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Post by superbrita on Sept 15, 2019 14:05:23 GMT -5
Hello everyone.Today i was cleaning my scooter and i noticed 2 thing that i was not sure what to do about.So the first one is my main jet size.I didnt saw any numbers of its size and i decided to measure it using a wire that fitted perfectly in it.Then i measured the wire and it turned out to be 60.So should i change it?My scooter is 75cc, 19mm Mikuni carb with moded air box and when i put needle washer in its highest position (it alows more fuel) i gain extra power.Will bigger jet size increase my scooter power.I live in the mountains and here atitude varies from 900m to 1200m. And the second thing i noticed is this:  This is where the cold air gets in.If i remove it will i decrease engine temperature and prevent overheating.Or it will get worse.Thanks |
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mattyslimz
Scoot Enthusiast
Posts: 222
Location: Northern Virginia
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Post by mattyslimz on Sept 15, 2019 14:37:14 GMT -5
A 60 main jet sounds tiny. With a big bore and nodded airbox I’d at least be in the mid to upper 80s in size, this of course is all up to your elevation and humidity, but a 60 is pretty small. I have a 95 in my 19mm carb with double layer pod filter and 70 kit. I drilled one big hole (3/8) in my 1e40qmb housing and smaller diameter star pattern holes (5/32) in my Zuma housing. I saw maybe a couple of degrees difference but that could’ve been my head telling me what I wanted to see. The cooling shrouds are designed by the factory after testing which keeps it reliably cool. I think for a big bore kit drilling a couple small holes in that area is beneficial. Also an larger fan that’s from the aftermarket will substantially help drop temps. The one pictured below is an example that I have installed.   |
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Post by superbrita on Sept 15, 2019 14:42:35 GMT -5
Ok i will drill some holes thanks for the tip.
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Post by aeroxbud on Sept 15, 2019 21:23:39 GMT -5
Might be worth getting a jet pack of different size jets to try. If you are running with the standard jet after fitting a big bore kit it will be running lean.
Have you checked the plug colour?
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Post by chehystpewpur on Sept 16, 2019 11:05:47 GMT -5
i wouldnt modify the bracket from my understanding there had been some testing done in the past and it will put you at risk of soft seize. the plate is there to keep air going over the fins instead of cold air hitting one side of the cylinder bore directly and causing it to cool rapidly or faster than the rest of the cylinder bore. with a higher altitude youll need less fuel than a stock scoot but the best thing you can do is send us some pictures of your spark plug color its the only way to determine proper jetting without a wideband 02 kit and thats pricy. drive.google.com/file/d/1C9EwZGG3GqU-u3ClPGhV5NAExsFCgAQ_/view?usp=sharingplug should look similar to this. nice ole doodoo brown color. drive.google.com/file/d/1dT3MeEyxbpwv8B6VupfTdMBZSvXSkvfj/view?usp=sharingor maybe a hair lighter and your squeeze a few more rpms/mph if your not hitting redline already. if you have a tach and stock motor keep it under 10k rpms for best durability. |
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Post by ThaiGyro on Sept 16, 2019 11:51:35 GMT -5
Might be worth getting a jet pack of different size jets to try. If you are running with the standard jet after fitting a big bore kit it will be running lean. Have you checked the plug colour? Bud makes a very good point. You really need to start far beyond a 60. Not even sure if I believe that number. Regardless, you should consider making everything fresh and understood before experimenting and potentially confusing things.
My rule with 2 strokes...any engine really, is to get the ignition perfect first. Proper charging output, (@4500+ rpm) New plug, proper gap set, no plug wire leaks. You need this to be OEM spec. (An ignition with no rev limiter is better) You need consistent spark.
Then clean your exhaust port and pipe...no goo inside. Then go carb playing. Anything different will have you chasing Casper the no-so-friendly-Ghost.
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