Hi guys,

After a recent trip to the mechanic, my XL125 is no longer accelerating as it should.

For a quick recap: the mechanic cleaned out the carburator (there had been a strange problem of the engine sputtering when it rained), checked a sound coming from the timing chain (turned out to be nothing) and adjusted it, and replaced the chain kit.

Since that visit, for whatever reason, the bike lacks power at low revs and takes quite a while to gain speed. This is especially noticable in 1st and 2nd gear, where there is a significant acceleration gap until above ~4000-5000 rpm. It's even worse when the engine is strained by going up a steep hill or with the extra weight of a second person, as the power is almost insufficient whereas before it could handle it easily. Also, if I throttle hard at low revs (even on neutral), the engine sounds bogged down and almost drops out before stabilizing.

Other than that, the bike starts instantly and idles fine. Outside of the power loss, there is no obvious issue. The carburator has been checked and double-checked by both the original mechanic and another with no obvious issue. The original mechanic also rechecked the timing chain and currently has no idea as to how they could have messed up the bike.

I'm certain that something the mechanic did is the cause of the problem, as I had done some fairly consistent riding in the weeks before without issue. Unforunately though, I'm running out of respectable mechanics to troubleshoot with as I'm located in Madagascar. Anyone have ideas on what could be the cause?

Appreciate any suggestions.

Kellen

deleted

Not fun!

Sounds like somewhere in the re-assembly process the mechanic got something wrong.

If it is idling OK, and running fine at wide open throttle it seems like the idle circuits and main jets are fine. This points the finger at the needle that passes through the main jet and meters fuel at mid throttle settings. Its possible when re-assembling the carb this has not seated properly in the slide and now is sitting too high. This would cause the symptons you describe by making the engine run too rich (ie get too much fuel). To check all you have to do is unscrew the top of the carburettor and pullout the slide when you can then have a look to see if the needle is fully seated. If this is gibberish to you even someone with basic knowledge should be able to do this check.

If its not that I'd still be suspecting an error in reassembly somewhere as the cause, so get a good parts diagram / manual and just check everything over on the carburettor against the standard assembly process and settings.

Good luck

__________________
Martin

finally back on the road again


http://awayonmybike.blogspot.com/

Are you sure the mecanic replaced the chainkit with a similar one?
If you now have a different gear ratio (bigger front sprocket or smaller rear) you could have the symptoms as described.

when you say chain kit, do you mean the timing chain or drive chain?
if he has got the timing out by a tooth or two (easy to do), that would give you the symptoms you describe. This is easy to fix.
Quick way to check, using a straw and a torch (nothing solid) take the plug out and get it to top dead centre, (or use the proper timing marks ideally). Then look at the cam timing marks.
My guess is that the cam is a tooth retarded, will give poor lower revs running, but free it up a bit at high rpm.

__________________
Harley Davidsons,
The most effective way of turning petrol into noise without the side-effect of horsepower

Thanks for all the replies guys.

Oil is not something I had thought of but I re-checked and although it is close to topped off it is not out of the ordinary.

The carburator has been the primary suspect all along. While I personally haven't taken it apart and verified, I've watched as one of the two different mechanics opened it, cleaned it, and adjusted it several times with no change. My eye is somewhat untrained here as I've only just started doing my own maintenance, but I feel like if there was a problem with the needle it should have been obvious to at least one of these guys.

The drive chain was the piece replaced and the sprockets are almost exactly the same size. Again, the bogging down is obvious even when I throttle hard in neutral so I don't think this should have an effect.

The timing chain issue sound likely, although the initial mechanic shop (who created this problem) did go back and re-adjust it again when I brought the bike back in. I'll give what you've mentioned a try and post the results.

Thanks again for all suggestions, really hoping I can bring this frustrating issue to a close!