After an hour of riding the bike wont kickstart

[Frostywire]

I have a crf250x when I first kickstart my Motobike is kickstarts straight away and Will continue to kickstart perfect for the next hour or so of riding, if I then stall it on something technical it will very rarely start when kicked and that's only after trying to kick it to hell and back. To get it started again I push start it and then usally after that if it stops again it's a 50-50% chance of will kick with no problem or just not kick over at all. I believe the bike is jetted right but who knows, I would love someones expert opinion

[RichIOM]

Are the valve clearances in spec?

 

Are you pulling the hot start lever when it happens?

 

[Frostywire]

I do try the hotstart lever amongst the many times I try to start it. I don't know a huge amount about valve clearances. Is there a kit to buy or something to adjust it or do you have to replace the whole things of they are incorrect?

 

[RichIOM]

No it’s a regular maintenance task you should be carrying out.

Based on your response I’d get your valves checked.

You just need a torque wrench and a set of feeler gauges.

There’s loads of tutorials online for checking them and it’s a fairly straightforward task.

[Jim Dettman]

Sounds like jetting to me.  A little more detail would help, age, number of hours on it, etc, but If it's jetted correctly, when it's hot you need to use the hot start.  The other thing that will impact starting is leaving the bike in gear.   Even with the clutch pulled, there is more drag.   You'll find that it starts far easier if in neutral.

How to check if the slow circuit in the carb is tuned properly.  On a fully warmed up bike:

1. Pull the hot start *slightly*,  You should get a rise in the rpms

2. Pulling the hot start all the way should kill the motor.

3. Pulling the choke out on it's own should kill the motor.

  If you can do this, it means you are slightly rich on the slow circuit, which is where you want to be.   If you can't do the above, the tuning is off.

The other issue is that you should really not be kick starting it, but using the e-start.   Matters more on the 450 where compression is higher, but the cases are thin and you can crack a case potentially.    These bikes were setup for the e-start to be used.  Kick start was meant as an emergency backup type of thing.

 I don't think it's valves (you'd have a tough time cold as well), but it's not going to hurt to check them either and know where they are at.    As the valve seats wear and the valves stretch, the gap closes up and that gives you hard starting.  To get the proper gap, different thickness shims are  used.   But the shims can only be so thin, so at some point, you can't get the correct gap.   At that point you need new valves.

Jim.

 

Edited January 26, 2020 by Jim Dettman

[Chuck.]

I agree with Jim. From years of owning big 4T singles I learned that the pilot circuit and mixture screw adjustment must be correct for easy kick starting. The difficult hot restarting after a stall, and the stall itself, indicates a carb problem. The stock jetting on these engine are very lean and that can create starting issues.  An aftermarket heavy flywheel makes the engine more stall resistant as does correct tuning; and covering the clutch lever at low speeds can also prevent stalling. I do all three and my engine runs very smooth at low speeds wo stalling, almost like a good running XR250R. 

The engine has estart and it will continuously spin the engine until it start vs the kicker which only turns the engine thru one cycle. 

The engine also has an automatic compression release to make starting easier but it reduces cranking compression to about 59psi (spec) and if a valve leaks, and/or the rings are worn,  and/or the timing chain is worn the cranking compression will be lower. When it drops to about 50psi the engine becomes more difficult to start, and if in the low 40s it will not start.

[Frostywire]

Hey guys thank you so much for the responses so far. I did have issues when trying to correctly jet this bike, before this one I had a 2004 crf250x and according to the manual it needed a 40 pilot jet, I changed that to a 42 which seemed to help although I could still never get it perfect. This bike is a 2007 I checked the jet and according to the manual I believe a 42 is required although it had a 40, I decided to leave it as a 40 as that's how I got it then I'm sure I'll be able to get it running good again like that. I originally go the bike tuned the best I could using the hotstart and the rpm raise to go off. It still wasn't perfect, I found when I put and after market thumb fuel screw it just automatically ran better, not sure if it was slightly differently shaped. I'm pretty sure I have turned my bike to do what Jim was saying altho I believe if I pull my choke out when it's warm I think it still just rises in rpms like it does when you first start it. I'll have to check. The reason I haven't been using estart as I have another issue there. It was working fine till the little relay on-top on the right of the dash started ticking. Apparently that could be due to bad battery but the previous owner told me he put a new battery in when he sold it to me, I plan on changing that relay but that's as far as I have gotten.