Harris STIC mod / PWK 38 for my 18' TC 250.......fuel mix?

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1/27/2019 8:37 PM

I sent an email to Derek today about picking up another STIC metering block from him , as I plan on switching over to a PWK 38. I'll be changing to a rad valve , changing the exhaust and milling the head to around "0.045 ( stock is around "0.065" + )

My goal here is , to be able to run the same fuel in my 125 and 250. Right now I'm running 40:1 / 927 with 1/2 and 1/2 Clean fuel and VP 110. I'm thinking of possibly changing both these bikes to a 36:1 ratio instead? I really don't want to run that synthetic stuff in my 250 , but with the stock carb / jetting I didn't really have a choice.

I guess I need to wait to hear from Derek on this , but if I make these changes , shouldn't I be able to make the switch to 927? In my 06' RM250 , i have been running 40:1 / 927 and she ran perfect.....but she also has a PWK 38 on it.

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

1/28/2019 11:11 AM

Was actually going to text you about this (related to your buddy's 150SX as well).

I run 32:1 in my '14 KTM 150SX and '17 Husky TC250; 93 octane (with 10% ethanol) and Lucas Oil semi-synthetic.

I installed a STIC metering block on my '14 KTM 150SX a few months ago. The bike was stock except for a slightly thinner base gasket (to tighten the squish). Never had any issues due to the compression ratio or fuel mixture. Performance-wise, it improved roll on/low end some and really improved midrange and top end/over-rev.

Recently, I swapped the carb from the 150 (PWK) to my 250 (TMX) for some testing. On my TC250, I only have a slightly thinner base gasket, again to reduce squish. Compression is very close to stock. With the STIC equipped PWK on my TC250, I had some pinging when I rode on a softer track that put a higher load on the engine. Performance wise, it was similar to the 150SX but a bigger change: much better roll-on/low end, more midrange, and much better top end/over-rev. But, I was unable to richen the jetting enough to not have pinging in the range I was having it (1/4 to 2/3ish).

Later, put the stock metering block back in and tested the PWK on the TC250 and the TMX on the 150SX. Both were actually better for me in this configuration. The roll on power is still better with the TC250, but without the benefit of the overrev added by the STIC. I do have a PC pipe and silencer on it and they make it better than the stock setup anyways. Also, the midrange and up on the 150SX with the TMX now feels better to me than the PWK. And since less time is spent at smaller throttle openings, the roll on isn't as much of a problem.

All that being said, with your race gas mix you should be fine. I had pinging that was unacceptable and I'm not buying race gas. But, you might ask your buddy with the 150SX to try out your TMX and you could try out the PWK on your TC at the same time.

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1/28/2019 2:21 PM

jeffro503 wrote:

I sent an email to Derek today about picking up another STIC metering block from him , as I plan on switching over to a PWK ...more

You don't have a choice? Why?

Just pick a middle of the road oil-ratio like 40:1 or 36:1 and jet around that for both bikes. Or buy two gas cans and a sharpie if that help you sleep better.

TMX or PWK can work well 20:1 to 100:1. Obviously you'll need to jet for those ratios.

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KTM250SX YZ125 YZ85 PW80 ZX6 FZX700

1/28/2019 7:44 PM
Edited Date/Time: 1/28/2019 7:46 PM

jeffro503 wrote:

I sent an email to Derek today about picking up another STIC metering block from him , as I plan on switching over to a PWK ...more

YZed250 wrote:

You don't have a choice? Why?

Just pick a middle of the road oil-ratio like 40:1 or 36:1 and jet around that for both bikes. ...more

Well , these new KTM / Husky's seem to finicky with their jetting. A lot of guys have dumped the Mikuni and went with the PWK ( like I did on my 125 , and it was a huge difference )

My buddy has a 2017 KTM 250. He went through some major testing on the Mikuni ( actually read a lot of what AJ595 on here has written ). He tried 40;1 with 1/2 and 1/2 race gas on 927 and the bike ran like complete crap. He then switched to Synthetic at 45:1....still ran like crap , tried 50:1 and it got better , and then finally settled on the 60:1 synthetic blend and his bike runs well with the Mikuni. But still has issues with small temp changes / jetting changes.

So I already know my bike won't run well at all ( no matter the jetting ) on 40:1 - 927 with this carb. Even has the JD jetting jet kit installed on his Mikuni , and it still wouldn't run right. Up here in Oregon , we deal with cold 35 degree days to 105 degree's and dry as a bone. The 125 / mikuni setup for me was a nightmare. I don't want to go through that same bullshit with my 250......so I'm getting the PWK. I honestly don't know if it's the absorbent amount of squish these bikes have , the crappy carb or bad reeds. I don't know what makes them want / need to run at 60:1 synthetic , which is way to lean for 927 and I won't run that.

@Erik....let me digest some of the stuff you wrote above , as I'm dead tired from work and my brain isn't functioning right.

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

1/29/2019 6:22 AM

I run 44:1 in my 250. I don't think the type of oil matters as the amount effects rich/lean more than anything. I think the few that have tried my jetting don't change out everything and miss out the important part of changing the needle jet from the stock s-1 to the s-4 with the slide and just try and change the brass. If I ran 32:1 I'd have to rejet because of less fuel to oil and the bike would run lean.

I have a 5.5 cut slide that I can send you if you'd like to try it. You'd have to get the needle, needle jet, PJ and MJ to go along with it, but the slide is whats the expensive part that nobody likes to buy. It's slightly richer than the 5.75 I run, But much leaner than the stock 4.0.

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2018 KTM 250sx
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1/30/2019 8:20 AM

erik_94COBRA wrote:

Was actually going to text you about this (related to your buddy's 150SX as well).

I run 32:1 in my '14 KTM 150SX and '17 ...more

Hey Erik.....all great info here. On the PWK , when you ran it with the STIC metering block , did you by chance experiment with a different needle? From what I have read , it seems like most guys that did any kind of compression change , did it on the head itself , and not with base gaskets. Also wondering if you had a chance to try some 1/2 and 1/2 race gas gas mix? I know on my old RM , it doesn't really care for just strait clean fuel. I was getting a little knocking as well , but with using a race gas mixture , most all of that went away. Btw , the head on the RM is milled slightly as well. But the PWK is all stock with correct jetting from what I remember.

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

1/30/2019 4:39 PM

erik_94COBRA wrote:

Was actually going to text you about this (related to your buddy's 150SX as well).

I run 32:1 in my '14 KTM 150SX and '17 ...more

jeffro503 wrote:

Hey Erik.....all great info here. On the PWK , when you ran it with the STIC metering block , did you by chance experiment ...more

I tried the N3EW and N3EJ with the PWK. Think I got to the 4th clip on the N3EW and it started feeling rich but still pinged. I didn't have a chance to try with any race gas, but I think a 50/50 mix would probably have gotten rid of the pinging.

I have previously ran my TC250 with a head cut down by 0.020". It ran great on pump gas even with the TMX. Then ran a 300 kit for about 10 hours and when I reinstalled the 250 cylinder, installed the stock cylinder head to remind myself how it ran. It is time for a new top end and I plan to install the cut head again and dial in the jetting with the PWK.

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1/30/2019 7:29 PM

erik_94COBRA wrote:

Was actually going to text you about this (related to your buddy's 150SX as well).

I run 32:1 in my '14 KTM 150SX and '17 ...more

jeffro503 wrote:

Hey Erik.....all great info here. On the PWK , when you ran it with the STIC metering block , did you by chance experiment ...more

erik_94COBRA wrote:

I tried the N3EW and N3EJ with the PWK. Think I got to the 4th clip on the N3EW and it started feeling rich but still pinged. ...more

Right on. AJ above has been a big help with dialing in the Mikuni , and I thought about getting all the stuff including the slide and see what would happen ....but damn it , the PWK's run so damn good on the 125 and RM 250 , I think I may just go that route. I'm more familiar with the PWK's as well , with plenty of Jets and needle's on hand. I just have nightmares having to change my jetting at the track every time the temps fluxuate up and down 20 degrees. The Mikuni on that 125 was a major pain in my ass!

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

1/31/2019 9:48 AM

jeffro503 wrote:

Hey Erik.....all great info here. On the PWK , when you ran it with the STIC metering block , did you by chance experiment ...more

erik_94COBRA wrote:

I tried the N3EW and N3EJ with the PWK. Think I got to the 4th clip on the N3EW and it started feeling rich but still pinged. ...more

jeffro503 wrote:

Right on. AJ above has been a big help with dialing in the Mikuni , and I thought about getting all the stuff including the ...more

With the shaved head on the TC and the TMX, I rarely had to adjust the jetting. This was similar on a Honda CR250 that I had the squish fixed on. I liked the Mikuni on it better than the PWK as well.

Will probably test again eventually and report back.

The PWK is definitely easy mode. My first attempt at jetting and it ran great with only a tweak on the air screw (175 MJ, N3EW 3rd clip, 45 PJ, 1.25 out on AS). It is a bit rich, but it ran good enough to not even worry about it.

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1/31/2019 12:50 PM

Correcting is the biggest improvement by far and totally helps in the jetting aspects.

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vomiting equals disqualification.

1/31/2019 4:48 PM

erik_94COBRA wrote:

I tried the N3EW and N3EJ with the PWK. Think I got to the 4th clip on the N3EW and it started feeling rich but still pinged. ...more

jeffro503 wrote:

Right on. AJ above has been a big help with dialing in the Mikuni , and I thought about getting all the stuff including the ...more

erik_94COBRA wrote:

With the shaved head on the TC and the TMX, I rarely had to adjust the jetting. This was similar on a Honda CR250 that I had ...more

Right on Erik....looking forward to your findings. And hey.....did you get your drywall issue resolved? If you have any more question's , feel free to get a hold of me. You got my number!

@BR8ES.....totally agree! I can understand Husky's and KTM's thought process on these bikes , as far as making them pretty mellow right of the floor. But at least the full on race motor is sitting inside these thing's , with a little tweaking. Which I don't mind at all , since I can never leave a stock bike alone anyways haha.

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

1/31/2019 5:06 PM

jeffro503 wrote:

Right on. AJ above has been a big help with dialing in the Mikuni , and I thought about getting all the stuff including the ...more

erik_94COBRA wrote:

With the shaved head on the TC and the TMX, I rarely had to adjust the jetting. This was similar on a Honda CR250 that I had ...more

jeffro503 wrote:

Right on Erik....looking forward to your findings. And hey.....did you get your drywall issue resolved? If you have any more ...more

Waiting to confirm leak is fixed before drywall repair. That should be another week or two. Will report back on that as well. cool

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2/1/2019 5:38 AM

I run 40:1 Klotz Super Techniplate in my 300XC. Took a few days of trying different settings, but I was able to get the bike to run excellent with the stock carb. There really is no reason why an engine will care what two stroke oil goes through it. The new KTM’s are still just a two stroke engine with a Mikuni TMX. Same setup most 125’s ran back in the 2000’s....and some 250’s too.

I have ridden a 300XC with a shaved head and Keihin carb (do not think it had the STIC mod though) and it was not much different than my bike. Maybe a bit more torque down low? But his powervalve was set up more aggressive.

If you take some time with the Mikuni you can get them to run very well, save you quite a bit of $ too.

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Tomac and/or Anderson for 2020.....

4/11/2019 4:43 AM
Edited Date/Time: 4/11/2019 5:40 PM

Jeffro and the group...

I put a PWK on my 18 TC 250 last year. It has V-Force reeds, Pro Circuit pipe & silencer. Stock motor otherwise. Plan on running 40/1 with 50% VP110 & non-ethanol 90 octane pump gas. I also have the STIC to throw at it, but I would rather jet it in without it for starters.

I did buy the JD kit for the PWK. It has been so long ago I forgot the brass I installed. Bike has not been started with the above mods done almost a year ago due to health issues, which have been corrected & the doc says I am good to go. I just pulled the TC out of mothballs and would like to hit the local tracks again.

I will find out tonight what brass I installed.

EDIT: 172-42-1 turn out-slide 65 (6.5?)-needle JD red middle clip

Questions being, anybody have some jetting specs I can start with with the PWK? Might save me a bit of time changing brass.

What about with the STIC? What is your jetting & impressions with it installed?
My STIC came with a 190 main & a 48 pilot from Derek.

Thanks bunches in advance!!

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A big thanks goes out to Donnie at Morgantown Powersports and RJ at Beaver Creek Cycles

4/11/2019 3:55 PM

If anyone is interested I have a brand new never installed STIC with 6 optional main jets and 2 pilot jets for sale. Comes with gaskets, screws, tools and float bowl screws. For PWK 38 $199 shipped.

Also have a Thunder Products Torque Wing for sale $50 shipped.

And a clean stock take off PWK 38 carb from a my 2006 RM project bike for $160 shipped.

Email me at gforcecoatings@gmail.com or text 608-556-5877

(payment via paypal and shipped next day via fedex)
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