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Post by encephalon on Jul 18, 2015 14:42:40 GMT -5
Finally had a chance to take it out for a spin and get the rings seated. Still think I need to upjet and get a proper spacer for the manifold. It ran great and pulled hard, but at times it was sluggish and got really loud. I'm thinking its running lean. So, time to get a pilot jet, main jet kit, and manifold spacer.
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Post by encephalon on Jul 18, 2015 21:29:29 GMT -5
Made an intake manifold spacer out of a cutting board. Cutting boards are typically polyethylene or polypropylene, and will soften/melt from the heat of normal operation - and likely fail. Better to use a proper (hi-temp plastic) manifold insulator, or make one from a block of micarta/phenolic. Bob Just as you said, the spacer I made had melted and warped, probably causing an air leak. Also some of the melted material had formed towards the intake port! Luckily none got actually sucked into the head, and luckily it was my stock head and not my shiny new BVH.  Guess the scooters down till I get those parts. |
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Moat
Scoot Member
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Post by Moat on Jul 20, 2015 4:18:55 GMT -5
For a very temporary solution, I'd hafta' think a nice, clear, knot/defect-free block of hard Maple might be worth a try, for a short while. I'd also guess it will eventually crack and leak (could leave a little extra "meat" on the outside for added strength) - but then again, Maple is pretty tuff stuff, and might actually last a while. Or maybe Mahogany, or even Ash, as a second choice... At least it won't melt - and won't get hot enough there to char/burn. Good heat insulator, too. Just a thought... in case you're absolutely desperate!  Bob |
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Post by encephalon on Jul 23, 2015 4:29:32 GMT -5
So I thought to myself, why run a spacer at all if it's just for a little clearance for the cooling shroud? So I did some research and many others are running no spacer on their manifold with no problems. Just a gasket. So I said why the F not? That's how cars do it. Manifold, gasket, to head. The only thing I can think of would be cooler air coming into the head. And that's not even much unless it's a phenolic material. Which the stock spacer isn't. Just high temp plastic right? The other thing I would worry about is the rubber portion of the manifold might degrade a little faster. W/e. So I threw in a #102 main jet that I had and bolted the manifold directly to the head with a gasket. Runs great. Been through about 70 miles with no problems. Except of course some sputtering from the big ol' main jet. Running a little rich but it evens out. Still can hit 40 mph whenever I want. On hills where it would only get to 16~17 mph, I'm now hitting 30 mph or greater. I can really feel the BBK breaking in. Which I must say was an AWESOME upgrade. It can only get better with proper jetting. So as of now, I'm running 50mm BBK, stock head, A9 cam, 5 gram sliders (bogged horribly with the 8 gram rollers the kit came with; My area has a lot of gradual up and down hills,) #102 MJ (need to go with a #95~#98,) and a Gates powerlink belt. I'll throw on the BVH once I get that bigger idle jet. Probably going to go with a #40. More to come!
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Moat
Scoot Member
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Post by Moat on Jul 23, 2015 22:07:33 GMT -5
Cool ya got it up and running!  I believe the insulators are primarily to help prevent heat soak/boiling away of the fuel in the float bowl - which can make an engine a bear to re-start after running on a hot day. Stable, cooler carb temps help provide more consistent fuel delivery (mixture), too - as well as a possible very slightly cooler, denser intake charge (more power!). Bob |
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Post by encephalon on Jul 24, 2015 22:28:42 GMT -5
Cool ya got it up and running! I believe the insulators are primarily to help prevent heat soak/boiling away of the fuel in the float bowl - which can make an engine a bear to re-start after running on a hot day. Stable, cooler carb temps help provide more consistent fuel delivery (mixture), too - as well as a possible very slightly cooler, denser intake charge (more power!). Bob Luckily, I haven't noticed any hard start problems. It's been getting to over 100 degrees where I'm at as well so that's good. Just ordered #40 pilot and #95 main. I have #90 and #100 main jets and those made the scoot run either too lean or too rich. So a #95 SHOULD be the winner. Also, one of my variator slides is warping so I ordered a new set of those as well. Hopefully those new jets will allow me to run that BVH. |
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Post by encephalon on Jul 28, 2015 19:28:47 GMT -5
Got a top speed of three runs on a flat. All hit 43mph. Can't wait to get those proper jets for a little more hopefully.  |
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Post by encephalon on Aug 14, 2015 21:55:45 GMT -5
Just an update, scooter is running GREAT. Swapped the #95 main jet to a #90 and its hauling some ass. 4 stroke 49cc scooterly speaking anyway. lol. #95 was a tad too rich. #40 idle jet is a tad too rich as well. Going to drop down to a #38. I like how I can get to 30 within a few seconds and 40mph with ease. BBK's are cool. Going to get a stroker crank and gears to make this thing a little more reliably faster. Might play around with a bigger carb to see how it does.
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Post by ohhbuddy on Aug 18, 2015 12:19:38 GMT -5
You believe 60 is obtainable? I never really got a chance to install a stroker crank, a9 cam and exhaust when i had a gy6 50
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Post by encephalon on Aug 18, 2015 15:01:47 GMT -5
You believe 60 is obtainable? I never really got a chance to install a stroker crank, a9 cam and exhaust when i had a gy6 50 I really don't think 60 is a reasonable goal with a 139qmb. lol. That'd be pushing to the LIMIT I think with every mod out there. even then, it'd be questionable. 50 however, i think i'll get whenever the stroker crank and gears are put in. |
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Post by iwiketuddlz on Aug 20, 2015 9:03:50 GMT -5
My fully built stroked 139qmb would only do 54mph with scrappy upgears and all!!! And that was pushing the crap out of it!!! Lol.... I agree 60mph is deff a no go for that engineIMO and experience......now a 2T.... Well diff story!!
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Post by Kick start on Sept 6, 2015 11:12:56 GMT -5
I like where your build is going. Depending on your air filter is like? Is it stock or is it thinner for more air flow? You can run a bigger main jet. I see your using a big valve head and if its modified sweet if not you should still be able to hit 60 still. But get a oil catch can even if you dont have a stroker crank but if or when you do get a stroker crank oil catch can is needed. RPM gauge will help on tuning try to stay under 10,000 RPM on stock valves springs i think they snap at 10,500 so just get the bigger gear. My old build that hit 61 i was using around a 120 main jet and 38 idle jet. My new build is unknown still lol i didnt put my big valve head on yet. Still waiting on oil catch can to come in. But did put the stroker cank in and still have to order my new speedo my stock one is pined at top speed lol
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Post by encephalon on Sept 14, 2015 21:45:24 GMT -5
you do know those stock speedos arent worth a crap right? pegged out at "50mph" i'm only doing 42~43mph gps verified.
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Post by encephalon on Sept 14, 2015 21:48:24 GMT -5
My scooter has been running super rich unfortunately lately. I'm suspecting a knackered petcock. Haven't had time to investigate though. Just started out of nowhere. Usual popping and gurgling. Won't stay on at idle unless i have the throttle turned just a touch.
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Post by 90GTVert on Sept 15, 2015 7:11:35 GMT -5
Check the float height and make sure it's not sticking.
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I believe the insulators are primarily to help prevent heat soak/boiling away of the fuel in the float bowl - which can make an engine a bear to re-start after running on a hot day. Stable, cooler carb temps help provide more consistent fuel delivery (mixture), too - as well as a possible very slightly cooler, denser intake charge (more power!).
