Bog off of idle 250sxf @ 45hrs

I am having similar problems to other people who have posted about a bog in the low rpms. But it's strange that mine is just now happening after 45hours. My bike won't idle anymore, and if the rpms are low and you blip the throttle it will cut out and die. I am thinking that mine is more of a jetting issue and not with the squirter thing and stuff. I think I am going to order the JD kit and see if that helps things out. What all is included in the kit? Does it come with multiple jets? I am pretty sure I want to drop 2 sizes on the pilot and try that out.

I've already messed with the idle, air screw, spray out the jets, and messed with the squirter adjuster bolt thingie. Any ideas why it just started this weekend?



Both 250SXF post sound similar so I will respond to yours to cover both.

I like the direction you’re going with jets. Let’s keep it simple before making big changes. Put on a clean air filter and try that. Turn your low speed idles up (that’s the one on the side of the carb) and your High speed (the slotted one on the bottom) out a half turn. Check your pipe to make sure you are not leaning it out to much. Run it and see if it improves or adds to the problem. Write down your current settings and any changes you make. See if you can clear it up without opening the carb.

If you think you are running lean you probably are. Try to get more gas through the carb by moving the clip one notch in from the end. Please note what slot it is in and move in one. In effect you are moving the needle out slightly to give it more gas. . Now try it again.

If it’s been running great I would not adjust the accelerator pump period.

You can go with a 180+ main jet without problems.

It should take you a few hrs to try a few things and if you start to pull your hair out, remember to test it like you race and ride it. I can bog mine with a fist full of throttle in 3 rd gear coming out of corner at 5 mph. Just try rolling the throttle on.

Without more detail about how the bike changed, I do not want to jump to conclusions, but my SXF developed dead spot off idle all of the sudden and it was corrected with a new set of rings. It would start and ride great for the first 15 minutes and once it got hot it lost all its power off idle. I rode it in the midrange and upper RPM without any problem, but it would die if I let it dip to 1000 RPM.

My local dealer put a set of rings and a piston in for $ 300 including labor. can get you the parts because they are a high volume dealer.

If changing your carb a little makes a difference, putting a James Dean Jet kit in would be the next step.

Please respond with more detail and settings please.

This issue started up friday while I was at Rolling Hills MX. I talked to a lot of people there including Al Albiker - Zack Osborn's Mechanic. He and I messed with the air screw and blew out the jets with carb cleaner and he fiddled with the accelerator pump a bit. Nothing really helped. I think my issue is actually too much gas not too little. The temperatures are rising and the humidity is increasing therefore the air is less dense, right? I already ordered the JD jet kit last night but it sounds like it doesn't come with a pilot jet. I think changing the pilot jet will fix most of the problem. And the JD jet kit will just help overall performance. I'll get back to you guys with more information as I continue to mess with the settings...

Sadly my symptoms sound a lot like your piston ring issue. Maybe it's time for a little overhauling :thumbsup:

Don't jump to conclusions to quick.

The symptoms for ring replacement on my bike were:

1. Starts and runs great cold to warm.

2. After 20 minutes, the bike got noticeably hotter in slow moving situations. Rock and log crossings. I am 100% off road; sounds like you are mostly MX.

3. Bike would stall off idle and would take lots and lots of kicks to get it going 8-10.

4. Bike would start and idle but to get it going you had to rev it to half throttle and keep it in the meat of the power. If you let off it would die.

5. Let the bike cool down for several hrs and it would start and run find for 10 minutes, then repeat above.

6. This condition came on almost overnight. Within two rides the bike went from being the most reliable starting machine to acting like the valves were completely out of adjustment.

When my SXF did this, I did not touch the carb. I knew something was not right so I called Munn. Had Canyon Motor sports put ring and piston in and the bike was like new. Starting and running great.

You have done so much to the carb that ………. well I hate to see you do rings unnecessarily. If you were satisfied with how the bike was running for the first 45hrs. Put your carb back to how it was and then maybe it is a ring issue. I caused my rings to wear prematurely with running to lean. Like all bikes, lean makes it run great, but ring wear will come on quick.

If you are trying to blip the throttle while on the stand like you can a two stroke that could be the problem. My experience with 4 strokes is that they like to have the throttle rolled on better. Mine will die if you twist the throttle too fast on the stand but runs great out on the track or trail. I have the JD kit and it runs great at 7000 ft. But still does not like to be restarted hot. Got too close to a cactus yesterday and had to stop to pull stickers. Then took 5 minutes to restart. Solution? Don't ram cactus with your hand.

But I ramble.


If I am on the track going into a corner and I pull the clutch and slam on the back brake the rpm's drop like normal then it will just cut out. I doubt it's the clutch cause it does this in neutral too.

Looks like you tried all the simple stuff. Do try a spark plug while you wait for the JD kit to arrive.

The only time my SXF acted like that it was the rings. I just could not keep it running. It came on almost overnight, but I had 70 hrs on it. Will it start and run well for 10 minutes and then start stalling????

The cost of the rings, piston and labor was minor. I have 70 hrs on the second set with no problems to date.

Give us an update after installing the jets, but I would not enjoy trying to trouble shoot worn rings with a jet kit.

looks like I am looking at about $100 in parts to do a ring job. They want $29 for a cylinder gasket... yeah right.

there are 2 rings, an oil scraper and a pressure ring. both are $28.65 each.

Plus 2 gaskets and I'll see what I come up with. Before I order the parts though I am going to open her up and shove my feeler gauges where ever I can heh... I'll get back to you. But relative to past bikes this bike has been a dream come true both in maintenance and performance.

try starting it in the dark and see if the plug or plug cap is arcing anywhere.......I know of this being a problem on a couple of sxf's locally. worth a shot.

Update: I was messing with the bike today and I did discover that my plug is arcing against the head. The arc is actually jumping from the boot to the head. When the plug is out of the engine you can visually see the spark on the boot and not on the plug. I am driving up tuesday to buy a new plug cable/boot. Hopefully that will solve it. I'm not sure how it went bad though.

Catatonic you were right on.

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