groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 18, 2019 19:50:48 GMT -5
I am at a loss, any advice would be great.
I have a wolf rx50 scooter that i converted to a 47mm big bore kit. It is a 73.4cc i think? Anyway here is my problem i followed the advice of a youtuber to put a 150cc carb on a BBK, his ran just fine. So I experamented with different jets and the close i got to was a size 100 main jet, i adjusted the needle to where the carb would still sputter but not as much. So several people told me on this fourm that i should return to my stock carb because the 150cc carb delivered too much fuel.
I feally like the sound the engine makes with the stackable air filter, i plan on putting the stock carb back in the bike with the free flow air filter, my question is since I have a free flowing muffler and a free flowing air filter, should I keep upsizing jets or should i just return to the stock airbox.
Would upjetting the stock carb with the free flow filter make any difference then when i upjetted the stock carb with the stock airbox on?
Thank you for your advice,
Alex
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Post by chehystpewpur on Sept 18, 2019 23:01:02 GMT -5
what does your plug look like? you made no reference to what sound you feally like? also from my time with the 4t bikes the bbk's just cause problems and there is a good chance your scoot has lost compression or is losing compression. stick your finger in the hole for the plug when you pull it out to check it spin your motor over by hand with the fan or the variator whichever is easier to get to for you. make a good seal with your finger so it wont leak. does it suck pretty hard. and does it try to push your finger out of the hole on the compression stroke? on a healthy motor with 90 psi of compression or more it will be pretty uncomfortable on suction and youll have to jam your finger in there on the compression stroke. if you stop before the valves open and close so its stuck on suction at its strongest and if you stop on compression at its highest does it lose force sitting there for a sec or 2? if it does you have something leaking. ive had my finger in enough holes to know what feels good and bad but if you cant tell borrow a compression tester from a local parts store and get a real number. 90-125 is pretty good. 125 is pretty uncomfortable for most people. feels like its gonna suck your fingertip clean off. 150-175 could leave some bruising if you dont have hands that are pretty tough and calloused. dont confuse the piston displacing air that feels like compression but is not. never spin a motor with your finger in the hole over with a starter if its over 10:1 rated or higher unless you know what your doing its happens so fast you could end up up with an interesting ER story depending on how you spin it lol. by hand if it gets uncomfortable you can stop or go back some and keep a finger. my current motor claims 14:1 and lets just say i dont like it but i do it often to chek for problems and also its a guilty pleasure i guess.
a motor cannot process fuel without compression bare minimum for most motors is 8:1 to run. fact and fact. yes some 2 strokes run on less around 6.5:1 if i remember right but those dont have valves and are different they will use volume vs pressure and use that air and fuel twice. so it still processes it but in a different way and combustion happens in the cylinder and exhaust unlike your motor.
if your motor is sputtering its not processing fuel either too much fuel or not enough compression. does the problem get worse the hotter it gets or does it get better with heat? if you havent changed your intake manifold to go with your free flowing exhaust there is a good chance air speed is very fast. over carbing an engine is very common for people in the big and small engine world and a small engine is going to show signs much faster. as there is no cylinder balance to pick up the slack or push the fuel somewhere else. if the carb is too big and air speed is fast its going to pull way more fuel into the motor than it needs and act the same as a motor that cant process the fuel due to low compression. stock intake for your bike is for the air volume and flow of 50cc therefore making your carb act like a 150cc engine is at stupid high rpms and give stupid high amounts of fuel but not flowing any more real air volume and over fueling like crazy.
for example my 2t i have right now is a 70cc kit but turns around 50% more rpms than your motor can 12k rpms yours is happy around 8-9k if your lucky but some spin higher. 2 strokes have 2 times as many combustion cycles as 4 strokes and im barely past a 100 main jet im back to a 105 right now but need to upjet after changing something in my intake platform. and i have a higher flow intake mainfold. if all things were equal that would be like a 200 main jet on your bike and yeah try breathing underwater your cylinder would be drowning just like if compression was super low for your bike. not saying this is fact because very motor and bike are diff butttt....
all that being said i think stock jet is around 68-75 stock for the 50cc 4 strokes i think with bbk id assume around 90ish would be closer to right. first things first look at your plug make sure its not wet after running it down the road. post some pictures and ill see if i can help you solve this the best i can. in the end all motors want the same thing proper air to fuel ratio around 13.7-14.7 to 1 pounds of air to pounds of fuel. and without pics of your plug i cant tell you for sure. with compression ratio and plug color/wetness we can get farther. i know im needy and long winded but there is no simple answer. it could even be as simple as a weak plug or coil but with some help on your end ill do my best or another member will chime in and give you what you need if they see what "sparks" the thought.
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Post by benhonda on Sept 18, 2019 23:30:54 GMT -5
i had a 50cc bike with free flow filter and high flow muffler, it needed a 110 main jet in the stock carb to run. It's amazing how restrictive the stock airbox is on these small engines. The larger 150cc carb may be allowing more air, not more fuel since the throat size is larger. If you put back on the stock carb, start with a 105-110 main jet and see what that gets you.
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groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 19, 2019 12:15:19 GMT -5
what does your plug look like? you made no reference to what sound you feally like? also from my time with the 4t bikes the bbk's just cause problems and there is a good chance your scoot has lost compression or is losing compression. stick your finger in the hole for the plug when you pull it out to check it spin your motor over by hand with the fan or the variator whichever is easier to get to for you. make a good seal with your finger so it wont leak. does it suck pretty hard. and does it try to push your finger out of the hole on the compression stroke? on a healthy motor with 90 psi of compression or more it will be pretty uncomfortable on suction and youll have to jam your finger in there on the compression stroke. if you stop before the valves open and close so its stuck on suction at its strongest and if you stop on compression at its highest does it lose force sitting there for a sec or 2? if it does you have something leaking. ive had my finger in enough holes to know what feels good and bad but if you cant tell borrow a compression tester from a local parts store and get a real number. 90-125 is pretty good. 125 is pretty uncomfortable for most people. feels like its gonna suck your fingertip clean off. 150-175 could leave some bruising if you dont have hands that are pretty tough and calloused. dont confuse the piston displacing air that feels like compression but is not. never spin a motor with your finger in the hole over with a starter if its over 10:1 rated or higher unless you know what your doing its happens so fast you could end up up with an interesting ER story depending on how you spin it lol. by hand if it gets uncomfortable you can stop or go back some and keep a finger. my current motor claims 14:1 and lets just say i dont like it but i do it often to chek for problems and also its a guilty pleasure i guess. a motor cannot process fuel without compression bare minimum for most motors is 8:1 to run. fact and fact. yes some 2 strokes run on less around 6.5:1 if i remember right but those dont have valves and are different they will use volume vs pressure and use that air and fuel twice. so it still processes it but in a different way and combustion happens in the cylinder and exhaust unlike your motor. if your motor is sputtering its not processing fuel either too much fuel or not enough compression. does the problem get worse the hotter it gets or does it get better with heat? if you havent changed your intake manifold to go with your free flowing exhaust there is a good chance air speed is very fast. over carbing an engine is very common for people in the big and small engine world and a small engine is going to show signs much faster. as there is no cylinder balance to pick up the slack or push the fuel somewhere else. if the carb is too big and air speed is fast its going to pull way more fuel into the motor than it needs and act the same as a motor that cant process the fuel due to low compression. stock intake for your bike is for the air volume and flow of 50cc therefore making your carb act like a 150cc engine is at stupid high rpms and give stupid high amounts of fuel but not flowing any more real air volume and over fueling like crazy. for example my 2t i have right now is a 70cc kit but turns around 50% more rpms than your motor can 12k rpms yours is happy around 8-9k if your lucky but some spin higher. 2 strokes have 2 times as many combustion cycles as 4 strokes and im barely past a 100 main jet im back to a 105 right now but need to upjet after changing something in my intake platform. and i have a higher flow intake mainfold. if all things were equal that would be like a 200 main jet on your bike and yeah try breathing underwater your cylinder would be drowning just like if compression was super low for your bike. not saying this is fact because very motor and bike are diff butttt.... all that being said i think stock jet is around 68-75 stock for the 50cc 4 strokes i think with bbk id assume around 90ish would be closer to right. first things first look at your plug make sure its not wet after running it down the road. post some pictures and ill see if i can help you solve this the best i can. in the end all motors want the same thing proper air to fuel ratio around 13.7-14.7 to 1 pounds of air to pounds of fuel. and without pics of your plug i cant tell you for sure. with compression ratio and plug color/wetness we can get farther. i know im needy and long winded but there is no simple answer. it could even be as simple as a weak plug or coil but with some help on your end ill do my best or another member will chime in and give you what you need if they see what "sparks" the thought. Thanks for the assistance, I'll give you a video sound clip and a pic of the plug tonight
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groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 19, 2019 12:32:57 GMT -5
i had a 50cc bike with free flow filter and high flow muffler, it needed a 110 main jet in the stock carb to run. It's amazing how restrictive the stock airbox is on these small engines. The larger 150cc carb may be allowing more air, not more fuel since the throat size is larger. If you put back on the stock carb, start with a 105-110 main jet and see what that gets you. With my stock gy6 49cc scooter the maximum jet size I could upgrade it to is a 98. Other bigger 100 size jets require a bigger carb, how can I get a 100 jet in a 49cc stock carb?
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Post by chehystpewpur on Sept 19, 2019 16:58:54 GMT -5
i will be awaiting pics of plug as that is the most important thing to me. its like doing an xray or camera to peer inside the body to see whats going on. the video clip will help too as i will be able to hear whats going on.
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groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 19, 2019 18:21:44 GMT -5
i will be awaiting pics of plug as that is the most important thing to me. its like doing an xray or camera to peer inside the body to see whats going on. the video clip will help too as i will be able to hear whats going on. Ok I have posted two video clips of my scooter and spark plug pictures
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groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 19, 2019 18:28:28 GMT -5
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Post by benhonda on Sept 19, 2019 19:33:15 GMT -5
i had a 50cc bike with free flow filter and high flow muffler, it needed a 110 main jet in the stock carb to run. It's amazing how restrictive the stock airbox is on these small engines. The larger 150cc carb may be allowing more air, not more fuel since the throat size is larger. If you put back on the stock carb, start with a 105-110 main jet and see what that gets you. With my stock gy6 49cc scooter the maximum jet size I could upgrade it to is a 98. Other bigger 100 size jets require a bigger carb, how can I get a 100 jet in a 49cc stock carb? My bad, it must have been a 105 main jet I was using, as that is the largest m4 50cc jet I could find online. Ebay has jet kits for 50cc 139qmb carbs that go up to 105. Larger than that, and you would have to go with a 150cc carb, which would be a whole different tuning setup as the carb would allow more air as well. If you had the stock carb with a 100 jet running close but still sputtering, then maybe a 105 jet will solve it.
A quick test I've done to see if my bike was running lean...tape over part of the air intake. If she runs better by limiting the air...then the carb is not providing enough fuel. If she runs worse with tape over part of the air intake (try covering 1/3, and 1/2 and 3/4) then the carb is providing too much fuel.
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Post by chehystpewpur on Sept 20, 2019 2:20:13 GMT -5
ok i watched videos but cant view the images. if i click on them it just takes me to the main page for the image hosting site. postimages.org/thats all she wrote. i hear a pretty loud rattling noise in both videos and im wondering did you adjust valves when you installed the bbk? if valves are out of adjustment no amount of fuel can make it run right. even on fuel injected cars improper valve lash will cause overheating and can cause tapping sounds like that rattle and weird running conditions/reduced power. the sputtering though does sound somewhat like its running out of fuel like when boosted cars are bouncing off the rev limiter. is your fuel system working as it should? and is fuel line staying full of fuel? or atleast a good supply to the motor? my scoots fuel line has never stayed full but always has fuel in the line for a few inches before the carb if there isnt fuel in the line before the carb your fuel petcock may be bad or possibly the vacuum line may have a pinhole or crack in it and isnt supplying enough vacuum to let your float bowl for the carb keep enough fuel in it. also do you know if your carbs float height is set properly or close enough to keep from emptying the bowl on wide open throttle? how old is your fuel filter? the 4t bikes dont go through filters as fast as 2t bikes do but it still happens. also the fuel tanks have a pre filter screen that can plug up as well and cause it to run out of fuel and make your life miserable trying to find an issue.
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groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 20, 2019 12:35:15 GMT -5
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groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 20, 2019 12:37:40 GMT -5
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groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 20, 2019 12:39:10 GMT -5
ok i watched videos but cant view the images. if i click on them it just takes me to the main page for the image hosting site. postimages.org/thats all she wrote. i hear a pretty loud rattling noise in both videos and im wondering did you adjust valves when you installed the bbk? if valves are out of adjustment no amount of fuel can make it run right. even on fuel injected cars improper valve lash will cause overheating and can cause tapping sounds like that rattle and weird running conditions/reduced power. the sputtering though does sound somewhat like its running out of fuel like when boosted cars are bouncing off the rev limiter. is your fuel system working as it should? and is fuel line staying full of fuel? or atleast a good supply to the motor? my scoots fuel line has never stayed full but always has fuel in the line for a few inches before the carb if there isnt fuel in the line before the carb your fuel petcock may be bad or possibly the vacuum line may have a pinhole or crack in it and isnt supplying enough vacuum to let your float bowl for the carb keep enough fuel in it. also do you know if your carbs float height is set properly or close enough to keep from emptying the bowl on wide open throttle? how old is your fuel filter? the 4t bikes dont go through filters as fast as 2t bikes do but it still happens. also the futanks have a pre filter screen that can plug up as well and cause it to run out of fuel and make your life miserable trying to find an issue. Here's another link for an image of the plug postimg.cc/PNLxxNcR
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Post by chehystpewpur on Sept 20, 2019 13:10:43 GMT -5
i can atleast view the image but its still tiny. did you upload a thumbnail of a photo by any chance? they are usually much smaller than the actual picture is. or possibly that site resized the image? i see alot of resizing options for the upload image thing and the avatar and thumbnail setting looks to be about the size the image came out to. i tried to download the image so i could atleast zoom in but it says its 113x150 pixels. my pictures are 4128x3096 pixels for example. im not trying to be rude or anything just trying to view so i can help you. if you resized to upload the image to the forum page dont. just go full size and drop the link on the page nobody will mind that way and its easier on the forum servers and easier on our eyes. drive.google.com/drive/folders/1J92O1CIkcq6zmQ7Nvp1FU9N6HSQKMHJ6?usp=sharingthats what it looks like on my end and i use a very large monitor so it makes it harder to see as the picture is about the size of my thumb on screen drive.google.com/file/d/1F8RyNHEtMEnHvUICJQKOniNfs2Uacokp/view?usp=sharingi use google drive as its free and doesnt do anything weird to images i upload so they come out good like that. it makes it easier on the rest of us.
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groundloosers
Scoot Member
Learn from your mistakes, live life and have fun.
Posts: 59
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Post by groundloosers on Sept 20, 2019 16:22:52 GMT -5
i can atleast view the image but its still tiny. did you upload a thumbnail of a photo by any chance? they are usuallcc y much smaller than the actual picture is. or possibly that site resized the image? i see alot of resizing options for the upload image thing and the avatar and thumbnail setting looks to be about the size the image came out to. i tried to download the image so i could atleast zoom in but it says its 113x150 pixels. my pictures are 4128x3096 pixels for example. im not trying to be rude or anything just trying to view so i can help you. if you resized to upload the image to the forum page dont. just go full size and drop the link on the page nobody will mind that way and its easier on the forum servers and easier on our eyes. drive.google.com/drive/folders/1J92O1CIkcq6zmQ7Nvp1FU9N6HSQKMHJ6?usp=sharingthats what it looks like on my end and i use a very large monitor so it makes it harder to see as the picture is about the size of my thumb on screen drive.google.com/file/d/1F8RyNHEtMEnHvUICJQKOniNfs2Uacokp/view?usp=sharingi use google drive as its free and doesnt do anything weird to images i upload so they come out good like that. it makes it easier on the rest of us. I sent you the images of my sparkplug, judging by the color it looks like it is running rich with the 150cc carb .I am ow back to my stock 49cc carb with the open stack filter.When I took the restrictive airbox out I noticed that the plug center electrode was completly white, My question is should I return the 150cc carb and continue to upjet the 49cc stock carb with the high flow air filter? or should I just go back to the restrictive airbox with the stock 72 main jet? plug was also dry when i pulled it.
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