Tc125 cutting out.

After the 0:50 mark of this video you can hear it again multiple times.
Both videos with the jetting mentioned first, I tested again at the same track, same ambient temps with the two steps richer main and the richer needle.

The plug reading for both videos was much whiter. Hence why I richened it up a little, I think I am on the right track with the needle setting but I am unsure of the main.

I really am hoping it is not my reeds already....

Man, I don't really hear it cutting out. If you are falling flat on the top end maybe just keep going richer.

Have you checked how far your power valve screw is in or out? That can also affect your bike falling flat up top. I like my 2016 Ktm at 1.75 turns in from all the way out.

CarlinoJoeVideo wrote:

Man, I don't really hear it cutting out. If you are falling flat on the top end maybe just keep going richer.

Have you checked how far your power valve screw is in or out? That can also affect your bike falling flat up top. I like my 2016 Ktm at 1.75 turns in from all the way out.

The 2015 has a different motor than your 2016, I am really wishing I had your motor as I have heard they are phenomenal.

This one is too, just having a minor issue. I have checked the powervalves on my bike though . They are set properly and operating properly! Mine is not adjustable with a spring.

I feel that it falls flat really early, but takes a minute to get there, almost laggy then nothing. I have the KTM Factory SXS ignition too that is supposed to allow these bikes to over-rev.

I just ordered that spark plug they say to run with it. Hoping that is my issue.

Joe, you can it it in this video too, and she just doesn't "scream" up top like I know she wants to or can!
This video is with the first jetting, the richer needle almost alleviated that cutting out issue! But still no over-rev, did I go the wrong direction and actually should have leaned out the main?

Ok yeah, more noticeable in that new video.

Have you looked into trying a JD jet kit? I just put one in my bike and it's phenomenal!

CarlinoJoeVideo wrote:

Ok yeah, more noticeable in that new video.

Have you looked into trying a JD jet kit? I just put one in my bike and it's phenomenal!

You know now that you mention it I remember having one of JD's needles in my yz125 and I remember it cleaning it up a bit!

We will see how it goes with testing this weekend, I should have those jets in a few days, as well as that super super special spark plug

Check all your electrical connections as well. Rule out all the silly things.
Does it cut out at a single throttle position? This could be a clue to jetting vs something mechanical

Bruce372 wrote:

Check all your electrical connections as well. Rule out all the silly things.
Does it cut out at a single throttle position? This could be a clue to jetting vs something mechanical

I am going to check them all this week, in a day or so once I have some free time!
It was mainly cutting out at mid-throttle. The richer needle cured this about 80%, if not more.

Right now I feel that with the richer main it pulled worse up top, so I think I went the right direction on the needle but the wrong direction on the main.

I am also going to be putting that special plug in this week as well.

Too much oil in fuel mix.
Fuel also a bit too high oct for what you need. All you need is 91-93 oct. Higher octane fuel burns too slow for your bike.

Paw Paw

Paw Paw wrote:

Too much oil in fuel mix.
Fuel also a bit too high oct for what you need. All you need is 91-93 oct. Higher octane fuel burns too slow for your bike.

Paw Paw

Please explain your reasoning, it says to use at the least 98 octane with this KTM factory/SXS ignition.

Manual says to run 40:1, should I start there?

Yes, go to the 40:1 the manual calls for , if that is what is called for. ( I would have bet it called for 50:1)
The octane stated in your book is a non US rating and that is much different than here. Our 93 pump octane is about what the other countries call 100 octane.
In truth, our US 100 octane fuel ( or the mix you are using) burns way too slow for your application.

Paw Paw

Ok, compression from about 5 full kicks, throttle wide open, I got about 160 PSI, COLD, in my sneakers. I would guess that with a single-ring forged piston that is a decent reading cold (68 Fahrenheit ambient temp) with squish at 1.22mm.

I went through all the electrical and found the ignition map wires connector to be pretty crusty and full of dirt... I took the harness off the bike, cut the connectors and soldered it together (both wires attached are the aggressive ignition map), because the connector was a little wiggly and I never use the soft map anyways.

I am going to get her warmed up and see what it is warm, just for funsies! I am also unaware of how accurate this compression tester is. It feels like a 125 when you kick it over... LOL.

I showed my father (Mechanic of 40 years) the ignition map connectors and he started laughing, we both think that was possibly attributing to it and decided the solder method would be best, for peace of mind at the least!

I double checked the manual again last night, in TWO different sections of the manual it specifies 98octane at 40:1

You were correct about the octane rating, thank you for the information as I was unaware of that previously.
I think I will get a can of 91 and mix that at 40:1 to start with.

178 main jet is in there now, just waiting for my spark plug now!

While you are waiting for your spark plug, check your float height in the carb.

Paw Paw

Paw Paw wrote:

While you are waiting for your spark plug, check your float height in the carb.

Paw Paw

Float height is spot on!

FOUND THE ISSUE!

Reed cage is warped, they do not seal. If you flip the reeds around on the cage they still do not seal...

So I took some measurements and sure enough, the cage is warped.

So I am unsure what to pursue. Neither Vforce or Boysen make a reed cage assembly for my specific year, but cross referencing I found some superseded numbers claiming that 06-15 is the same.

I found a rad valve for a good price but have been told Boyesen is junk. I have only had experience with vforce and really liked them on my yz125!

What about this on eBay?
https://www.ebay.com/itm/281623258031

CarlinoJoeVideo wrote:

What about this on eBay?
https://www.ebay.com/itm/281623258031

I have one on the way, but for a much better price ! I am relieved I found the issue finally!

Every 17 model I have read had gaps around reeds,,mine too. I flat sanded the cage and put on aftermarket reeds...but I do not think that is the solution...Id be checking leads,, leaning main jet if this has been on going problem, and or testing hi speed coil after a ride when it's acting up,,or finding a way to heat stator plate up to temperature that it reaches when cutting out and checking it again. Some times shorts or resistance build up with heat causing high speed popping and cut-out.

riv187 wrote:

Every 17 model I have read had gaps around reeds,,mine too. I flat sanded the cage and put on aftermarket reeds...but I do not think that is the solution...Id be checking leads,, leaning main jet if this has been on going problem, and or testing hi speed coil after a ride when it's acting up,,or finding a way to heat stator plate up to temperature that it reaches when cutting out and checking it again. Some times shorts or resistance build up with heat causing high speed popping and cut-out.

Well it is a 2015 like the title states, so a completely different motor lol...

I leaned the main out 3 more than what it was, from a 180 to a 172 and still the same problem, went to a 190 main, same problem, just took longer for the RPM to build with that rich main.

There was a pool of fuel behind the reed cage, and they do not seal at all, you can completely suck through the back side of the cage (the inlet side, carb side).
I flipped the 3 that clearly weren't sealing around and same issue, then took some measurements and the cage is fairly warped.

Even if it is not the issue, it is an issue nonetheless...

I ordered a vforce cage, had great success with them on my Yz's, so at least it is worth a try.

It always does it, regardless of temp. (Of course I warm my bike up before revving it to the issue..).
I pulled the harness off the bike and sent 12v regulated DC through every single wire, did Voltage drops for every single wire... I swapped CDI/ignition boxes, same issue.

Only thing at this point it can be if indeed it is not the reeds, would be an ignition coil or stator. Both check out resistance wise, but I never trust ohm readings alone, so I need to do some voltage and current ramp testing for stator output.

Sounds like your on top of it. My TC250 didn't make a big differenc with perfect sealed reed and new reeds,,,it started well before,,,maybe a little better after.
My past 125 wows on different brands when they start acting up halfway into the moto is the high speed coil breaking up from heat. Shows a wet plug of course and leads to leaning the main....this was catastrophic one time on a CR 250 micro-sprint motor when it sputtered and fouled plug in practice, we leaned main for heat race and it completing shut-off after a few laps,,,,we switched everything cdi,stator coil and went back out for main event and melted piston...we should've went back to original main jet when we swapped everything and we'd been fine...

riv187 wrote:

Sounds like your on top of it. My TC250 didn't make a big differenc with perfect sealed reed and new reeds,,,it started well before,,,maybe a little better after.
My past 125 wows on different brands when they start acting up halfway into the moto is the high speed coil breaking up from heat. Shows a wet plug of course and leads to leaning the main....this was catastrophic one time on a CR 250 micro-sprint motor when it sputtered and fouled plug in practice, we leaned main for heat race and it completing shut-off after a few laps,,,,we switched everything cdi,stator coil and went back out for main event and melted piston...we should've went back to original main jet when we swapped everything and we'd been fine...

This bike has actually been one of the longest (most kicks) 125's I have ever ridden, most started 1st or 2nd, this bike is always like 4th or 5th kick until really warm/hot.

Oh yeah, that is crazy!!! Thank you for the useful information!

Reeds/cage assembly cured the issue. Bike pulls hard all the way through now, no cutting out! Felt like it had full power again and no more fuel pooling up in the carb boot!

I'm happy you found the solution.I just got a 18 TC125. Im not 100% on it's jetting and will be checking out the reed cage on it. Maybe some of it's jetting difficulties are like yours.