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Post by aeroxbud on Oct 16, 2017 7:56:19 GMT -5
I am going to change my carb from the standard 12mm carb to a 17.5mm PHBN Motoforce. Standard 50cc, with the airbox, with a sports pipe. I was thinking about starting around a main jet size 75 or 76. Will this be a good starting point? Going to order a few sizes anyway.
Can I just run the standard oil pump without a problem? As this is a daily ride, I would like to keep the auto lube if possible.
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Post by tsimi on Oct 16, 2017 16:54:09 GMT -5
Not sure about the jetting but you know what they say better start rich and work your way down. 75-76 sounds not bad.
With a Dello 17.5mm you can use the stock oil pump system. Just make sure you have some spare tubing around just in case the stock length is too short and not worn down.
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Post by aeroxbud on Oct 17, 2017 4:54:00 GMT -5
Not sure about the jetting but you know what they say better start rich and work your way down. 75-76 sounds not bad. With a Dello 17.5mm you can use the stock oil pump system. Just make sure you have some spare tubing around just in case the stock length is too short and not worn down. Thanks, I was going to order a few jets and work my way down. Just nice to have a second opinion. I have always just junked the pump before and run premix. As this is my work ride it would be good to keep the pump though. |
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Post by aeroxbud on Oct 29, 2017 14:56:12 GMT -5
Seems I was way out with the jetting. It would only run with a 78 jet with the choke on. Once off it just ticks over, but any throttle it dies.
Put a 90 in and it runs now, but still will only pull away properly with choke. Just seems strange that it needs a jet this big. Oh well will have to order some more jets.
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Post by tsimi on Oct 29, 2017 17:19:31 GMT -5
What about the pilot jet? What size is that?
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Post by ThaiGyro on Oct 30, 2017 5:35:05 GMT -5
Two strokes are as everyone says...individual. I run 19mm carbs on 49cc tuned engines way more than 17.5's. That said, a near stock engine that can breathe properly will require more mid range fuel. I started my last adventure with a 92 and ended with an 88, I think. We are unusually humid this year, so who knows?...Winter starting. Temps down to high 70's...brrrr!
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Post by aeroxbud on Oct 30, 2017 9:21:17 GMT -5
What about the pilot jet? What size is that? Looks like a #94 |
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Post by tsimi on Oct 30, 2017 9:33:34 GMT -5
A #94 pilot jet? You mean a #94 main jet right?
Or are you saying you are running a 94/90 jetting?
The pilot jet or sometimes also called idle jet is the jet that handles the low end speed or/and idle.
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Post by aeroxbud on Oct 30, 2017 11:17:12 GMT -5
A #94 pilot jet? You mean a #94 main jet right? Or are you saying you are running a 94/90 jetting? The pilot jet or sometimes also called idle jet is the jet that handles the low end speed or/and idle. It says 94 on it got my daughter to check it too. Perhaps it's a 3, but sure looks like a 9. Did think This is crazy big. This jet www.49ccscoot.com/faq/pics/Dellorto_Pilot.jpg |
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Post by tsimi on Oct 30, 2017 17:16:31 GMT -5
I don't think that's a 94, 34 maybe?
As far I know the largest pilot jet is around 60. A pilot jet should be around 32-40 somewhere in that range.
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buzzscoot
Scoot Member
Posts: 52 
Location: Georgia
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Post by buzzscoot on Oct 30, 2017 19:35:13 GMT -5
For what it is worth I have rebuilt two 2t 50cc Scarabeos (Minarelli motor) and swapped out the 12mm carb (70 main) with the Dellorto 17.5 PHBN. Both were sourced from different suppliers, and both Dellorto's came with 90 main and 34 pilot. This carb is an exact " plug and play" for the 12mm carb- hoses ,cables, and cable tops/screws need no alteration. I did have to change out the 90 main with a 78. I needed no change in the pilot jet. Both screws are set 1 1/2 turns out.
I assume your bike is an Aerox with a Minarelli?, so the Motoforce PHBN carb (really a dellorto??) should be the same swap.
Because Aerox is liquid cooled as opposed to my air cooled you may need a slightly leaner mix and lower jet. I have a very mild pipes though, a LV SP3 and a Technigas Silent Pro, so if you have a more aggressive pipe that might raise the jet. So I would guess that with a very mild pipe , you will need a little lower main jet than mine, maybe a 70-75???
All this assumes that your keeping the stock airbox setup.
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Post by aeroxbud on Oct 31, 2017 9:56:16 GMT -5
Thanks buzzscoot it's a Yamaha slider. The air cooled vertical engine. The exhaust is a Technigas next R, so nothing special. The standard throttle cable would not fit. Even with all the adjustment as loose as it would go, the slide was nearly all the way open. I would be inclined to agree with you about the jetting, but it would not even run with a 75 jet. It is very strange. So much for what should be an easy bolt in job. 😆 I appreciate your suggestions, as I was thinking along the same lines, before I came to fit it. |
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buzzscoot
Scoot Member
Posts: 52
Location: Georgia
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Post by buzzscoot on Oct 31, 2017 20:18:25 GMT -5
Sorry, from your user name I assumed it was the Aerox. I don't know anything about the Slider or its vertical engine so my info is probably not applicable nor can I help you. One thing to keep in mind though , is if the jetting seems likes its getting much too big (especially when using a stock airbox), it is wise to check for air leaks. I know this from experience and you can chase your tail with trying jets and CVT changes when all you have is a air leak. I first make sure the leak is not between the airbox and the carb where the plastic can sometimes split, and then if there is no leak there, I perform a leakdown test (described in the Tech Library). Actually, I always perform a leakdown test when I do any significant scooter work.
The performance suffers because of these air leaks and can cause jet sizes to appear to increase significantly and not really fix the performance issue.
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Post by aeroxbud on Nov 1, 2017 5:28:42 GMT -5
Sorry, from your user name I assumed it was the Aerox. I don't know anything about the Slider or its vertical engine so my info is probably not applicable nor can I help you. One thing to keep in mind though , is if the jetting seems likes its getting much too big (especially when using a stock airbox), it is wise to check for air leaks. I know this from experience and you can chase your tail with trying jets and CVT changes when all you have is a air leak. I first make sure the leak is not between the airbox and the carb where the plastic can sometimes split, and then if there is no leak there, I perform a leakdown test (described in the Tech Library). Actually, I always perform a leakdown test when I do any significant scooter work. The performance suffers because of these air leaks and can cause jet sizes to appear to increase significantly and not really fix the performance issue. There was not any splits in the box of intake. But where the snorkel goes through is not a really tight fit. I have cleaned it up and covered the joint in sealer. Has to be worth a shot. Thanks |
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Post by bendover on Nov 15, 2017 15:51:52 GMT -5
Just dumping this here might help: I had aerox, 70cc and 17.5mm with 86 main jet being perfect on stock exhaust and stock air box.
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