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Old 01-20-2012, 03:48 PM   #271
phantomaz
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hello all ,I am new in this forum ,but I am happy I found this tread and decided to join you as I have some questions about this carb.
First I want to introduce myself because I was busted in another forum for being started directly with the questions ,so I hope you are not so sensitive here but anyway ;) . My name is Ivan ,I ride ducati monster 900cc / L-twin 2v/ ,my english is broken ,and I need an advice for some pumper carb .

As I see a lot of people here are using tm40 ,so I hope I can find some information about this carburetor:

1. I live on the sea level but I am riding sometimes to around 7000ft ,and I am worried about the sensitiveness of the TM40 /and the pumpers at all / to different altitudes. What should I change to make the carb working on other altitude ,to open the carb and change some parts or just loosen or tight something with the screwdriver?

2. as my bike is 2cyl. I need 2 carbs ,and there are many offers on ebay for 2 carbs for around 100$ ,but from snowmobile, as I read here the carb for 2 stroke engine is with completely different jets etc. The question is ,is it possible to change the parts so the carb can work for 4 cyl. engine ,and which parts should be changed, will that be expensive ?



this is how the carbs look like ,the montage will be easy as my OEM mikuni bst38 are not separated but just like these.

3. But I am concerned that my carbs are mounted by angle ,and all the pictures of tm40 I saw were in vertical position, is it a problem if the carbs are not vertically mounted?






4. there was written on some of the other forums I read ,that tm40 don't have ball bearing supported slide ,and this reflects to the smoothness of the opening and closing the throttle , do you have some problems with this ?

p.s. thanks in advance, any help regarding the questions I have already asked you will be appreciated . About mounting it on to ducati engine and correct jetting I will ask in ducati forum ,but I doubt they will know something about tm40 as they use fcr kit ,but anyway I should collect all the info I need to make it work ,thank you!
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Old 01-21-2012, 01:15 PM   #272
phantomaz
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I have new info about the snowmobile tm40 carb. Sadly it does not have an accelerator pump ...
Anybody knows if accelerator pump can be installed on snowmobile tm40 without one? Too many questions in my head.
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Old 02-09-2012, 09:30 AM   #273
heetseeker
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xr with tm40 stalls at idle

After the install on the tm40, the xr650r will stall at idle once warmed up....any suggestions on which area to start with? I double checked the pumper rod and the white knob is 1 1/2 turns out...

Thanks
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Old 02-09-2012, 02:50 PM   #274
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Couple of questions for you.

Stalling at idle could be, to lean or to rich or idle speed to low.

Does it start without the choke? If it will start without the choke and you live somewhere with a cold to temperate climate then it sounds like a rich condition.

If it starts with choke but not easily then then stalls after choke is off then it is lean.

Is the idle erratic? Does it surge at cruising speed? These are all signs of a lean condition.

Does the idle slowly roll up then down? When you give it gas does it stutter and blubber? That is a rich condition.

It is possible your intake boot and or airbox boot are not sealing. Test for this by spraying carb cleaner around the boots. If the idle changes then you have an air leak.

Finally, perhaps you just need to turn the idle speed up?
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Old 02-10-2012, 07:24 AM   #275
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great!

Ok, lots to look at on Monday...

I haven't tried to start it without the choke, as I assumed that the choke was needed on cold engine starts...oops.

"If it starts with choke but not easily then then stalls after choke is off then it is lean""
runs good at cruise, no surging, idles ok .... until it coughs and dies

"Does the idle slowly roll up then down? When you give it gas does it stutter and blubber? That is a rich condition."
Did stutter a little when warm when I blipped the throttle...sounds like a rich condition. Several times now, the engine stalled and I had to open the throttle full and clear the cylinder with 10 kicks with the comp release on before it fired up. That was THE only way it woud get started...sounds rich at idle, right?

So if it's rich at idle, up or down on the jets and which one?

The boot is sealed well and the idle is on the high side now...

Thanks a million!
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Old 03-20-2012, 06:22 AM   #276
BuRPsa
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Phantomaz,

If your english is broken someone glued it, no worries ma china
Your native tongue, French or Dutch? I suspect the latter, think I recognize bits.

Yes, you must watch the angle of the carbs, and also, you will need bigger-bore intake manifolds anyway! A bigger carb will not help if there's a longish manifold which then will be the restrictive part, it must 'grow' too. So there you have an additional problem, you'll need to make your own manifolds.
The TM40 may be mounted at an angle though - don't ask me where the limit is, but some angle won't hurt it. This type of carb has the float-chamber around the main jet, kind of circular, hence in the middle - where the jet is - the level will remain constant. Best though is to keep it as level as possible, should be logical.
Roller bearings & smoothness? No rollers, quite smooth operation, don't understand your question actually.
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Old 04-19-2012, 07:10 AM   #277
DerViking
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Hey all
Looks like this thread is still getting a bit of traffic.

I have read all of the previous 19 pages, and damn, lot of good information, which has me in the ballpark on my TM 40. My XR is uncorked, with an aftermarket slipon exhaust, mostly open. 7000 ft. I am running the 140 main, which seems about right so far, runs good opened up. From what Ive read, I think I need to raise my needle (all the way down now) which hopefully freshens up the mid a bit more. Love the carb, worlds more responsive than the stocker, a whole new beasty on trail in particular.

But.... Having trouble with the pilot circuit. When I close the throttle, it idles very very high for awhile, enough to be challenging to control (nearly rear ended a car on my commute the first day out). It will drop down, especially if I feather the clutch out against the rear brake. When the engine is hot it is considerably exacerbated. I can improve things quite a bit by closing the air jet (front adjuster) all the way, but then it doesn't idle that great, and has a tendency to stall. I am guessing that I must be rich on the air jet, or rather lean on air, rich on fuel, need a bigger air? Running the 22.5 pilot, thinking the 25 would be too rich. Not sure what the air jet is, assuming the 1.1 that seems to be the stock setting from sudco.

Anyone have any advice?

Thanks
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DerViking screwed with this post 04-19-2012 at 05:52 PM Reason: Atrocious Spelling...
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Old 04-20-2012, 09:34 AM   #278
JIPPERR
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Quote:
Originally Posted by DerViking View Post
.... When I close the throttle, it idles very very high for awhile, enough to be challenging to control (nearly rear ended a car on my commute the first day out). It will drop down...
i'd check for air leaks around where the carb attaches to the air box and on the other side as well.
Good luck!

JP
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Old 05-24-2012, 01:07 PM   #279
tannerc
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Talking

Anyone running a TM40 with the stock bars? I'm wondering about throttle cable length, how much too long are the stock cables in stock handle bar configuration? I'm going to be adding a set of rox 2" risers and a set of protaper woods high bend bars, would this be enough to eat up the slack of the stock cables when switching to a TM 40?
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Old 05-24-2012, 02:29 PM   #280
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Cable length

`[QUOTE=tannerc;18759615]Anyone running a TM40 with the stock bars? I'm wondering about throttle cable length, how much too long are the stock cables in stock handle bar configuration? I'm going to be adding a set of rox 2" risers and a set of protaper woods high bend bars, would this be enough to eat up the slack of the stock cables when switching to a TM 40?

Stock bars - no risers on mine, cables supplied with the carb are the correct length, wouldn't want them any shorter.
Suggest you order longer or have them made up longer with risers.
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Old 05-24-2012, 06:40 PM   #281
tannerc
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Laugh

Ok, what i am doing is buying just the carb right now, no kit with cables. the carb is on its way but im planning on lifting the bars and adding pt woods high bend bars. so it looks like im going to just have to wait until i get everything in place before i go looking for cables.
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Old 05-29-2012, 12:22 PM   #282
BMKTW2
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I just ordered the Mikuni carb from the barn. Should I call them and tell them which jet to put in it?
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Old 05-29-2012, 10:46 PM   #283
smoothride
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I have a 00 XRR it has a 11:1 piston it is piped an 2 stage cam my jetting is pilot 27.5 main 140 needle at 3rd clip with the plastic washer on the bottom fuel mixture at 3/4 turn starts good idles good. I got the carb from xrs only but it didn't have those jet's in it. I am at 600 ft above sea level.
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Old 07-02-2012, 10:33 PM   #284
tannerc
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pilot circuit

Alright got my tm40 carb on and the bike fired up after a few shin bashings..
BUT... it will run for a bit and then backfire into the carb and die.. it would not start with three turns out on the fuel air screw... Im thinking its lean on the idle circuit. And im also guessing lean because i was guessing the more turns out on the fuel/air screw the more air in the mixture and it not wanting to start at three turns out... I could be wrong its happened once or twice..
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Old 07-02-2012, 10:38 PM   #285
tannerc
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Settings

#140 Main Jet
9DJY01 Jet Needle (3rd notch with washer under so like 3.5 notch)
568 Y-4 Needle Jet
#25 Pilot Jet
1.1 Air Jet
45 Accel pump nozzle

1726 Ft elevation
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