Horizons Unlimited - The HUBB

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-   -   Can someone please tell me about this-link inside. (https://www.horizonsunlimited.com/hubb/yamaha-tech/can-someone-please-tell-me-34513)

Yobbo 14 Apr 2008 08:45

Can someone please tell me about this-link inside.
 
Was searching the net and found a link from this site to another - XT-Tipps
I have used online translators to try to find out what's being said,but I can't make it out.
What I'm after is the bit about half way down about drilling a bigger hole in your secondary carb slide plate.
What is this ment to do? When translated it doesn't really make any sense other than something about response.

aukeboss 14 Apr 2008 08:54

Response
 
- Ansprechverhalten
Im Sekundärvergaser hat der Unterdruckkolben eine kleine Bohrung im Boden. Es macht Sinn, sie ein klein wenig zu vergrößern. 3,0 - max. 3,5 mm Durchmesser. Das macht sich im Ansprechverhalten bemerkbar. (Hat aber rein garnichts mit mehr Leistung zutun).

It is about the little hole in the secondary slide that 'communicates' the vacuum in the throat to the top of the membrane. This vacuum lifts the slide, opens the throttle.
If you increase the diameter to 3 mm, from 1,8 mm, the response to opening the throttle will be faster, as more air can flow through the larger hole. No increase of power though.

Auke

spooky 14 Apr 2008 11:19

right,.... faster throttle response, one of the cheapest way to do a bit tuning on the carb.
I done it on my Mikuni Carb for my KTM LC4 640, opened this holes from STD-6mm to 8.5mm-9mm but left the stronger STD spring to prevent bouncing of the slider for off-road riding.
The SuperMoto guys additionally fit a softer spring as well, but only move there bikes on tarmac, if used offroad or on bad tracks, the slider will bounce to quick and the result is a splutter in the carb.
Bike factories have to keep the set-up down to get there bikes road legal and usable for many conditions, tuning is not on there mind.

And yes change the jet's and needle and your bike will be all different, with a lot more fun factor in it.... ;o)

Yobbo 14 Apr 2008 11:24

So instead of opening at 1/2 throttle as per normal,it'll open sooner? Is that how I'm reading that?

spooky 14 Apr 2008 14:50

Quote:

Originally Posted by Yobbo (Post 184492)
So instead of opening at 1/2 throttle as per normal,it'll open sooner? Is that how I'm reading that?

well sort of... ;o)
you will get a easier, faster and better throttle response with less effort on your gas hand, the vacuum will do a bit more of that job for you, more than STD, all part of the puzzle in addition with the bigger jets and needle game.
I was sceptical in the beginning too, but like it a lot now.

there are some rally people in Germany who are in to Yamaha bikes and speak English too, have a look at: Home
they sale all sort of tuning stuff specially for the XT bikes, and will tell you a lot on what sort of setup will be best for you and your bike.

As I'm riding a KTM LC4 I had all my data for tuning my carb from K T M - S O M M E R
I'm saying that be course it's not that easy to just throw any kind of bits together to find a good tuning, there are some tried and tested variations, but to open the slider holes up to the right size will be a start any way.... (don't over do it... 0.5mm to 2mm can make a big difference)

Yobbo 14 Apr 2008 20:08

Thanks for that,might have to have a go at it in the weekend.

aukeboss 15 Apr 2008 06:41

Not quite
 
The throttle will not open more, but will open faster. The stable throttle opening position will be the same, but will be reached earlier.

Auke

Yobbo 15 Apr 2008 07:47

Just did it,took it out to 3mm,makes quite a noticeable difference.

bacardi23 16 Apr 2008 23:25

Yobbo....What do you notice more now? :thumbup1:

Yobbo 17 Apr 2008 06:15

Just seems like more grunt from down low.I guess thats because both carbs are opening pretty close together.
Example being - give it full throttle,4th gear at 40km/h and it just takes off.It used to anyway,but you can feel a bit more surge or urgency about it.


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