86 LT230 quadrunner getting to much air

[tjakes680]

I have a 1986 LT230GE quadrunner shaft drive machine ran very good up till about 2 months ago I rebuilt carb and had to much air coming in I found it was a loose duct then I relized throtle cable was getting stuck so I changed that . Now again to much air everything is tight no leaks in ducts from what i see Infact I had another OEM carb I rebuilt and put that on just incase i messed up rebuild of first carb and same problem the only way I can get it to stop racing is blocking off the white long air box that goes from air filter to under dash board in fact when I pull up choke it will slow down when i block air box . Does it sound like a duct is leaking the white air box goes into a leather bag i guess thats a filter but its doesnt seem to do much and the air fuel mixture and idle screw are basically useless on carb ! Should I possibly change the hight of needle in carb to give it more fuel but will that fix the problem ? Im at witts end any suggestions will be apriciated and helpful im going to seal all duct joints tommorw but should i block off the main air vent (white one ) its more of a band aide fix I would really want to fix it right thanks 

[Mech]

Well... Is this a diaphragm carby or an old fashioned one with the throttle cable going straight onto the slide ?

If you throttle on and then off quickly with the engine turned off, can you hear the throttle clack back against it's stopper ? What's the idle mixture problem, seized screw or damaged so the screwdriver doesn't engage ? If you are sure the throttle is closing right off, and it races, it might be just the idle mixture. The needle in the slide only effects from 1/8 throttle and up, so it shouldn't be the problem. The only place an air leak in would effect things is if it's between the carby and the engine, on that rubber manifold.. which can get old and cracked when you work on them.

[tjakes680]

1 hour ago, Mech said:

Well... Is this a diaphragm carby or an old fashioned one with the throttle cable going straight onto the slide ?

If you throttle on and then off quickly with the engine turned off, can you hear the throttle clack back against it's stopper ? What's the idle mixture problem, seized screw or damaged so the screwdriver doesn't engage ? If you are sure the throttle is closing right off, and it races, it might be just the idle mixture. The needle in the slide only effects from 1/8 throttle and up, so it shouldn't be the problem. The only place an air leak in would effect things is if it's between the carby and the engine, on that rubber manifold.. which can get old and cracked when you work on them.

Its a mikuni round slide im almost 100% the slide is going all the way down im going to change the fuel mixture screw thanks for reply im going to look into the flange where carb hooks up it is pretty old 

[Mech]

So a mikuni without a diaphram .. the cable goes straight to the slide ?

[tjakes680]

2 hours ago, Mech said:

So a mikuni without a diaphram .. the cable goes straight to the slide ?

Yes im pretty sure its sliding all the way to bottom i will test it today

Im also will take some pictures today maybe it will help

[tjakes680]

9 hours ago, Mech said:

Well... Is this a diaphragm carby or an old fashioned one with the throttle cable going straight onto the slide ?

If you throttle on and then off quickly with the engine turned off, can you hear the throttle clack back against it's stopper ? What's the idle mixture problem, seized screw or damaged so the screwdriver doesn't engage ? If you are sure the throttle is closing right off, and it races, it might be just the idle mixture. The needle in the slide only effects from 1/8 throttle and up, so it shouldn't be the problem. The only place an air leak in would effect things is if it's between the carby and the engine, on that rubber manifold.. which can get old and cracked when you work on them.

Is it possible that the top of cylinder haad could be pulling in air ? There is deff alot of old crudded up oil and gunk on it im going to dig into it today, im going to dissconect throtle cable and see if it will start with slide all the way down and ill know for certain it is if its still racing i can then say possible air leak i have chked every possible spot on air box and air lines i just dont see any cracks and ill chk boot that carb hooks into engine with its deff old but seems ok .I know its a easy overlooked simple fix but its so hard to find Like i said if I block off air  case intake it seems to work fine but what would cause this to change from never being blocked off ? Here is a blue print of air intakes 

[tjakes680]

Went back at it today slide is going down all the way had it good for about 1 hour and then it started riving high again i checked all air lines ducts couldnt see any visible tears or cracks I did howere seal one duct that comes out of air box i believe it was glued in from factory looked fo have a gap but i couldnt seal intire joint to tight to get bottom I may get a new air box saw one on ebay for 30$ its worth a shot. I just dont know where this air is coming in from Does anyone know of a way to check for a leak on air box ?

[Mech]

If it's sucking air in from anywhere before the carby, it will just mix that air with the air going through the air cleaner, and not do anything.. except let dust in ..haha.

If it had a big air leak after the carby, between the carby and the engine, it should just run lean, or not run at all.. It would only make it race if it was also getting more fuel than it's meant to.

I've seen them race when the idle mixture screw was set wrong. So... is the idle mixture screw near the engine or near the aircleaner end of the carby ?

[tjakes680]

1 hour ago, Mech said:

If it's sucking air in from anywhere before the carby, it will just mix that air with the air going through the air cleaner, and not do anything.. except let dust in ..haha.

If it had a big air leak after the carby, between the carby and the engine, it should just run lean, or not run at all.. It would only make it race if it was also getting more fuel than it's meant to.

I've seen them race when the idle mixture screw was set wrong. So... is the idle mixture screw near the engine or near the aircleaner end of the carby ?

Neear engine side it just revs so high im going to spray some carb cleaner or starter fluid by boot going into engine it has to be leaking there i would think

[tjakes680]

1 hour ago, Mech said:

If it's sucking air in from anywhere before the carby, it will just mix that air with the air going through the air cleaner, and not do anything.. except let dust in ..haha.

If it had a big air leak after the carby, between the carby and the engine, it should just run lean, or not run at all.. It would only make it race if it was also getting more fuel than it's meant to.

I've seen them race when the idle mixture screw was set wrong. So... is the idle mixture screw near the engine or near the aircleaner end of the carby ?

So basically what ur saying is engine side air leak is only way it will affect idle speed ? I actually had it running ok and seemed a little fast but then it went off once i hooked up throtle cable to thortle so i dont know if i moved the carb its on very tight the carb so i dont think itll move I also have a bigger clap on engine side of carb maybe its too tight and cutting into boot so hard to tell .Its so bad fuel air screw is basically useless manual says 2-3/8 ths turns but that seems like alot on fuel air screw i will spray boot with some starteer fluid and maybe ill see if it leaks Thanks for ur help its a very time consuming and fustrating process 

[Mech]

Yeah that's right mate.. air getting in before the carby is just more air.. it gets all the air it needs anyway through the aircleaner so a bit more unfiltered air makes no difference.

Starter fluid is a good way of finding leaks. Try that around the manifold.

If you wind the idle speed screw right out the slide should go right down and clack on the carby body, if you then screw the screw in you should be able to hear a different sound as the slide lands on the screw. If you make sure the slide  is going right down every time that would be a good start. Then wind it back out till the slide's sitting on the carby body. Then, wind the idle mixture screw right in, gently so you don't damage the screw or seat, and it should not run at idle at all. Start it up with a bit of throttle and see whether it dies right back to stopped when you throttle right off. If it does die then, then wind the idle speed in a turn or two and wind the mixture screw out a couple of turns. After that you wind the speed up till it will idle, then adjust the mixture till it runs at the highest revs it will, then adjust the speed either up or down as needed, then the mixture in or out to give the highest revs it will do at that speed setting. Keep doing those two adjustments till you get it at the highest revs it will with the least amount of slide lift. If it will idle, wind the mixture screw in and out to find the highest revs, then wind it in slowly till the revs just start to drop.. That's called best lean mixture and is where it should be when hot.

If those adjustments don't work, then you must have done something wrong in the rebuild. Perhaps the slide needle is in the wrong place, or the float level's to high, or the choke mechanism isn't operating properly.. Is the choke a butterfly, or a plunger ? If it's a plunger, check it's going right in.

It all started since the carby work, so it's either a bad(very rich) mixture combined with an air leak, or something wrong with the carby work.

Try those checks and adjustments, especially the slide going right down, and for an air leak around the manifold, and let us know how it goes.

Perseverance always wins.. giving up never does..  You'll win.

[tjakes680]

6 hours ago, Mech said:

Yeah that's right mate.. air getting in before the carby is just more air.. it gets all the air it needs anyway through the aircleaner so a bit more unfiltered air makes no difference.

Starter fluid is a good way of finding leaks. Try that around the manifold.

If you wind the idle speed screw right out the slide should go right down and clack on the carby body, if you then screw the screw in you should be able to hear a different sound as the slide lands on the screw. If you make sure the slide  is going right down every time that would be a good start. Then wind it back out till the slide's sitting on the carby body. Then, wind the idle mixture screw right in, gently so you don't damage the screw or seat, and it should not run at idle at all. Start it up with a bit of throttle and see whether it dies right back to stopped when you throttle right off. If it does die then, then wind the idle speed in a turn or two and wind the mixture screw out a couple of turns. After that you wind the speed up till it will idle, then adjust the mixture till it runs at the highest revs it will, then adjust the speed either up or down as needed, then the mixture in or out to give the highest revs it will do at that speed setting. Keep doing those two adjustments till you get it at the highest revs it will with the least amount of slide lift. If it will idle, wind the mixture screw in and out to find the highest revs, then wind it in slowly till the revs just start to drop.. That's called best lean mixture and is where it should be when hot.

If those adjustments don't work, then you must have done something wrong in the rebuild. Perhaps the slide needle is in the wrong place, or the float level's to high, or the choke mechanism isn't operating properly.. Is the choke a butterfly, or a plunger ? If it's a plunger, check it's going right in.

It all started since the carby work, so it's either a bad(very rich) mixture combined with an air leak, or something wrong with the carby work.

Try those checks and adjustments, especially the slide going right down, and for an air leak around the manifold, and let us know how it goes.

Perseverance always wins.. giving up never does..  You'll win.

Thank u my friend I deff will say choke is working and slide is going down I actually used 2 diffrent carbs and they both do the same.The only thing I may have done wrong  but i dont think so is the mixture screw in manual showed screw spring rubber seat metal washer and what I always knew and have done is screw spring metal washer and rubber seat But thats how I have rebuilt every carb I appricaite ur help and will post when im done I will get it sorrted out thanks again my friend

[Mech]

That's no trouble, these things can be frustrating. Even mechanics get frustrated, and often it turns out to be the simplest thing. Sometimes we walk away and have a coffee and when we come back everything just falls into place. You sound experienced and competent, you'll get it.

I've been assuming that you've checked any vacuum hoses it has...

Well if both carbies did it, and you say it was going right for a bit till you refitted the throttle cable perhaps it's just the cable ? Frayed wire in there perhaps ? No free play, routed wrong so it gets pulled when the bars are turned .. If you leave the cable off, and the duct from the aircleaner, then you could use a small screwdriver to operate the slide from the back, to test it's dropping properly when there's vacuum on it.

 

[tjakes680]

13 minutes ago, Mech said:

That's no trouble, these things can be frustrating. Even mechanics get frustrated, and often it turns out to be the simplest thing. Sometimes we walk away and have a coffee and when we come back everything just falls into place. You sound experienced and competent, you'll get it.

I've been assuming that you've checked any vacuum hoses it has...

Well if both carbies did it, and you say it was going right for a bit till you refitted the throttle cable perhaps it's just the cable ? Frayed wire in there perhaps ? No free play, routed wrong so it gets pulled when the bars are turned .. If you leave the cable off, and the duct from the aircleaner, then you could use a small screwdriver to operate the slide from the back, to test it's dropping properly when there's vacuum on it.

 

So I used the starter fluid on boot idle speed went up even higher so i asume there is a leak  now on the boot is a nipple that pulls vacume for fuel pump witch i just installed a used fuel pump a month ago , when i pull that line off and put my finger over the nipple idle slows down a measurable amount till it runs out of fuel , so i tryed a new line to fuel pump same problem is it possible the fuel pump could have a small leak or a small vacumn leak in one of the lines coming off it and thats pulling to much air or is putting my finger over it just blocking more air so itll slow anyway ,but again the starter fluid deffintly sped up idle when sprayed on boot . My next problem lol is screws holding boot ofcourse have chewed up heads lol im going spray liqud wrench hopefully they come out without having to score them with dremal ughhhhh I deff know slide is good and working and boot has leak somewhere ! I think its around the nipple where vacumn goes 

Getting closer!!!!!!!!!!!!

[tjakes680]

So I started the whole process over and took it all apart took out and installed new fuel mix screw and it ran great for about 10 min or so i mean absolutly perfect no backfire no pop no high idle maybe about 15 -20 min and wharn it got warmed up and hot it started high idle all over again I would think the rubber boot heated up and expanded and started leaking because when its cold i can get it running perfect once heated up no good so time to find a boot on ebay 

[tjakes680]

Just ordered new intake boot for engine sode with new bolts and ordered a aftermarket carb 40$ just to give it a shot but im almost 100% my carbs are good but ill do the boot and take it from there ill post what happens when boot is installed 

[Mech]

Good work.. The thing about things like this is that we have to be methodical, and really thorough.. we have to know absolutely that the first thing we checked really is right before we go doing any more steps.. otherwise we end up going around in circles..  Probably is a small split underneath somewhere you can't see. If you suck on that vacuum hose going to the pump it should build up vacuum and not keep flowing air.

After you've fixed the rest adjust the mixture to best lean and it should be right.

Good luck with the bolts on the manifold. Sometimes giving them a tap with a hammer and punch on top to spread the hex out a little works, and it lets the spray get down the threads.. and single hex sockets are good for rounded bolts. That manifold probably has an O ring between it and the head.. best change that too.

[tjakes680]

1 hour ago, Mech said:

Good work.. The thing about things like this is that we have to be methodical, and really thorough.. we have to know absolutely that the first thing we checked really is right before we go doing any more steps.. otherwise we end up going around in circles..  Probably is a small split underneath somewhere you can't see. If you suck on that vacuum hose going to the pump it should build up vacuum and not keep flowing air.

After you've fixed the rest adjust the mixture to best lean and it should be right.

Good luck with the bolts on the manifold. Sometimes giving them a tap with a hammer and punch on top to spread the hex out a little works, and it lets the spray get down the threads.. and single hex sockets are good for rounded bolts. That manifold probably has an O ring between it and the head.. best change that too.

Yes i also ordered a new oring new bolts but noone has a new boot had to get a used one but from a place I buy alot of used parts from they chk parts and rebuild some so should be good thanks again ill post final results should have all parts by Feb 2-5 

[tjakes680]

Ok so I finally have a day with out freezing temps so going back at it again . I have a new boot ( used but looks good ) and a new round gaskit for inside boot a new OEM carb ( again a rebuild) all new fuel and vent lines a used air container the one on front of quad( the long white one )  not the air box a new air fiter for the long white vent  piece air container I believe its called all new clamps for vent ducts to air box and used but in great shape air ducts So basically rebuilding the fuel and vent systems on quad I will post results after this im out of options but going into this with a positve additude !!!!!!!  Ohh and not forget new throtle cable lol 

Edited February 10, 2022 by tjakes680

[tjakes680]

Here is what im changing and all the fuel and vent lines as well ! Got these from a really great seller on ebay who just took these off a running quad for me same exact machine 

[tjakes680]

So got the high idle issue solved but now im bogging out at full throtle 

[Mech]

Are you absolutely sure the spark plug's good..  Tried it in another bike, put a good bike's plug in there, got a new plug ?

Only full throttle, or somewhere between 1/4 and 3/4 throttle(or a bit more) doing it ?

[tjakes680]

1 hour ago, Mech said:

Are you absolutely sure the spark plug's good..  Tried it in another bike, put a good bike's plug in there, got a new plug ?

Only full throttle, or somewhere between 1/4 and 3/4 throttle(or a bit more) doing it ?

I changed plug old was fould out lean its at full throttle from 3/4 - full

1 hour ago, Mech said:

Are you absolutely sure the spark plug's good..  Tried it in another bike, put a good bike's plug in there, got a new plug ?

Only full throttle, or somewhere between 1/4 and 3/4 throttle(or a bit more) doing it ?

I stupidly put a old carb on i had 3 in a box and of course i picked the one that was dirty has to be that im going rebuild it tommorow 

[Mech]

Oh yeah.. It might be worth checking the fuel pump delivery is right before pulling the carby off..  It's simpler to do. And bad fuel supply could give your problem.

Pull the fuel delivery hose off the carby and lay it into a bottle on it's side. Start the bike and let it idle and the fuel should be squirting out full diameter of the pipe... Er, squirting out of the pipe full diameter of the pipe. A trickle is a bad pump and may or may not get it up big hills, or when the tank gets low.

And that "boot" you are mentioning, between the carb and head, that's called a manifold... If you're mentioning it in the future.

Edited February 11, 2022 by Mech

[tjakes680]

29 minutes ago, Mech said:

Oh yeah.. It might be worth checking the fuel pump delivery is right before pulling the carby off..  It's simpler to do. And bad fuel supply could give your problem.

Pull the fuel delivery hose off the carby and lay it into a bottle on it's side. Start the bike and let it idle and the fuel should be squirting out full diameter of the pipe... Er, squirting out of the pipe full diameter of the pipe. A trickle is a bad pump and may or may not get it up big hills, or when the tank gets low.

And that "boot" you are mentioning, between the carb and head, that's called a manifold... If you're mentioning it in the future.

So i just started quad from ice cold sitting about 4 hours off and it starts and idles but dies when i hit thumbb throtle sound slike its choking on air I did replace the fuel pump about 2 months ago I think its a dirty carb The carb was off another quad same year that was sitting in a shop for awhile and stupidly i never cleaned it or rebuilt it i have a rebuild kit so ill rebuild in am 

[tjakes680]

So put a brand new carb on and idle is perfect quad can idle for days full throtle at idle is perfect until i start riding and at 3/4 to full throtle quad bogs down I dont know what it can be i made adjustments to jet needle no change I put in a new spark plug no diffrence i put in a new air filter my only thing left is I have a new oem fuel pump and and i also have new fuel filters that go in fuel tank I will try changing them also what can this be im at witts end im really just stuck any ideas????

[Mech]

If it starts to go ok for a second or so at wide throttle, then falters, it sounds like a fuel supply problem. If it falters as soon as you open the throttle wide, and recovers quickly when you back off, it sounds like jets, air or fuel jets.

You can test the pump and in tank filters by testing it as I suggested.

Here's another test though that might show us something.. Take the fuel pipe off the carb and lay it in a bottle on it's side. Pull the vacuum pipe off the manifold and suck on it two or three hard sucks, then let the vacuum off suddenly. It should shoot out a good full flow squirt of fuel. Then connect the vacuum hose to the manifold and start the engine and let it idle, it should flow petrol still at a good flow, near full diameter but not so fast as the first test. Then blip the throttle wide open while watching the flow of fuel. If it drops right off, it's because of low vacuum, which will be dropping right off when the engine's under load and the throttle's open.

So check you've got good fuel flow, and vacuum, and then vacuum under load. You could load the engine to test for weak vacuum by putting it in gear, brakes on, sitting on it of course, and then open the throttle till it's labouring on the centrifugal clutch.

The hole in that pipe poking out of the manifold needs to be a good size. Check it's the same size as the old manifold's one. It should be more than about three mills. On later models there are different vacuum ports for different purposes and if you use the small port(about 1.5mill), the pump struggles, use the big port(about four mills), and it's all good. The vacuum hose going to the fuel pump needs to be thick walled, fuel hose is best. If you use a thin walled vacuum hose, that's hose sold as vacuum hose, it gives/collapses too much with the pulsing vacuum. The pump has to get a good pulsating vacuum to it. A partially collapsing hose gives a steady non-pulsating vacuum.

 

[tjakes680]

1 hour ago, Mech said:

If it starts to go ok for a second or so at wide throttle, then falters, it sounds like a fuel supply problem. If it falters as soon as you open the throttle wide, and recovers quickly when you back off, it sounds like jets, air or fuel jets.

You can test the pump and in tank filters by testing it as I suggested.

Here's another test though that might show us something.. Take the fuel pipe off the carb and lay it in a bottle on it's side. Pull the vacuum pipe off the manifold and suck on it two or three hard sucks, then let the vacuum off suddenly. It should shoot out a good full flow squirt of fuel. Then connect the vacuum hose to the manifold and start the engine and let it idle, it should flow petrol still at a good flow, near full diameter but not so fast as the first test. Then blip the throttle wide open while watching the flow of fuel. If it drops right off, it's because of low vacuum, which will be dropping right off when the engine's under load and the throttle's open.

So check you've got good fuel flow, and vacuum, and then vacuum under load. You could load the engine to test for weak vacuum by putting it in gear, brakes on, sitting on it of course, and then open the throttle till it's labouring on the centrifugal clutch.

The hole in that pipe poking out of the manifold needs to be a good size. Check it's the same size as the old manifold's one. It should be more than about three mills. On later models there are different vacuum ports for different purposes and if you use the small port(about 1.5mill), the pump struggles, use the big port(about four mills), and it's all good. The vacuum hose going to the fuel pump needs to be thick walled, fuel hose is best. If you use a thin walled vacuum hose, that's hose sold as vacuum hose, it gives/collapses too much with the pulsing vacuum. The pump has to get a good pulsating vacuum to it. A partially collapsing hose gives a steady non-pulsating vacuum.

 

Sounds good i actually have a new vacumn hose i didnt use its OEM for this machine  im getting a pulsating fuel flow when i took fuel line off today not steady stream but pulse i actually have a OEM brand new fuel pump im going try cant hurt . Do u think i should also empty tank and change the fuel filters in tanak i have a set i orderd and never used when i think of when all this started a few months back my problem started that i couldnt start quad  in on position of fuel valve only on reserve and I put a used pump on and new fuel valve I feel the problem is around there  why would it idle so well I have a video of idle and full throtle at idle and its perfect  also going to try a new iridium spark plug Hey thanks for all ur help its so close 

[Mech]

You could also check the fuel has a little pressure. Put your finger over the pulled off fuel hose while it's idling, it should squirt with a tiny bit of pressure. The vacuum sucks a diaphragm against a spring, and the spring sets the pressure. If the spring's weak it might have flow, but not enough to shove it past the float needle at the right rate. It's only about three or four pounds of pressure it's meant to have.. I think..haha

It should squirt a little distance though, a foot or so..

If you pull the hose off the tank and try the tap you'll see if the filters are blocked.

[tjakes680]

5 minutes ago, Mech said:

You could also check the fuel has a little pressure. Put your finger over the pulled off fuel hose while it's idling, it should squirt with a tiny bit of pressure. The vacuum sucks a diaphragm against a spring, and the spring sets the pressure. If the spring's weak it might have flow, but not enough to shove it past the float needle at the right rate. It's only about three or four pounds of pressure it's meant to have.. I think..haha

It should squirt a little distance though, a foot or so..

If you pull the hose off the tank and try the tap you'll see if the filters are blocked.

When i replaced fuel pump the line came off fuel tank and fuel flew right out im deff going change pump its a easy swap and i have a brand new never used oem so its deff worth a shot at this point and ill change the vacumn line to manifold as well again thanks I cant wait to hit the mark as solution button on here lol I will let u know what happens