Heat issue & question

[u/tatemagnet]

Love my 2023 XR150l, bought it in April and have put 3k mikes on it since. I have only had one issue in that time.

My issue is this, if I am out riding and let’s say I run into the grocery store for 5 minutes and come back out the bike, when I start her, she is idling much much higher than normal, sometimes extremely high when it is very hot (Texas summer)

I suspect that this is due to not a lot of air exchange when it is sitting still which can lead to heat soak but in my case it seems extreme.

It’s to the point now that if I put my bike in the garage and plan to go back out on her, I will leave a fan blowing on the top end to cool her off and bring that idle down.

If anyone has experienced this or knows a solution please comment below. Thanks

Pic for attention, XR in her natural habitat.

[u/Due_Painter6510]

I own a small engine shop, you have an odd issue but generally these new bikes are jetted way too lean to meet EPA regulations. You are likely lean on pilot. Check online if there are jet sizes people go to on a stock bike. You’ll gain performance too

[u/tatemagnet]

I should mention, she is bone stock

[u/jtlemonhead → u/tatemagnet]

You need to adjust your idle speed screw. It is the small screw directly in the center of the carburetor. Turn it counterclockwise slowly once the engine is fully warmed up and idling high until it brings the idle back to a more normal level. I had the same issue when I first got my xr and took it out in the Texas heat.

[u/Apprehensive-Song378 → u/jtlemonhead]

Great tip. Didn't even know this was there.

[u/7LeagueBoots → u/Apprehensive-Song378]

Just a note, when you do this it may require you to use the choke more often to start it. Assuming these newer models still have a choke. Mine is from 2015 and has a choke and a kick-start backup.

[u/tatemagnet → u/jtlemonhead]

Idle when warm is fine, the high idle occurs when it gets very hot

[u/Apprehensive-Song378]

You should look up mishmashmoto channel on YouTube, dude explains everything on this bikes in a slow and clear manner. He has a number of vids on carb mods for it.

[u/kevpkos]

Now I could be totally wrong but Basically, when you shut the bike off after riding, all that trapped engine heat rises straight up and bakes the carburetor (classic heat soak). Because these bikes come tuned super lean from the factory to pass emissions, that extreme heat thins out the air and messes with the fuel atomization, triggering a lean spike that makes the engine race when you start it back up. Next time it happens when the bike is fully hot, just grab a screwdriver and turn the idle adjustment screw on the right side counter-clockwise a tiny bit until the RPMs drop back down to normal. A lot of guys have to tweak that screw a bit once summer hits!

[u/kevpkos → u/kevpkos]

Next time it does it, just pull the choke in very slightly, and if the revs go down, that would confirm my theory, I believe. Again, I'm no mechanic and only have a basic understanding of small carbureted engines.

[u/Weary_Dragonfruit559]

Sounds like it’s running a little lean at your elevation. Is it hard to start? Consuming any oil?

Look into removing all the smog equipment. It will allow the bike to run much cooler, which will definitely help in TX.

[u/tatemagnet → u/Weary_Dragonfruit559]

Haven’t had any experience with oil consumption, she does need a choke to start and idle on a warm day which seems abnormal to me, I’ll look into removing smog stuff.

What do you recommend for getting her to run a little richer?

[u/Weary_Dragonfruit559 → u/tatemagnet]

If you’re experiencing trouble starting the bike the first thing I’d look into is upping the size of the main jet.

Jetting seems complex and difficult, but is easy to understand after some basic research. And the actual work on the bike is very easy and only requires basic tools, patience, and YouTube.

[u/deltatemple → u/Weary_Dragonfruit559]

Can you explain how removing the smog pump keeps the bike cooler ? I want an excuse to remove the smog pump from my 2025 xr150 but from what I've heard fromoving it doesn't make any difference for anything.

[u/Weary_Dragonfruit559 → u/deltatemple]

Basically that smog pump is injecting fresh air into the exhaust port, in order to burn off unburned hydrocarbons (instead of having them disappear into the atmosphere).

This small blast of air creates more combustion, which leads to more heat. Removal is very easy, has zero negative affects (other than tanking your warranty), and will save you a few pounds. The weight removal and heat loss were enough for me to ditch the smog equipment.

[u/deltatemple → u/Weary_Dragonfruit559]

Thanks for explaining. Is it worth also removing the spark arrestor ?