17' TC250 Jetting Help

sandman768
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sandman768 6/1/2018 5:42am
6/1/2018 5:42am
At 30.0hrs my wheels are holding up good, the usual spoke check before every ride, spokes seated pretty good at this point, I don't ride on very hard/ rocky terrain. The 37.5 pilot is what I run & switch back & forth between 450-460 mains. I"m about yo pull the head off & inspect piston /cylinder...Will perform squish test to see what it is...AJK: assume you are running some race gas with head cut to 1.2? Did tightening the squish clean up low end jetting?
AJK
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AJK 6/1/2018 7:47am
6/1/2018 7:47am
sandman768 wrote:
At 30.0hrs my wheels are holding up good, the usual spoke check before every ride, spokes seated pretty good at this point, I don't ride on...
At 30.0hrs my wheels are holding up good, the usual spoke check before every ride, spokes seated pretty good at this point, I don't ride on very hard/ rocky terrain. The 37.5 pilot is what I run & switch back & forth between 450-460 mains. I"m about yo pull the head off & inspect piston /cylinder...Will perform squish test to see what it is...AJK: assume you are running some race gas with head cut to 1.2? Did tightening the squish clean up low end jetting?
No need for race gas, just 98 RON pump gas (I think it's same as your 93). Yes, it did clean up low end jetting and improved torque too. With 304 silencer the powerband is much longer than stock which means a couple of less shifts per lap.
sdhuskyrider
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sdhuskyrider 6/2/2018 2:27pm
6/2/2018 2:27pm
Caved in and bought a Pro Circuit Works pipe. My only words for it are WOW. It's got more low end, the same hard mid range hit and WAY more top end. Good buy. The stock pipe was absolute junk compared to this pipe. The only changes I made to jetting was opening up the air screw from 0.5 to 2.0. My 9oz flywheel weight showed up today, so I'll be trying that next weekend.
AJ565
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AJ565 6/2/2018 2:32pm
6/2/2018 2:32pm
sdhuskyrider wrote:
Caved in and bought a Pro Circuit Works pipe. My only words for it are WOW. It's got more low end, the same hard mid range...
Caved in and bought a Pro Circuit Works pipe. My only words for it are WOW. It's got more low end, the same hard mid range hit and WAY more top end. Good buy. The stock pipe was absolute junk compared to this pipe. The only changes I made to jetting was opening up the air screw from 0.5 to 2.0. My 9oz flywheel weight showed up today, so I'll be trying that next weekend.
I put mine on this week, but I won't be able to go ride with it for a week or so. Isn't it crazy how the stock pipe is side by side the PC pipe? No wonder that thing doesn't rev. It also sounds amazing with it, like a 250 2 stroke should.

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sdhuskyrider
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sdhuskyrider 6/2/2018 4:40pm
6/2/2018 4:40pm Edited Date/Time 6/2/2018 7:06pm
sdhuskyrider wrote:
Caved in and bought a Pro Circuit Works pipe. My only words for it are WOW. It's got more low end, the same hard mid range...
Caved in and bought a Pro Circuit Works pipe. My only words for it are WOW. It's got more low end, the same hard mid range hit and WAY more top end. Good buy. The stock pipe was absolute junk compared to this pipe. The only changes I made to jetting was opening up the air screw from 0.5 to 2.0. My 9oz flywheel weight showed up today, so I'll be trying that next weekend.
AJ565 wrote:
I put mine on this week, but I won't be able to go ride with it for a week or so. Isn't it crazy how the...
I put mine on this week, but I won't be able to go ride with it for a week or so. Isn't it crazy how the stock pipe is side by side the PC pipe? No wonder that thing doesn't rev. It also sounds amazing with it, like a 250 2 stroke should.
Yea I'm guessing they make it crap so they can sell FMF pipes from the hard parts division. No way KTM would purposely sell with such a crappy pipe without an alterior motive.

On another note....anyone been paying attention to Chris Alldredge? I kind of want to put together a Go-Fund me for the kid and help him try to get into the top 10. Man that would be sweet.
nascarnate326 6/3/2018 4:29am
6/3/2018 4:29am
Really curious to see how you guys like the flywheel weight. I’ve consodered one but love the bike as it is.
sdhuskyrider
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sdhuskyrider 6/3/2018 8:52am
6/3/2018 8:52am
nascarnate326 wrote:
Really curious to see how you guys like the flywheel weight. I’ve consodered one but love the bike as it is.
From what I gather, many of the old factory 250 2 strokes used them and it makes sense. Can't go fast when the wheel is spinning in place. I know for a fact MC used one.
sdhuskyrider
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sdhuskyrider 6/3/2018 7:44pm
6/3/2018 7:44pm
Some more tidbits of info I've discovered about squish clearance on this motor...VHM's 250 dome has a squish clearance of 1.6mm (0.063") and I have been told by XPR and now Pro Circuit that tightening squish on this motor only takes away top end power. I'm sure they have all done the math to determine this and I know VHM has dyno proof. While tightening squish to .040" may help with the carburetion, I can be fairly confident that it comes at a cost. I'm going to recut my head but I'm going to do so by copying VMH's dome.
BR8ES
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BR8ES 6/3/2018 9:15pm
6/3/2018 9:15pm Edited Date/Time 6/3/2018 9:20pm
Before I went to the Smart Carb, I was running the Suzuki 16/17-62 needles, 5.75 slide and the 35/460 main(mostly), great thread though!

I use a 12.5oz clutch weight on my 17sx, works real nice. Question for the OP and anyone with some hours on your bike.... have you done the long bolt mod for the idler gear or heard of the case issue? On another website, it seems to be an epidemic.
AJ565
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AJ565 6/4/2018 6:11am
6/4/2018 6:11am
BR8ES wrote:
Before I went to the Smart Carb, I was running the Suzuki 16/17-62 needles, 5.75 slide and the 35/460 main(mostly), great thread though! I use a...
Before I went to the Smart Carb, I was running the Suzuki 16/17-62 needles, 5.75 slide and the 35/460 main(mostly), great thread though!

I use a 12.5oz clutch weight on my 17sx, works real nice. Question for the OP and anyone with some hours on your bike.... have you done the long bolt mod for the idler gear or heard of the case issue? On another website, it seems to be an epidemic.
Are you talking about the gear that breaks when you start it? A guy I ride with broke something in his and said its pretty common on 17's and you can feel it in the kick level before it breaks.
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BR8ES 6/4/2018 6:16am
6/4/2018 6:16am
AJ565 wrote:
Are you talking about the gear that breaks when you start it? A guy I ride with broke something in his and said its pretty common...
Are you talking about the gear that breaks when you start it? A guy I ride with broke something in his and said its pretty common on 17's and you can feel it in the kick level before it breaks.
Yep, the small, 12mm length 6mm bolt holding the idler gear to the case. Horrible one year design, you can't even get 17 year cases now. The quick fix is to run a 18-20 bolt in place if the 12.
AJ565
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AJ565 6/4/2018 6:29am
6/4/2018 6:29am
AJ565 wrote:
Are you talking about the gear that breaks when you start it? A guy I ride with broke something in his and said its pretty common...
Are you talking about the gear that breaks when you start it? A guy I ride with broke something in his and said its pretty common on 17's and you can feel it in the kick level before it breaks.
BR8ES wrote:
Yep, the small, 12mm length 6mm bolt holding the idler gear to the case. Horrible one year design, you can't even get 17 year cases now...
Yep, the small, 12mm length 6mm bolt holding the idler gear to the case. Horrible one year design, you can't even get 17 year cases now. The quick fix is to run a 18-20 bolt in place if the 12.
I haven't looked into it as I have an '18. Hopefully it was only the one year that had the problem.
BR8ES
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BR8ES 6/4/2018 6:33am
6/4/2018 6:33am
AJ565 wrote:
Are you talking about the gear that breaks when you start it? A guy I ride with broke something in his and said its pretty common...
Are you talking about the gear that breaks when you start it? A guy I ride with broke something in his and said its pretty common on 17's and you can feel it in the kick level before it breaks.
BR8ES wrote:
Yep, the small, 12mm length 6mm bolt holding the idler gear to the case. Horrible one year design, you can't even get 17 year cases now...
Yep, the small, 12mm length 6mm bolt holding the idler gear to the case. Horrible one year design, you can't even get 17 year cases now. The quick fix is to run a 18-20 bolt in place if the 12.
AJ565 wrote:
I haven't looked into it as I have an '18. Hopefully it was only the one year that had the problem.
You are good to go, only a 17 model year issue. They went back to a proper design. I have a set of 18 cases to replace my 17s... just not sure if I want to pro-act or react.
sdhuskyrider
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sdhuskyrider 6/5/2018 9:37am
6/5/2018 9:37am Edited Date/Time 6/5/2018 9:55am
What parts do I need to replace on my 17' before the kickstarter breaks my cases? Looks like the idler gear system changed but, the only thing I can do is install the longer bolt.
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BR8ES 6/19/2018 12:01pm
6/19/2018 12:01pm Edited Date/Time 6/19/2018 12:01pm
sdhuskyrider wrote:
What parts do I need to replace on my 17' before the kickstarter breaks my cases? Looks like the idler gear system changed but, the only...
What parts do I need to replace on my 17' before the kickstarter breaks my cases? Looks like the idler gear system changed but, the only thing I can do is install the longer bolt.
If you are running the 17 cases, only thing you can do is the long bolt mod. Otherwise it is the 18 cases, updated idler gear, etc. Pretty involved. I would just do the long bolt mod and ride on, lots of people with the original 12mm bolt and plenty of hours. Am 18-20mm bolt should keep you in the clear.

I have all the 18 parts finally, will probably wait til the off season at this point for the update.
AJ565
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AJ565 7/24/2018 2:57pm
7/24/2018 2:57pm
I had the bike on the dyno. Its still a touch rich if you slowly roll on the throttle you can hear it. I'm going to drop the pilot one size and tune the air screw. I'll give it a try this weekend if I get to go ride as I also need to test out the front suspension revalve to see if I like it.


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riv187
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riv187 7/24/2018 3:40pm
7/24/2018 3:40pm
Thanks for posting dyno. Is all 3 pulls with same jets or ?
AJ565
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AJ565 7/24/2018 3:49pm
7/24/2018 3:49pm
riv187 wrote:
Thanks for posting dyno. Is all 3 pulls with same jets or ?
Yes, As the pipe heat up it started making more power.
sdhuskyrider
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sdhuskyrider 7/24/2018 3:57pm
7/24/2018 3:57pm
Just as much peak HP as the old motor plus the torque of the new motor once you sort jetting out. I'd like to see a 17-18 on the dyno with a Keihin. I bet you lose peak HP.
AJ565
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AJ565 7/25/2018 6:31am
7/25/2018 6:31am
sdhuskyrider wrote:
Just as much peak HP as the old motor plus the torque of the new motor once you sort jetting out. I'd like to see a...
Just as much peak HP as the old motor plus the torque of the new motor once you sort jetting out. I'd like to see a 17-18 on the dyno with a Keihin. I bet you lose peak HP.
Talked to Derek about that as well and he said he believes you'd loose peak power as well. He said if I wanted to buy a Keihin to try he'd hook me up with one and we can put it on the dyno and see. I'm happy with my carb though so no need to waste money.
nascarnate326 7/26/2018 5:49pm
7/26/2018 5:49pm
Put Boysen Rad Valve in my 2018 and now I feel it runs like shit. Go back to stock reeds or get a lectron?
sandman768
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sandman768 7/26/2018 7:25pm
7/26/2018 7:25pm
in my experience rad valves tend to warrant much leaner jetting ..
yz133rider
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yz133rider 7/27/2018 6:59am
7/27/2018 6:59am
Any guide/feed back on the pv springs and adjuster? Mxa contradicts themselves which direction does what.
opyguy
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opyguy 7/31/2018 9:23am
7/31/2018 9:23am
yz133rider wrote:
Any guide/feed back on the pv springs and adjuster? Mxa contradicts themselves which direction does what.
I laughed when I got my MXA review of the 18 250sx because it was indeed entirely contradictory to what they said in 2017...in any event, I have spent over a year trying different things, I can tell you w/out a doubt, turning the P/V adjuster inwards makes the power more linear, if you go too far in you get almost no top end. Turning the adjuster out lets the P/V open sooner (more hit), the caveat being if it opens too soon you will get a bog before it explodes onto the pipe.
hope that helps.
AJ565
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AJ565 7/31/2018 11:33am
7/31/2018 11:33am
yz133rider wrote:
Any guide/feed back on the pv springs and adjuster? Mxa contradicts themselves which direction does what.
On my '18 I turned it all the way out and currently I'm at 1 3/4 turns in.
nascarnate326 7/31/2018 4:44pm
7/31/2018 4:44pm
yz133rider wrote:
Any guide/feed back on the pv springs and adjuster? Mxa contradicts themselves which direction does what.
opyguy wrote:
I laughed when I got my MXA review of the 18 250sx because it was indeed entirely contradictory to what they said in 2017...in any event...
I laughed when I got my MXA review of the 18 250sx because it was indeed entirely contradictory to what they said in 2017...in any event, I have spent over a year trying different things, I can tell you w/out a doubt, turning the P/V adjuster inwards makes the power more linear, if you go too far in you get almost no top end. Turning the adjuster out lets the P/V open sooner (more hit), the caveat being if it opens too soon you will get a bog before it explodes onto the pipe.
hope that helps.
What would you recommend a normal rider do for turns out? I have yet to play with the PV adjuster.
opyguy
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opyguy 7/31/2018 6:13pm
7/31/2018 6:13pm
Take a few laps in stock position, then back it out 1 full turn and go ride for 1/2 hour, see how you like it ( write your opinion down ) Then turn it in back to stock and then go 3/4 in and ride for 1/2 hour... see how you like it. Then compare your opinion of each change.
For what it’s worth I dicked around for about six months and I think I’m actually back to stock, about three in from full out , Bike runs great
Keating
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Keating 9/25/2018 1:43pm
9/25/2018 1:43pm
yz133rider wrote:
Any guide/feed back on the pv springs and adjuster? Mxa contradicts themselves which direction does what.
opyguy wrote:
I laughed when I got my MXA review of the 18 250sx because it was indeed entirely contradictory to what they said in 2017...in any event...
I laughed when I got my MXA review of the 18 250sx because it was indeed entirely contradictory to what they said in 2017...in any event, I have spent over a year trying different things, I can tell you w/out a doubt, turning the P/V adjuster inwards makes the power more linear, if you go too far in you get almost no top end. Turning the adjuster out lets the P/V open sooner (more hit), the caveat being if it opens too soon you will get a bog before it explodes onto the pipe.
hope that helps.
So, was your experience that closer to full out was a harder hit off the bottom and a longer pull on the top end?

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