XT600 rough at low revs - ideas?

Northern jock

Well-known member
UKGSer Subscriber
Joined
Sep 8, 2005
Messages
5,176
Reaction score
753
Location
Kingussie
I have an XT600 which, after a few idle years was brought back to life, including a new exhaust, a carb overhaul and new air filter (amongst much more work). When it was stuck in the corner a few years ago it ran okay but the revs kept running up - so new inlet manifolds which has cured that.

The running though is rough below about 3000 rpm, the idle stumbles, it backfires a lot on the over run and it stalls occasionally on tickover. I have adjusted the mixture as that wasn't quite right but it's still not quite there.

All I can think of is, after much searching, replace the main jet with a larger one.

Any ideas?
 
Put a new pilot jet in.
When left for a period of time the fuel residue leaves a varnish in the jet.
 
I'd check and most likely clean the pilot jet...like Tim said, despite an "overhaul" the pilot jet orifice is likely fully or partially blocked.
I brought my "posh" Ural back into service after a 5 year lay up last week, and even though I stripped and cleaned the carbs, float bowls and all jets, after a few miles it was popping and stumbling at low speed....only running properly when I put the choke on the left carb, but even then it wouldn't tick over.
The left carb's pilot jet was blocked....the orifice is smaller than a strand from a wire brush, and it doesn't take much to block it.

I know it's an arse to do on an XT600, but it's carbs out and strip again mate.
Main jet's not the problem.
 
Might even be worth going one size up on the pilot if your running a less restrictive slip on :thumb2

Different bike but a similar scenario in that a previous bike ( CCM644 ) felt a bit strangled and had a slightly ' hanging ' idle when hot, bought it with a very free flowing ( noisy ) slip on and then added a K & N air filter....ended up increasing the pilot jet from 25 to 27.5 and the main jet from a 130 to a 150 and raising the needle by one notch ( or lowering the clip ). The other significant difference was that the air filter lid had to be left on but slightly ajar, other than that it wouldn't run clean..took me a while to figure that lot out :blast
Went like an absolute rocket afterwards...another bike that I wished that I'd had more storage space and held onto !
 
If you haven't done so already, pop in a new plug.
 
It's a new plug so not there. Pilot jet next then, I'll order a new main just to have as another option

And yes, a job for a long wet and miserable day
 
Standard pilot jet is size 48, I've found a size 50 from Kedo but can't find a 52.5 which I've seen recommended on the Thumper website. Any sources out there?
 
Standard pilot jet is size 48, I've found a size 50 from Kedo but can't find a 52.5 which I've seen recommended on the Thumper website. Any sources out there?

If you consider that a stock bike with the original size pilot jet starts and runs fine, I'd still go back to checking yours for even the slightest bit of cack in there.
 
If you consider that a stock bike with the original size pilot jet starts and runs fine, I'd still go back to checking yours for even the slightest bit of cack in there.

Yup, definitely worth checking but it's pain to remove and replace the carbs so I'd rather have the new jet in hand just in case
 
Definitely worth trying to source the next size up pilot jet with the free flowing end can, also maybe go up from a 130 to a 135 main...either that or get hold of a standard can and stick with a totally stock set up ( including needle position ) and put the dismantled carb through a sonic bath.
 
The old can was done so I had to bin it, not many used ones around but looking, certainly the easier option if one turns up - though they are rather heavy lumps
 


Back
Top Bottom