Ryobi Tuning
04-04-2007, 07:27 PM
#1
Thread Starter
Ryobi Tuning
In prep for building a Balsa USA 1/4 Cub, I started breaking in a Ryobi today. The firewall will need set back using the Ryobi and so I want to make sure the motor is rock solid before committing.
Using a 16 x 8 APC yielded 8400 rpm and all seems well except the following condition. Full throttle for more than 10 seconds or so often yields a little richening of top end and if the throttle is cut suddenly during this richer period, it yields a rich and very rough and shaking idle for a few seconds until the motor clears. If the idle is set under 2500, it will sometimes stop during this condition. Leaning the top end doesn't seem to be what is needed as doing so seems to cause a little lean initially with broken transition up. Prior to the onset of the loading on top end... it transitions up and down fine.
Am I doing something wrong with the tuning? Am I slightly under propped and getting too many revs or is the reed valve restrainer opened slightly too far?
The prop is balanced well and tracking within 1/16" and the motor runs smooth except when decelerating during this rich condition. I've rotated the prop to three different positions with no effect.
Also, I have the fuel line connected to the line opposite side of the needles and the line next to the needles has a piece of tubing with a screw in it... is this right?
Any ideas?
Using a 16 x 8 APC yielded 8400 rpm and all seems well except the following condition. Full throttle for more than 10 seconds or so often yields a little richening of top end and if the throttle is cut suddenly during this richer period, it yields a rich and very rough and shaking idle for a few seconds until the motor clears. If the idle is set under 2500, it will sometimes stop during this condition. Leaning the top end doesn't seem to be what is needed as doing so seems to cause a little lean initially with broken transition up. Prior to the onset of the loading on top end... it transitions up and down fine.
Am I doing something wrong with the tuning? Am I slightly under propped and getting too many revs or is the reed valve restrainer opened slightly too far?
The prop is balanced well and tracking within 1/16" and the motor runs smooth except when decelerating during this rich condition. I've rotated the prop to three different positions with no effect.
Also, I have the fuel line connected to the line opposite side of the needles and the line next to the needles has a piece of tubing with a screw in it... is this right?
Any ideas?
04-05-2007, 12:37 AM
#2
RE: Ryobi Tuning
Do you have adequate clearance between the firewall and the carb? Could be restricting and richening it up if it's too close. Check to make sure the throttle butterfly is not going over center too. Common problem. Sometimes a little slop in the carb linkage will let the engine suck the butterfly over center....
Also, 8400 is on the high side for a Ryobi. Better to prop in the 7500 bracket.
AV8TOR
Also, 8400 is on the high side for a Ryobi. Better to prop in the 7500 bracket.
AV8TOR
04-05-2007, 04:06 AM
#3
Thread Starter
RE: Ryobi Tuning
Av8tor... Good points. The firewall is 5/8" from the carb. Will try a throttle shim to ensure the butterfly is not over centering. You are likely right that it's simply going to many revs for the air flow of the carb. Will up prop and see what happens. Thanks
04-06-2007, 01:49 AM
#5
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RE: Ryobi Tuning
The tube with the screw in it is where the primer bulb was attached in the weed trimmer..The bulb has a one way valve in it...when the bulb is taken off the tube must be blocked lest fuel leak out of the carb....Remote primer bulbs use the tube, carbs with primer bulbs in the cover don't need the tube blocked...
The pump gets the pulse from the hole in the carb body via the hole in the carb gasket via the hole in the carb insulator...works well unless there's a leak or the carb is rotated and the hole is blocked...
The pump gets the pulse from the hole in the carb body via the hole in the carb gasket via the hole in the carb insulator...works well unless there's a leak or the carb is rotated and the hole is blocked...
04-06-2007, 05:01 AM
#6
Thread Starter
RE: Ryobi Tuning
Report... I ran the motor again with an 18-6 zinger with no change except of course less rpms.
Standoffs were added to the test setup to provide more aft carb clearance. I've not added a static tube and vent yet though cupping my hands over either of the two open sides of the mount don't seem to have any effect at eliminating high end richening.
I've determined that there are two issues in play instead of one... I was allowing the throttle to be snapped close by the spring and think it now unreasonable to expect a reasonable down transition doing that. Manually moving the throttle from high to low usually provides enough time for transition adjustment solving some of the rich idle problems noted.
The occasional richening of top end continues and if transitioning down during one of those periods, a low end shake occurs unless the transition down is given extra time to clear the rich condition. Given a reasonably idle setting, the motor often will stop during this condition. Most likely the shake is do to the idle going too low. When the rich condition clears and the idle climbs back to around 2300 shaking clears. If idle is adjusted very slow, the shake occurs independent of having a rich/lean adjustment.
The flywheel was checked and found to be grossly out of balance and wouldn't make a round when given a slight roll. After some effort, 8-10 turns result from a similar nudge.
The idle speed will work and the transitions are good when made considering servo speeds but I won't feel good about this motor until the high end stabilizes. I'm wondering if the needle seat just hasn't had time to wear in as the richening seems to have reduced slightly. Will clean the carb and if that doesn't solve the problem, will try to get hands on another.
Thanks to all for the input and I'll try to remember to post a final outcome.
Standoffs were added to the test setup to provide more aft carb clearance. I've not added a static tube and vent yet though cupping my hands over either of the two open sides of the mount don't seem to have any effect at eliminating high end richening.
I've determined that there are two issues in play instead of one... I was allowing the throttle to be snapped close by the spring and think it now unreasonable to expect a reasonable down transition doing that. Manually moving the throttle from high to low usually provides enough time for transition adjustment solving some of the rich idle problems noted.
The occasional richening of top end continues and if transitioning down during one of those periods, a low end shake occurs unless the transition down is given extra time to clear the rich condition. Given a reasonably idle setting, the motor often will stop during this condition. Most likely the shake is do to the idle going too low. When the rich condition clears and the idle climbs back to around 2300 shaking clears. If idle is adjusted very slow, the shake occurs independent of having a rich/lean adjustment.
The flywheel was checked and found to be grossly out of balance and wouldn't make a round when given a slight roll. After some effort, 8-10 turns result from a similar nudge.
The idle speed will work and the transitions are good when made considering servo speeds but I won't feel good about this motor until the high end stabilizes. I'm wondering if the needle seat just hasn't had time to wear in as the richening seems to have reduced slightly. Will clean the carb and if that doesn't solve the problem, will try to get hands on another.
Thanks to all for the input and I'll try to remember to post a final outcome.
