100% synthetic oil not when below 0o C?

[Leon_gasgas]

Hi!

My new '07 EC250 does not like full throtle in temperatures below freezing. The bike is crisp and nice until you try to give it full throtle quickly. It hesitates. If I close a bit the throtle, it revs out nicelly. Scared of the engine not getting enough petrol, I tried a 185 main jet after break in. Not good at all, rich everywhere... Went back to the 180 and emmediatelly was much better. I played as well with the air screw and things got even better. Currently at 2 turns out and tonight I am going to try 2,5 turns.

The manual says not to use 100% synthetic oil when it's cold. I used Mobil 1 and now Castrol TTS with no difference between the two. And of course here in Finland we use antifreezing liquid... Also, I get a lot of the black spooge out of the silencer.

Should I try a semi-synthetic oil following the manual, or keep trying setting the jetting right? I didn't have any similar problems with the '98 as long as I used the correct main jet. And always I used 100% syn oils.

Thank you for any replies!

Leon

[GMP]

That doesn't sound right. I've never read an '07 manual but have never heard of that before. My bikes have run fine from around 10 to 100 deg F, same 36:1 Amsoil Dominator premix, minor jetting changes. I never even needed to block one rad off. Kent A rides all winter in Sweden and has no problem either.

Does it bog/surge hesitate, or blubber hesitate?

What do you mean by "antifreezing liquid"?? If you mean a fuel additive like ethanol to absorb moisture and prevent fuel line freezing in automobiles, that could really lean your jetting out in addition to the cold. You shouldn't need that as long as you use known good fuel.

My guess is your lean on the needle, maybe boarderline lean when its warm so it feels worse when cold and possibly compounded from your fuel. The carb circuits have more overlap than you think.

[Dave]

Leon,
Does your '07 have an intake restrictor? One of those would really reduce top end power.

[Leon_gasgas]

Thank you for the replies!

Yesterday with -10 C and the screw 2,5 turns out the bike worked better. I didn't want to press it but one or two times I tried a bit and the top power felt right. Still this black spooge comes out of the silencer but I think it was less.

I received the bike ready for competition. There are no restrictions. With the throtle open (let's say) 95% the bike was revving out nicelly. As I wrote, I tried a 185 main jet and it didn't like it at all. It was barely moving... With the 180 now I don't think I am on the lean side because the bike works very nice. Good torque and everything except this tiny hesitation on really full throtle.

My friend with a KTM250EXC '06 mentioned as well that with the one size bigger main jet in the winter, the air screw had to be 2,5 turns out in order for the bike to work good.

I called as well the main distributor of Finland asking if somebody else had this problem and said no. From my description he recomended to try even a 178 jet. I won't do it. I want to be on the safe side because the bike does not foul plugs and works great generally. Especially right now.

I have to think about this antifreezing liguid.. Thank you Glenn for mentioning it.

Leon

[Leon_gasgas]

Glenn, thinking your comment about this liquid, I am going to remix new petrol (with the recommended amount of oil) with the petrol there is now in the tank. I think I have been using too big amount of this antifreezing liquid being afraid that the petrol can freeze too easily. I remember I never used that much of this liquid in the '98 EC250 and the bike never had such a problem. Good that our paths here are slow and technical. I never pressed the bike near the redline during these 22 hours I have driven it. Mainly low and mid to start of top end revs.

Thank you again for this comment!! You might just have saved the life of this amazing 07 engine!

Leon

[iancp5]

Leon,

I don't have much experience with below freezing running but ....
You are running mostly tight tracks, when you go for full throttle is it just an instant & you back off or do you spend a while trying with it wide open?

Reason is when I was playing with my jetting a while back when it was too rich I had loads of black spooge and after a while in the woods it would hesitate on full throttle and take a few seconds to clear, then it would rev out.

Try it on a flat open bit - maybe cover the rad to make sure you don't cold sieze. Obviously it wont run right if the engine isn't getting hot enough - warm it up and see if it'll run WFO. If it clears after a few seconds then revs out you probably are too rich.

I once fully covered both sides of my rad (thinking I would remove one side later and forgot) when it was about 0 deg C. It ran for 1.5 hours before boiling and I think that was only because the air temp had risen to about 5 deg C.

Ian.