MVVS77 floppy throttle arm
06-25-2005, 05:33 PM
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MVVS77 floppy throttle arm
Breaking in an MVVS77 with short pipe today, 5% nitro, castor/synth blend with added castor to 20% lube, Enya #4 plug, 13x6 Zinger with tips cleaned up, after 15 rounds of one-minute full throttle rich needle with cooling to 100Ëš in between (ambient temp 95Ëš), I get smooth and sustained 11,100 rpm, which makes me happy.
At 11,100 I get head temperature of 235Ëš, which is OK, but what I don't like is the throttle arm, which is black plastic, is limp and bendy. Before I even started the engine up I thought the plastic arm was somewhat on the soft side, but on a hot engine it takes a fair amount of servo movement before the arm moves at all. This is not good. I don't like slop anywhere, and definitely not in the throttle.
So I will pull the arm off tonight and see if I can make a reasonable duplicate out of sheet aluminum. I have no idea whether MVVS has a metal alternative, but I guess we all know that Morris Hobbies is not famous for their parts support on this line. Has anyone else struggled with this problem? I'm hoping Dar or Pe or Jaka will have something helpful to contribute--hats off to each of them for many useful posts. This is too nice an engine to have to put up with this little shortcoming.
At 11,100 I get head temperature of 235Ëš, which is OK, but what I don't like is the throttle arm, which is black plastic, is limp and bendy. Before I even started the engine up I thought the plastic arm was somewhat on the soft side, but on a hot engine it takes a fair amount of servo movement before the arm moves at all. This is not good. I don't like slop anywhere, and definitely not in the throttle.
So I will pull the arm off tonight and see if I can make a reasonable duplicate out of sheet aluminum. I have no idea whether MVVS has a metal alternative, but I guess we all know that Morris Hobbies is not famous for their parts support on this line. Has anyone else struggled with this problem? I'm hoping Dar or Pe or Jaka will have something helpful to contribute--hats off to each of them for many useful posts. This is too nice an engine to have to put up with this little shortcoming.
06-25-2005, 10:12 PM
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RE: MVVS77 floppy throttle arm
Majortom..
You said there's a "considerable amount of servo movement before the throttle arm moves".....
That seems to suggest the slop is elsewhere in the chain does it not?
I have an MVVS .49, and .61 and neither has the least amount of "slop" in the carb linkage.
'Race
06-25-2005, 10:26 PM
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RE: MVVS77 floppy throttle arm
Tom, I did replace my arm also because it was kinda flimsy. I had a metal one in my box of stuff you never throw away, cause you might need it some day
By the way, my .77 is my favorite engine. Starts on one flip, great transition, runs fantastic on 5% fuel and just screams my Ultra Stick .60 across the sky!
By the way, my .77 is my favorite engine. Starts on one flip, great transition, runs fantastic on 5% fuel and just screams my Ultra Stick .60 across the sky!
06-25-2005, 10:27 PM
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RE: MVVS77 floppy throttle arm
Well, I take it all back. RaceCity is correct, the slop is due to a poor servo mount. I have the throttle servo mounted to the beam of a GP plastic mount, and it looks like the vibrations of a new engine were too much for the servo mount, causing one end to crack loose, and that's where the slop originates. So, my apologies to MVVS. I will do a stouter mount and move on from there.
06-26-2005, 12:15 PM
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RE: MVVS77 floppy throttle arm
Glad you found the problem. The arm on mine would have worked OK but it was a bit flexible, so I just switched it out. My carb is very smooth and has excellent transition. You are going to really like the .77. I still think that MVVS engines are the best kept secret in the hobby. I just wish we could get a better US distributor. Last time I called Morris Hobbies to buy one, they told me they had no MVVS engines in stock and would be out for 3-6 weeks. I found the one I needed at Sheldons in California.
