2000-2001 lta500 quadmaster - Idle jet adjustment

[Kuba]

I hope it will be 😁😁. If not I’m going to look for rebuild kit with it . 

If it’s not a problem what rebuild  kit did you used?

[cfauvel]

On 12/17/2020 at 3:50 PM, Kuba said:

I hope it will be 😁😁. If not I’m going to look for rebuild kit with it . 

If it’s not a problem what rebuild  kit did you used?

I looked but can't find where I bought it from ...but found the package 
Moose Racing part # 1003-0555

I think I bought it JUST for the brass doohicky to hold the throttle cable...but since I had a brand new carb there was nothing I needed from it

[Mech]

Hi. I'd like to make a few suggestions.. It's important that the idle speed screw is at the right setting or the choke mechanism doesn't work properly. The choke doesn't actually choke off the air supply as a butterfly type does. In the carbys with the plunger, the plunger being lifted when you put the choke on is meant to let extra air and fuel through a separate passage to assist with cold starting. That won't work though if the throttle is open, or the idle is set too high. The choke has to have good vacuum to suck the fuel up high to that plunger, and through that extra passage, and it can't do that if the throttle is too far open lowering the vacuum. So don't give it throttle while you're trying to enrichen it for starting, that stops the choke/enrichener from working, as does having the idle speed wound up too high. With a conventional butterfly choke that doesn't apply and you can give it throttle while the choke is on and it will still deliver extra fuel.. but not with the plunger ones.  If the choke/enrichener doesn't seem to be working, try winding the idle speed screw out a little.. count the turns so you can set it back again if it's not the problem. That often gets them firing and then you can slowly open the throttle to get them to start.

Secondly, there are two types of idle mixture screw setups. If the idle mixture screw is near the inlet manifold, as most suzukis are, then its cutting off the fuel as you wind it in, making the mixture leaner. In the other setup the idle mixture screw is near the air-cleaner end of the carby and as you screw those in they cut off the air supply to the idle mixture making it richer. This applies whether the screw is underneath or on the side of the carby. If it's near the engine it's cutting the fuel off, making it leaner, and if it's near the air-cleaner it's cutting the air to the idle mixture off making it richer. 

Hope that helps with the understanding what's going on.

 

[Kuba]

Carb ordered , can’t wait to installing and see what will happening. 

Mech- very detailed explanation, that’s will help me for sure during new carb set up. 

 

[Mech]

No trouble.

I should add that it's important that the idle speed adjustment is in the right position when you are adjusting the mixture too. When the throttle butterfly is in it's closed position there is the hole where the idle mixture fuel comes out into the venturi, and that hole is between the butterfly and the engine by a tiny amount, about one mill perhaps, but there is another hole that comes out into the carby just about a mill or less on the aircleaner side of the butterfly. Both holes are connected and when the butterfly is closed the air gets drawn down through the hole nearer the aircleaner, and that air mixes with the adjustable idle mixture and dilutes it a little and atomises it thoroughly before it comes out the other hole on the engine side of the butterfly. As the throttle is opened the air stops getting dragged down and mixed and the mixture richens a little.. It works a bit like an accelerator pump does on a car carby. On some carbys both holes end up discharging fuel into the engine. If you try and adjust the idle mixture with the butterfly open too far the idle mixture isn't getting atomised properly and you get flat spots and/or difficult idle mixture adjustment..  So the procedure is to go around in circles adjusting the idle speed, then adjust the mixture till it's running at the highest revs you can get with the mixture screw, then raise or lower the idle speed, then adjust the mixture to the highest revs again, then the idle speed screw again..

Most problems people have are either starting technique (no throttle while you are giving it choke), or adjusting the idle speed too high thinking that will make it start or adjust easier... 

Good luck with it.

 

 

[flyinbrian365]

I just worked on one of these machines for a customer of mine. I completely rebuilt the carb, sometimes at idle it would load up like it was running too rich. The another issue he was having was it would suddenly stall when you came to an idle then start right back up. Both of these problems are caused by a bad fuel valve, the vacuum diaphragm gets deteriorated and starts pulling fuel through the vacuum hose or doesn't flow fuel correctly. I've had 2 customers with 2 different Suzuki model ATV's with the same issues a bad fuel valve assembly. There are no rebuild kits and the oem valves are much higher quality than after markets so just spend the money and put a good one on it.   

[Kuba]

Carburetor installation update

Im sorry for all language mistakes , English is not my primary language 😁.

I opened new chaineese carb before installation and noticed main jet size is #180 stamped on body . Package included small ziplock with screws for throttle cable cover , throttle cable mount and also jet#140 and I did swap them . 

Cleaned all passages with carb cleaner and compressed air , don’t check how many turns was mixture screw in or out , but before  engine starting I also replaced fuel tank valve . I go with aftermarket one from Yamaha , Off-On-Res positions. After that I closed vacuum port on carburetor, one which go to original fuel valve .

Need to drill out thread inside throttle cable mount , but that was not a problem . Attached enricher cable (all necessary components was inside carb ).

Enricher open , butterfly throttle  close completely , and started cranking- nothing . 

Moved throttle adjustment a little bit , just to crack open and trying again . 

Started nice in a second , keeps high rpms , I let it warm up and turned enricher off , rpms slowdown and starting mixture adjustment to get a nice throttle response. 

I’m not sure how many turns I did , but finally i got nice and fast response, no backfire, will see how will work after I finish primary clutch rebuild ( parts awaiting).

Thanks you guys for all your explanation about carb adjustment and how is it work. 

This make my job easier . 

For testing purpose I did keep ATV outside for two days 28-30 Fahrenheit temperature and trying start again. 

Enricher on , first crank and running  smooth and nice . For now I’m happy.

Hope going to stay like that .

More updates after primary clutch fix and test runs. 

[cfauvel]

Very cool.... you did exactly what I did to get it idling right...bravo.

what IS your primary language?

What I like about forums and youtube...you get to interact with EVERYONE around the world. It really makes me see that  we are all really doing the same things.

We play music, we make music, we play with boats, we play with ATVs....all over the world.

Edited December 30, 2020 by cfauvel

[Kuba]

I’m from Poland , but living  in Streamwood, Illinois.

[Mech]

Kuba... That jet you changed.. When we are fine tuning bikes we adjust the size of that jet by 5 at a time normally, so like from 180 to 175. Going from 180 to 140 is a huge change and may make the bike run far far too lean at full open throttle. Running mixtures lean makes bikes overheat very quickly. They might know you need that 140, or perhaps you've read in the manual it does.. I don't know.. So..

That jet controls the mixture at full throttle and you need to be very careful about doing that(running full throttle) until you are sure it's going to be ok.

Before you change that though you have to check that the throttle slide's needle is in it's correct setting. It's best to have a new spark plug in there to do it, or a nice clean on anyway. You do the test by giving the bike a run on a long flat road for about twenty or more seconds at more than one quarter throttle, and less than three quarters throttle. The nearer three quarters the better. At the end of the long straight you have to pull the clutch in(if it has one), or throw it into neutral, and switch the throttle off immediately. Don't let it go into overrun or idle. Roll to a stop and then take the spark plug out and see what colour it is. It should be starting to colour up the new whiteness. If it's too white the needle jet in the  throttle slide too low. If it's black or dirty, the needle jet in the slide's too high. Adjust it one notch down or up with it's circlip and try the test again. Keep testing and adjusting until the sparkplug is a nice light tan brown or grey colour. This adjustment will probably already be correct but you have to be sure before you do the full throttle adjustment.

Once that setting's correct you do the same testing and adjusting process but at full throttle. So full throttle for at least twenty seconds(If you can, it can get tricky, find a quiet road), then out of gear and switch the motor off as you are knocking it out of gear. Roll to a stop and check the colour of the plug. It should be starting to show a light brown/tan or grey colour. If it isn't, you need to change that main jet, the 140 one. Depending how (presumably) white it is going to be you are going to have to make a judgement call on how much to change the jet by. As I say five or ten is a good change.

Be careful not to run it to hard if it is lean.. It's better to err on the side of rich rather than lean.

[Kuba]

Mech - now I will a headache 🤣🤣🤣.

This China’s carb has only two jets sizes 

#140 and #180. Looking at them I can see holes size difference. I choose smaller cause I did checked how big is in original carburetor and looks like is #135 . 

For now I can only testing engine without  driving, but once I get it ready will do a spark plug color testing .

Need to check if a needle jet is adjustable. 

 

[Mech]

Oh ok, and hi to you Kuba. From 135 to140 isn't much, and it's richer which is the safe way to go. It should be fine.

[JABAWOKI]

As an electrician, I once though I could measure the volts across a 4 cylinder vehicle ignition coil. I quickly learned the limits of my meter in regards to voltage as it instantly became a useless pile of plastic. NEVER try to measure the volts of an automotive ignition coil: The voltage is in the range of 10's of thousands of volts. I believe the car I was working on was rated at around 30 or 40,000 volts.  I'm new to quads and own a 500 Quadmaster now. I'm not sure what the voltage being pushed to the plugf is, but I'm sure as heck going to research it before I stick my $400 Snap On meter to it. But that story brings me to another point I've long been making in the mechanics realm, but is especially true to CDI boxes on quads an such. OK, so a coil can have its resistance measured, or "Ohmed Out" on a non-energized circuit (another great way to turn a meter into rubbish is to measure Ohms on a live circuit.) NEVER MEASURE OHMS ON LIVE CIRCUITS.. However, a CDI box is not so easily measured, as there's much more going on in there than the easily measured electrical properties found in a simple coil of wire. With capacitors, diodes and so on, how is it best determined whether you're getting enough spark? If there was a sure proof way, like ohming a coil to know your spark, this "fuel" issue could've instead been an "Electrical" issue, no?