zzmeyer

I would like to use a 735 in a balsams a 1/4 scale sop with camel. 15-18 pounds. Am I on the right track? Recommended prop?

BobH

My Feedback: (2)

That's plenty enough engine. More than enough actually. I think that engine calls for a 22x12 ? something in that neighborhood.
Have you bought the engine yet?

chorner

That's definitely not enough engine to push a 22x12 that's for sure...

Maxam

My Feedback: (62)

The 7-35 is a delicate engine and the max prop is an 18x8. The 7-77 flies 15 to 30 pound planes well. 15 pound for strong aerobatics to 30 pound scale. In your 1/4 scale the 7-77 will be running at half throttle most of the time sounding very scale and swinging a nice big scale prop like a 24x12. Also for that short nose moment the weight would help with balance. The Saito 325 radial would be good in this plane too. -Tom

BobH

My Feedback: (2)

I put my 770 in my GTM 1/4 DVI. It was a good fit but I couldn't run the collector ring
Did not need nose weight but it makes for a heavier plane. I had issues (like everyone else) getting it to run right and replaced it with a Laser 200 which runs great.
I have since bought the OS carb and adapter from C&H and plan to put the engine in a TF Corsair.

zzmeyer

I haven't bought it yet. The 777 will fit also but appears to be overkill. The 777 also appears too large for many medium large arf s. I fly my larger planes scale.

chorner

There's quite a difference between "flying my planes scale" and not having enough engine to begin with... which of course all depends on the airframe. Most WW2 giant scale models (i.e - 24lbs + planes) will be underpowered with the 7-35. However, models like the Sopwith from Balsa USA, have very low wing loading and are very light for their size. A 7-77 might break the thing in two without some better reinforcement So I'd agree, the 7-35 is a good match for it and will have more than enough power.

jspauld2

Tom, thanks for your dedication to this engine and this thread! Although it is difficult to monitor all threads that discuss our products, we try to check in on these threads occasionally to see what our customers are thinking. That being said, I apologize that we have not monitored this thread in a while. We do appreciate your efforts in making your engine run the best that it can.

For those that have had issues with obtaining parts to your Evolution radials, I apologize for our lack of assistance in the past. If anyone experiences difficulty in getting parts from our Product Support or Service Center staff, please send me a PM and I will get the appropriate team working on the problem. We originally did not intend for many parts to be available to customers due to these engines being quite a bit more complicated than standard single-cylinder 2- and 4-stroke engines. But after seeing the response and desire from customers wanting to repair their own engines, we may be willing to sell replacement parts to those who need them. Please contact our Product Support team in order to request those parts.

We appreciate the efforts to improve the engines by modifying or replacing carburetors and we will investigate any improvements that can be made in fuel delivery.

Please let me know if there's anything I can do to help.
Jimmy

Maxam

My Feedback: (62)

Jimmy, Thank you for your reply. Yes it is good to supply parts as Saito and OS supply parts on their complex engines. We have been fighting the carbs poor fuel flow for now for many years. Watch your own promo video for the 7-77 very carefully. When the engine goes to full throttle it slows down! All three of my UMS's were set where full throttle is 3/4 open on the carb. The 7-35 has the same problem. Yes the OS carb is expensive but its high precision and excellent fuel flow and metering make for a really great engine. You should see what it does for the Saito 325! As I said long ago in this thread these engines have brought great satisfaction to many people and we appreciate your increased support. Fix those carbs!!! Those OS's cost 80.00 each and I bought 3! -Tom

Maxam

My Feedback: (62)

Jimmy, Another point. It is true the carbs run richer as the oil content goes down. (fuel to oil ratio increased) Problem is the lower oil content results in black oil draining from the lower follower guide after a flight. At 9-10% oil amounts the oil drains crystal clear. My older 7-70 and 9-90 are strong after 4 years and around 150 flights each and I want them to last a lot longer yet. The higher oil still runs really well with 7% nitro. The OS carb still delivers plenty of fuel at the higher oil content. OK I will now stop OS carbing you! -Tom I hope you do understand, I really want to help improve a great engine.

chorner

Maxam, if you want a better price (to the tune of 50% off what you paid) PM me.

But in general, I have to agree and happy to see Horizon change their tune. I emailed, called, and was treated quite poorly via email asking for parts support for my 7-77 by some punk ass kid in tech support. I would presume it was a supervisor who called me back, and assured me he'd get me some parts in ~3 weeks or so (this was back in December). At which point, the guy in tech support manning the emails fudged up some information, and was generally a little bugger so I told him to shove it and forget the order.

In 3 weeks, I had parts shipped to me directly from UMS for more than likely half the cost Horizon would've gotten them to me for anyhow. I recommend contacting UMS in Indian directly if you're given the runaround and skip Horizon if they don't offer part support for a $1,200+ hobby engine.

Pretendpilot

my application requires extending the prop by about 15mm but, when I do this, the shaft is too short to secure the nut except for a few threads. certainly cant use the clip-ring. this is holding me up.

extension from HH BUT i want to use a CDI. and Adrian says the HH adapters wont work with the CDI, but he'll make it the length it needs to be. great.
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problem is, i cant see how to fit the prop nut on, and hub, when the prop and plate are already at the end.
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maxam, you say you use the HH 10mm extension...how does that extend the shaft/crank?
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anyone have any ideas? does the threaded part of the shaft unscrew from the crankshaft with possibility of adding a longer one?

Maxam

My Feedback: (62)

You get the extender bolt and special washer with the extension. My prop just happened to be thin enough so I did not have to use that heavy bolt.

Pretendpilot

so the "extender bolt and special washer" screws onto the crankshaft and requires that the prop center hole be enlarged?

TimD.

My Feedback: (207)

I was able to get the OS carb installed today. I made my own sleeve from a piece of scrap aluminum rod that I had, Easy enough took about an hour to turn and tap it. Made a tight fit with oring seals.

I ran a Biela 22x12-3blade (wide blades) WOT was 4000 rpms steady. Engine ran smooth and was especially pleased with the idling RPM , it would hold a rock steady 1200-1250 rpms WITHOUT GLOW assist. I do not think glow assist is even needed with the OS carb. IMPRESSED.

Maxam

My Feedback: (62)

To Pretend Pilot; yes! To Tim D. Fantastic! -Tom

Pretendpilot

...I guess I don't have to mention that needing to enlarge the hole in a prop is not as easy as it sounds. all the reamers I can find only go to 10mm (stock evo 777 shaft size). besides that, there are other considerations, like once a prop is enlarged, it cant be used on another plane (without a sleeve/shim). has anyone tried to enlarge a carbon fiber prop? seems that wouldn't be advisable.
.

chorner

It's not really as tough as you make it sound The GP reamer, despite being advertised to go to 10mm goes up to 12mm. I have 2 of them from my LHS. Further to that, an adjustable reamer is pretty easy to find - Amazon.com has a whole selection of reamers for very cheap. I bought one that adjusts up to 14mm.

Also, all carbon fiber props I know of have a hardwood prop hub meant for drilling. Just ream it out like usual, and seal the wood with a bit of CA etc. then you're in business.

Pete S-RCU

I have the Evo 7260 radial that I'm putting on a BUSA Stearman.
This is my first radial, so I have a few questions.
I've read most of this thread and didn't see anything about the E7260.
The carb has two fuel fittings on it, one for fuel and another for a primer.
Do I need to use a tee and connect both lines even though I can't reach the primer.
It's a Walbro WT 621 carb.
The ignition has a double connector on it, one for the bat and the other has a square end on it.
Looks like an ignition sensor, but no place to mount or connect it?
Maybe it's used for a tach?
The number one and seven cyl's have a fuel line from the intake pipe to a tee and then to a nylon spacer between the carb and the crankcase.
What is this for?
I'm going to use a 34x12 prop on it.
Thanks for any information......

chorner

Can't answer all questions as I don't have the 260 but the T between the two cylinders produces the pulse required to operate the pumping action in the walbro carb

Maxam

My Feedback: (62)

Pete there is a gas evo thread but I think it is dead. Do not bother the y tube from the intake to the carb. C Horner is right, it provides the pulses for the carb to pump fuel to it. The prop sounds too small to me. I would suggest a 34x16.

Pete S-RCU

Thanks for the help, I won't get to run it till spring, still kind of cold here in the frozen tundra.(Minnesota)
What kind of oil do you guys use on the valve train?
Does it get messy putting oil on an open valve mechanism?

Maxam

My Feedback: (62)

Pete, use redline in the oil gas mix as well as an ounce of Sea Foam/ gallon. The Sea Foam helps to prevent carbon buildup internally and prevent the exhaust valves from sticking. On the rockers, any light machine oil. Once in a while clean out the exhaust valve stem area outside the engine with brake clean. Then oil right away.

Pretendpilot

redline is quite expensive - wont the synth's in the mix be sufficient? sea foam...heh heh...just gave me an idea...leave out the sea foam for a few dozen flights, then add it and, vualah, you have a free smoke system!

Maxam

My Feedback: (62)

Your engine is expensive too.