2LikesGo-Tech Engines Thread
05-27-2010 | 03:12 PM
Tech Elite
Joined: Nov 2007
Posts: 2,983
From: Auckland, New Zealand
in this case, both aerodynamic and fluid dynamic laws apply here. Smooth surfaces have less drag coefficient, due in part to reduced turbulence generation and reduced exposed surface area. The only advantage that a less smooth surface could provide would be increased atomization. Due to the velocity of the air moving through the engine at operating speed, this is a moot point. The vaporization point of nitromethanol in a vacuum environment (carburetion) is typically below the operating temperature of these engines anyways. This will vary, based on lubricants and additives.
Lastly, from the point of entry (carb venturi) to the cylinder, the fuel/air mixture is under vacuum. That is unless you're running forced air induction (supercharger). So, the mixture is being pulled- not pushed.
Lastly, from the point of entry (carb venturi) to the cylinder, the fuel/air mixture is under vacuum. That is unless you're running forced air induction (supercharger). So, the mixture is being pulled- not pushed.
When you "suck" liquid up a straw all you are doing is removing the air from within the straw and creating a vacuum. Gravity then pushes the liquid up the straw once the air is removed. In theory (and practice), if your straw was over 10 metres long the liquid would not flow any higher - no matter how hard you sucked on the straw. This is the maxium theoretical lift provided by gravity. Same applies in the motor. Once a vacuum is created in the crankcase - cylinder area, gravity pushes the air fuel mixture in to fill the void.The rest of the flow theory and things I will leave up to you guys
05-27-2010 | 03:29 PM
Intake passages are left slightly textured, exhaust passages are polished ! Port matching and surface texture are two completely different topics..... A 220 grit finished surface will allow a mixture to pass over it with less obstruction then a mirror polished surface....
05-27-2010 | 07:26 PM
That crank in your pics is an OS Speed crankshaft. It is drilled and THEN filled as 22racer said. The drilling is what does the real magic in that it lightens the crankshaft making throttle response more crisp. The epoxy just fills the empty void created by drilling, and brings crankcase volume back to what it was before the drilling. Simply adding epoxy to the crank ramp will not do anything other than further decrease case volume and slightly obstruct the flow of fuel/air mixture if you go too far with it.
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05-28-2010 | 07:25 AM
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From: taguig
today i change my glowplug to an os p3,change my fuel(tornado)change my fuel tubing,clutch springs and i tought that its gonna be the end of my problem tuning my engine,but nothing changes.
still dying when i try to start,sometimes it will start then idle on top of the box then rpm goes high and flames out,then sometimes the rpm drops then flames out again,this is the first time i encountered this kinda problem on my go engine,or maybe should i change or clean my pipe?im using the dynamite 053 on my go 7port oh btw im using a a 7port sleeve on a 5port crankcase,but still using the 5port head.i read on this forum that the 5 and 7 port share the same crankcase.pls correct me if im wrong..thanks!
still dying when i try to start,sometimes it will start then idle on top of the box then rpm goes high and flames out,then sometimes the rpm drops then flames out again,this is the first time i encountered this kinda problem on my go engine,or maybe should i change or clean my pipe?im using the dynamite 053 on my go 7port oh btw im using a a 7port sleeve on a 5port crankcase,but still using the 5port head.i read on this forum that the 5 and 7 port share the same crankcase.pls correct me if im wrong..thanks!
05-28-2010 | 08:19 AM
Tech Fanatic
Joined: Aug 2008
Posts: 891
From: Texas
The R21 crankcase used on the GX and previous generation are the same for 3, 5, and 7 port motors. So, the sleeve will work for you.
it sounds like you have an air leak. Ensure that your exhaust gasket doesnt have a tear in it, check the rear of the crankcase (remove the rear bulkhead, clean the surface and inspect the seal). Also, if your carburetor gaskets are reddish in color, replace them with the new black nitrile gaskets. This goes for the high speed needle, low speed needle, the base of the carburetor neck, and the seal that goes inside the hole where the carburetor neck fits in.
lastly, check your carburetor pinch bolt. make sure it has black seals on it as well.
Guys... if you're having tuning problems, start here. We've had none of these kinds of issues with the new GX engines, using the black synthetic nitrile seals- none. They're that solid.
Question- if I were to put together packs of seals that included all the ones you need to replace on older motors, would you guys be interested?
it sounds like you have an air leak. Ensure that your exhaust gasket doesnt have a tear in it, check the rear of the crankcase (remove the rear bulkhead, clean the surface and inspect the seal). Also, if your carburetor gaskets are reddish in color, replace them with the new black nitrile gaskets. This goes for the high speed needle, low speed needle, the base of the carburetor neck, and the seal that goes inside the hole where the carburetor neck fits in.
lastly, check your carburetor pinch bolt. make sure it has black seals on it as well.
Guys... if you're having tuning problems, start here. We've had none of these kinds of issues with the new GX engines, using the black synthetic nitrile seals- none. They're that solid.
Question- if I were to put together packs of seals that included all the ones you need to replace on older motors, would you guys be interested?
05-28-2010 | 08:45 AM
The R21 crankcase used on the GX and previous generation are the same for 3, 5, and 7 port motors. So, the sleeve will work for you.
it sounds like you have an air leak. Ensure that your exhaust gasket doesnt have a tear in it, check the rear of the crankcase (remove the rear bulkhead, clean the surface and inspect the seal). Also, if your carburetor gaskets are reddish in color, replace them with the new black nitrile gaskets. This goes for the high speed needle, low speed needle, the base of the carburetor neck, and the seal that goes inside the hole where the carburetor neck fits in.
lastly, check your carburetor pinch bolt. make sure it has black seals on it as well.
Guys... if you're having tuning problems, start here. We've had none of these kinds of issues with the new GX engines, using the black synthetic nitrile seals- none. They're that solid.
Question- if I were to put together packs of seals that included all the ones you need to replace on older motors, would you guys be interested?
it sounds like you have an air leak. Ensure that your exhaust gasket doesnt have a tear in it, check the rear of the crankcase (remove the rear bulkhead, clean the surface and inspect the seal). Also, if your carburetor gaskets are reddish in color, replace them with the new black nitrile gaskets. This goes for the high speed needle, low speed needle, the base of the carburetor neck, and the seal that goes inside the hole where the carburetor neck fits in.
lastly, check your carburetor pinch bolt. make sure it has black seals on it as well.
Guys... if you're having tuning problems, start here. We've had none of these kinds of issues with the new GX engines, using the black synthetic nitrile seals- none. They're that solid.
Question- if I were to put together packs of seals that included all the ones you need to replace on older motors, would you guys be interested?
05-28-2010 | 09:25 AM
today i change my glowplug to an os p3,change my fuel(tornado)change my fuel tubing,clutch springs and i tought that its gonna be the end of my problem tuning my engine,but nothing changes. still dying when i try to start,sometimes it will start then idle on top of the box then rpm goes high and flames out,then sometimes the rpm drops then flames out again,this is the first time i encountered this kinda problem on my go engine,or maybe should i change or clean my pipe?im using the dynamite 053 on my go 7port oh btw im using a a 7port sleeve on a 5port crankcase,but still using the 5port head.i read on this forum that the 5 and 7 port share the same crankcase.pls correct me if im wrong..thanks!
still dying when i try to start,sometimes it will start then idle on top of the box then rpm goes high and flames out,then sometimes the rpm drops then flames out again,this is the first time i encountered this kinda problem on my go engine,or maybe should i change or clean my pipe?im using the dynamite 053 on my go 7port oh btw im using a a 7port sleeve on a 5port crankcase,but still using the 5port head.i read on this forum that the 5 and 7 port share the same crankcase.pls correct me if im wrong..thanks!did you put in new piston & rod at the same time ?
how easy is the motor to turn over cold & warm ?
does the v spec carby u are using have a plastic heat shield around the neck were it goes into the crankcase ? if so check that it hasn't gone brittle & cracked.
as ruune said change all your seals to the new nitrile seals & your exhaust seals as well.
is this 7 port sleeve out of your old 7 port u were having trouble with this time last year ?
Last edited by MAGPIE-121; 05-28-2010 at 09:44 AM. Reason: another Q
05-28-2010 | 10:15 AM
how easy is the rod to get on the crank pin ? & is there any play in it at TDC ?
05-28-2010 | 10:58 AM
today i change my glowplug to an os p3,change my fuel(tornado)change my fuel tubing,clutch springs and i tought that its gonna be the end of my problem tuning my engine,but nothing changes. still dying when i try to start,sometimes it will start then idle on top of the box then rpm goes high and flames out,then sometimes the rpm drops then flames out again,this is the first time i encountered this kinda problem on my go engine,or maybe should i change or clean my pipe?im using the dynamite 053 on my go 7port oh btw im using a a 7port sleeve on a 5port crankcase,but still using the 5port head.i read on this forum that the 5 and 7 port share the same crankcase.pls correct me if im wrong..thanks!
still dying when i try to start,sometimes it will start then idle on top of the box then rpm goes high and flames out,then sometimes the rpm drops then flames out again,this is the first time i encountered this kinda problem on my go engine,or maybe should i change or clean my pipe?im using the dynamite 053 on my go 7port oh btw im using a a 7port sleeve on a 5port crankcase,but still using the 5port head.i read on this forum that the 5 and 7 port share the same crankcase.pls correct me if im wrong..thanks!
05-28-2010 | 07:59 PM
That crank in your pics is an OS Speed crankshaft. It is drilled and THEN filled as 22racer said. The drilling is what does the real magic in that it lightens the crankshaft making throttle response more crisp. The epoxy just fills the empty void created by drilling, and brings crankcase volume back to what it was before the drilling. Simply adding epoxy to the crank ramp will not do anything other than further decrease case volume and slightly obstruct the flow of fuel/air mixture if you go too far with it.
tested my epoxy ram filled crankshaft earlier today, simply fill the crankshaft without lightening process is not a good mod at all, unnoticeable power change but the runtime reduce... now only can get just a liltle over 7 minutes per tank... it used to be over 9 mins. got to grind off the epoxy..
05-28-2010 | 11:44 PM
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Joined: Nov 2007
Posts: 2,983
From: Auckland, New Zealand
update;
tested my epoxy ram filled crankshaft earlier today, simply fill the crankshaft without lightening process is not a good mod at all, unnoticeable power change but the runtime reduce... now only can get just a liltle over 7 minutes per tank... it used to be over 9 mins. got to grind off the epoxy..
tested my epoxy ram filled crankshaft earlier today, simply fill the crankshaft without lightening process is not a good mod at all, unnoticeable power change but the runtime reduce... now only can get just a liltle over 7 minutes per tank... it used to be over 9 mins. got to grind off the epoxy..
At least it's only epoxy and will be easy to take out again.
05-29-2010 | 11:59 AM
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