tm 40 jetting

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tm 40 jetting

Post  wetdog on Mon Sep 24, 2012 9:48 pm

Hey all ,I know this topic has been beaten like a dead cat but I've got some real first person data.
I got the mikuni TM 40 because my stocker was all worn out,I did tons of research and figured that an uncorked pig with a header pipe and air box open would be as such. Aj 1.2 mj140 PJ. 20 needle y4
Well my bike ran horribly changed toaj 1.1. Mj 140 PJ 27.5. Needle y6
Pig runs so good its silly its the Carb IV always wanted ,







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Re: tm 40 jetting

Post  BuRP on Tue Sep 25, 2012 5:35 am

"... airbox open..." - you mean the plugs out or the opened sidecover, std headers, what pipe, and at what altitude?
Makes all a big difference. I just come back from a trip at 1300m hasl and am sure the mj140 is too big, with opened sidecover & headers & pipe. The ij25 is too small, it runs too hot too quick at small openings, I'm going back to a ij27.5 with aj1.2. You can run it though if you've got a working fan, mine wasn't for this trip.
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Re: tm 40 jetting

Post  wetdog on Tue Sep 25, 2012 9:57 pm

Yes you are right every bike is different, sea level big gun system,air box plugs out and cover vents,uncorked intake manifold.
The pig ran too hot with the 25 PJ it almost melted my Rad shroud,I just got back from extensive test ride and no stalling popping or any weird stuff all with the 27.5 .
I think the pig is running the way it should have from the factory, third gear throttle wheelies are the bomb with a 15 /45 setup.
Mike at the powerbarn.com was super helpful in giving me jets on either side of what I suggested, as a side note mikuni USA is currently out of TM 40s and no one has them till spring its a great Carb and will make the pig so fun you will pinch yourself. beat head
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Re: tm 40 jetting

Post  wetdog on Tue Sep 25, 2012 10:00 pm

If anyone has some insight on tuning the accelerator pump I'm all ears mine is set to just off idle and seems good just wondering what's best.
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Re: tm 40 jetting

Post  BuRP on Wed Sep 26, 2012 10:51 am

'Ere ya go Hound:
There's 2 adjustment facilities for the pump, the start and finish of its stroke - find them. If you dunno where they are or how they work: take off carb and go for a crap whilst you play with it there.
The finish of the stroke you set somewhere halfway the 'stroke' of the slide, so it won't pump anything in the top half of the throttle - what's the use, the engine is already hammering by that time.
The start you set such that the slide opens a bit first, and only then the pump starts squirting. Too early and it may bog down on you, too late and you'll feel it - just find the sweet spot. This bit adjusts easily with a mounted carb also, so playing around will tell you 'where' to set it.
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Re: tm 40 jetting

Post  wetdog on Wed Sep 26, 2012 2:13 pm

Awesome and thanks i think im close in the start but the stroke limit screw is gonna be hard to get to with 4.6 tank .
I have to say this site rocks its like having a gkod buddy that knows all about the pig just down the street.
You all have my heartfelt thanks. 2 thumbs
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Re: tm 40 jetting

Post  BuRP on Wed Sep 26, 2012 2:46 pm

I actually will be soon sortof close to you, LA for me next month. So, in case I manage to barely dodge a wheelying hooligan on a red thumper with a facking loud exhaust... I'll lasso you in so you can buy us a beer razz
You're welcome bro, it's what these sites are for.
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Re: tm 40 jetting

Post  wetdog on Thu Sep 27, 2012 3:02 pm

+1000 2 thumbs
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Re: tm 40 jetting

Post  Mad Frosty on Tue Apr 09, 2013 10:02 pm

What are you running now Burp ,
this is what i found on the nets that should be close at sea level -

25 pilot jet
150 main jet
screw 2,5 turns out
9DJY4 needle
that is on a stock bike ( uncorked )

you are in warmer climate , i have the hotcams stg1 and HRC open tip exhaust , i think that i should go notch richer if i get this carb .
what are you running ?
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Re: tm 40 jetting

Post  BuRP on Tue Apr 09, 2013 11:18 pm

No idea bout me needle (got 3 diff one's here), but your mj should be better 140* - go try a full run?
*Unless you've got a ported head, but I doubt that.
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aa

Post  Mad Frosty on Wed Apr 10, 2013 2:05 am

AFTER READING THIS -
http://www.xr650rforum.com/t1493p25-2005-xr650r-titled

I think that 142,5 main +- 2,5 / or plus minus one size
25 pilot ( or 27,5 )
1,2 air jet

should cut it , considering that i am at sea level and colder climate . Higher altitude = smaller jets, higher air temperature = smaler jets again , open sidepanel = bigger jets , openn exhaust system bigger jets ,...
I have read that you went back to the 25 pilot , that should be about right for you at the altitude , what radiators are you running ? If the answear is the stock ones you might consider the fluidine thicker units , after all you live in Africa and the fan might not be enough .( bigger rads hold more water and that helps too , not just the surface area )
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Re: tm 40 jetting

Post  BuRP on Wed Apr 10, 2013 1:29 pm

Madder,

I clicked 'reply' before I read that you already read that I'm back at ij 25 (with aj 1.2) - and it purrrrrrrs again.
The idle-circuit's bor really dependant on altitude neither on open/std sidepanel etc, the pipe though may make a lil diff - so I'd recommend you try it.
But hold yer horses here.... cam std? If not then use the T&E method, invented in 1637 by a certain F. Iddle

Fuidyne rads.
I want their sizes, H/W/Thickness, and have asked a memeber already, but to no avail. Can someone help here?
I need to know where they differ (in thickness only apparently, but let's have sizes), ie is there more 'body' at the front, at the rear or where?
I run the std one's now, but am comtemplating to have bigger (wider!) one's made for a special Safari 44 liter tank I'm busy fitting on the bike - which allows for this.
So: who has Fluidynes, and will you give me comparative measurements with the std rads please?
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Re: tm 40 jetting

Post  Mad Frosty on Wed Apr 10, 2013 1:35 pm

I believe that they are the same size , except the thickness and you might have issues fitting the fan .
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Re: tm 40 jetting

Post  Mad Frosty on Wed Apr 10, 2013 1:36 pm

You can contact one of the sellers and ask for measurements naughty
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Re: tm 40 jetting

Post  BuRP on Wed Apr 10, 2013 1:38 pm

Oh, no Maddy, sorry.

More fluid in rads makes no diff (like in absolutely zero), only the surface-area does - and keep in mind that this area is a 3-dimensional thing so the thickness is important too as it also determines the surf ace area.
The Fluidynes (as far as I understand) are thicker only, hence have a larger surface area and therefore will exchange heat 'longer' with the ambient air flowing though it. It follows that the air exists at a higher temp then when using std rads.
A paper-thin rad would cool very little, therefore heat the air up little too, hopes this makes sense.
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Re: tm 40 jetting

Post  Mad Frosty on Wed Apr 30, 2014 6:59 pm

I was not going to tell you this but for some strange reason i have changed my mind  Twisted Evil 

Your words -
" More fluid in rads makes no diff (like in absolutely zero), only the surface-area does "

Well you are wrong  ( or talking total bullshite as you would put it ) , how is that ?
Lets start with a very basic/ simple lesson in the physics -
best shown on a experiment , you know like the ones some of us did in young age at school
, take two identical  pans  ( biggish ones )  fill them both with water , but put 500 ml in one and 1000 ml in the other one  , place them on top of identical  heat source  and masure the time it takes to boil the water  then compare the times between the two , ..... bingo
you have learned one of the laws of physics ,  BIGGER MASS TAKES MORE ENERGY  TO HEAT UP THAN SMALLER MASS , so to return to the cooling system on a motorbike  , if you beef up your cooling system not just by adding more surface to your radiators  but also doubling the amout of coolant inside the system  , you will be able not just dissipate more heat but also  you will gain more time before your bike boils over as it takes much longer for the heat source  to heat up the increased amount of water in your system .
SO bigger rads = more surface and more volume = better cooling performance .
There you go , ( this is simplified version of the matter for Burp , it is little bit more complicated than this  but i am not feeling the need to go any deeper , do the experiment for your self if you dont believe me  Bump  )
BTW , i used to work in cooling ( air cons , fridges , industrial freezers ,... )  and server building  ( some are water cooled ) just in case you have wondered how i know how to keep things cool .
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Re: tm 40 jetting

Post  SkidMark on Wed Apr 30, 2014 7:57 pm

took you a year though to come up with that...  razz
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Re: tm 40 jetting

Post  Mad Frosty on Wed Apr 30, 2014 11:33 pm

Incorrect , just waited for the right moment .
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Re: tm 40 jetting

Post  Mauser on Thu May 01, 2014 7:42 am

Being a noob I would say 2 factors come into this....heat generated verses heat lose, if you generate more than you can lose you will overheat...if you have capacity to lose more than you generate you will never over heat...... listen up  there that's my simple thinking lol

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Re: tm 40 jetting

Post  BuRP on Fri May 02, 2014 11:08 pm

Wait: late night, her taste still on my....  razz 
Oh yeah, Maddy: nope bru, the amount of fluid in the rads plays zero diff, in fact time plays neither! Heat does not need time to flow, however the 'flow' depends on the area through which heat is exchanged >> hence surface area!
Imagine a tiny rad... you know it's not enough, even when the coolant flows like mad!
Now imagine a huuuuuuuge rad... you know it's an overkill, hence you'll rely on the thermostat to limit the coolant flow to attain the minim um operating temp.
Now enter the dual-core Fluidyne's (or other brands but dual core = ~double the surface area) - they will have a way bigger capacity to cool the temperature therefore the thermostat comes into play more than with rads which are marginally big-enough - enter std rads without fan.
Clear enough I hope?  Bump 
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Re: tm 40 jetting

Post  BuRP on Fri May 02, 2014 11:16 pm

Now reading your response fully: nope, more mass in the system just creates a bigger storage (read: temporarily) reserve, that's all... the heat still needs to be shed to ambient, but can take more time for this because it is - temporarily! - 'stored' in the liquid coolant.
If you'd calculate the heat-storage with double the coolant qty in our bike then you'll find that you've won only some seconds of operating, neglectable at best  Wink 
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