2019 KX450 Starting / Idling Issues

freeride1
Profile picture for user freeride1
Posts
5
Joined
10/11/2021
Location
Magna, UT, USA
freeride1
Hey everyone,

I have a 2019 KX450. Bike has 70hrs on it. Very well taken care of. I’m having issues with it starting and idling. I cranked on it for over 20 minutes and it finally fired up (and a couple backfires) with the air screw pulled out and some throttle. After it fires up, it won’t idle for at least 5 minutes until it’s really hot. I’m constantly messing with the idle screw as well. After the bike is warm, zero problems. Idles fine, starts fine.

I checked the batter, it’s pulling 13.8V.
I replaced the spark plug.
Oil is changed.
Airfilter is clean.
Only ran 91 Non-Eth

Thanks for the help!
|
kb228
Profile picture for user kb228
Posts
6153
Joined
1/31/2018
Location
Mansfield, OH, USA
kb228 10/11/2021 12:32pm
10/11/2021 12:32pm
Did you check your valve clearance?
freeride1
Profile picture for user freeride1
Posts
5
Joined
10/11/2021
Location
Magna, UT, USA
freeride1 10/11/2021 12:35pm
10/11/2021 12:35pm Edited Date/Time 10/11/2021 1:23pm
kb228 wrote:
Did you check your valve clearance?
I didn’t. I wanted to see some opinions before I pay someone to do it. I’ve never torn into an engine like that before.
Factor E
Profile picture for user Factor E
Posts
969
Joined
9/22/2011
Location
So Cal, CA, USA
Factor E 10/11/2021 6:21pm
10/11/2021 6:21pm
70 hrs
valves out of spec
need leak down test
poss head rebuild
kb228
Profile picture for user kb228
Posts
6153
Joined
1/31/2018
Location
Mansfield, OH, USA
kb228 10/13/2021 9:33am
10/13/2021 9:33am
kb228 wrote:
Did you check your valve clearance?
freeride1 wrote:
I didn’t. I wanted to see some opinions before I pay someone to do it. I’ve never torn into an engine like that before.
70 hours is about when a top end needs done. Take it to a shop

The Shop

See All »
FGR01
Profile picture for user FGR01
Posts
6130
Joined
10/1/2006
Location
USA
Fantasy
908th
FGR01 10/13/2021 10:54am
10/13/2021 10:54am
This also sounds like possible symptoms of a bad coolant temp sensor. The purpose of the sensor is to tell the ECU when the coolant is cold so that the mapping can be richened accordingly. The fact that the symptoms clear up when the coolant reaches full operating temp suggests this sensor may be bad.
Paw Paw 271
Profile picture for user Paw Paw 271
Posts
3632
Joined
4/3/2013
Location
Benton, LA, USA
Paw Paw 271 10/13/2021 2:26pm
10/13/2021 2:26pm
CHECK VALVES AS ALREADY STATED.

PAWPAW
freeride1
Profile picture for user freeride1
Posts
5
Joined
10/11/2021
Location
Magna, UT, USA
freeride1 10/14/2021 8:01am
10/14/2021 8:01am
Well guys, it ended up being the valves. They were tight. Adjusted them and the bike runs perfectly. Appreciate all the insight!
1

Post a reply to: 2019 KX450 Starting / Idling Issues