jfstrama

After getting several requests, here are the instructions for changing the choke on an Evolution 26cc from the spring return type to a friction type. (I hoped to have pics too, but that didn't happen!)

First, these instructions are for the stock WT-613 carb (the one with the black plastic spring return choke arm), if yours is different your steps maybe different.

Tools needed: Small Screwdriver and Oil.

Step one.

Go to any Walbro (even your local small engine service shop) parts dealer (I used http://www.outdoordistributors.com/ this doesn't mean I endorse them, they were kinda slow to get the parts to me) and order the following:

1ea 40-922-1 Choke Arm Shaft ($3.82)
1ea 89-13-8 Steel Detent Ball .125DIA. ($0.41)
1ea 98-162-7 Detent Friction Spring ($0.49)
and if your smart you'll get an extra choke plate screw because you are bound to drop it someplace and not find it again!
96-475-7 Screw - valve ($0.41)

Step two.

With your parts in hand.
Release the spring tension on the black plastic part by slipping a small pick or screwdriver under the spring and unhook it from the plastic.

Step three.

Close the choke (so you won't drop the choke plate screw into the engine!) and unscrew the screw in the center of the choke plate.

Step four.

While holding the choke plate in place to keep the screw from falling in the venturi, remove the screw completely and then the choke plate (save these you'll need them in the re-assembly step).

Step five.

Unscrew the choke lever screw that is threaded into the end of the choke arm shaft and remove the screw completely.

Step six.

Slide the choke arm completely out of the carb (this may be difficult depending upon which muffler you have on the engine).

Step seven.

You should now see the small hole running down into the carb on the side that had the screw holding the choke arm on. Drop the small spring into the hole.

Step eight.

Drop the steel ball onto the spring and follow that with a few drops of oil for lubrication.

Step nine.

Slide the new choke shaft arm into the hole from the same side that you removed the old one until the pointed tip is just touching the detent ball. If necessary, use the tip of the screwdriver to gently depress the ball until you can slide the shaft all the way in and feel it lock in the ring cut in the end (the ponted end should just come out of the hole on the end.

Step ten.

Replace the choke plate with the choke plate screw (once again without dropping it into the carb) and tighten it most of the way. Open and close the choke until the plate operates freely and covers venturi completely. Then tighten the screw. (A little locktite on the screw never hurts).

Step eleven.

Go and fly.

The entire operation took me less than 5 minutes.
Hope this helps!

MadDog Joe

the Wasp

My Feedback: (1)

myself I have no idea why anyone would want to mess with it, I love the auto choke release on my MVVS,, one finger sets the choke closed, flip till it pops, blip the throttle stick to open the choke and then 2 more flips to start her,,, simple !!

Jim

jfstrama

The_Wasp - Please read the post thoroughly before you comment, I never said anything about the auto release choke!

This particular variant was not the auto release choke as you have, just a spring return that either required a servo (with a very difficult arrangement to connect it with a muffler in the way) or strange screw attachments and other hokey setups to try and emulate the auto release choke. So for those of us that have the spring return arrangement this engine was a real bear to get started properly, and the Evolution instructions "assumed" you would just give up and use a large electric starter. Not really an optimum solution. For myself (and several others stuck with this particular variety of carb) this is a low cost solution to avoid purchasing a $60+ carb to correct something on an already overpriced engine.

This is the only thing that stopped me from dumping this engine. If you have the newer auto release choke I'm sure you like starting your engine, I (having the WT-613 carb as stated in the instructions) was just getting angry and frustrated. Since all the other gasoline engines I have took a few flips with the choke on, pop, a few flips with it off and I was enjoying a start to my flying day, I decided to modify this carb to match.

pe reivers

Are you not exagerating your problem and talking down your ability to solve it? If you want to be in the model flight hobby, some problem solving is required. This is not a plug and play world. There are too many things that need a wee bit of basic knowledge before you get as far as even flipping that prop for the first time.

rmh

Hold on - In the USA, some expect plug n play on everything.
Some retail stores will accept ANY return item with no questions asked.
The Walbro chokes are almost always sent out with no arm /linkage which would allow a simple hookup.
DA engines does provide arms for their engines and RCShowcase sends retrofit arms
So far, everyone else leaves it up to the buyer and many setups do not allow good geometry or mechanical advantage
Here are a couple of pics I did for an article .

jfstrama

pe_reivers,

I was not exagerating the problem, I was stating an opinion. I plain old didn't like this engine / carb combination, I found it frustrating (on the edge of infurating) in having to come up with a solution to a problem that should not have existed (there are plenty of other walbro carbs that could have been on this engine and if Evolution / MVVS found it to be such a great combination, why did they change it to the Auto-Choke release type ANYWAY?).

If I had known that the auto release choke was on the horizon, I would have waited, I didn't so I bought the engine. I didn't feel that the spring return would turn out to be such a hassle, for me (and apparently the dozens of people that have emailed me asking what I did to change it since mentioning it in another forum, I'm not the only one) it turned out to be nothing but trouble.

I did apply problem solving (and my wee bit of knowledge as an engineer that designs electronic ignitions for gas UAV engines / 2.4 Ghz radio control links / brushless speed controls, etc. for the hobby industry), I searched the database of 11.11mm Walbro carbs until I found a part combination that solved it (no small task if you look at the number of them to search through).

Frankly, I find your tone a bit condesending and yes, when I buy an engine that costs $100 more than a comparable 26cc from other manufacturer's, I do expect it to be plug and play.

If you look at my original post, I wasn't bashing the product, I suggested a change that many people have found useful. The only responses I've got have questioned my intellect for wanting to make the change, or my abilities as a modeler suggesting I don't even have a wee bit of knowledge of how to use an engine.

If this is the quality of the posts here, I'll take my knowledge elsewhere!

jfstrama

Dick,

I hadn't seen your post, before making my last one.

I did see your examples before and appreciate them, they just didn't work in my application, so I went to the standard choke arrangement found on many of the other manufacturer's engines. I didn't think my original post bordered on heresy, but from the emails and posts here you'd think I said the engines stunk. That couldn't be farther from the truth.

Now that the choke has been solved (to my liking, it doesn't have to be anybody elses), It is one of my favorite engines.

Joe

pe reivers

I know that Dick, and there have been ample posts explaining how "hard" it is to hook up a walbro carb. MVVS/evolution just require a straight (maybe slightly bent) connection, like the ones shown in your pictures. The side mounting flange even presents itself to fit an extra support stay for the pushrod. Please excuse me if I cannot see a hookup like this as a problem. I would not like to see the planes that such people fly, if they fly at all!

Before you get a plane aloft, there are too many things that need to be done right. This has nothing to do with the shops. Most are just selling without asking questions. After all, an ignorance induced crash or accident is not their problem is it? I may be cynical at times, but I do believe that a pilot should have the expertise to maintain his plane, or have a mechanic who knows what it is all about. This is not culture, country or person specific. It is just plain sense that needs to be followed if we are to have this hobby and live to tell about it.
I know you agree with me. This rant is not directed at you.

pe reivers

I still do not see your problem. You solved it didn't you?
A manufacturer will never be able to supply an engine that will fit all applications that we think of. The MVVS/evolution front carb engines are as easy as glow engines in their setup. These are not suited for all installations either.
A step by step guide with pictures would have served better here, since reading is harder than looking at pictures. It took me longer to read your manual, than to set up a throttle or choke control. I do suppose you posted this for others to learn something?

jfstrama

PE,

I have no problem with Walbro carbs, as to a "slightly bent" connection, perhaps you would show one that will get around the black muffler pictured in Dick's post? Now I'm somebody who would cause an ignorance induced crash? I don't have the expertise to maintain a plane?

You don't know me and from your tone I would prefer to keep it that way!

Joe

jfstrama

I didn't think to take pictures of the change at the time, YES I SOLVED MY PROBLEM, I WASN'T ASKING FOR DETAILS OF HOW TO HOOK UP THE CHOKE FROM THE MANUFACTURER!

All I wanted was a standard choke that 99% of the other engine manufaturers use (in example my DA, my Brillelli, my Fuji, my 3W, my Echo conversion) when I mentioned that I made the change elsewhere I got a flurry of emails asking what parts and how!

So I gave the info, sorry it wasn't to your liking, I wasn't writing it for you, obviously you are an expert at creating "slightly bent" connections and ignorant people like myself shouldn't bother posting here.

pe reivers

Is there a need to get personal? Did I call you names?
Since I do not know you, I may, or may not like you. That has nothing to do with the subject

I still think that your approach to the problem, as being the manufacturers fault that you cannot fit any muffler type and still have a plug and play engine. is wrong.
You solved it, and called it a hassle, yet it took you only 5 minutes to do.

GBR2

My Feedback: (1)

I don't get what all the hassle is about. I also found the spring return choke not easy to hookup or operate, so I modified it in a similar manner to the method described in the first post. Certainly makes things simpler. The orginial poster was merely providing the information on how to do this for those that think it is a better arrangement than what MVVS chose to use in the first place.

rhd-RCU

My Feedback: (36)

ditto

davebart

I have to agree with GBR2 and rhd-RCU. I have been trying to figure a solution to the choke for some time. It has really held up finishing this airplane. I think I am going to set up a servo and leave the return spring off.

davebart

Dick Hanson,

Can you provide a link to that article?

Thanks, Dave

fujiman

My Feedback: (133)

anyone know the o.d. of the walbro adapter stem that fits into case bore?

GeorgeAgs

For me it's very interesting this thread, because you don't know how many times I was searching for information.

Now I have an auto release choke and my question is.

Can you just close the choke without force the throttle servo because the throttle arm moves a little when the choke is closed?

Thanks in advance

Jorge M.

jtsails

My Feedback: (2)

I have to agree with the original poster. The early choke were a PIA, the least convenient I have encountered. Yes, it is solveable, but at the price of this motor it would have been nice if horizon/mvvs had come up with a better arrangement from the start.
JT

THYKKO

I have one MVVS 26 and one Evolution 26. One in a Ultimate 120 and one in a GS 600 (Lap-Map ) . Both planes are left in a corner of my house, because of the CHOKE that is a great incovenient once in the field. I have read on old article in another forum , wrote by Mr. PE Reiver, explaining how to do a simililar work as the one described by jfstrama, using a pen spring , a steel ball from old ball bearing, and doing a small depression in the original choke shaft to hold the ball.The main difficulty is how to find and mark the right position of the depression in the shaft. If Mr. PE Reiver spent his time to explain this whole thing , obviously he knows how bad is the the original choke system. I would like to say "thank you very much " to fjstrama for his explanation. Probably I will not be able to find and buy the cheap parts here in Brazil, and this really makes me very sad, because the engines are good.The problem IS THE CHOKE.

davebart

THYKKO,

If you cannot find the parts or cannot get Outdoor Products to send them to you in Brazil, I will. It may take some time and I am not sure of the shipping costs, but we can work out the details. If you would like to pursue this, email me. I have made the modification that jfstrama describes and it works great.

Dave

y2k6vette

jfstrama,

Right on, Man! Both of my MVVS26cc engines have this stupid spring return choke system and I was disappointed from the very gitgo! Eventually, I had to remove the spring connector and operate the chokes with a servo.....problem solved I suppose, but the problem never should have existed in the first place!

Thanks for your post of a quick fix.....I'll be doing it soon for both my engines. Just wish I had read your post earlier before I went the other (servo) route.

Just a note: when we criticize another RCU member for suggesting a solution to a problem, we are all abused! jfstrama has my support and gratitude for offering this solution; and if others don't appreciate it....well, you know where the sun don't shine!

Steve

Antique

My Feedback: (4)

A lotta words for something that has a simple solution...Spray a little WD40 in the venturi with the choke open...You might have to to do it twice...Or drill a little teeny hole in the cowl for the plactic tube on the can...

THYKKO

Mr. Dave;
Thank you very much, IĀ“ve sent you an e-mail about your fine offer. It was not possible to buy the parts from Outdoor Products because the storeĀ“s site only offers crazy shipping costs to Brazil. More than US$ 200,00 for those very light parts.Something must be wrong in the site. IĀ“ll be very happy if we can find a way so that you could send me the parts. That was a very generous offer from you, and I`m really grateful. My e-mail is [email protected], please send me your e-mail .
Sincerelly;
Fausto

davebart

I now have 3 sets of the parts necessary to upgrade your choke on this engine. Just send me a PM or email and I will communicate re: price and shipping. (Both very reasonable.) ... Dave