2018 TC 125 bog

Toaster16
I am a +40 rider just getting back in to the sport. I bought a new 2018 TC 125 but it has a horrible bog bottom to mid range. Once your past that it rips. Even a slight slip of the clutch does not help. I live at 2200 elevation and I race at a junior to intermediate level. I love the bike but it is un rideable it is so bad. I would rather ride my 2004 KX 125 instead. Please help. Thanks !
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kb228
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kb228 10/14/2018 8:08am
10/14/2018 8:08am
Id look into a bigger pilot jet or adjusting your needle height
BR8ES
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BR8ES 10/14/2018 8:49am
10/14/2018 8:49am
your current specs may help diagnose and fix this.
BR8ES
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BR8ES 10/14/2018 8:56am
10/14/2018 8:56am
I can give you the 19 specs as that works pretty well in my 19. Lots of jetting threads about these bikes, many just take the quick way and go JD Jetting and call it a day. I would drop the clip a spot and go from there, your bike does come with other jets, so give a test day. Easy enough, just tedious.
Toaster16 10/14/2018 9:02am
10/14/2018 9:02am
I had a chance to try it again in a field near my house but not yet again at the track. I turned the air mixture screw in and it got worse. I am now at 4 turns and it is getting better. I think I will try dropping the pilot jet 1 size and move the needle clip up 1 position. What do you guys think ? BR8ES you mentioned JD Jetting, if you think they are the way to go I can try them I don't mind spending some money as long as it gets results. One other question, what plug do you all run in the 2018 TC 125 ?

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BR8ES
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BR8ES 10/14/2018 9:25am
10/14/2018 9:25am
I run a fancy Denso plug, but the stock BR9ECM is plenty fine.... the JD Jetting kit is around 80 dollars, not too bad. Have used them in the past and most like what they get from them. Just follow their instructions. Could go pretty deep with this bike, slide mods and the like. Give your testing a bit more time and trying, you may be able to skip the kit.
AJ565
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AJ565 10/14/2018 4:50pm
10/14/2018 4:50pm
Cut the slide or buy a 5.5 slide from an 2004 Kx125. Read this thread

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dtl210
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dtl210 10/15/2018 8:33am
10/15/2018 8:33am
Sounds just like my bike. Read the thread that AJ linked! I can't believe the difference that cutting the slide made.
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BR8ES
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BR8ES 10/15/2018 1:10pm
10/15/2018 1:10pm
if you need the 19 specs, I can give them to you. Slide mod is easy and worthwhile or just buy one. But.... if you have it running good, then just ride. The whole jetting thing can be an internet wormhole.
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riv187
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riv187 10/16/2018 7:13am
10/16/2018 7:13am Edited Date/Time 10/16/2018 7:15am
I'll grind yours just like I did mine,,,I'm the one who told him his problem and posted my specs, and posted pictures of my workmanship. $20 plus shipping. AJ and Slipdog led the charge a couple years ago on TC250s. I Applied it to my 18 TC125.
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murph783
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murph783 10/16/2018 10:35am
10/16/2018 10:35am
AJ565 wrote:
Cut the slide or buy a 5.5 slide from an 2004 Kx125. Read this thread

Click
By the sounds of it you’ve got a 2004 kx125 as well? Could drop that slide in and give er a try, see if you like it
AJ565
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AJ565 10/16/2018 11:22am
10/16/2018 11:22am
AJ565 wrote:
Cut the slide or buy a 5.5 slide from an 2004 Kx125. Read this thread

Click
murph783 wrote:
By the sounds of it you’ve got a 2004 kx125 as well? Could drop that slide in and give er a try, see if you like...
By the sounds of it you’ve got a 2004 kx125 as well? Could drop that slide in and give er a try, see if you like it
No I don't. A member on here by the name if Digger posted that information and some base jetting to try and going off that info I've been able to fine tune that to the point we're at now.
Toaster16 10/16/2018 5:40pm
10/16/2018 5:40pm
Yes I do also have a 2004 KX 125, I will leave it as is because it runs so well. I will order a new 5.5 slide and put it in my TC 125. Winter is coming quick here in Canada so I don't know if I will get this done and a chance to ride before the bikes are put away until next year. Thanks everyone for all your help.
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AJ565
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AJ565 10/17/2018 8:49am
10/17/2018 8:49am
Toaster16 wrote:
Yes I do also have a 2004 KX 125, I will leave it as is because it runs so well. I will order a new 5.5...
Yes I do also have a 2004 KX 125, I will leave it as is because it runs so well. I will order a new 5.5 slide and put it in my TC 125. Winter is coming quick here in Canada so I don't know if I will get this done and a chance to ride before the bikes are put away until next year. Thanks everyone for all your help.
I don't remember off hand what slide is in the KX125 stock, but the 5.5 is an option slide you can order. It would basically be taking the same slide out of your bike and putting it back in thinking there would be a change in how it ran.
Toaster16 10/21/2018 4:14am
10/21/2018 4:14am
I raised the clip on the needle 1 position dropping it slightly lower, replaced the slide to a 5.5 and put the air mixture screw back to 2 turns out. What an amazing difference ! It has a very slight lag on bottom end but nothing unusual for a 125. Keep the revs up a tiny bit more or slip the clutch slightly and its gone. Now I wish I can get this old body of mine in shape as easy as I did this bike. Thank you to everyone who posted here, you have been a huge help.
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jeffro503
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jeffro503 10/22/2018 10:52pm
10/22/2018 10:52pm
Just a little advice from a fellow TC 125 owner. I was having bogging issue's off the bottom , and really bad on " full throttle for a few seconds , then throttle off , then total bog ". I thought my motor might of been starving for fuel at the end of the full throttle period , which wasn't the case. On off throttle , it was splashing the plug with raw fuel because the jetting was to rich. The Mikuni seems to be a pain in the ass as far as being temperamental. I ended up throwing in the towel and bought a PWK 38....and life has been pretty damn good since then.
jeffro503
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jeffro503 10/22/2018 10:56pm
10/22/2018 10:56pm
Toaster16 wrote:
I raised the clip on the needle 1 position dropping it slightly lower, replaced the slide to a 5.5 and put the air mixture screw back...
I raised the clip on the needle 1 position dropping it slightly lower, replaced the slide to a 5.5 and put the air mixture screw back to 2 turns out. What an amazing difference ! It has a very slight lag on bottom end but nothing unusual for a 125. Keep the revs up a tiny bit more or slip the clutch slightly and its gone. Now I wish I can get this old body of mine in shape as easy as I did this bike. Thank you to everyone who posted here, you have been a huge help.
I guess I should have read through all the replies haha. Great to hear you got her running right. And no worries on the very bottom being a little sluggish / bog. I think they all do that , to make the last 90% of the throttle work good. If it runs crisp right off the bottom , usually mean's she's a little to lean , and will stay slightly lean all the way to the top. At least that's what I've learned on these little bikes. Definitely a key is to keep the revs up just slightly so you don't get it down into the bogging territory.
AJ565
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AJ565 10/23/2018 6:30am
10/23/2018 6:30am
jeffro503 wrote:
Just a little advice from a fellow TC 125 owner. I was having bogging issue's off the bottom , and really bad on " full throttle...
Just a little advice from a fellow TC 125 owner. I was having bogging issue's off the bottom , and really bad on " full throttle for a few seconds , then throttle off , then total bog ". I thought my motor might of been starving for fuel at the end of the full throttle period , which wasn't the case. On off throttle , it was splashing the plug with raw fuel because the jetting was to rich. The Mikuni seems to be a pain in the ass as far as being temperamental. I ended up throwing in the towel and bought a PWK 38....and life has been pretty damn good since then.
Reading your other posts I can see you're willing to try new things. If you have your stock carb you should really give the slide mod a try with the jetting I posted for it and ride them back to back. I think you'll be impressed with it as the Mikuni makes more power than a PWK. Once you have a base line setting on them they are no more temperamental than a Keihin when it comes to temperature changes.

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