAB]

I have had this bike for a few months.  It has been a power house until the past couple of rides.  

 

I did have it washed down really good before I did any maintenance.  Though.... when I pulled the old plug out, it was a bit tight and rusted pretty good.  Now when I put it, or the new in, it feels like a possible cross thread.  I have not given it a good tightening past hand, but hand tight isn't as far as I wold think.  Two threads maybe.

 

Any good ideas on cleaning the spark threaded hole without removing the head or cylinder? 

 

Here's what we used to do way back when I worked in dealerships if someone crossthreaded their plug but didn't want to pay for the big bucks to remove the head.  Take an old spark plug.  Cut four vertical grooves in the threads like a tap.  Grease your newly made plug hole tap and carefully run it in the hole, theoretically the grease will hold any debris.  Carefully swab out the hole with a long q tip.  Put new plug in.  I AM NOT RECOMMENDING YOU DO THIS, BUT IT IS AN OPTION.  We used to make people sign a release for any damage that may result if they opted for this.

[scott_01_xr400]

when you pulled the old plug that was pretty tight and rusted pretty good, did you happen to put in a new plug ?    could be a weak spark in the old plug is causing your problems.

[Muzz67]

If you've given it a bigass pressure wash, the first thing I'd do is drain the carb.

   Only takes a drop of water past the air filter to settle in the carb bowl to make starting a bitch and run awful on WOT.

       Drain carb every time you pressure wash is my advice.

[bwhollifield]

Here's what we used to do way back when I worked in dealerships if someone crossthreaded their plug but didn't want to pay for the big bucks to remove the head.  Take an old spark plug.  Cut four vertical grooves in the threads like a tap.  Grease your newly made plug hole tap and carefully run it in the hole, theoretically the grease will hold any debris.  Carefully swab out the hole with a long q tip.  Put new plug in.  I AM NOT RECOMMENDING YOU DO THIS, BUT IT IS AN OPTION.  We used to make people sign a release for any damage that may result if they opted for this.

 

Thanks for the tip creeper!  I was able to find the spark plug spec, 10mm x 1.0, I found a tap, applied a small amount of grease to the tip and cleaned up the threads.  Keeping an eye on my depth of 3/4", I was able to repair the threads and get a new plug in with no problem.  Tried to kick it again, and again... backfire in the exhaust.

 

I tried to roll it off just to see if it would continue to fire, and nothing.  I started looking at the coil wire and it fell out of the boot.  I was able to find another coil in a box of parts from the PO.  Tried that one with the same results.

 

So now I am talking to a shop.  Only because I do not have the time to repair it and ride in two weeks.  But while talking to my shop guy... he thinks I bent a valve, running the tap in without checking the TDC mark.  Knowing I had a penetration of 3/4" I am quite sure i didn't go but max 3/8" so I don't see how this is possible.  Besides... Isn't the spark plug in the center of the head, between valves? 

 

I will drop it off this afternoon and they will tear into it on Friday.  I should know something at the start of next week.  Thanks guys for caring to post and I will send some results soon.

[Firestone]

Sounds like a potential failing stator or CDI. Under haevy manifold pressure settings (high throttle at lower RPM) you see the worst spark breakdown. A bent valve? Take it away from that mechanic. A bent valve would be a total loss of compression and be like kicking with the decompressor in... very obvious. 

[bwhollifield]

Ok...so the mechanic says that the leak down test indicates that the intake and/or exhaust vales are leaking. $350 in labor to rework the head. Not sure how much in material until top end tear down.

This is on an 2003 with 10k miles

[bwhollifield]

Ok got the xr back yesterday and yes I need a valve job. I will be doing the repairs myself so wish me luck

[Firestone]

Send the head to XR's only for big fins if you have the time and money.

[Wonderspoon]

Ok got the xr back yesterday and yes I need a valve job. I will be doing the repairs myself so wish me luck

Going kibblewhite? Let me know what you find in there. My manual seems pretty bad/inaccurate so I'm curious to see a few things.