I have a 28 oz. Tank, usually fly 9 or 10 min. Flights, with spare fuel left could probably get 12 or 14 minutes, but don't go that long, and not full throttle, unless doing loops or hammer heads or climbing up high, its Been a great engine!

Thanks slskn.
I have a long build ahead . I'll keep you posted.
If and when you get a chance, would you be able to get a picture of the engine mounting to bulkhead area
No rush, would like to see if poss.
Cheers,
Shaun.

Hello
A question for you who has the small 7-35 engine.
have you experienced that there is a radial gap in the rear bering.
I've changed my mind, pretty soon came the gap
The engine runs very well
I might buy a higher grade ball bearing
Lars

If and when, please post the specs so we can, too! SKF <3

-tih

My Balsa USA 1/4 scale Sopwith Pup fuselage is constructed to the point where I can now start worrying about mounting my Evolution 7-35 radial. I have purchased a SonicTronics on-board glow system to keep all of the plugs hot at low throttle settings. (Don’t tell the wife about the price)! As I start to lay out what holes to drill in the firewall - it forces me to decide what to do about the choke problem on the Evo.

I have no experience with engines that require a choke. If I use the stock Evo carburetor on my 7-35 I will need to construct a recessed (and fuel-proofed) box behind the firewall for the choke-valve diaphragm and that will force the fuel tank farther behind the CG. Also, reading this thread tells me that using this stock carb will require expert tinkering with the needle settings (I'm not very experienced with this fine-tuning)!

I am used to pre-starting any of my existing Saito engines (all single-cylinders from .82 to 1.25) using the procedure where I hold a finger over the exhaust and rotate the prop until a little fuel comes out of the exhaust and there is a slightly ‘juicy’ sound indicating fuel is in the carb. BTW ~ there is a pressure tap on the exhaust collector ring of my 7-35 Evo.

So, here are the questions ~ [I'm hoping that the answer to question #2 is yes - then all the others won't matter]!

> Question #1: Is the choke necessary for starting the Evo 7-35?

> Question #2: I want to follow the advice of many contributors to this thread who recommend replacing the stock carb with the one for the Saito 90 radial (Saito carb stock # is SAI-90-R3-382-1). If I use this replacement - I notice the Saito carb has a priming nipple on the carb intake. Will priming using this method mean that my Evo won't need a choke?

> Question #3: If I do use the Saito carb - but a choke is still necessary - the whole choke assembly location for the Evo will need to be completely re-engineered to fit the Saito carb intake which faces straight-up - whereas the Evo carb intake faces straight-back (into the firewall). Has anyone used the Saito carb replacement and then moved the Evo choke assembly to work with the Saito carb? One difficulty in doing that is that - on my engine the choke assembly cannot be removed. None of the grub-screws on the back of the mounting plate will unscrew! The metal used for the grubs is too soft and it appears that some very aggressive thread locker was used.

Any help will be appreciated ~ thanks!

–Dave Johnston

I have the EVO 77, EVO 99 and the ASP 400. Don't need the choke to start in fact I removed them from the engines. I use a three line fuel tank so to start I open throttle fully, pinch one vent line closed and blow into the other until fuel comes out the carb. Reduce throttle to 1/3 turn on glow and hit with electric starter. Starts right away every time. Hope this helps.

Hi TS! I do the same thing kinda. I throttle the engine to full, blow into the vent tube to pressurize the tank, squeeze the tube so the pressured tank fills the carb while flipping the prop 3 or 4 times, let go of the vent tube, turn on the glow plugs and I hand start at idle. Works like a champ. I made a long convenient blow tube to do this operation that is easily removed. -Tom.

Evo 7-35 Choke & Starting
 

TS & Maxam

- Thanks for your good advice - I really appreciate it!

--DJ

DJ you are welcome. A lot of what I learned about these engines was on this forum. Most of which was contributed by Maxam. I did forget to mention in my startup procedures that just before I put the electric starter to the engine I pull several blades by hand in case there might be hydraulic lock. I always remove the bottom two glow plugs after the last run to help prevent that however.
Have fun,
Tom N.

Hello Tom -

Good idea - I’m just in the process of making cuts in the cowl & I will need to check on how and where to access those two bottom plugs...

–DJ

Hello
I have removed the rear cover to control the gap in the rear bearing.
What I see now there is a gap between the front cover and the sealing ring.
I'll take the engine more to see what I can do.
The bearing and seal ring are new, these are going to be fun.
Lars

Securing the Saito Carburetor
 

I have replaced the stock carburetor on my Evolution 7-35 with the new Saito 90 carb and I have purchased the appropriate adapter from CH Ignitions. The adapter uses the original Evo O-ring, and fits into the engine housing perfectly. The CH adapter includes a hole in the side for one of the two engine grub screw to lock it in place.

However, I do not know how to secure the new Saito carb after it is inserted into the adapter. The O-ring on the Saito carb is a good fit inside the CH adapter but the carb itself rotates around and can be pulled out fairly easily.

What recommendations does anyone have for locking down the Saito carb to the adapter?

–DJ

Are you sure you haven't overlooked something simple, like a grub screw in the wall of the adapter itself? Or that one of the grub screws holding the original carb should be replaced by a longer one, going through the hole in the adapter wall and holding the new carb?

-tih

Hello tih in Norway - thanks for responding!

Sadly, there are no apparent easy remedies as you suggest. I thought about using J.B. Weld to permanently bond the new carb to the adapter but before that I was hoping that someone who had installed the Saito carb on the 7-35 might offer what method they used.

–DJ

Are you really sure? I don't have that adapter myself, but I'm staring at your photograph, and at my 7-35, and it really looks like the adapter is made to be locked to the engine using one of the original grub screws, with the hole in it in front of the other one, so that when you insert the Saito carb, you can use a longer screw instead of that second grub screw, reaching through that hole to hold the carb. I'd sort of expect CH to include a suitable socket head screw for the purpose. Will the hole not line up properly?

-tih

Hello tih - thanks again for your help!

I maybe should have given you all of the ‘hurdles’ that I encountered when I mounted the carb & adapter to the engine. Other than the adapter, there was nothing else in the package from CH Ignitions.

Everything fit fine as I slipped on the O-rings and inserted the carb on the adapter and then tightened the two grubs screws on the engine. Then I stripped the top of the second grub screw trying to tighten it enough to keep things from slipping! Fortunately I was able to get it out.

I think the problem was twofold; the grub screws are probably not made using the best material, and I had been afraid to file a flat spot on the beautiful (but thin) aluminum CH adapter.

So, with your suggestion I will carefully file a flat spot on the adapter and then go to the hardware store (we have no hobby shop in our town) to get a socket head screw replacement for the grub with the stripped head. It looks like about a 4-40 size but it could be metric. Our local hardware store can size it for me. Once again, I thank you for your assistance!

–DJ
Roseburg, Oregon

I screwed the adapter with 2 M3 hexagonal screws.
As I slipped down for fitting into the engine.
Lars

Hello Lars!

Thanks for your info: I just returned from the hardware store where I purchased some socket head screws of the correct size.

I have now installed the adapter and carburetor on the engine and they are both locked down like they are supposed to be ~ thanks!

–DJ

I've never heard the term "grub screw", but I looked it up and it is a known synonym for "set screw". Never too late to learn I guess. Just curious if the guy at the hardware store knew what you were asking. :)

I installed the saito 120R3 carb on my 7-35 with Adrian adaptor and it went perfectly, secured and does not move. It had two screws one is a grub screw if I remember correctly.

EVO 735 Newbie
 

I finally pulled the trigger on an EVO-735 this year.
My buddy and I bought two, and we're doing up a pair of "Canada 150" GP 120 size Super Stearmans, and we're going to try aerobatics together.

I have read this entire thread and believe that I've absorbed some of it!
Anyhow, I'm ready to start the break in and just wanted to call out for any last minute pointers or advice.

So Far I've:
1- Removed glow plugs
2- Added after run oil to the new engine, and lubed the valve train;
3- Turned engine over to distribute oil and loosen up;
4- Mounted engine on Test Stand;
5- Used All Large fuel lines and Filter;
6- Spun with electric starter to clear out excess oil (plugs still removed);
7- Checked valve lash as per Maxam's write up;
8- Installed short piece of black heat shrink on push rod ends, and shrank with 1/16" overhang, to prevent rods from falling out;
9- Removed Choke assy. Will prime through blowing into vent line;
10- Installed an air filter on the carb. I have done this to other glow engines. Tends to limit top end by 100 RPM, but the carb draws fuel and transitions better. Maybe this has the same effect as Maxam's suggestion of running 1/2 to 3/4 carb opening to change the choke area?
11- Tapped inside of collector ring exhaust nipple, for 2-56, and plugged off with short 2-56 pan head screw; and
12- Fuel is 15% Cool Power with Castor (4oz) and Methanol (120 oz) added.
Break in Mixture is:
1.6% Castor (Sig);
8.6% Synthetic;
7.6% Nitro; and
82.2% Methanol.
13- Break in prop is 17x8 Xoar
14- Re-install Glow Plugs!!

There was a previous post on easily delivering after run oil to the engine's innards. I do like the idea of a vent tube, aka a traditional blow by lubed 4 stroke. But I don't like the idea (warranty) of tapping holes in the serial numbered back plate of my new 735.
Turns out that the seven 3mm x 8mm back plate bolts are not into blind holes; yes they are drilled clear through to the crankcase!
So here's what I'm planning:
a- Remove the back plate screws behind Clyinders 1 & 4;
b- Replace the back plate screws behind Clyinders 1 & 4 with 3mm x 8mm pressure nipples; and
c- Bring a line from each nipple and connect them together outside the cowl.

Now you can pump fogging oil in the bottom until it flows out the top and leave the lines disconnected during storage.
If the plane is stored on it's wheels, the bottom nipple will allow the crankcase to drain and, you could do the aquarium pump thing via the top nipple.

Thanks Maxam and all contributors for a fantastic resource.
I wouldn't have made the leap without knowing that your thread is here to support us newbies.

L8R,
Mark

Hi Mark, Tom here. The only concern here is heat shrink on the pushrods. The valve springs are weak on this engine and I firmly believe the resistance of the heat shrink will affect the operation. I have never lost a pushrod in 8 or 9 years of operating these engines.

Thanks for the feedback Tom!

I kept the heat shrink overhang short enough that the heat shrink doesn't actually touch the Cam Follower Pins or Rocker Grub (adjustment) Screws.
But I will remove the heat shrink to be on the safe side.

Thanks again,
Mark

EVO 7-35 Glow Plug Harness
 

I remember reading here that someone couldn't get the plug caps to lock on.

I had the same problem with my new 7-35 Glow Plug Harness

I tried an OS plug and the caps work fine. The OS plug measured 0.165" along the stem. The stem on the OEM plug is 0.250" long.
This means that the inner black sliding insulator is bottoming out before the outer sleeve can reach past the bottom of the plug.
It's like the harness was made to match OS plugs.

I chucked each of the OEM plugs in my cordless drill and touched the stem to the bench grinder a few times with the drill running. I didn't allow the stems to get too hot by dipping them in water a couple of times during the process.

I used the same technique with my Dremel to clean up the sharp edges.

All the caps go on fine now. A little tight, but doable by hand (without tools).

I would not recommend cutting the stems down with pliers.
I believe that the shock could damage the insulator.

L8R,
Mark

Hello
I have looked at the UMS website that they updated all methanol engines.
And they come with a range of petrol engines as well.
so UMS will remain for a long time I think
Lars
Radial Engine 7-35