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I have 40p, NECJ 3rd, 158m, as 2. It seems good, maybe fat on the bottom. (i’m guessing, i have been mostly riding slow rocky technical single track rides lately, and there is a stream of splooge running down the silencer at the end of the ride (silencer new))
i was thinking dropping to 38p, raising clip one or going to a NEDK needle
suggestions?
thx
Matt
I just put a PC pipe on my 250 (the stock one lasted 9 hours before it cracked)
On the PC pipe my stock springs are loose and don't hold the pipe snug back to the cylinder.
They aren't stretched out or damaged and worked fine on the stock pipe.
I wonder if PC welded the hooks in the wrong spot and I need shorter springs now?
The parts fiche shows the stock KTM springs as 62mm so I'm think I'm going to try ordering a set of 57mm springs.
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and by fine i mean it takes 2000 ft lbs of torque to stretch that spring to the hook point. feels like youre about to hit yourself square in the face.
take a set of calipers to both pipes and measure distance from the hangar to the end of the pipe.
I own a 14 sx 250 and while I'm currently out with a broken collarbone, plan on a few upgrades.
I've already had the suspension revalved and sprung for my weight and have just ordered the PC linkage arm.
I've got the ktm sxs (made by doma) front pipe, which I did run with the PC304 silencer but the weld snapped where the pipe goes in the can so I've just bought a fmf powercore2.
I was thinking of adding the 300 kit, but have decided against it. I like to keep my bike in the revs so not sure the 300 will be for me. Instead I'm going to have the 250 motor worked on and also having the carb oval bored to 38mm.
also been looking at the vforce 4, but not decided yet, all depends how funds are looking when it comes to putting the bike back together.
Tom.
Ridden with it twice and am getting it sorted but so far it starts with one kick, no splooge and is much easier to adjust. Don't have to take the carb or float cap off to change jets, just adjust idle screw or power jet screw. 10 second adjustments and less than $500 for the whole kit with throttle cable and Rods. I wasn't bad at jetting, or maybe I was, but after what seemed like 100 different combos in my climate is had enough.
Pit Row
I have a TE250 2015. It has at the moment these engine mods:
1. Left hand side panel has four 1” holes drilled for improved breathing. This mod is just for Husqvarnas restricted airboxes not needed for KTM.
2. Keihin PWK 38S carb (38 mm two mm larger than std 36 mm)
3. Jetting 175 main jet, 42 pilot jet, Suzuki RM 250 2008 NECJ needle in 3rd (middle) clip position, air screw 2 turns open, 6.5 slide
4. V-Force 4 reed cage
5. TC250 cylinderhead milled 0.5 mm (squishband 1.20 mm)
6. TC250 CDI and heat range 8 NGK Iridium spark plug
7. Red power valve spring in place of std yellow spring and adjustment screw flush (not turned in or out)
I have ignition map switch but run this bike only with more agressive setting = high setting
With these above engine mods it has totally changed this bikes performance. It is basically now modified TC250. I have different gear ratios as it is TE250 with 6 gears and high gear ratios. In Europe we have as std 14-50 sprockets but I have 12-42 so even higher ratio.
Next it will get RK Tek head and Wiseco 1-ring Racers Elite forged piston. Also Bill’s Pipes full exhaust system. I have ordered and paid my Bill’s Pipes nickel coated pipe many months ago but there are some delay with the coated ones (coating itself). It will get carbon fiber silencer. RK Tek head and this piston are waiting to be installed when I get my Bill`s Pipes exhaust and silencer first. I will also do a few small things to the cylinder when I change that piston. Later maybe another RK Tek head insert and I will raise the cylinder with 0.75 mm extra base gasket to get a bit longer transfer ports and exhaust ports duration. But this must have the correct head insert so the squish is correct.
With the carb, the only year ktm put a 38mm carb in the 250sx was the 03, and they swapped it for the 36mm, but they never changed the intake block either, from 03-16 the engine was setup for a 38mm carb, same part number since 03
Duke Kaboom
9000 rpm 21,6 m/s
9500 rpm 22,8 m/s
10000 rpm 24,0 m/s
Here are the very same piston speeds for a comparison for Husqvarna TC 125 with a stroke lenght of 54.5 mm and these are always equipped with only 1-ring piston:
11890 rpm 21,6 m/s
12550 rpm 22,8 m/s
13210 rpm 24,0 m/s
So it seems like this 1-ring Wiseco Racers Elite piston is good for high rpm use. Or actually high piston speeds.
I also agree that a little more crank/flywheel weight is good for traction. TE250 has more crank/flywheel rotating weight than TC250 because of the electric starter originally.
1-ring piston has many benefits and in 2-ring piston the top ring is the only ring which really matters as it is in contact with combustion gas/pressure and can really seal. I mean as long as the top ring does not have blow by. Second ring is just hanging in there until the top ring starts to leak pressure and then it tries to seal but usually at that time both rings are already in changing condition anyway. I think the only real benefit for second ring is the heat dissipation but even this task is mainly done by top ring anyway.
In my opinion it is more about how good quality piston, piston ring and piston ring groove are than just if it is 1-ring or 2-ring piston. Race engines have usually only 1-ring. Wiseco has that ArmorPlating in these Racers Elite pistons. It makes piston ring groove much more wear resistant and creates better piston ring sealing with the piston ring groove according to Wiseco. And these pistons are made of 2000 series alloy not 4000 series.
But 250’s are not so much at very high rpm than 125’s or like your modified 144. But like I wrote in my previous message there is quite high piston average speeds anyway and in my opinion this is what matters. I will try this 1-ring piston anyway when I next change my piston. There is now normal Wertex 2-ring piston in it. I will do some casting clean up to the cylinder when I take it off. No real porting but just some small things.
How much rpm do you think these modified 250’s have? Stock engines will rev at least to 8000 - 8500 rpm so I assume these will be in the 9000 - 10000 rpm range.
As for the single vs twin, the bottom
Ring in a twin ring, does a lot for suction, and pulling a new charge into the engine as all the suction comes from the underside of the piston moving upwards, and then the same upon the piston coming down from top dead centre after combustion, it helps to then push the newly brought in charge of air and fuel up through the transfer and boost ports. The heat dissipation is a bit better than a single setup for sure, as the double ring faces transfer more heat to the cylinder wall over the single ring setup, but there in lies the advantages of the single ring piston, less ring resistance will mean the piston will travel more freely, and less friction from ring tension to the cylinder wall, will also decrease cylinder wear, and with the reduced friction, it will be free to make more top end power. I run single ring wiseco pistons in my 144, tried vertex replacements from ktm as they are a better grade of metal used when ordered from ktm, but I felt the twin ring top end wore out faster, made less power up top, and a bit better low end, so I pulled the wiseco piston I just pulled out of the top end, got new ring, wrist pin, and bearing, and sent my piston out to koolcoat to have the sides redfinished with teflon, and a ceramic coating added to the top to refect heat build up. I got alllllll the power I lost back.
One thing I find really helps a single ring hold compression better though is more mix, helps that little ring stand strong and cool in the face of high rpm danger lol.
I have to agree As well, the piston speeds of a 250 will be much higher at a lower rpm due to rod angle and stroke length.
And as for rpm range, a stock 125 tc or sx will both rev to about 12,000rpm, but with the sxs ignition I got for my 144, has raised the rpm range to probably 13,000rpm. It was well worth the 200 bucks I paid for it.
But for going with the piston, I'd just look into your rpm range that you usually spend time in, are you flying wfo? Or up and down using 100% of the rpm range idle to redline. That should be a defining factor to what power your looking for. Little tip when it comes to rings as well, I may have used a yz250 piston in the bike, but I used Honda ti piston rings in conjunction with it. It's a pretty rad combo, with exceptional wear life.
My goal is to get wide rpm range usable power and believe it or not to make it easier to ride and less tiring by getting smoother power/torque curves. Red power valve spring is in now and will stay anyway as I like how it gives more power sooner. Adjusting screw set flush with the cover like you had also so power valve starts to open at 5700 rpm and is fully open at 7300 rpm. This is quite small rpm range only 1600 rpm vs. stock yellow power valve spring setting (flush) starting at 5700 rpm and fully open at 8000 rpm = 2300 rpm range for power valve to open fully. But I really like how the red spring gives the power out as it has more power sooner at lower rpm and I feel like I will be faster with it. If I used this bike for enduro I would put back that yellow spring.
That RK Tek head and Bill´s Pipes exhaust will also improve wide rpm range power not only high rpm. Actually RK Tek head may even give a little less high rpm power as I ordered it to have wide rpm range (13.5 marking in the head). It is ordered for pump gas 98 RON with 5% ethanol and sea level altitude mx use. It has around 0.9 mm squish band in it but there is more volume in the heads combustion chamber.
What I have read RK Tek head also likes to be fed by more fuel so I will definitely feed it more so this will help to keep piston ring cooler. I run 50:1 mix and unfortunately I have to use pump gas with 5% ethanol. Piston ring would seal better if more oil was used in the fuel mix like 32:1 or even more but I don´t want to use more oil as then carb settings has to be changed as it changes to leaner settings with the same jets/needle as fuel content is smaller and oil content is bigger.
I have now 175 main jet with stock FMF exhaust and I have 178 and 180 main jets to test with. I have also NEDJ needle to test with if needed. It should be the same as NECJ but half clip richer. I have now in it 42 pilot jet and have also 45 here. I will change my jetting when I install RK Tek head, Bill´s Pipes exhaust and that Wiseco 1-ring piston. Jetting is now very good and no spooge from the silencer.
You gave me again more to think about with your comments about second rings other tasks like suction of intake charge. But do you believe 1-ring pistons only piston ring doesn´t be able to work just as well if ring seal is good? It should work as it works in 125´s and smaller. One thing is these 250´s have 66.40 mm piston diameter. Two rings help to stabilize the piston better in the bore. But it depends how well the piston itself is designed as there are many other things like how the piston skirt is designed and how the exhaust/intake side of piston are balanced so the piston "rocks" less in the bore etc.
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