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Post by scooterted on Oct 15, 2019 8:10:39 GMT -5
Really though. Gas mileage is really relative. For example, is it a stock 49cc 4t? Or a hyper race 100+cc 2t?
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Post by scooterted on Oct 15, 2019 8:07:28 GMT -5
I wonder that myself. I remember seeing people say theyll get 100+ mpg, but that could just be hyperbole.
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Post by scooterted on Oct 15, 2019 8:02:57 GMT -5
I tried to calculate one time, I got 80 something MPG with a 49cc. A/F ratio was hella rich though, and im a big guy.
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Post by scooterted on Oct 14, 2019 8:14:32 GMT -5
Definitely a better way to measure carbs. Doesnt change the fact that the naming conventon of using the tb diameter to identify these carbs is already established though.
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Post by scooterted on Oct 14, 2019 8:08:59 GMT -5
Super cool jar. I cant tell, is it vented anywhere? Or just to the crankcase?
You're smoking problem might be leaky valve stem seals.
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Post by scooterted on Oct 13, 2019 15:46:32 GMT -5
People do it. Ive been wondering just how much it raises compression myself.
Im about to do it with the airsal set that has a DOMED piston. I expect it to work, but im unsure what my compression ratio will be and am concerened about detonation.
Ive run a compression check on my engine every change i made, from stock to 72cc. I intend to do it when i get the rings broken in with this upgrade. So ill at least have *something* to compare. Ill have my first word in a week or two.
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Post by scooterted on Oct 12, 2019 17:54:41 GMT -5
To those who have deleted their stock airbox, what have you done with youre crankcase vent tube?
Im guessing ill just ziptie it to the frame up top.
Just wondering if others had a better solution.
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Post by scooterted on Oct 11, 2019 11:37:08 GMT -5
Does it stumble?
If you havent yet, I would unseal the carb so i could fully tune it.
To me it sounds like the accelerator pump. You might be able to tweak the lever that moves the pump to either increase or decrease how much fuel gets pumped while you open the throttle.
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Post by scooterted on Oct 10, 2019 18:22:09 GMT -5
That seems like a slow idle to me. Usally around 1700rpm or so.
The enricher probably will heat up. It gets 12v while the engine is running. The 12v slowly warms it up inside and it turn slowly pushes a plunger to close off a port in the carb that lets extra fuel inside.
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Post by scooterted on Oct 10, 2019 15:40:20 GMT -5
I did know that its suitable with the stock head. But a 50mm piston with the stock combustion chamber, AND the extra domed area on the airsal piston should increase compression substantially, and id really like to stick with the ethanol free 90 octane fuel i have access to. Also, the head i bought is supposed to have oversized valves (which i will measure to be sure). I figured the extra valve size might be better than the extra compression. But im open to discussion. Thanks for the jet advice. With the 47mm and stock head and airbox im right on with a 92 jet. I figured i would start with a 98 and see where i end up. Edit: In fact i was hoping that the airsal piston would partially negate any lost compression from the bigger head. Plus its light af for a 50mm piston. Well, if you look at the design of the crown, the piston is slightly taller, by I think .5mm, but then it cuts down in to a channel all the way around. Almost like a full-circle valve relief. The center is then raised again, but all this adds up to a safe compression value. When I purchased it I thought I was getting some crazy domed, super high compression piston but that isn't the case. As far as the head, I played around with the "SMM Big Valve head" with 23/21mm valves. The ports were smaller than the valves! This isn't good, having the port taper bigger towards the valve will actually slow down the air flow speed. I did end up cracking that head, believe it or not, right between the valves and up to the little chamber where the spark plug sits. Best head on the market, the SSP-G 50mm head has 125cc port sizes (23mm intake tapers to 21.5mm valve) and the exhaust is the same way just slightly smaller. This is the head I know run. Allows the use of a 24mm carb and intake, keeping the entire intake system very close to port matched. Thanks. Something to chew on for sure. I hadnt considered port size. I might go with the stock head. So do you have any idea what kind of compression one would have with the airsal and stock head? Or any ancedotal evidence of necessary octane?
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Post by scooterted on Oct 10, 2019 14:11:15 GMT -5
I had a 47mm bbk with a9 cam on my 139qmb, i was always dissapointed with my top speed of 39mph (im a big dude). So today I bought a 50mm airsal, big valve head and a uni filter. Im actually not sure if ill have time to install and tune it. Ill have it for later at least. You know the Airsal 50mm kit was developed to use the stock head? You may get a little bit lower compression with the BVH, as some just use a huge bowl as a combustion chamber. Little less power, little more life though. Keep in mind too, that with the UNI filter and that setup you should be 88-95 with the main jet, depending on altitude and temps... I did know that its suitable with the stock head. But a 50mm piston with the stock combustion chamber, AND the extra domed area on the airsal piston should increase compression substantially, and id really like to stick with the ethanol free 90 octane fuel i have access to. Also, the head i bought is supposed to have oversized valves (which i will measure to be sure). I figured the extra valve size might be better than the extra compression. But im open to discussion. Thanks for the jet advice. With the 47mm and stock head and airbox im right on with a 92 jet. I figured i would start with a 98 and see where i end up. Edit: In fact i was hoping that the airsal piston would partially negate any lost compression from the bigger head. Plus its light af for a 50mm piston.
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Post by scooterted on Oct 10, 2019 13:08:52 GMT -5
This isnt really the correct section for troubleshooting. The 4 stroke troubleshooting section would probably be more helpful.
Its probably one problem causing all those things. Im thinking a compression loss. But it could be several things.
If it were me, I would: Inspect/change the spark plug. Clean the air filter. Do a compression test. Check camshaft alignment. Inspect cvt while i was at it. Clean carb while I was at it.
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Post by scooterted on Oct 10, 2019 8:39:52 GMT -5
How fast does it cycle between 1600 and 2000?
Have you tried retuning the idle mixture? I have to retune mine for seemingly no reason sometimes.
You could check for a vacuum leak by spraying carb cleaner around the intake area. If spraying in a a particular area causes a change in the way it runs is a good place to start looking.
I wouldnt expect the enricher to do that. It operates pretty slow.
Edit: i really would expect idle surge to be lean. Could have a clogged or restricted idle passage. If all else fails, you might have to pull the carb out and clean it.
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Post by scooterted on Oct 9, 2019 13:53:48 GMT -5
I had a 47mm bbk with a9 cam on my 139qmb, i was always dissapointed with my top speed of 39mph (im a big dude). So today I bought a 50mm airsal, big valve head and a uni filter.
Im actually not sure if ill have time to install and tune it.
Ill have it for later at least.
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Post by scooterted on Oct 9, 2019 12:31:52 GMT -5
Did you tune the carb? Especially idle mixture?
How unsteady is the idle?
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