Honda XR125L Stuttery throttle

[Shoka]

Hi.

The exhaust on my XR has gradually deteriorated through the winter, and I figured I'd wait until now before getting a replacement, so it didn't get completely wrecked with the salt on the roads.

There was a hole in the exhaust, and it eventually got so bad that it was spluttering and struggling to accelerate until you got into about third gear, and had some reasonable speed going. It eventually got so climbing hills was getting embarrassing. So, I just bodged some plate over the hole with some jubilee clips and some sillicone sealant. That definitely improved things, but it wasn't perfect, and I just figured there was air getting out somewhere else. It always tended to get worse as the engine warmed up. But it was at least workable, so I left it like that until I had it replaced.

I've just had the exhaust replaced and been to pick up the bike today, and to my dismay, with a brand new exhaust, I still get the same trouble, albeit reduced.

Once the engine has warmed up a little, if you have to rev from reasonably low RPMs up, it feels as though you let off the throttle then jam it back on again, after which it goes fine right up to the redline. If you rev it just in neutral, just after the engine RPM starts rising from neutral, it hits point where it splutters and burbles, but if you give it a bit more throttle, it revs past it.

The fact that this still happens after the exhaust has been replaced has baffled me. I don't know if maybe the spark plug got all fouled up when the exhaust wasn't right, or what.

Any help would be much appreciated.

Thanks.
Steve.

[Blue_SV650S]

Thats carburation, you are running too rich.

How many miles has the bike done?

When is the last time you changed the airfilter?
____________________
The purpose of life is to fight maturity.

[Shoka]

The bike has done just over 8000 miles.

As for the air filter, honestly, I've never changed it, and I've had the bike since 3500 miles.

*edit* I've just had a thought. The hole in the exhaust before was just where it tapers up to the rear can, and it was on the upper side as well, just facing the airbox. I guess it could be that the airbox has got clogged with crap from the engine

[Shoka]

Yeah, I've just had it in bits, and the air filter is absolutely clogged with black sooty crap out of the exhaust. A new air filter I think.

https://shoka.zapto.org/xr125airf.jpg

[Blue_SV650S]

[Shoka]

I've not replaced the filter yet, but I took it out at work today and blasted it with an airline. Loads of soot came out of it, and sure enough on the way home, it was like a different bike. It pulled like it hasn't done in months, and none of the stuttering at all.

Thanks ever so much. Next stop, new filter.

Cheers,
Steve.

[Pete.]

Looks like the inside of a hoover-bag
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Blue_SV650S]