jetting a problem?

[KDX607]

right now were at about 40 degrees f. jetting is 160/48. dont know the elevation, mods are powercore silencer. anyway, im soon to install boyesen power reeds. my jetting is too rich now, after the reeds im guessing it will be worse? what combo do you think will best fit after reed installation? 152/42?

 

[Dist1740b]

Rich is good when its 40 degrees out.
I would leave it.I had to set my air screw at 1/2 a turn out
(As rich as I could tune it while out riding)
The reeds slightly richen things .
Speaking of reeds those 607 reeds are funky!?
There mostly one big reed and a 1/8 bigger all the way around for the one seating on the Block.

Nothing like the ones that go into the MX'ers.
When I put them on a CR250 it was night and day
on my '03 KDX 200 I can't tell a difference really!?
HTH

 

[KDX607]

Rich is good
on my '03 KDX 200 I can't tell a difference really!?
HTH

maybe you didnt re-jet?

 

[strider80]

right now were at about 40 degrees f. jetting is 160/48. dont know the elevation, mods are powercore silencer. anyway, im soon to install boyesen power reeds. my jetting is too rich now, after the reeds im guessing it will be worse? what combo do you think will best fit after reed installation? 152/42?

160/48 is going to be too rich anywhere you go, I have not heard of anyone having good luck with the stock combo.

Again, at your own risk, I would try 155/45 to start with, should be safe. I run 152/42 1173 needle with a FMF desert/TCII, Boysen power reeds and a FRP torque ring. This works for me from 0-6000ft (gets a little rich high up) in Washington State. I just ran a 25hr team enduro in E. Wash. it was about 1500ft and in the mid 30's at night, bike ran great, plug looks good.

Keep any eye on the plug and how the bike sounds and you will be fine.

 

[Dist1740b]

I am running a 152/45 I have a 42, I'll try it out !?

Thanks

 

[strider80]

I ran 152/45 for awhile, I found that it liked to load up with prolonged lugging/tight trails. The packing was also really oily. Now I run a 42, and is much crisper when getting back on the throttle with less spooge.

I have heard a few times for what it's worth, "you will never burn up a motor on the pilot, tune the pilot for rideability," I tend to agree. I don't think the motor will ever make enough heat at 0-1/4 throttle to cause a problem, but too lean or too rich on the pilot will hurt rideabilty and throttle response. Maybe a Pro will chime in and call me an idiot, I dunno.

Tuning the main you need to be aware of what is happening, because you can cause damage with improper jetting due to the heat load.

 

[foots]

If your running down a long stretch and then chop the throttle, if your pilot is too lean you will seize the motor. The pilot won't be allowing enought oil/gas mixture too keep the cylinder/piston lubed at a higher rpm chop.

Makes sense?

 

[Dist1740b]

Just another curve ball, I am running 52:1
I am going back to 40:1 and I'll see how that goes without changing the jetting.

Thanks

 

[strider80]

If your running down a long stretch and then chop the throttle, if your pilot is too lean you will seize the motor. The pilot won't be allowing enought oil/gas mixture too keep the cylinder/piston lubed at a higher rpm chop.

Makes sense?

I am sure this could happen, but is it likely? I don't know, just curious. Are you talking a really lean pilot? Or say, one size too lean? Seems like a lean pilot shows up with off idle response before engine problems occur. Or is this more of a general problem with premix 2-strokes that is accentuated by a lean pilot? Hence the advent of oil-injection for snowmobiles and road bikes etc.?

With the throttle chopped all the way closed, is a 42/45/48 pilot really going to make much of a difference on the raw volume of oil deliveried to the engine? Seems like it would be a pretty small percentage difference at those low flows at closed throttle.

 

[foots]

But if your running at a high RPM say in 4th or 5th gear and shut offthe throttle, using the engine braking, the only lubrication would be coming through the pilot circuit.

 

[strider80]

I agree, but will a jet size lean or rich under that circumstance really matter? Seems like the engine will be starving for oil either way, of course it will be slightly better richer. Seems like us 2-stroke guys need to avoid that situation if possible by pulling the clutch.....just thinking out loud. I have not heard of KDX guys seizing motors this way, have you?

 

[John Harris]

I run 155/42 good for all year and conditions with slight pilot screw adjustments. I tried the 40 pilot and it worked when the weather was hot, but clearly too lean when it was cool/cold. My experience is that it is hard to damage a two stroke at lower rpm, but I agree it is possible with the high rpm engine braking situation described above. Jet for your bike and conditions. I agree the pilot jetting is critical for good low, mid range performance. Cheers John