Worn TMX needle or else

[Paulnobodyimportant]

My out of the box TS1225 has an open mouth TMX35 carb. It has a 55 needle and was originally set up and dynod by Chiselspeed on setting P3, ie 3 clips from the top. Over the last 5000 miles I have lowered the needle, in half a clip increments and plug chops to keep it running sweet. The needle is currently on the top setting, ie P1 but after say around 500 miles is now running rich at around half throttle. Now I understand that you cannot replace the needle jet, which may be worn. Therefore, do I get a new 55 needle or use another thicker needle.
FYI the carb is jetted as follows
Main 340
Needle 55P1
Pilot 17.5
Slide 60

And advice would be welcomed.

Thanks

Paul

[Dimitrios_231]

This is an exact copy-paste from the Scooterotica forum.
It was available to download in a Word type format using tables.
ScooterLoopyJohn was kind enough to re-edit the tables and post it in a readable 'forum text' format.
It might help you.




This has helped me and i think should help all of you, complied by James Pennington (Australia).

Mikuni TMX35 needles
All TMX35 needles are of 6EN11 pattern.

6 signifies needles between 60mm and 70mm long (all 66.3mm long in this series)
E represents the total included angle of the first taper (1.25° or 1° 15’)
N represents the total included angle of the second taper (3.5° or 3° 30’)
11 is a “reference number”, relating to taper starting points (all the same in this series)

6EN11 needles are available in 7 sizes (52 to 58). The “working portion” of each needle comprises a straight section, a first taper section and a second taper section. The straight portion of the richest needle (52) is 2.52mm in diameter, whereas that of the next (53) is 2.53mm, making it a slightly leaner needle, and so on, until the leanest needle (58) at 2.58mm (a larger diameter needle passes less fuel, making the mixture leaner).

Each needle has 5 clip positions. Position 1 (top) is the leanest, while position 5 (bottom) is richest. Changing the needle clip by one position displaces the needle by 1.0mm.

Needles in the 6EN11 series are directly comparable. For example, the diameter at any point on a 6EN11-56 will always be 0.01mm larger than the diameter at that same point on a 6EN11-55. The starting point of each taper is the same on each needle.

On E taper, diameter changes by 0.02mm for every 1.0mm length
On N taper, diameter changes by 0.06mm for every 1.0mm length


Table 1 – Portions of needle in use, relative to clip position and throttle position (for all 6EN11 series needles)

Clip position Throttle closed ¼ throttle ½ throttle ¾ throttle Full throttle
1------------ S------------ S------------ E------------ N------------ N
2------------ S------------ E------------ E------------ N------------ N
3------------ S------------ E------------ E------------ N------------ N
4------------ S------------ E------------ E------------ N------------ N
5------------ S------------ E------------ N------------ N------------ N


S = Straight section
E = E (first) taper section
N = N (second) taper section

Even at full throttle, with the clip in position 5, approximately 5mm of needle remains in the needle jet. Thus, it appears that fuelling at full throttle is never dependent on the main jet alone.


Table 2 – Diameters of various needles, relative to clip position and throttle position


Needle Clip position-- Throttle closed-- 1/4 throttle-- 1/2 throttle-- 3/4 throttle-- Full throttle
6EN11-55 1------------ 2.55------------ 2.55------------ 2.34------------ 1.94------------ 1.41
----------- 2------------ 2.55------------ 2.51------------ 2.32------------ 1.88------------ 1.35
----------- 3------------ 2.55------------ 2.49------------ 2.30------------ 1.82------------ 1.29
----------- 4------------ 2.55------------ 2.47------------ 2.28------------ 1.76------------ 1.23
----------- 5------------ 2.55------------ 2.45------------ 2.24------------ 1.70------------ 1.17
6EN11-56 1------------ 2.56------------ 2.56------------ 2.35------------ 1.95------------ 1.42
----------- 2------------ 2.56------------ 2.52------------ 2.33------------ 1.89------------ 1.36
----------- 3------------ 2.56------------ 2.50------------ 2.31------------ 1.83------------ 1.30
----------- 4------------ 2.56------------ 2.48------------ 2.29------------ 1.77------------ 1.24
----------- 5------------ 2.56------------ 2.46------------ 2.25------------ 1.71------------ 1.18
6EN11-57 1------------ 2.57------------ 2.57------------ 2.36------------ 1.96------------ 1.43
----------- 2------------ 2.57------------ 2.53------------ 2.34------------ 1.90------------ 1.37
----------- 3------------ 2.57------------ 2.51------------ 2.32------------ 1.84------------ 1.31
----------- 4------------ 2.57------------ 2.49------------ 2.30------------ 1.78------------ 1.25
----------- 5------------ 2.57------------ 2.47------------ 2.26------------ 1.72------------ 1.19
6EN11-58 1------------ 2.58------------ 2.58------------ 2.37------------ 1.97------------ 1.44
----------- 2------------ 2.58------------ 2.54------------ 2.35------------ 1.91------------ 1.38
----------- 3------------ 2.58------------ 2.52------------ 2.33------------ 1.85------------ 1.32
----------- 4------------ 2.58------------ 2.50------------ 2.31------------ 1.79------------ 1.26
----------- 5------------ 2.58------------ 2.48------------ 2.27------------ 1.73------------ 1.20



Table 2 shows the needles most commonly used for Lambretta applications. Relevant dimensions of the other needles in this series (52 to 54) can be calculated using the information provided.

With reference to Table 2, it should be possible to adjust fuelling at specific throttle positions by changing the needle AND clip position in one go (and to predict the outcome based on the previous setting).
If changing the needle and/or clip position, do not change any other carburettor settings (main jet, pilot jet, air screw etc.) at the same time.

[Eden]

My tmx 35 lasted about that long. I was already running on the weakest needle on the top clip so I had to bin the carb. Thats why I changed to the airstriker.

[jonoy]

eden what was your fuel economy like with
the the 35 tmx

[Eden]

shit

[jonoy]

shit

can you elaborate on that
how much to the
tank
by the way thank you for recommending source for rock oil 10 litres ordered. i think i gonna need it.

[Eden]

tbh the engine I used it on is very thirsty any way, its shit with the airstriker too.

26 mpg

[Paulnobodyimportant]

Thanks for the above post Dimitrios.

I had already found that page on this Forum and used it to great advantage. In that I took the plunge and upgraded the needle from a 55 on P1 to a 58 on P2. Did a 180 mile round trip to the AF 50th anniversary and it ran a treat with a great plug colour. Only trouble is that once the 58 needle is worn, do I have to throw the carb away as Eden did.

As for fuel consumption, it always seems to be 10 miles to the litre.

[Dimitrios_231]

I remember few people had used with success the larger diameter needles from TMX 38.

I had a TMX35 on a 252cc Rapido,fuel consumption was less than 10 miles per litre

I changed to an Amal MK1 32mm and the consumption is worse