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2020 sportsman 850
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Me to but shinny attracts buyers 馃ぃ ppg makes a awesome product called flex n flat . It鈥檚 great for atv plastic and it鈥檚 not shinny. Actually makes it a little more durable than the gloss
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If you look close those you can see the faint variance in the red . Back is little darker . It originally looked horrible was all faded and scratched . But we use waterborne base coat and I didn鈥檛 want to chance trying to spray red base on basically raw plastic . And definitely didn鈥檛 want to seal it all. If your trying to make one slick this works. But if your just trying to bring a little color back and get rid of scratches on old plastic a heat gun is best .
 

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Oh yeah, I understand. It looks super nice and should bring top dollar.
I'll be keeping that product in mind for future rehab projects.
 

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Oh yeah, I understand. It looks super nice and should bring top dollar.
I'll be keeping that product in mind for future rehab projects.
Thanks ! Well it probably would鈥檝e brought decent money but my wife and I have been discussing it today and I鈥檓 thinking about giving to my son in law for Christmas . Maybe selling off a few old Honda 300s I mean I got 4 of the old wore out things lol .
 

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Your son in law is a lucky man.
Yep, those old 4trax are a classic machine and still very popular in these parts.
 

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Discussion Starter #45
Here's the specs on the OEM carb:
View attachment 143080
Here's the breakdown on the carb
View attachment 143081
There is a thick plastic spacer under the needle e-clip and a spring seat on top of the e-clip

If it was a Mikuni BST-34 or 40 carb, then the assembly is as pictured - if it is a Chinese counterfeit, it's anybody's guess as to what is right. Only the carb manufacturer knows and they are many times defective. For my money, I would find one or two Mikuni carbs and get a quality Shindy or All Balls carb rebuild kit as a starting point.

I see you do not understand the operation of the CV carb.

As the velocity of air passing through the venturi increases, the slide rises - if you are holding the engine speed steady and the slide has risen 1/4 inch and you 'snap' the throttle open, the slide drops - this is in an attempt to keep the velocity of the air passing through the venturi constant - as the engine speed increases (and thus the velocity of air) the slide will rise - at idle the slide is usually only slightly 'bouncing' or is bottomed out and stationary - as you increase engine speed, the slide will rise and drop with the 'pulse' of air passing through the venturi as the intake valve opens and closes.

Being a mechanic is one thing, being a tuner is another thing and being able to solve a puzzle is extraordinary.

You have made excellent progress, not it's just a matter of getting it tuned - don't waste time on a POS Chinese carb, but don't get me wrong - there are quality Chinese carbs to be had - I have had success with KF Standard of Japan, Kun Fu and on small two strokes Sun, but it's easier to tune with Mikuni and Keihin because you can get parts - with the Chinese counterfeit carbs, they might look the same, but Mikuni and Keihin parts usually will not fit - the main jet for a Mikuni may not have the same threads as the Chinese carb and the main jet in the Chinese carb does not usually have a size stamped into it - this is because the Chinese size the jet to the flow characteristics of each individual carb - their quality control is not good enough for every carb to be jetted the same as the next one - thus 10 (or more) of the same brand, same size and same model of Chinese carb may all have different sized jets and since the drilled air passages are not precise, the settings of the slide needle and fuel screw are all different - there is no published factory setting - the setting is the setting that gets the carb from the assembly line to the box that it is sold in. When working with Chinese carbs, they must be calibrated for the engine they are installed on and that is the job of the mechanic installing the part and tuning the engine.
Hey i have been catching up on other stuff lately so i haven't done much to the scrambler for a few days but i did do some investigating , i got two carb rebuild kits from the Ebay seller, i told him the first kit was not working properly so he sent me another one, and it wasn't the float needle would not seal, but anyway i looked closer at some of the parts in the kit compared to the parts i took out of the carb, The jet needle is slightly different , its just a little longer, but the needle jet is slightly longer also so it probably works about the same, but the jet needle itself in the kit has 10 holes in the sides, while the needle jet in the original has 6 holes, also i can not read the old main jet size but the new main jet is a 145 , and its shaped slightly different than the original. so i have been cleaning the cement like deposits from the old parts and will try to re install them, i would think that needle jet alone would cause it to be to rich or not? And is a 145 main to heavy? i mean i am at low altitude , less than 1000 ft, usually around 500 ft. anyway i was just wondering what your take on this is.
 

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3130559MAIN JET,#125 (#125)
3130728JET,NEEDLE,(P-3) (P-3)
3130668VALVE,NEEDLE,(1.5) Substituted by 3130531 (1.5)
3130526JET,PILOT,#42.5 (#42.5)
3130667JET NEEDLE,(5D78-2) (5D78-2)
3130625JET,AIR,#160 (#160)
 

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Discussion Starter #47
3130559MAIN JET,#125 (#125)

3130728JET,NEEDLE,(P-3) (P-3)

3130668VALVE,NEEDLE,(1.5) Substituted by 3130531 (1.5)

3130526JET,PILOT,#42.5 (#42.5)

3130667JET NEEDLE,(5D78-2) (5D78-2)

3130625JET,AIR,#160 (#160)
so the main is to heavy , i can't find numbers on any of the other parts yet, but i'm thinking the way it all works the main jet alone would contribute to being to rich from 3/8 throttle to WOT even though the main is mostly a factor in full throttle situations. just from looking at the way the other rebuild kit parts are made, with more holes and all in what i call the needle jet it has to be to heavy also, would you agree?
 

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Discussion Starter #48
3130559MAIN JET,#125 (#125)

3130728JET,NEEDLE,(P-3) (P-3)

3130668VALVE,NEEDLE,(1.5) Substituted by 3130531 (1.5)

3130526JET,PILOT,#42.5 (#42.5)

3130667JET NEEDLE,(5D78-2) (5D78-2)

3130625JET,AIR,#160 (#160)
I think I'm on the right track if i just tear the carb apart again and extensively clean the old parts up and re-install them it will work right, i have one problem that bothers me though, the old float needle is missing it's keeper spring that holds it to the float , meaning it could get stuck closed in theory, i would assume the fuel pump pressure would push it open , but i just don't feel right about it, and i certainly don't want to buy another entire rebuild kit to get that one tiny little part , i might try to use one of the rebuild kit keeper springs , but i can already tell that will be really hard to put in the right place just because of how tiny it is. I'm guessing a very small set of needle nose pliers and maybe a razor knife blade will be my tools, lol.
 

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Discussion Starter #49
Hey i have been catching up on other stuff lately so i haven't done much to the scrambler for a few days but i did do some investigating , i got two carb rebuild kits from the Ebay seller, i told him the first kit was not working properly so he sent me another one, and it wasn't the float needle would not seal, but anyway i looked closer at some of the parts in the kit compared to the parts i took out of the carb, The jet needle is slightly different , its just a little longer, but the needle jet is slightly longer also so it probably works about the same, but the jet needle itself in the kit has 10 holes in the sides, while the needle jet in the original has 6 holes, also i can not read the old main jet size but the new main jet is a 145 , and its shaped slightly different than the original. so i have been cleaning the cement like deposits from the old parts and will try to re install them, i would think that needle jet alone would cause it to be to rich or not? And is a 145 main to heavy? i mean i am at low altitude , less than 1000 ft, usually around 500 ft. anyway i was just wondering what your take on this is.
Yes, you have to have the airbox lid AND "snorkel" on and just removing the snorkel alone messes up the vacuum needed.

I'm not sure exactly why, because the CV carb used on the Z400/KFX400/DVX400 responds just fine to no airbox lid, a pod filter & rejetting. But these on the Scrambler and Sportsman 500s absolutely do not. They do exactly as you describe yours is doing without the factory setup on it.



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i put all the old cleaned up parts back in the carb and it runs much better, and i can tell a difference when i close the airbox, the symptoms i described before were similar but much worse, so yeah them cheap ebay rebuild kits might work for later year carbs , and the list of carbs they work on is like 1997 through 2009 or something like that which sounds wrong already, lol.
 

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Discussion Starter #50
Yes - an experienced rider will stab the throttle open for a short distance, but few get out where they can hold it wide open for more than 100 feet
i got around to putting all the stock components back in the carb, and it runs much better without the breather box, but it seems to run right with the breather box, but still it seems to rev really slow, but keep in mind this is the first time i am really experiencing a scrambler 500 , the only scrambler i rode before was one of the first 400 2 strokes and it had some kind of aftermarket clutch pack and it kept up with or maybe even edged out my very strong running honda 250 R in a drag race in a field. But anyway i was looking at some charts for jetting and noticed the sportsman from the same year , engine and carb had a heavier main jet , why is this? Also i was looking at elevation and temperature recommendations for jetting and the factory setting for the scrambler at least was at the highest elevation and the highest temperature. This ATV is for my girlfriend , it does not need to be race fast but i would like it to be a little better, i might get a real jet kit or just a slightly heavier main jet eventually. I just want it to be good enough that its not a complete dog that has so low of power its more dangerous than to much power. Anyway i got a brand new NGK spark plug and have not put it in yet, still running that old champion that was not looking so good, and i have to get a hose clamp for the breather box to the carb it was in the 20's last night when i was outside with a flash light doing all this and them rubber pieces do not like to cooperate , lol. But the fact that it started right up with carb cleaner and PB blaster residue in the carb in mid 20 degree weather impresses me. Hopefully i got it right now and running in gear actually it pulls good but it just seems so slow revving even at its best. Hopefully i didn't mess up the stator plate timing , i haven't owned a timing light or used on for 20 years or better, lol.
 

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They only pull 6500-6800 RPM, so it's not gonna rev high, and stock clutching is very conservative making them feel weak.

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Discussion Starter #52
I think I'm on the right track if i just tear the carb apart again and extensively clean the old parts up and re-install them it will work right, i have one problem that bothers me though, the old float needle is missing it's keeper spring that holds it to the float , meaning it could get stuck closed in theory, i would assume the fuel pump pressure would push it open , but i just don't feel right about it, and i certainly don't want to buy another entire rebuild kit to get that one tiny little part , i might try to use one of the rebuild kit keeper springs , but i can already tell that will be really hard to put in the right place just because of how tiny it is. I'm guessing a very small set of needle nose pliers and maybe a razor knife blade will be my tools, lol.
i tried the carb again after doing all of the fuel lines right , with the air box on, with the filter on, today i got it to run about half way. it takes gas some but not really good unless you open the air box and manually raise that slide, although i did try an experiment , i turned the fuel valve from the fuel tank off and it started running correctly until the bowl was completely empty, but it took gas like i imagine it should and pulls pretty decent but not for long until it runs out of gas, I do not think the float level is to high since it does not run out the overflow , i do have the float needle just in there with no keeper spring and did not recieve any parts for the float needle seat repair if there is such a thing. I think im just going to shit can this carb, it probably has a crack somewhere or something corroded to far beyond repair but obviously with the fuel valve on and the pump pumping gas it will overflow the carb on the inside but not enough to run out the overflow , i have the air screw at 2 turns out just like the manual says, and i don't know how much that could effect it taking gas , but if its really bad i guess it could. Any thoughts? Oh and trying to start it is really hard , it wants to flood out immediately , i had to finally get it started with the fuel valve off and run the bowl empty then use a little manual splash of fuel and turn the fuel valve on while it was running. but like i said if i use a stick or screw driver and raise the slide it takes gas perfect, or if i turn the fuel valve off it seemed to take gas really good.
 

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Discussion Starter #53
Yes - an experienced rider will stab the throttle open for a short distance, but few get out where they can hold it wide open for more than 100 feet
i tried the carb again after doing all of the fuel lines right , with the air box on, with the filter on, today i got it to run about half way. it takes gas some but not really good unless you open the air box and manually raise that slide, although i did try an experiment , i turned the fuel valve from the fuel tank off and it started running correctly until the bowl was completely empty, but it took gas like i imagine it should and pulls pretty decent but not for long until it runs out of gas, I do not think the float level is to high since it does not run out the overflow , i do have the float needle just in there with no keeper spring and did not recieve any parts for the float needle seat repair if there is such a thing. I think im just going to shit can this carb, it probably has a crack somewhere or something corroded to far beyond repair but obviously with the fuel valve on and the pump pumping gas it will overflow the carb on the inside but not enough to run out the overflow , i have the air screw at 2 turns out just like the manual says, and i don't know how much that could effect it taking gas , but if its really bad i guess it could. Any thoughts? Oh and trying to start it is really hard , it wants to flood out immediately , i had to finally get it started with the fuel valve off and run the bowl empty then use a little manual splash of fuel and turn the fuel valve on while it was running. but like i said if i use a stick or screw driver and raise the slide it takes gas perfect, or if i turn the fuel valve off it seemed to take gas really good.
 

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Shit can that carb my way - I will pay the postage and give you $20 to boot.

Sent you a PM
 

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Discussion Starter #55
Shit can that carb my way - I will pay the postage and give you $20 to boot.

Sent you a PM
what would make it act like that? is it the float needle? it doesn't spill over out the overflow but floods the engine apparently, and i have to say i have rebuilt several carbs before and never had problems like this, this is very embarrassing for me. This entire ATV has been frustrating, lol. Who would ever thing an atv that acted like carb problems would have a busted fly wheel and mangled stator and stretched cam chain and out of time ? with a brand new looking cam? then all these repairs get done and it still just wont do right ? By the way i cleaned up all the old stock jets and re installed them and still have the rebuild kits that were jetted wrong . all i used front them are the rubber gaskets at this point.
 

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No - it's not likely the float needle causing the problem and I can't say with any certainty cause I haven't seen it, but I suspect a problem in either the slide diaphragm, the internal vacuum passage to the vacuum chamber or perhaps the jet block (the plastic insert in the carb body held in place with tamper proof torx screws. I collect the things and have a few that are unrepairable, but I usually figure out what it takes to repair one or at least why it can't be repaired
 

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At this point, I gotta pose the possibility of how healthy is this engine? You may be chasing your tail and not even be a carb/fuel delivery problem?

You said someone fucked with it swapping cams and Lord only knows what else?

Is this thing even cam timed correctly? Is the valve lash too tight, too loose? How's the piston & cylinder itself? Have you compression tested it?


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Discussion Starter #58
At this point, I gotta pose the possibility of how healthy is this engine? You may be chasing your tail and not even be a carb/fuel delivery problem?

You said someone fucked with it swapping cams and Lord only knows what else?

Is this thing even cam timed correctly? Is the valve lash too tight, too loose? How's the piston & cylinder itself? Have you compression tested it?


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engine is very healthy, it has great compression, new looking cam, new timing chain, timed right, fresh oil, fresh spark plug, sludge has been cleaned out , like i said it runs really good if i shit off the fuel supply until the bowl runs empty, or if i manually raise the slide with a stick it runs really good, so it isn't the engine , the valves are also adjusted right.
 

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Discussion Starter #59
At this point, I gotta pose the possibility of how healthy is this engine? You may be chasing your tail and not even be a carb/fuel delivery problem?

You said someone fucked with it swapping cams and Lord only knows what else?

Is this thing even cam timed correctly? Is the valve lash too tight, too loose? How's the piston & cylinder itself? Have you compression tested it?


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i bought an ebay carb from maxspeedingrods , i chose them because i bought good parts in the past from them, i know a carb is more sensitive and the way they do things are not exactly right, like they can't have an actual ATV sitting there to test with. But anyway this new carb runs great and has lots of surprising power and pull, but it is opposite the old carb, it has trouble idling and will run like its on the rev limiter and smoke black if i put the lid on the airbox, i also pulled the exhaust clean out plug but have not isolated its effect yet, so now it runs like a scalded dog but has trouble idling, lol. oh and the old carb , i pulled the top off again and the very small thin amount of gasket maker RTV i used caused the diaphragm to remain glued to the top cover , just around the outer thicker o ring type gasket and i turned it upside down and the needle fell inside the slide and diaphragm and spring , so apparently i had not gotten the spring keeper that is supposed to sit on top of the needle and its its keeper on right, otherwise the spring would hold the needle down, for all i know this could be the only thing wrong with the carb at this point but am sick of messing with carbs, never in my life has a carb issue been so annoying and cumbersome, lol. What are your thoughts on this new carb? air screw? i can not get a smooth idle and when i adjust it up to where it does idle it wants to rev to high .
 

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4s carbs are fuel flow screws to fine tune idle-1/4 throttle mix, 2s are air flow screws.

My thoughts are a vacuum leak if it's racing at idle and no real adjusting seems to help. Or the pilot jet in this aftermarket carb is way too lean.

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