Author Topic: [2020] 300 se factory, no power/stuttering on high rpms  (Read 1020 times)

Majkel

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[2020] 300 se factory, no power/stuttering on high rpms
« on: June 10, 2021, 07:45:32 AM »
Hello,
Recently my 300 we factory started to loose top end power, it never revs out and instead starts stuttering. It will continue to run (not bogging dead) if I keep holding full throttle but never revs out/kicks. Low/middle works like a charm and no starting or idle issues.
I didn't have any problems before, but noticed last ride that it started to go a little unclean on higher rpms. But it revved after 2-3 seconds with full throttle. Now as meantioned, it cannot rev out at all.

Current jetting: main 172, pilot 40, n8re second clip, 1 1/2t,  running 40m above sea level.

I have checked following:
- Power valve is not stuck.
- No bad cables etc.
- Cleaned carb.
- Tried leaner jetting
- Checked reeds.
- No air leak

I haven't done any electrical measurements.

I start to suspect that the power valve servo is malfunctioned or it might be bad coiling... but maybe someone here have an idea what the problem could be?

jamracing

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #1 on: June 10, 2021, 07:51:01 AM »
Replace the coil...
2020 300 SE Factory

Majkel

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #2 on: June 10, 2021, 07:58:18 AM »
Ok, thanks for input, I will try that, I was also thinking of that before but felt unsure because it runs ok on lower middle.

jamracing

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #3 on: June 12, 2021, 11:01:56 AM »
I had the same situation, ran fine down low and mid, but had starting issues once it was hot. The bad coil still showed proper resistance numbers when cold as well.
2020 300 SE Factory

Gartzza

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #4 on: June 16, 2021, 04:05:52 AM »
yep, the coil.

possiblytoofast4you

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #5 on: June 20, 2021, 12:19:24 AM »
Id recommend chasing a better jetting spec, you've got some power left on the table. unless you're riding sand. 

try
40,
n8rf or n8rg(leaner) clip 2
170

Majkel

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #6 on: June 20, 2021, 05:21:28 AM »
I kittet up with some additional jettings, so will try your suggested jetting.
Honestly when looking back, I have not put much attention to the the jetting before buying this bike, but I have learned a lot about this when troubleshooting and searching for info. So thanks for all inputs.
Also I have a new coil now (not fitted yet), so hopefully this will not be a problem when everything is in place.

Gartzza

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #7 on: June 21, 2021, 04:14:11 AM »
I kittet up with some additional jettings, so will try your suggested jetting.
Honestly when looking back, I have not put much attention to the the jetting before buying this bike, but I have learned a lot about this when troubleshooting and searching for info. So thanks for all inputs.
Also I have a new coil now (not fitted yet), so hopefully this will not be a problem when everything is in place.

I don't know, if the coil in 2020MY is old style (no cdi box included), but if it is, then also get your ECU updated at your dealers, as you'll get the new style coil (Kokusan coil with cdi box [from Athena probably]). It may need that for best ignition, spark and starting. Actually, it's good to get ECU updated time to time (send it to dealer), because manufacturer is making some changes for it time to time. According to dealer, after updates bikes may get better, but never worse.

eralha

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #8 on: July 06, 2021, 04:10:47 AM »
Hi, i had an issue whit my Se 300 2021, one day in the winter the bike started to not having power on high RPM's, good bottom end but no topend.

What i found was the water was getting into the PV electric connection and that would stop it from working, i put a little bit of Teflon on the connection and never had problems agains, check this connection.

ditezz

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #9 on: July 18, 2021, 07:47:43 PM »
Classic Reed symptoms .Is it hard to start?

ditezz

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #10 on: July 18, 2021, 07:50:08 PM »
Start with the easiest.......Change the plug

Majkel

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #11 on: November 20, 2021, 04:58:14 AM »
Very late update about what solved the problem and my thoughts.
- First a switched to a new plug (no change).
- Tried different needles etc. No change
- Checked reeds, no problems.
- Checked exhaust valve, no problems.
- Found that upper engine mounts (the ones that mounts to the top) was cracked.
  Replaced those and also could see that there is a grounding point there.
- Replaced ignition coil.
 
Now it's a beast again, insane change :)

But what i think was the actual problem was the broken upper engine mount  with the grounding point, and not the actual ignition coil.
I haven't switch back to old ignition coil, but my gut feeling is that i would work perfectly even with the old one.

So, as a first check if you have mine symptoms, check upper engine mounts and also check the fitting of the grounding point.

« Last Edit: November 20, 2021, 05:00:07 AM by Majkel »

TTBadDog

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Re: [2020] 300 se factory, no power/stuttering on high rpms
« Reply #12 on: November 21, 2021, 05:33:33 AM »
Thanks for the update, it is good when you update what the fix was. Sherco forums are very lightly attended.
2022 250 SE Factory