2013 GTX155 Flat spot between 4000 to 5000 rpm

[Divenuno]

Hi guys

My GTX155 I have noticed to what seems to be a flat spot/ stall like it is getting starved of fuel or air between 4000 to 5000 rpm. Strangely this only happens when I initially start it, I idle run past the 100m shore line buoy, open up the throttle and it splutters at 4-5k for about <10 seconds, once it gets through that everything is fine, I can come back on revs and up again no problem. Any ideas?

 

[Sportster-2001-951C-Stock]

I'd bet the spark plugs need to be replaced with a fresh set properly gaped, if that's never been done. That's the first thing I'd do.

 

[KK40384]

I'd bet the spark plugs need to be replaced with a fresh set properly gaped, if that's never been done. That's the first thing I'd do.

Agree with this. Change plugs and report back

 

[Jafo]

Plug change will fix it

 

[Sportster-2001-951C-Stock]

Be certain they're correct, also.

Make sure they're the right plugs too, exactly to the letter. Could be, someone has installed the wrong plugs, so always confirm the new plugs are the factory specified plugs to the letter. Generally, it's best not to substitute any other plug brand or number other than the originally specified ones b/c the fuel and spark maps were developed under specific conditions.

 

[Divenuno]

Hi guys,
Thanks for your input, I have replaced the plugs with factory spec plugs and verified the gaps, all i need now is some time off to go test it on the water. I'll let you know how it went.
Cheers.

 

[Sportster-2001-951C-Stock]

Were the center electrode insulators quite light in color all nearly identical? If one or more is dark or black and sooty, that may indicate there's a problem.

 

[Divenuno]

Here they are, looks pretty good to me, but its still worth a shot.

 

[Sportster-2001-951C-Stock]

Yes, they do look pretty good. The center one seems to have slight oil deposits on the insulator nose which is common from proper storage oil fogging (they look good though, if these plugs have a season of more of use you're doing okay!) and the left one seems to be running slightly colder of the three.

My money remains on the plugs needing replacement but I'm sorta wondering what's going on with that left plug, maybe nothing to get excited over. It it happens again, I'd yank that one out and look for moisture. Compression check all three cylinders as well.

 

[Divenuno]

OK report back...its still doing it. So my next thought is to buy one ignition coil and fit it to each cylinder one at a time to eliminate a possible duff coil. What do you guys think?