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The Shop
Honestly , if the carb becomes an issue , I had thought about going with a Lectron on this bike , instead of the PWK / STIC mod like I did on the 125. Any advice on a new 250 here , on where to start my jetting and so forth?
I haven't opened my carb or checked the reed's just yet , and was wondering what a good starting point may be? And also.....do I stick with 40:1 , or should I do the 60:1 like I've seen some guys mention?
For fuel mix...60-1 in the 250,,,40-1 in 125...Don't fight what factory tuned it too. They specified JASO and 60-1 for good reasons.They call for 'JASO' rated. Thats the highest most recent japanese test, I understand. Belray and Motul they recommend are JASO. I searched high and low for other cheaper easier to get JASO oils and found KLOTZ snowmobile is and cheap by the gallon. https://www.amazon.com/Snowmobile-TechniPlate-128-Ounce-Gallon/dp/B000G…. I raced 2 stroke Karts back in the day, 17,000 rpms on Super techniplate,,so I'm good with there products.
There's 100000 opinions on oil and brands,,I have several brands for different bikes in my own shop from Benol to Pennzoil,,...but this Klotz is JASO, so I use it, 95% of others are not.
With T2 or u4.4
MJ 490
PJ 37.5 (when cooler out, below 65*) 35 when above 65*
AS 2.0 turns out
NJ S-4
Needle 42-75 3rd clip (4th clip when above 80*)
Slide 5.75
PV 1.75 turns in
With C12 the jetting I was running.
MJ 460
PJ 32.5
AS 2.0 turns out
NJ S-4
Needle 42-75 3rd clip
Slide 5.75
PV 1.75 turns in
Straight C12 mixed 60:1 with amsoil dominator
stock .yz250s sound crisp..i want ours to sound like that, any suggestions? thanks
Pit Row
52 yr old shitty rider
MJ 470
PJ 35
Slide 5.5
Needle 42-75
Clip 4th (or 3rd weather depending)
Needle jet s-4
AS 0.5
If you look at AJ565's specs, it looks like we have zeroed in on the ideal spec. If you apply the correction factor for the difference in specific gravity of pump vs C12, we essentially have the same spec.
On the stand you can tell its fat. It doesn't load up, but its not as crisp as with the u4.4. Out on track it runs just as well as the u4.4 did. No bog, hesitation, load up, nothing. It just pulls hard with instant throttle response. I forgot my camera so I haven't gotten any video of the updated jetting to listen to.
Here's a modifiction I did on my 18 TC125 .The powerjet kit was only$25. Most would build up a boss with JB WELD to install it in,,but I TIG welded a lump and then shaped it with dremel tool and drilled tapped for mine. This really is nice as I can tweak the carb off to the side of track just by reaching down and twisting the knob. with air changing from morning to afternoon 20+ degrees here in florida , I find it nice to just go off to back lane from track prior to 2nd moto and make a couple 'hits' to test/adjust it before going to starting line. I rarely ride my TC250 so haven't done it yet,,,but it would work just the same to find that ideal sweet spot. The other change was the RK head mod. Worked to smooth out the power and broaden delivery. Squish is exactly .030 vs .045+ on stocker. It maybe a mod the 250 may like based on taste.
https://www.ebay.com/itm/VITOS-EXTERNAL-POWER-JET-KIT/112586520209?hash…
I weighed the thought of spending $$$$ for the intelijet,,,but principle and operation is same,,,just I reach under and twist dial rather than it remotely mounted needle elsewhere,,,and I spent $30 vs $300. The range of adjustment is like 3-4 mainjet sizes. I dropped 2-3 on my main to start,, and use the dial 1-2 turns out. It really is noticeable when you find the sweet spot and the engine is like on afterburner. Most people "just ride" a bike...this isn't for them...they are happy to be close and not fouling plug..others like you or I are always looking for that little extra and this gives it. without getting out the jets and tools
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