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Help 2011 CRF250R (CW270)hard starting when cold.

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Hey everyone,

 

I have a 2011 CRF 250R with a Cylinder Works 270 top end, and a ported and polished head. The bike runs great, but when it's cold it is very difficult to start. I have a Yoshimura PIM2, and I tuned it on the dyno and at the track. The only issue is cold starts. Once the bike warms up it takes 1 to 3 cranks max to start it up.

 

 

Engine Mods,

1. Ported/ polished head

2. CW 270 top end

3. Hot Cams stage 2

4. Yoshimura PIM2

5. Athena Full exhaust

 

Thanks!

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Have you checked your valve clearances ?
I did the valves when I installed the new top end. I have 11hrs on it now, and I'm going to check them this week.

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Adjust your fuel screw with a hot motor to reach maximum idle speed, then lower the speed as needed with the idle screw

If you are below 1 or over 1.75 turns out, your pilot is the wrong size.

Try twisting the throttle 3 times before starting.

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Adjust your fuel screw with a hot motor to reach maximum idle speed, then lower the speed as needed with the idle screw
If you are below 1 or over 1.75 turns out, your pilot is the wrong size.
Try twisting the throttle 3 times before starting.
Thanks but the 11' is FI

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23 minutes ago, ///M5 said:
27 minutes ago, THE KRAN said:
Adjust your fuel screw with a hot motor to reach maximum idle speed, then lower the speed as needed with the idle screw
If you are below 1 or over 1.75 turns out, your pilot is the wrong size.
Try twisting the throttle 3 times before starting.

Thanks but the 11' is FI

I new that. (doh)

Is the TPS in factory spec? If you moved it, it will change fueling at closed throttle, which is your problem. Recalibrate. 

**A big bore pulls more vacuum across the Throttle body, so your are probably rich at idle, when cold.

You need to do a 'passive reset' of your ECU first once you get it to start cold with NO THROTTLE. It won't reset (re-center) until you can do this.  A passive re-set is starting the bike with no throttle for 3 min, and then shutting it off. The collant must reach 200 degrees before shutting off. When you restart, the bike will be calibrated to the surround air pressure, changing the mapping slightly.  This will only work when you can start and run with zero throttle.

Have you used the 'fast idle' knob position?  Will it start then?

If not, you are probably very rich at idle and need a remap.

Before you do that:

Service you FI system.

Pull the pump, replace the filter, pressure clean the nozzle, replace the nozzle oring (no matter what).

** If it still starts poorly, get your dealer to re-map the FI (or buy the dongle and software and do it yourself)  at the closed throttle position for the correct AF ratio. A littler leaner is all you are looking for.

 

Edited by THE KRAN
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I new that. (doh)
Is the TPS in factory spec? If you moved it, it will change fueling at closed throttle, which is your problem. Recalibrate. 
**A big bore pulls more vacuum across the Throttle body, so your are probably rich at idle, when cold.
You need to do a 'passive reset' of your ECU first once you get it to start cold with NO THROTTLE. It won't reset (re-center) until you can do this.  A passive re-set is starting the bike with no throttle for 3 min, and then shutting it off. The collant must reach 200 degrees before shutting off. When you restart, the bike will be calibrated to the surround air pressure, changing the mapping slightly.  This will only work when you can start and run with zero throttle.
Have you used the 'fast idle' knob position?  Will it start then?
If not, you are probably very rich at idle and need a remap.
Before you do that:
Service you FI system.
Pull the pump, replace the filter, pressure clean the nozzle, replace the nozzle oring (no matter what).
** If it still starts poorly, get your dealer to re-map the FI (or buy the dongle and software and do it yourself)  at the closed throttle position for the correct AF ratio. A littler leaner is all you are looking for.
 
Thanks

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I did not move the TPS when I did the install, and I calibrated the TPS via the Yoshimura software prior to the Dyno tuning, so I dont think that would be the problem. Once I get a chance, I will check the TPS and valves again. 

Question though...Would tight valves cause a difficult cold start, and go away when warm???

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Yes - just like your body when you wake up - cold and stiff until you warm up and flexible again   :excuseme:

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Yes - just like your body when you wake up - cold and stiff until you warm up and flexible again   :excuseme:
Ok, I'll report back when I check the lash. Hot Cams recommended these specs vs oem. 201709042128401000.jpg

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On 9/3/2017 at 7:12 PM, ///M5 said:

I did not move the TPS when I did the install, and I calibrated the TPS via the Yoshimura software prior to the Dyno tuning, so I dont think that would be the problem. Once I get a chance, I will check the TPS and valves again. 

Question though...Would tight valves cause a difficult cold start, and go away when warm???

Lash and leaks are not related. Old valves leak.

16 hours ago, ///M5 said:

Ok, I'll report back when I check the lash. Hot Cams recommended these specs vs oem. 201709042128401000.jpg

 

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So you don't think it's related to valve clearance? Compression is Good, and it's actually hard to crank.

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On the 2010 there are two temperature sensors, one in the air box and one in the engine.  Mine was hard to start cold until I replace both of them and now it starts in 4 to 5 kicks cold and 1 to 2 hot.  If the ECU doesn't know the engine is cold it won't be able to compensate.

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