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2019 TM EN250 2T Jetting

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Hi all… Just wanted to share some of my jetting experience with the new TM. Before I purchased this bike, I had a 2017 Beta 300rr (standard), which was super easy to jet; put a NECJ needle on the 3rd clip with a 38 pilot and called it a day. I set it at 1.5 turns and it was always good enough. I believe I had a 168 main in it too, but I do not recall. This set-up worked well from the start to the end of the season here in the Western New York area. Typical ride elevations are roughly 500’ to maybe 1,500’. Sometimes the bike had a little drip from the pipe, other times none. Regardless, the power delivery always felt spot on for what I was riding – single track to open flowy trails to the occasional hare scramble. Fuel is 90 ethanol free with Motul 800 Offroad mixed at 50:1 for both the Beta and the TM.

 

My jetting experience to this point has been quite limited. I’m learning.

 

On the TM, the stock jetting came as 45 pilot, NOZE needle on the 3rd clip, and a 175 main. First couple of rides were at roughly 500’ to 1,000’ elevation with the ambient temperatures around 45F-55F. The bike ran very rich from the bottom to the mid-range. In the mid to upper range the thing was an animal trying to rip your arms off! Starting was difficult when warm and I never attempted to start it without the choke cold, but I suspect that it would have started right up. The power delivery from the bottom seemed sluggish and gurggly and there was always a hearty oil stream coming from the pipe; the warmer the weather was the larger the stream – not a drip, but stream. The bike was rideable though, and never fouled a plug. When starting it warm, you could not twist the throttle and expect it to fire. It had to be on the pilot to start and even then, you needed to work the starter or kicker. The air screw made very little difference with the idle and performance from the bottom end. For the first adjustment, I checked the float level. The float level seemed a little high, so I lowered it a little. After putting it back together, I found the float needle was hanging up allowing gas to flow through the overflow while the bike was sitting on the side stand as well as riding (I could smell it every time I stopped). Being the bike is new, I took the carb off and brought it to the dealer and asked him to double check the float height and see if there was a needle valve issue (or did I goof something up). He confirmed the float height was good and polished the needle seat and noted that he did not see any other issues. Without making any other jetting adjustments I rode it, the bike seemed a bit better but still too rich. I dropped the NOZE by one clip and rode it. The result was slightly better off the bottom without a noticeable difference in the mid-range. Next, I dropped the pilot from the stock 45 to a 42 and rode it. Starting warm was still difficult (and the warmer it was the more difficult it was), but the response from the bottom end was improved. I rode the bike a couple of times with this set-up. Mid-range and up seemed unchanged and the air screw still did not offer much influence. As I read through various jetting articles/blogs, I found one that mentioned the influence of the needle’s straight diameter on the pilot circuit. As mentioned already, I found the NECJ triple taper Suzuki needle to work very well in the Beta (by recommendation from another Beta rider at the time). Unfortunately, I didn’t have that needle kicking around in my collection, as I left it in the Beta when I sold it. I did have a N2ZW needle in my collection though. Leaving the 42 pilot in place, I dropped in the N2ZW needle on the 3rd clip (yes, 4 sizes leaner on the straight diameter) and gave it a whirl. A massive difference! A bit too lean off of the bottom though, as I needed to reduce the air screw to about 1 turn to get the lean bog out when chopping the throttle from idle. It was about 70F-72F at out at an elevation at about 600’ with this trial. Having to richen the air screw up to that point seems too lean to leave it. I would rather let it run a little rich for the shorter hot weather we have around here while not running too lean for the balance of the season (yes, I would like to find a good enough jetting recipe for the majority of the season – as much as possible at least). I am good with a little drip out of the pipe if the engine characteristics are good. Naturally, I do not want to run too lean for engine longevity and performance reasons. Next I swapped out the 42 pilot for the stock 45. I rode it and the results were very good! The bike would start on idle and with giving it some throttle. I will note that the TM starting is not quite as instantaneous as the Beta, but still good. With the N2ZW needle, 45 pilot, and the 175 main the response was good from the bottom and ripped like crazy from the mid to the top. I played with the air screw a bit and found it best for bottom response and idle at about 2 turns out at an elevation of roughly 600’ with the ambient air temperature at 85F-89F. Again, I’m using 90 ethanol free mixing Motul 50:1. At these conditions I did had a drip, not a stream. I am good with that.

 

If you have stayed with this long-winded discussion so far, I am hoping that you can stick with me a little longer and help me out with some needle taper tuning advice/education. With the straight diameter and pilot jet mix that I have, I feel pretty confident I’m getting what I need from the engine with enough adjustability to keep from re-jetting for every small weather swing we experience in this area. What would like to do is smooth out the mid-section a bit. I don’t know what the difference is in taper profiles between the NOZE, N2ZW, and the NECJ. I do understand the last letter designation with the straight diameter, and I found some discussions on the clip position layout with a NECx vs a NEDx. What I would like to know is how does the N2Zx compare with the NEC(or D)x and NOZx series on the tapers? I found the NECJ smoothed out the Beta very nice. Should I expect the same for the TM using a NECW? I believe the NECJ would be a bit too lean.

 

Thanks for sticking with the read!

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Aren’t the heads/squish on these TMs cut for Race Fuel only at lower altitudes?  Did you ever try a thicker head gasket?

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4 hours ago, kxlubber said:

Aren’t the heads/squish on these TMs cut for Race Fuel only at lower altitudes?  Did you ever try a thicker head gasket?

No I haven't, but swapping out gaskets is not out of the question if I cannot get the jetting sorted out. I'm feeling confident that I will be able to though, given the progress that I have already made.

I believe dirt bike magazine noted using race gas in their 2019 EN300 review. This was one of the questions that I had for the dealer before I purchased the bike. He said that's not the case. He actually has the exact same bike and rides the same, or similar, areas. He noted that his jetting is stock as mine was. The only difference is that he runs a different premix oil brand than I do. Ratio is the same and he also uses ethanol free 90 as well. TM also doesn't publish a jetting chart. I suspect because of the possible variation with squish and porting, if that makes sense?

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It's my understanding that all the TMs require race fuel.  I know that the guys in our riding group that tried pump gas in their bikes had instant problems with detonation especially down low lugging the bike off the bottom.  I've read that some have success with mixing race fuel with pump gas, my experience is it's not worth the risk.  You can jet the pilot and needle rich which might keep it from detonating but then you're going to be fouling plugs and losing the crisp throttle response.  The way TM sets the bike up for race fuel is a major reason why they run better than the other brands that are set up for pump gas.  It's more than just the squish it's also the porting and the spark curve.  Also the head gasket is an "O" ring so the only thicker gasket you can use is the base gasket which running a thicker one changes the port timing as well as the squish.

I'm confused by those who buy what is basically a factory race bike and pay 10K plus their personal add ons and then cheap out over a few dollars on fuel.  Any detonation at all is extremely hard on your entire engine not just the rings and piston top...  It hammers your crank and rod bearings and sends harmonics through your drivetrain that fatigue transmission gears and bearings.  Even if you can't hear it detonating it can still be doing it's damage and you will only discover it when you disassemble the engine for hourly service, then it's too late.

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31 minutes ago, lankydoug said:

It's my understanding that all the TMs require race fuel.  I know that the guys in our riding group that tried pump gas in their bikes had instant problems with detonation especially down low lugging the bike off the bottom.  I've read that some have success with mixing race fuel with pump gas, my experience is it's not worth the risk.  You can jet the pilot and needle rich which might keep it from detonating but then you're going to be fouling plugs and losing the crisp throttle response.  The way TM sets the bike up for race fuel is a major reason why they run better than the other brands that are set up for pump gas.  It's more than just the squish it's also the porting and the spark curve.  Also the head gasket is an "O" ring so the only thicker gasket you can use is the base gasket which running a thicker one changes the port timing as well as the squish.

I'm confused by those who buy what is basically a factory race bike and pay 10K plus their personal add ons and then cheap out over a few dollars on fuel.  Any detonation at all is extremely hard on your entire engine not just the rings and piston top...  It hammers your crank and rod bearings and sends harmonics through your drivetrain that fatigue transmission gears and bearings.  Even if you can't hear it detonating it can still be doing it's damage and you will only discover it when you disassemble the engine for hourly service, then it's too late.

Cost of race gas wouldn't be an issue if that is the actual need. However, according to the dealer using 90 ethanol free at 50:1 is perfectly fine.

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2 hours ago, epearce said:

Cost of race gas wouldn't be an issue if that is the actual need. However, according to the dealer using 90 ethanol free at 50:1 is perfectly fine.

My son rides for TM USA and they recommend mixing race gas with pump gas. Two gallons of C12 to three gallons of 91 pump gas, so that’s what we do. Now don’t tell anyone, but when we where out of race gas he has practiced with pump gas only. Bike didn’t run any different, it just would ping a little when he rode it hard, so it does need some race gas. At least for his riding. 
 

We’ve only messed with 300’s so can’t help on exact setting on a 250, but I will say this having had Beta’s. The TM is way more sensitive to changes than a Beta.  On the Beta we could go up to race in Denver and maybe change the needle one clip, the TM needed much bigger changes. 
 


 

 

Edited by Cullins
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47 minutes ago, Cullins said:

My son rides for TM USA and they recommend mixing race gas with pump gas. Two gallons of C12 to three gallons of 91 pump gas, so that’s what we do. Now don’t tell anyone, but when we where out of race gas he has practiced with pump gas only. Bike didn’t run any different, it just would ping a little when he rode it hard, so it does need some race gas. At least for his riding. 
 

We’ve only messed with 300’s so can’t help on exact setting on a 250, but I will say this having had Beta’s. The TM is way more sensitive to changes than a Beta.  On the Beta we could go up to race in Denver and maybe change the needle one clip, the TM needed much bigger changes. 
 


 

 

Not sure about the sensitivity of the engines, but we run 89-91 non-ethanol fuel with no issue. We're not grinding it out like some though.

I think the biggest contributor to carburetion sensitivity is that the TMs run the 38mm AS1 (screw top) carbs, and the Betas run the 36mm AS2 carbs. The Betas are incredible wrt jetting stability - set it once in the spring, once inthe fall.

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45 minutes ago, Cullins said:

My son rides for TM USA and they recommend mixing race gas with pump gas. Two gallons of C12 to three gallons of 91 pump gas, so that’s what we do. Now don’t tell anyone, but when we where out of race gas he has practiced with pump gas only. Bike didn’t run any different, it just would ping a little when he rode it hard, so it does need some race gas. At least for his riding. 
 

We’ve only messed with 300’s so can’t help on exact setting on a 250, but I will say this having had Beta’s. The TM is way more sensitive to changes than a Beta.  On the Beta we could go up to race in Denver and maybe change the needle one clip, the TM needed much bigger changes. 
 


 

 

Thanks for the response, Cullins. I haven't noticed any pinging; I'm sure I couldn't ride it hard enough! Like lankydoug said, it could be something I'm just not hearing.

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14 hours ago, motoxgiant said:

Not sure about the sensitivity of the engines, but we run 89-91 non-ethanol fuel with no issue. We're not grinding it out like some though.

I think the biggest contributor to carburetion sensitivity is that the TMs run the 38mm AS1 (screw top) carbs, and the Betas run the 36mm AS2 carbs. The Betas are incredible wrt jetting stability - set it once in the spring, once inthe fall.

I’ve heard the same from a couple other people regarding the 38mm vs the 36mm.  If it turns out this bike will be too finicky to tune with the 38, I may look at a 36, or even an SC2. The SC2 for this bike is a 36. 

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For what it's with I'm really liking the Lectron I put on my 2017 en300, I expect it will need little to no adjustments when the air density changes.  

Also it's been my experience that generally the more performance you get out of an engine the more sensitive it becomes.

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8 minutes ago, lankydoug said:

For what it's with I'm really liking the Lectron I put on my 2017 en300, I expect it will need little to no adjustments when the air density changes.  

Also it's been my experience that generally the more performance you get out of an engine the more sensitive it becomes.

Thanks, lankydoug. How well was it tuned when you first installed it? Lots of trial and error, or good to go pretty quickly?

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I started with a new needle (4-2m) so I measured the overall length of the previous needle and put the new one at the same height.   That is not ideal but it got me close enough to start.  The key to a Lectron is to get a good strong idle and a crisp first 3/4 throttle all by adjusting the needle and once you have it close then tune the power jet circuit by adjusting the external screw on the top.  The TMs are a dream to access the carb so it only took me about 30 minutes and maybe 4 tries.  Mine was rich at first so I went a couple turns at a time until it was close and then a 1/2 turns or 1/4 turns.  Then it did the top end power jet.  

 

The carb which used to be mine had a 3-1xl which was perfect on a Husky 250 2 stroke.  I posted about the entire process on my 2017 en300 thread

Edited by lankydoug

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2 hours ago, lankydoug said:

I started with a new needle (4-2m) so I measured the overall length of the previous needle and put the new one at the same height.   That is not ideal but it got me close enough to start.  The key to a Lectron is to get a good strong idle and a crisp first 3/4 throttle all by adjusting the needle and once you have it close then tune the power jet circuit by adjusting the external screw on the top.  The TMs are a dream to access the carb so it only took me about 30 minutes and maybe 4 tries.  Mine was rich at first so I went a couple turns at a time until it was close and then a 1/2 turns or 1/4 turns.  Then it did the top end power jet.  

 

The carb which used to be mine had a 3-1xl which was perfect on a Husky 250 2 stroke.  I posted about the entire process on my 2017 en300 thread

Thanks, good info. I will definitely check that thread. 

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On 7/6/2020 at 9:04 AM, epearce said:

 

 

If you have stayed with this long-winded discussion so far, I am hoping that you can stick with me a little longer and help me out with some needle taper tuning advice/education. With the straight diameter and pilot jet mix that I have, I feel pretty confident I’m getting what I need from the engine with enough adjustability to keep from re-jetting for every small weather swing we experience in this area. What would like to do is smooth out the mid-section a bit. I don’t know what the difference is in taper profiles between the NOZE, N2ZW, and the NECJ. I do understand the last letter designation with the straight diameter, and I found some discussions on the clip position layout with a NECx vs a NEDx. What I would like to know is how does the N2Zx compare with the NEC(or D)x and NOZx series on the tapers? I found the NECJ smoothed out the Beta very nice. Should I expect the same for the TM using a NECW? I believe the NECJ would be a bit too lean.

 

Thanks for sticking with the read!

Maybe I can help you some in regards to the taper profiles and general evaluations I've read over the years.

N2Zx has 2 tapers, while NED/Cx and NOZx have 3 tapers. Did you notice that the tip of the needle was much fatter on N2Zx vs. NOZx? This is due to the third taper, the end result being the fatter tip on N2Zx will require a larger main jet than the skinnier tip of NOZx/NEDx, generally @ two sizes. From what I can tell the second and third tapers of NOZx and NEDx are identical, the difference then is in the first tapers. The first taper of NOZx isn’t as steep as most others, but it begins much sooner. Due to the early start of the first taper, the NOZx and its 1/2 clip relative N1Ex tend to run rich/rough (described as “stutter or “blubbery”) very early in the throttle opening. Most woods riders don't care for these needles, but there are a few that do. The early stutter is difficult to tune out with pilot jet, needle diameter, or clip position changes. It may be cleaned up better with a leaner slide cutaway but slides are probably @$80. For that, one could try several needles or a JD kit. Do you know what slide # you have?

N2Zx uses the same second taper as NOZx and NEDx, its first taper begins in the same area of most other needles but it is steeper and runs a little further down the needle before blending into the second taper, it runs richer than most other needles in the area from @ 1/8 - 1/4 throttle. Some users really like this profile and/or it's 1/2 clip relatives N8Rx, N3Ex, and some users don't. Is the split 50/50 I cant say, but it seems those that like em prefer the grunt/torgue the feel early in the throttle. Those that don't like them experience some stutter early in the throttle and or a power surge or "hit" near mid throttle. You might try a larger main jet with your N2Zx in an effort to smooth out "the mid section a bit".

 I would think the NEDx/NECx could work well for you also, but as with the other needles it will take finding the right combination of all components to maximize ones satisfaction. The good part is your experimenting with some different profiles/settings and along the way your realizing what your preferences are!      

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17 hours ago, hallsy said:

Maybe I can help you some in regards to the taper profiles and general evaluations I've read over the years.

N2Zx has 2 tapers, while NED/Cx and NOZx have 3 tapers. Did you notice that the tip of the needle was much fatter on N2Zx vs. NOZx? This is due to the third taper, the end result being the fatter tip on N2Zx will require a larger main jet than the skinnier tip of NOZx/NEDx, generally @ two sizes. From what I can tell the second and third tapers of NOZx and NEDx are identical, the difference then is in the first tapers. The first taper of NOZx isn’t as steep as most others, but it begins much sooner. Due to the early start of the first taper, the NOZx and its 1/2 clip relative N1Ex tend to run rich/rough (described as “stutter or “blubbery”) very early in the throttle opening. Most woods riders don't care for these needles, but there are a few that do. The early stutter is difficult to tune out with pilot jet, needle diameter, or clip position changes. It may be cleaned up better with a leaner slide cutaway but slides are probably @$80. For that, one could try several needles or a JD kit. Do you know what slide # you have?

N2Zx uses the same second taper as NOZx and NEDx, its first taper begins in the same area of most other needles but it is steeper and runs a little further down the needle before blending into the second taper, it runs richer than most other needles in the area from @ 1/8 - 1/4 throttle. Some users really like this profile and/or it's 1/2 clip relatives N8Rx, N3Ex, and some users don't. Is the split 50/50 I cant say, but it seems those that like em prefer the grunt/torgue the feel early in the throttle. Those that don't like them experience some stutter early in the throttle and or a power surge or "hit" near mid throttle. You might try a larger main jet with your N2Zx in an effort to smooth out "the mid section a bit".

 I would think the NEDx/NECx could work well for you also, but as with the other needles it will take finding the right combination of all components to maximize ones satisfaction. The good part is your experimenting with some different profiles/settings and along the way your realizing what your preferences are!      

Hallsy, thanks for response. Great info! I’m not certain of the slide (6.5 maybe?). The NECx/NEDx needles seem to be fairly popular in this area for the type of riding I do. Though I admit that I haven’t tried one yet as I’ve been waiting on one to come in, which hadn’t before I was out riding again. I did ride with my existing setup at a little higher elevation with increasing elevation back in the hills during the ride. It ran a bit richer than testing the settings at 500’/600’. That makes sense, but at some points back in the hills I found the bike would stall at idle. At closer to the base elevation it felt a bit rich, but otherwise ok. Definitely could have resolved it with leaning up the jet mix, but I’m looking to not rejet every time I ride someplace new (lazy, I know). With that, I’m actually going to give a Lectron a shot. A big cost adder, but this bike is the best bike I have ridden so far, so I’m good with the investment to make it work best for me. Once I get some hours on the Lectron, I’ll share my experience. 

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2 hours ago, epearce said:

 I’m actually going to give a Lectron a shot. A big cost adder, but this bike is the best bike I have ridden so far, so I’m good with the investment to make it work best for me. Once I get some hours on the Lectron, I’ll share my experience. 

The up side is you can use your Lectron on future bikes since they offer so many needles and custom throttle cable set ups.  My Lectron was used in place of a Mikuni on a 09 Wr250 and I made the mistake of selling the original carb so when I went to sell the bike I had to let the Lectron go.  The next owner used it on a 2013 CR 125 Husky, then a GasGas 300 in place of a Keihin then I bought it back and used it on my TM.  Just don't make the mistake I made and sell your OEM carburetor.  I think the Smart carb is very similar but more expensive and bulky.  

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21 hours ago, lankydoug said:

The up side is you can use your Lectron on future bikes since they offer so many needles and custom throttle cable set ups.  My Lectron was used in place of a Mikuni on a 09 Wr250 and I made the mistake of selling the original carb so when I went to sell the bike I had to let the Lectron go.  The next owner used it on a 2013 CR 125 Husky, then a GasGas 300 in place of a Keihin then I bought it back and used it on my TM.  Just don't make the mistake I made and sell your OEM carburetor.  I think the Smart carb is very similar but more expensive and bulky.  

Yep, my thoughts exactly... Metering rods and cables are actually reasonably priced. 

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I've been thinking about the finicky nature of the TM and the occasional plug fouling and I'm wondering if it has something to do with the fact that the power valve opens at a different rate depending which gear you're in.  I was thinking that what might be going on is when you tune it in say 4th gear then when you're in second and the power valve isn't fully opening or at least opening as soon as it would be in a higher gear which means it's not going to breathe as free as when the the power valve is wide open.  It would take a really forgiving carburetor to work well in all those circumstances.  

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That's an interesting thought.... I'm not sure, but that makes sense..

Much of my riding is single track, so I'm lugging it often from 1st to 3rd gear. Then getting on the pipe a bit more in the more open flowy sections as well as those aggressive hills where momentum is everything. I can comfortably get through all of the tight stuff on this bike, honestly better than the Beta, but I will say the quicker you move on this machine, the better it feels. I was able to put a couple of hours on the 38mm H-Series Lectron this weekend doing just all of that, and without a doubt the Lectron delivered. The power still feels all there, but is linear and smooth with the bottom end response significantly improved. Out of the box it seemed a little lean though, as the idle was hanging a bit, which was easily resolved with a quarter turn in (tilt the cab, pop out the slide).  I feel good about the investment.

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1 hour ago, epearce said:

That's an interesting thought.... I'm not sure, but that makes sense..

Much of my riding is single track, so I'm lugging it often from 1st to 3rd gear. Then getting on the pipe a bit more in the more open flowy sections as well as those aggressive hills where momentum is everything. I can comfortably get through all of the tight stuff on this bike, honestly better than the Beta, but I will say the quicker you move on this machine, the better it feels. I was able to put a couple of hours on the 38mm H-Series Lectron this weekend doing just all of that, and without a doubt the Lectron delivered. The power still feels all there, but is linear and smooth with the bottom end response significantly improved. Out of the box it seemed a little lean though, as the idle was hanging a bit, which was easily resolved with a quarter turn in (tilt the cab, pop out the slide).  I feel good about the investment.

I had the same experience with my Lectron.

 

One of the reasons I think the problems are related to the power valve is that my riding buddies with a 2019 and a 2020 en300 had problems with the power valve getting out of adjustment and they had to buy the wiring harness to reset the electrical power valve controller.  When the problem occurred the power valve wasn't opening all the way and the bike ran like the exhaust was plugged up... especially when wide open.  The plug would look like it had baked oil on the porcelain and then shortly after it would fuel foul.  The guy with the 2020 had the problem happen so severely his reed valve were broken and chipped up with less than 30 hours on it.  I think the back pressure from a closed power valve and a wide open throttle in 5th gear caused this.  Both of these guys are resetting their power valve every 5-10 hours and putting a new plug in before every race.  

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