Jump to content
Sign in to follow this  

XR250L Hard starting - I know its been done to death but...

Recommended Posts

Hi Guys,

I think this is probably my first post here, I'm having trouble cold starting my '96 XR250L and I'm hoping there is some good advice out there. I've been through the multitude of threads on this topic, so many solutions its mind boggling.

I rebuilt the engine to a 280cc with a Thumper Racing kit recently, sent them the top end and carb for the machine work, valve grind and re jetting.

Put the engine back together, checked valve clearance/auto decompressor play and they are perfect. New plug, coil, lead (resistor is still in there), timing is spot on.

The bike is very difficult to start cold and I suspect the choke, once it starts it runs perfectly and the mixture looks spot on by the plug with nice crisp power.

Cold, after about 5 mins of kicking with the choke off it will sputter, a few more kicks and it will catch. Put the choke half on or full on and it will not fire even once. I'm used to seeing a butterfly for a choke so this setup is new to me, once it does start and I pull the choke on halfway there is a significant increase in the revs. I would guess its about 2000-2500 rpm, I have not checked that with a tach. There is a tach on my timing light so I plan to do this.

Any ideas on what I should look at for this issue? I'd like to use the bike more, it needs to start more readily from cold before I can depend upon it.

It still has the stock exhaust on it, I'm wondering if this might be gummed up inside (I'm sure the PO never cleared out the carbon, I haven't either yet!). Maybe I'm just using the wrong starting procedure......

Si

Share this post


Link to post
Share on other sites

Here's how I start my 91 XR250L, but keep in mind, mine is stock, except for the accelerator pump spring modification. I pull the choke out all the way. I then position the kick starter until I feel like the piston is at TDC on the compression stroke. I will then give it a kick. It will usually start after about 5 kicks. I leave the choke on for about 3-4 minutes. Cutting the accelerator pump plunger spring helped out imensely with throttle reponse. Hope this helps.

Share this post


Link to post
Share on other sites

Thanks Slip, what RPM would you say you motor runs at when the choke lever is fully out? I'm wondering if the choke isn't set right, I know its not adjusted to the factory setting as the tamper proof paint/thread lock is gone.

Si

Share this post


Link to post
Share on other sites
Thanks Slip, what RPM would you say you motor runs at when the choke lever is fully out? I'm wondering if the choke isn't set right, I know its not adjusted to the factory setting as the tamper proof paint/thread lock is gone.

Si

I'd say probably 2000 - 2500 RPM's. Just a guess, as I haven't put a tach on it.

Share this post


Link to post
Share on other sites

Me thinks I am flooding the motor with the choke then, the motor sounds like its doing over 2000rpm with the lever out halfway. I guess here is what I need to do at a minimum:

1) Check for air leaks

2) Adjust idle

3) Adjust fast idle

4) De coke muffler for the hell of it

Thanks for you input :-)

Si

Share this post


Link to post
Share on other sites

I've noticed with my 280L I only need full choke on days less than less than 60F. And even then I usually take it down to half choke as soon as it's running. On warmer days (75F-90) it is hard to start on full choke so I just start in on half. My friends XR300 was similar but even less Dependant on choke. That being said both were still cold blooded Honda's and needed to warm up completely before they would run right.

I'm running a pre '96 XRR Carb (138/40), XRR Header, DPR9Z Plug (Coldest), and XRR Oil Cooler.

Share this post


Link to post
Share on other sites

Thanks Guys, I'll have a play with it this weekend. The good weather is just around the corner, need get some use out of the bike to justify what I spent rebuilding it ;-)

Si

Share this post


Link to post
Share on other sites

when you pull the choke cable it not only actuates the choke butterfly but should also open the throttle a little bit. watch your carb when you pull the choke and make sure its doing this. I never had problems starting my xr250l cold. hot? another story....

Share this post


Link to post
Share on other sites

Just wanted to give you guys an update on how I got on, the bike will now start with 5-10 kicks which I guess isn't too bad. I adjusted the choke by backing off the nut, I think it was too rich and flooding the motor. I also took the battery off and gave it a good charge, the connector in the battery compartment was a bit crusty also.

So I guess that's about as good as it gets. Makes me jealous of my friends CL175 that starts first kick everytime!

Si

Share this post


Link to post
Share on other sites

Limmey, did you cut the spring for the lever that pushes on the accelerator pump plunger. This really got rid of the off idle bog on mine and also improved the throttle response. Look on the right side of the carb while turning the throttle fully. You will see that the stock spring hardly moves the plunger. My bike will start on 5 kicks at the most when cold. I'm too lazy to take the carb off to clean it, but I figured that it runs so good, why bother.

Share this post


Link to post
Share on other sites

Haven't tried that one yet Slip, its on the todo list along with the resistor removal mod. I'm doing a ground up restoration on a 1968 Mini Cooper S at the moment, its been balls to the wall trying to get it ready for paint next week. The fork seals (plural!) started leaking last week, its the bike showing me its displeasure at the lack of attention.

Si

Share this post


Link to post
Share on other sites

being as you put a 280 kit in it, did you change jetting? main and pilot ? increasing the bore almost always is a need for more fuel, For cold starts, bump the pilot jet up to begin with, go to www.jetrus.com and look at the jet ranges, I would start by going up 2 on the pilot and the same for the main, adjust the air fuel screw out about 1 7/8 to 2 turns. A fatter / richer pilot circuit (jet) will remedy the cold starts forever.

Share this post


Link to post
Share on other sites

Thanks Moto, Thumper Racing rejetted the carb for me when they did the machine work. I asked at that time how to make the adjustments to the jetting once I built it back up, they told me that the settings they put in are correct 99% of the time. So far it runs like a champ once its going, no hesitation when rolling on WOT and a nice power increase - I guess they have done a few before. These carbs are way too complicated for me, I'll limit myself to adjusting SUs ;-)

Si

Share this post


Link to post
Share on other sites

Limmey, I did the resistor removal mod by replacing it with a longer spring. Wow, I only took the bike out for a few minutes, but did notice a significant difference. I measured the resistor and the resistance is 4700 ohms. This resistor apparently drops a lot of voltage across it, there by reducing voltage to the spark plug. The bike feels peppier due to a stronger spark. 👍

Share this post


Link to post
Share on other sites

Slip, what was the purpose of that resistor -to reduce interference to electrical equipment nearby? If that's the case then I will be happy to remove it if it makes the bike run better ;-)

Si

Share this post


Link to post
Share on other sites
Thanks Moto, Thumper Racing rejetted the carb for me when they did the machine work. I asked at that time how to make the adjustments to the jetting once I built it back up, they told me that the settings they put in are correct 99% of the time. So far it runs like a champ once its going, no hesitation when rolling on WOT and a nice power increase - I guess they have done a few before. These carbs are way too complicated for me, I'll limit myself to adjusting SUs ;-)

Si

try this - I was impressed with the results on my 86 XL600R.

http://www.dynojet.com/jetkits/motorcycle/honda.aspx#250_500

Share this post


Link to post
Share on other sites

Check out dynojet and see if they have a carb kit for it, I installed on in my 86 XL600R and wow oh wow, easier starting and crisp jetting / throttle response.

Share this post


Link to post
Share on other sites

Those kits look cool but I have to careful with that stuff, the county in AZ I live in requires emissions testing for motorcycles. Crazy I know! It passes the test with the Thumper Racing setup so I'm inclined to leave it at is it.

Si

Share this post


Link to post
Share on other sites
Slip, what was the purpose of that resistor -to reduce interference to electrical equipment nearby? If that's the case then I will be happy to remove it if it makes the bike run better ;-)

Si

I'm not quite sure? That's why the use resistor ignition wires in cars, to reduce radio interference. But for a bike, it makes no sense in my opinion. But it does feel like it makes a difference. Try it out, you can always throw it back in. 👍

Share this post


Link to post
Share on other sites

I guess the downside is I won't be able to talk on my cell phone while riding... ;-)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...