43F carburetor tuning?

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84_XT600L
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meble kuchenne Ruda Śląska Rybnik Tychy
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43F carburetor tuning?

Beitrag von 84_XT600L »

Hello guys,

What is the procedure to tune the YDIS carburetor on the XT600 43F? Do i have to start on the primary carburetor first then make the setting on the secondary one? Thanks

Jack
YAMAHA. The way it should be ;)

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Steffen
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Re: 43F carburetor tuning?

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Hi Jack from Australia.

I assume you want to have the carb working and not tuned-up in the sense of getting more HP out of it?

First things first: clean it up very carefully. Maybe you need a new gasket for the float bowl on the sec. carb and also maybe a new floating needle and valve set, maybe some rubber hoses) - should be not more than 20$. The additional hoses are not neccessarelly needed, onbly the two between the carbs and the one to the fuel tank.

You're right, the main carb ist to be tuned up first (after cleaning both carbs). The second carb comes on ca. 4500 U/min.
Do you have a repair manual? The usual tune-up steps are written down very exactly in clymers book, chapter 8.

Most of the tuning happens with the carb deinstalled like the float arm high, even the pilot air screw and the "transmission" between both carbs (sometimes also called synchronizatrion, but thats not exactly what it is...) . Only the idle can be changed when the carbs are installed.

Get me some details, what exactly your problem is so the people here or I can help more detailed.

Have a good time

Stef

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84_XT600L
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Re: 43F carburetor tuning?

Beitrag von 84_XT600L »

Hello Stef,

So now the carburetors are clean with new gaskets , o-rings etc. I synchronize the carbs at around 5mm and 2.5 turns out on the mixture screw as per instructed on the service manual.

Work fine so far however i'm still a bit unhappy about the performance on 5th gear. I'm currently running 15/40 sprockets and on the freeway i wind it up to 120 km/h - 5000RPM and it doesn't want to go anymore beyond this, however, it only happens in 5th gear otherwise it's runs smooth all around.
YAMAHA. The way it should be ;)

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Steffen
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Re: 43F carburetor tuning?

Beitrag von Steffen »

Hi Jack

Thats one step in the right direction if you have the carbs cleaned now.
With 15/40 the engine should run at least 145km/h and even more. But it's quite normal that the 5th gear is coming on like chewing gum from 5000rpm on. Especially on a worn out bike with original configuration.

helpful information: for reinstalling the carbs leave the side to the air box open. Install the rubber connectors between carbs and air box at last. Use a warm water bath for the rubber parts f they are hard. Install them while they are soft & warm, but dry (shake to dry). You can also heaten them with a hair dryer, that will also do.

If there's no coughing arount 5000rpm in the fifth gear then try to get more air into the system, maybe it's running on too much gas in the mixture. An easy way is to run it without air filter. Some new air filters are too tight and leave the engine running too fat. You can also check your spark plugs after running on full throttle (use the kill switch and brake the bike, then check if colour is white, brown or black, see repair manual).

Ensure that the second carb (right one) is working properly. You can watch the carb coming up if you run the engine without the right rubber connector (see above).

Other idea: check the additional valve on the left carb
https://xt600.de/xt_werkstatt/+special/ ... ventil.htm

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External:

Engine head valves and compression should be okay. All electric connections should be okay.

Check the fuel. Open the fuel tank (1/3 filled up), maybe the air is not coming into your tank fast enough. This will give the carb not enough gas to run on high speed. Also ensure that the floater in the carb is adjusted correctly. Otherwise the engine cannot run on high speed.

Very often these days: the generator. The ignition coil gets direktly energy from the generator (not from the battery). When these windings on the generator are broken the symptom can be the same. Sometimes it gets more the hoter the engine gets, up to completely not working. But sometimes its like that the ignition doesnt happen every turning and that leads to increased top speed. The problem is not easy to track.
You can test the generator while it is mounted, hot and cold, and if the values measured are far from those in the book than the generator windings are maybe broken. But if the values are okay the generator can still be damaged, but you cannot measure it. Easiest way is to borrow a working generator from a friend (whos machine is running on 150km/h top speed)
Most of my generators for the XT are repaired, and it started around 2010 when they got all broken (I have the 2KF model from 87-90). On the 43F model from 84 to 87 it happened earlier.

Good luck

Stef

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84_XT600L
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Re: 43F carburetor tuning?

Beitrag von 84_XT600L »

Hello Stef,

Thanks you for your detailed explanation and i really appreciate your help :)

From what i know after going for a ride on the highway it runs very smooth that's not even missing a beat like what i see on some other people's TT/XT's. I did a bit of research as well that the OEM air box is actually not providing enough air flow for the engine's need therefore i believe that is primary reason that's causing it.

I have a 1983 IT250 as well and when i first bought it, it has a bunch of holes drilled to the air box lid so it must of suffered the same issue. Do you believe it's a good idea if i do the same of adding some holes on the XT's air box lid?

The secondary carburetor is inspected to day as well with the rubbers off. It's working perfectly fine and adjusted to Yamaha's specification. I also soak the rubbers in a bucket of hot water for 40-60 secs prior to installation. Just makes it much easier and enables the rubber to be tighten by the clamp for a stronger seal.
YAMAHA. The way it should be ;)

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XTsucher
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Re: 43F carburetor tuning?

Beitrag von XTsucher »

If the engine don‘t get enough air then usually something is wrong with the carburetor‘s nozzles - it provides too much fuel... but never heard or read about drilled airbox lids.
Grüße, Frederik - der jetzt 1VJ fährt.
Original ist schön und gut - ich fahre lieber.
Projekt 2019:
- LED Zusatzscheinwerfer - dauert :-)

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84_XT600L
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Re: 43F carburetor tuning?

Beitrag von 84_XT600L »

It's a fairly common mod that's been around forever. Even the factory Yamaha team done it on their production based YZ490 in 1985 for Broc Glover.

The nozzles are free of gunk as i clean them thoroughly in some high point solvent and blew it clean with compressed air. The bike overall runs beautiful with no signs of sputtering due to improper mixture however just doesn't seem to do very well in top gear and reached 120km/h.
YAMAHA. The way it should be ;)

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XTsucher
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Re: 43F carburetor tuning?

Beitrag von XTsucher »

84_XT600L hat geschrieben:
Mi 1. Jan 2020, 03:32
It's a fairly common mod that's been around forever. Even the factory Yamaha team done it on their production based YZ490 in 1985 for Broc Glover.
Yes, true, but they always adapt the carburetor to this - without adaption you will have other negative consequences in different speed ranges.
Are you sure that the secondary carburetor opens 100% at full speed?
Grüße, Frederik - der jetzt 1VJ fährt.
Original ist schön und gut - ich fahre lieber.
Projekt 2019:
- LED Zusatzscheinwerfer - dauert :-)

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Maybach
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Registriert: So 14. Okt 2012, 12:24

Re: 43F carburetor tuning?

Beitrag von Maybach »

@XT-Sucher
Das hat er doch bereits geschrieben: The secondary carburetor is inspected to day as well with the rubbers off. It's working perfectly fine and adjusted to Yamaha's specification.

@84_XT600L
How old is your air filter? Is it clean?
A dusty airfilter may use exactly the results you describe ...

And btw: we hope you will get the bushfires extinguished soon down under.

Maybach

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84_XT600L
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Re: 43F carburetor tuning?

Beitrag von 84_XT600L »

Yes it's clean and lightly oiled to ensure it's not clogged.

Thank you very much Maybach i'm hoping so too. Btw good choice for your username :) Maybach was also a technologically advanced company in the production of the power plant for the German Panzer during WW2. A good example would be the well known HL230 v12 petrol engine which saw action in the Tiger :)
YAMAHA. The way it should be ;)

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