Suddenly running poorly

[ChrisK]

It's my M900 again. As some of you may know I recently rejected the carbs. I fiddled with it for quite some time and got it running well. Since the rejet I've ridden hundreds and hundreds of miles.

I rode it yesterday and it was great. I rode it to work today and it was great. Went to ride after work on one if my favorite routes and it starts to kind of bog down, just barely noticeable at first. Then it started getting worse and worse and finally quit. I got it running again and it ran for like 5 miles but there were periods of sudden power loss, then it quit altogether again. Running with choke on improves it a bit.

It feels like a fuel delivery issue, does that sound right? The fuel lines from tank to carb are unkinked. Where should I check for a blockage? I'm going to start by taking the air box off and checking the small filter right at the carb. Any other suggestions?

The only other thing is that I changed the oil on Saturday. Put in Amsoil 10W-40 and its at the right level. And also ridden 100 miles since then.

[ChrisK]

Nvm, I'll post a pic when I get a chance

[ducpainter]

Did this start right after a refuel?

[koko64]

If it runs better with the choke on then there is every chance of a fuel blockage.

Had the same symptoms  and found a new fuel filter full of scale from the fuel tank shedding a layer due to inactivity (yard sale).

Vacuum or manual petcock?
Breather line to tank kinked?

[kokis]

Sparks? What about sound and pipes temperature?
Once one of my sparks melted, it was terrible.

[koko64]

Putting the choke test aside, if the bike is jetted way, way rich, like needle in richest posn or massive pilot jet, then over time the plugs can foul and reach a point when they give up. Sooty black plugs and will no longer fire. Easy to check. If they are white you may be starved of fuel.

[ChrisK]

This was the small fuel filter at the carb:



I cleaned out that debris, put it back together, and it ran great.

[koko64]

Good outcome.
It only takes one bad load of fuel.