f2racer

OK got my 35cc gasser which I intend to use on a GP Pitts Special ARF (should work since GP recommends the US Engines 41 and the MVVS 35 should be both lighter and more powerful). The "manual" was a little light. What prop should I be using for break in? And what are the proper procedures for break in so that I can get the maximum performance outta the engine? I'm guessing the Pitts will end up weighing around 16-17lbs and the MVVS should be capable of between 20-22lbs of thrust so the plane should be fun pretty fun!

Thanks!

pe reivers

Start out with much oil in the mixture, about 1:25 of any good two stroke oil.
Set the engine slightly rich, but still peaked. It should fall into fourstroking when you reduce throttle, then go into two-stroking again.
For the first pint, keep the 1:25 mix, and do not exceed 5000 rpm using a 18x10 prop. Play the throttle.
Then switch to 1:30 for the next gallon. Do not ask the engine to work hard for prolonged times. Gas engines do not like that when still tight. Believe me, MVVS are tight engines. Working the throttle a lot, and up to 6000 rpm will limber up the engine a bit.
Now switch to 1: 35 for the next gallon, tune and ask for max power for short bursts, which may be prolonged bit by bit. Keep playing the throttle.
The third gallon can be mixed 1: 40. That is the mix I still use, and I intend to use it for some time to come.
My engine starts running better and better. I use Menz !8x10 and 20x8 props.

pe reivers

Update:

I now run the engine on a 1:32 mix again. It runs smoother, and gains some rpm. (MVVS tuned pipe)
After a while, the black exhaust residue completely vanished. The engine needs much running in time.
Performance on a 20x8 Menz is terrific with 20 lbs measured thrust, but I busted a few on landings, so now I use the 18x10 all the time (18 lbs thrust, measured). With 18x12, flight performance is better, but the tow plane torque rolls more on power application. The 7'4" 18 lbs plane just hangs on the prop, and has towering vertical when not called upon to perform towing duties.

splais

My Feedback: (25)

Pe,

I would be interested in your comments on the new MVVS 58cc engine. it is intriqueing at an advertised hp of 8. However I can find little information available and to speak planly, this engine is very expensive for its size. I wonder why I should consider it over the ZDZ60 to be specific.

David_Moen

Expensive for it's size? In Canada, they are priced competitiveley with engines of similar size. Although there are no reviews out yet, build quaility is magnificent and the performance numbers coming from Morris Hobbies and JustEngines seem to back up the manufacturer's claims.

pe reivers

I have one engine on the test stand, but it is still looking for a proper exhaust.
Equipped with the 35cc pitts muffler, it turns 6200-6500 (4.5 hp) using a 22x10 Smart prop (Menz-clone, wood)
Since this exhaust is too small, and very restrictive, this realy is nothing you can go by.
Just engines's test confirm low power on their larger volume pitts-type muffler, and have shown how this baby reacts to a (wrong) 35cc tuned pipe with a 1400 rpm jump to 6.5 hp
I know that Krumscheidt is working on a dedicated pipe, and I intend to get one. What I can say now is:

Starting- after two cold choke flips, open choke, turn on ignition, then two more flips get her going. Kickback is absent.
The needles are factory set very rich. The engine, when in the box, feels rough. This totally disappeared after the first 1/2 minute run, though the engine still felt tight.
After initial coarse, and still rich adjustment, and at 1:25 mix, idle is fantastic, acceleration is crisp, mid-throttle is a smooth pace. Now my once scruffy workshop now is utter chaos, because everything blew away. At very low idle, the engine may kick back, and resume at a steady pace in the opposite direction. It has no real preference for CW or CCW rotation. Maybe for CW running at full throttle the timing is not advanced enough. I did not test, because my workbench was in the line of fire!
I have an Extra 300 of 84" span on the bench to serve as testbed. Estimated flight weight will be about 20 lbs, but the plane is a loooong way from finished.

It seems that the claimed >8 hp on a well tuned pipe is no bragging. My 50cc 9,5 hp MXracer produced less than 5hp without the pipe. Price in Europe is just short of Euro 500, so without tax That should be less than USD 500 with the current exhange rates. That is usd 62.50 per HP, by no means expensive, and very competitive both HP-wise, and as compared to ZDZ and 3W.

96S14

pe reivers, what type of plane are you using for towing, and in your opinion, how large a glider can you (safely and easily) tow using the MVVS 35cc motor?

Which is your final preferred exhaust system for this motor?

I am looking at building a towplane, and I can get an MVVS 35cc gasser for a very good price. I'm just trying to decide if it's a waste of money and whether I should just spend twice as much to get a ZDZ 50 or 60 and be done with it.

Opinions and comments are greatly appreciated.

Thanks,

Ryan.

pe reivers

I use a 90" span Freight train (own design) or a Multiplex biglift.
the 35cc engine has towed gliders up to 18 lbs and 5 meters span without any problems. Larger ones were not available, so I cannot tell how it would have performed.

96S14

Thanks for your comments. Have you any preference for an exhaust system for this engine? And are you still using the 18" prop with 18lbs of thrust?

On an unrelated note, where is Arcen in relation to Eindhoven and Maastricht? I have visited that part of Holland many times (~16) and have never heard of Arcen. The landsacpe in the photos looks very familliar....

Thanks again,

Ryan.

pe reivers

I use the MVVS tuned pipe.
On the 35cc engine I use the Menz 18x10 prop (ground clearance) though the 20x8 performs better.

Arcen is due East from Eindhoven, and due North from Maastricht, a mile and a half away from the German border.

microdon2

My Feedback: (47)

PE - I picked up a used MVVS 35 a few years ago on an H9 80" Mustang. Great running engine, till I crashed the plane, into a sandy beach. Last year I tried running the engine again and it just didn't seem to rev high - was running rough. I now want to get that engine running well for a new installation (a Great Planes 72" Super Stearman - would be a perfect match.) Any suggesttions on how to get this engine purring again? I'm guessing start with a carb rebuild kit and also go back to default needle settings? Can you tell me what the defaul needle settings are? Thank you in advance.

Mike D

the pope

Unfortunately PE died a few years ago now . The threads last post was 2003 ! Maybe look on Flying Giants forum for some more help . Cheers the pope

timlan

I dont understand using a "break in prop", different oil./gas mixture, break in stands? I raced 2 stroke karts for 25 years and have been flying gas airplanes for 15 years. All that stuff is unnecessary. Use 40/1 gas/ oil, the prop you intend to fly with and mount the motor to the plane. Run it for about 10-15 minutes at high idle, then go fly it. Fly gently for a tank or so and your good to go. Never had any problems that way. Some RC'ers overthink this stuff. My 2 cents