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Post by jerseyboy on Jan 31, 2015 9:36:13 GMT -5
....You may be able to draw more fuel through the same size jet if you have more vacuum,,just like more pressure behind a garden hose causes it to squirt farther with the same size nozzle. Very interesting thread bro...will be fun to follow.. Larger carbs on the same size intake port will create a smaller less powerful vacuum, I'm pretty sure we had a thread about that recently. It's the same amount of air being pulled by the engine, so a lager orifice results in a smaller vacuum effect. Looking forward to hearing about your results, I love being proven wrong when real world experiments work out, forces me to learn something!  Well it aint gonna happen anytime soon jerry,,its -20 out here with wind...it will be zero monday and tues with no wind...my furnace is groaning. |
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Post by JoeyBee on Jan 31, 2015 10:11:19 GMT -5
I wish there was a way to measure the volume of fuel and air being sucked into the chamber to see if there is any change at certain rpms even if it is minimal. That was my thoughts also. What kind of methodology could be used to ensure accurate testing between a large and standard size carburetor? |
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Post by dmartin95 on Feb 2, 2015 1:17:47 GMT -5
I wish there was a way to measure the volume of fuel and air being sucked into the chamber to see if there is any change at certain rpms even if it is minimal. That was my thoughts also. What kind of methodology could be used to ensure accurate testing between a large and standard size carburetor?O2 sensor, fuel flow meter, vacuum gauge etc etc..... I would first start with a stock GY6 150cc and get some readings for a baseline. Then start testing different stuff.... |
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Post by geh3333 on Feb 3, 2015 3:07:09 GMT -5
That was my thoughts also. What kind of methodology could be used to ensure accurate testing between a large and standard size carburetor?O2 sensor, fuel flow meter, vacuum gauge etc etc..... I would first start with a stock GY6 150cc and get some readings for a baseline. Then start testing different stuff.... That may get some answers , but I'm not sure if we would be able to tell the volume of fuel and air entering the chamber on each rotation . or would you just take the amount of fuel flow and divide that by the rpm rotation ? Let's say u run the engine at 5000 rpms for I min. So we would take fuel flow ÷ 5000 ? Then we try 6000 rpms but we would have to calculate when to stop the engine so that it only rotates 5000 times . this would show us if we are pulling in more fuel as the engine works harder . we would also have to test the same for the air flow . I guess if the volume of fuel rises and the o2 sensor stays the same we would know the volume of air also has increased. |
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Post by rcq92130 on Feb 3, 2015 3:25:47 GMT -5
Those are very interesting things to know, but i think the issue is simpler than that. Unless the small 24mm carb fully satisfies the max. desires of a GY6 engine (and we KNOW that is not the case, since a larger carb. gives more power), then the issue isn't what the engine desires but how to best set up the larger carb.
The O2 sensor is perfect for this. With that either the smaller carb OR the larger carb can be set up to optimally burn the air & fuel. So, with that the optimum jet can be found - both at idle and then under load. And since these carbs are so much simpler than an injection system, all there IS to properly tune is to find the correct jet size.
Then it's easy. Run a 24mm carb, optimally jetted, and note performance. Then run a larger carb, also optimally jetted, and note performance. Unless you and I have been mistaken, we will see better performance with the larger carb and we will have our answer.
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Post by jerseyboy on Feb 3, 2015 8:58:43 GMT -5
More than likely the larger carb will perform better as long as the motor can take the larger air/fuel mixture and burn it efficiently there is no question.
Maybe we should try turbo charging a GY6 one day,,that will force air/fuel into the intake,,if it shows improvement with turbo then it certainly will with a bigger carb as long as its jetted accordingly.
Wonder if youtube has a turbo GY6 video?
Ive seen Briggs turbo motors and was not impressed.
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Post by rcq92130 on Feb 3, 2015 11:02:52 GMT -5
Someone had a GY6 turbo'ed for race purposes using a "small engine turbo. Results, as i recall, were not stellar (to my surprise) ..... or I would have already tried it on my scoot.
The EFI kits are expensive, though they seem to help quite a bit.
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Post by geh3333 on Feb 5, 2015 20:36:29 GMT -5
Those are very interesting things to know, but i think the issue is simpler than that. Unless the small 24mm carb fully satisfies the max. desires of a GY6 engine (and we KNOW that is not the case, since a larger carb. gives more power), then the issue isn't what the engine desires but how to best set up the larger carb. The O2 sensor is perfect for this. With that either the smaller carb OR the larger carb can be set up to optimally burn the air & fuel. So, with that the optimum jet can be found - both at idle and then under load. And since these carbs are so much simpler than an injection system, all there IS to properly tune is to find the correct jet size. Then it's easy. Run a 24mm carb, optimally jetted, and note performance. Then run a larger carb, also optimally jetted, and note performance. Unless you and I have been mistaken, we will see better performance with the larger carb and we will have our answer. Yes ! This was done earlier this summer by a member here and he noticed a major performance increase . he stated that his scoot felt 30% stronger with the bigger carb. Now whether it was actually 30% stronger or not , it was obviously a very noticeable increase by using the bigger carb. |
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Post by JoeyBee on Feb 5, 2015 21:04:54 GMT -5
Those are very interesting things to know, but i think the issue is simpler than that. Unless the small 24mm carb fully satisfies the max. desires of a GY6 engine (and we KNOW that is not the case, since a larger carb. gives more power), then the issue isn't what the engine desires but how to best set up the larger carb. The O2 sensor is perfect for this. With that either the smaller carb OR the larger carb can be set up to optimally burn the air & fuel. So, with that the optimum jet can be found - both at idle and then under load. And since these carbs are so much simpler than an injection system, all there IS to properly tune is to find the correct jet size. Then it's easy. Run a 24mm carb, optimally jetted, and note performance. Then run a larger carb, also optimally jetted, and note performance. Unless you and I have been mistaken, we will see better performance with the larger carb and we will have our answer. Yes ! This was done earlier this summer by a member here and he noticed a major performance increase . he stated that his scoot felt 30% stronger with the bigger carb. Now whether it was actually 30% stronger or not , it was obviously a very noticeable increase by using the bigger carb. The other member perceived it to be noticeable, but did they provide actual statistics? I'll try to find the thread tonight while I'm sitting around at work. |
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Post by rcq92130 on Feb 5, 2015 21:18:33 GMT -5
Those are very interesting things to know, but i think the issue is simpler than that. Unless the small 24mm carb fully satisfies the max. desires of a GY6 engine (and we KNOW that is not the case, since a larger carb. gives more power), then the issue isn't what the engine desires but how to best set up the larger carb. The O2 sensor is perfect for this. With that either the smaller carb OR the larger carb can be set up to optimally burn the air & fuel. So, with that the optimum jet can be found - both at idle and then under load. And since these carbs are so much simpler than an injection system, all there IS to properly tune is to find the correct jet size. Then it's easy. Run a 24mm carb, optimally jetted, and note performance. Then run a larger carb, also optimally jetted, and note performance. Unless you and I have been mistaken, we will see better performance with the larger carb and we will have our answer. Yes ! This was done earlier this summer by a member here and he noticed a major performance increase . he stated that his scoot felt 30% stronger with the bigger carb. Now whether it was actually 30% stronger or not , it was obviously a very noticeable increase by using the bigger carb. I'm sorry, but we have been told we are mistaken about this. Q.E.D., I guess. |
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Post by geh3333 on Feb 5, 2015 21:54:18 GMT -5
The member was having problems with a certain member because he wanted to use a bigger carb. So he and I kept in touch through messages . I'll send u the message to anyone who wants the proof.
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Post by geh3333 on Feb 5, 2015 22:58:54 GMT -5
The member was having problems with a certain member because he wanted to use a bigger carb. So he and I kept in touch through messages . I'll send u the message to anyone who wants the proof. Here is the message I posted it to the wrong thread Here is the message sent by the member. He had a cheap 30mm carb and could not get it to work properly . he sent it to a shop where they were also having problems. They could not get it to work correctly even with a 115 and smaller main jet. He has the gy6 200 from scrappy which is a 61mm bbk setup . even the shop didn't know why the 30mm would not work , so he decided to go with a mikuni 28mm racing carb . here is his message. well its done and i have it back. so he ended up putting on a mikuni racing carb. part #001-023, description w28-418. box says "not legal for use in california." so in short its a 28mm carb, and the scooter hawls . i hit 70 on the freeway today, and it may have a little more in it. maybe 72-73. and the acceleration is nice. I would say overall its 30% stronger. they tuned it on a dyno, so it should be dialed in just right. when light permits ill take a pic and send it. thank you again for all your help. if you want the old carb illl send it to you for free. maybe you can figure out what was going wrong with it. you can have all the jets too, since mikuni jets dont size the same as ours. for example, the jet that they ended up using is a 170, which is there biggest, and they still had to drill it out another.070" any way im happy i did it, but now i wont be selling this scooter. |
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Post by geh3333 on Feb 5, 2015 23:00:17 GMT -5
The member was having problems with a certain member because he wanted to use a bigger carb. So he and I kept in touch through messages . I'll send u the message to anyone who wants the proof. Here is the message I posted it to the wrong thread Here is the message sent by the member. He had a cheap 30mm carb and could not get it to work properly . he sent it to a shop where they were also having problems. They could not get it to work correctly even with a 115 and smaller main jet. He has the gy6 200 from scrappy which is a 61mm bbk setup . even the shop didn't know why the 30mm would not work , so he decided to go with a mikuni 28mm racing carb . here is his message. well its done and i have it back. so he ended up putting on a mikuni racing carb. part #001-023, description w28-418. box says "not legal for use in california." so in short its a 28mm carb, and the scooter hawls . i hit 70 on the freeway today, and it may have a little more in it. maybe 72-73. and the acceleration is nice. I would say overall its 30% stronger. they tuned it on a dyno, so it should be dialed in just right. when light permits ill take a pic and send it. thank you again for all your help. if you want the old carb illl send it to you for free. maybe you can figure out what was going wrong with it. you can have all the jets too, since mikuni jets dont size the same as ours. for example, the jet that they ended up using is a 170, which is there biggest, and they still had to drill it out another.070" any way im happy i did it, but now i wont be selling this scooter. He used a 170 main which is equivalent to a 145 khein main jet. Which is the proof that these engine can take more then what was thought. |
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Post by dmartin95 on Feb 5, 2015 23:29:44 GMT -5
Do you have a set of micro drill bits? I had the same problem with an unstamped main jet from a carburetor from Scrappy Dogs. Using those I was able to determine the jet was probably a 100. Hey, that's a great idea! I do have a micro drill bit set. Nice to know for the future! BTW, The seller got back in touch with me and told me it was a 100 #128 main jet. Does anyone know off the top of their heads what size is the stock jets for a PD24J? |
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Post by JerryScript on Feb 6, 2015 9:28:45 GMT -5
30 didn't work, 28 did, bigger is not always better. Have we finally cleared that up? |
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