Zenoah carb specifics

[bigrcr]

With the current problems with the supplied WT-677 carb that is now coming with the G-26 and G-231's, many pilots have been wondering about the carbs that can be used and the differences. I have been getting daily calls about the Walbro carbs and issues with them. I have been talking with Bill Meader and Chris Bergen a good bit lately on this subject as the 677 has really turned into a real bear to work with.

The following is a start on some information on these carbs that should help out.

The WT-643 is not an aftermarket carb as many have asked about. Until recently the 643 carb was the stock unit on the G-231 since it's inception and many of the G-26's. The G-231/G26 both are being shipped currently with the WT-677 unit.
The WT-167 was the older G-23 carb that transitioned poorly and needed a real lean oil ratio mix to get to work. Bill Meader was the leading man in making these things work and finding a suitable carb and/or solution to making these things work. Some of these were made to work though.

The WT-603 was an upgrade for the WT-167 carb and really started to make the gas motor perform. It is also a good secondary choice to the WT-643 carb as a replacement for the WT-677.

The WT-644 and WT-645 are the same basic carb as the WT-643 except the 644 has a choke in the body and a primer bulb. The WT-645 has no primer bulb and a choke and was original equipment on the G-26 airplane version. The WT-643 has no choke.

The WT-677, well, has many problems and really seems to NOT be a good carb to use at all. The transition point on this carb is terrible and the carb is designed to be a "enviro-friendly" unit. In simpler terms this means that the EPA and other powers to be have started to put mandates on the commercial/industrial power equipment to lessen or get rid of the pollutants that they create. This carb follows those guidelines. In order for the motors to meet tighter emission standards they have to run hotter than ever before (this in most cases means leaner :cry: , not good for us). The oils used in these two cycles are going to have to do a much better job lubricating and keeping these motors cool and the formulation has to be one that the oil does not burn and/or crystallize in the motor or on the plug, fouling it.

I have heard from a very reliable source 8) :wink: that Zenoah/Walbro are realizing that the 677 carb is not going to cut it for helicopter use and the next production run of the G-231 (don't know about the G-26) to be made and shipped will once again come with the WT-643 unit. Let's hope this happens!

Some of the WT-677 carb seem to work well for some people. This so far has yet to be explained. So if yours is running good, leave it alone!

Sorry to be long winded! Bill, Chris, Carey feel free to step in and correct any errors on my part in the descriptions.

Hope this helps!

[Billme]

Sounds ok to me john, but on the 677...I would not idle a engine with this carb...:)
I currently have the g26H running smooth with a 603 BTW...I'm going to test the 643 on it this week...
As always,
Good job
Bill

[cbergen]

Very Good info, John.

I have been flying one of our Observers this week quite heavily with the G26 and 677 Carb. The biggest difficulty as mentioned has been the transition between low and high needles.

While I have been able to get it to work, it is being finicky.

The good news is of course, that zenoah and Walbro are aware of the problem and are beginning to take steps to work with us on it. Thanks to Bill!!

[bigrcr]

Chris, FWIW, I spoke with Walbro the other day and also expressed my displeasure with the WT-677 and found a few things new to me. Walbro still makes and will continue to make the WT-643,4,5 carbs. They are available through the Walbro distribution centers ( I have the telephone numbers for them). The selection of carbs used on the Zenoah motors is up to Zenoah to decide upon. I also got confirmation that the 677 is in fact an environmental friendly carb and that it may be better suited to a weedy wacky motor. The carb will make the motor run hotter as that is the exact intention of it's design on the emissions standpoint.

So it seems that all of the pressure needs to be diverted to Komatsu/Zenoah to get the WT-643 carbs put back on the motors (not just for the next run of production).

Carey Shurley says that he is having an issue with the needles being too "broad" between rich and lean also.

Later,BIGRCR- John Garst

Miniature Aircraft field rep.
Magnum Fuel rep.
Amsoil Dealer.

[Billme]

Thanks Chris
There is still much to do, but I'm working on it...Horizon has steped up to the plate, and is sending me what I need to do the job.... The more I fly the engine, the better I like it...It has great potential...Right now, I'm just getting time on it to see what else she wants to say...
Best Regards,
Bill Meador
Century Helicopters

[Billme]

Well, if you look at the fuel tank while you run this carb, even in a rich needle setting, I saw nothing but foam, which indicate to me pre-deton due to a lean conditon..What fuel is there, does not atomize correctly..
Believe me, this is not good for a split crank, with a heavy flywheel on the end:)

Regards,
Bill

[Ltcol13gene]

Thanks John, I think that was the problem I was having, I just got the 643 carb yesteday and will try it this weekend, I had the 677 on it and it would only perform in different temps, Lee and I worked on it all day to get it running right, without success, thanks again for the post.

LtCol Gene B Healey, USMC

[carey shurley]

The original operators guide for the Spectra, included needle settings for the WT677 and WT643. In the last revision, I changed it to simply recommend not using the WT677. It is more trouble than its worth.

A few folks have indicated their willingness to get to the bottom of the problem and insist on using them. In my opinion, this is not a good use of time. As John indicated, the 643 works well and can be acquired from several sources for not very much money so why bother. If you have a 677 and you're model is misbehaving, spend the $40 to get a 643/644 and spend your time flying instead.

[Flying Tivo]

John and Bill:

In my quest to find a similar rotary type carburator, a walbro representative gave the closest fit to the 603 but in Rotary type WYK-33. Its very difficult for me to try and test this. If anyone is willing to try this is the best bet. This carb has high and low adjustable needles.


Felipe

[bigrcr]

I am always interested in new stuff for the gas models!

[UpstateRotor]

I am always interested in new stuff for the gas models!

John,
Have you done any testing with the wt-257? If not, and you're interested, start at 2 out on the low and 1 out on the high and tune in from there. I had my needles set on 3 TRM marine 260s at 1 7/8low and 7/8high at 1000MSL and they ran very well. I'm not sure if the "gain" provided by this carb in a boat translates to a heli motor but it's worth a try. :mrgreen: I'm planning on trying one on a TRM 231 in the near future.

Shawn

[bigrcr]

As we speak! :wink:

The 257 works well on the G-231.
Working with a modded 257 is in the works!!

Later,

[WillJames]

Whats your username on JRCBD Shawn? Not many heli guys know anything about a 257! :shock:

[UpstateRotor]

Baja-
Name is the same as here, although I don't frequent "the dock" nearly as much as I used to. I sold all my boat stuff to try my hand at the heli thing. A small amount of knowledge I got from running the PUM Zenoahs has transfered over to the gasser helis, I just need to get my flying up to speed. :wink: Another carb to try if you prefer the primer bulb is the wt488. It is basically a 257 w/ a primer bulb.


John-
What mods are you testing? Opening the throat and counter-sinking the mounting bolts or is there more to it? I'm hoping that a successful use of the 257 will result in more power, specifically out of the modded engines and a slightly simplified fuel system setup...one less line without the primer bulb. Right now I'm still breaking in a stock 231 w/ 643 but I've got a TRM231 sitting here ready to go. I think I'm going to "play" with a modded 257 (probably CC Racing) on my stock motor before mounting up the TRM. Let me know what ya find out.
Shawn

[WillJames]

I have not been back to the dock in a couple of years, but I used to be a major junkie and I was a moderator there long ago.... I only have one boat left myself, as helis consume your life man.

Funny thing gasser helis, the heli guys have not figured out the difference between Hanson and Toxic motors yet on the heli side. :DOH I bet you know the difference.

Glad to see you over here.

[cbergen]

I'm not sure anyone has explained the difference! You know these gassers guys can be hardheaded sometimes....... :glasses2:

By the way, I converted mine back over to the EB (again), so I'll be doing a side by side comparison between the EB with top secret TRM 26, and Turbine with 54mm wheel!

Are you up for the vids, Will??

[WillJames]

Oh HELL YEA Chris!! I would DEFINITELY be interested!! :smokin:

What is your impression of the TRM 26 now that you got some serious time on it? I'm sure John would be very interested to hear to, you know he has a stage 2 TRM 26 prototype, yours is the very first one done. :)

You ROCK Chris, can't wait to see. :shock:

Wish I loved closer to shoot it.

[UpstateRotor]

Speaking of closer, how close are you to Hickory, NC? I get down there every once in a while. I might just have to stop in for some lessons. :shock: :mrgreen: :glasses:

Shawn

PS IMHO

Hanson :badair:
Toxic :smokin:

[WillJames]

I am 1.5 hours from Hickory. You are very welcome to come fly with us once it warms up a little and we are flying again. I fly with Hammer, Shannon Davis and Lamebird a good bit and we really enjoy others joinig us any time.
We all fly at Black Sheep field a lot to.

Hope to see you soon.

[bigrcr]

Down and Locked,

Right as of yet, I cannot disclose what is being done with the 257 carb. Al has a couple of tricks up his sleeve and one particular mod that no-one that we know of has yet done (his own special mod- if you will). One note on a stock 257 (or slightly modded). This carb has a bit more sensitive needling and may not be a good application for those who are not as familiar with tuning a Zenoah properly yet.

Later,

[cbergen]

Will, you saw it at B'ham this spring where I thoroughly enjoyed scaring small children and Utah State Troopers with it :glasses: , as seen in the video you made there. http://www.augustoheli.com/videostuff/videoarchive/HelifreakArchive/C/CBIntrepidGasTRM26-1.wmv

Now we'll see what happens with 800 blades and some "optimized" control system setup. If the dang snow would quit flying so I can get more than 5 minutes of flight at one time to finish some testing...........

[mickmurphy]

Gday john i am new to the gasser seen i have a 677 on my 231 motor the over week i was hovering and i noticed that the primer bubble started to empty out a mate that i fly with said that there is filters in the carby and that you have to take them out is that true. I have ran about a gallon of fuel my fuel ratio is 25/1. And i am gust wondering if thay no there if a problem with the 677 carby Y don,t thay offer to replace it with the 643 :cool:

thanks mick

p.s the boys in Australia liked the build video u done on the Spectra-g

[bigrcr]

Whatever you do, do not remove the "filter" screen in the carb!! This little "filter" protects the internal passages and seats from getting foreign material in them. If this screen has been clogged, it can be carefully removed with a pin or small instrument and cleaned. Be very carefull when removing and re-installing that you do not damage the screen and make sure that it gets re-seated into it's well.

The 677 carb is nearly a worthless carb for our purposes. It is an enviro-carb that is designed to make the motor run leaner (hotter) so that more of the hydrocarbons are burned so that the end result is less emissions. Zenoah WAS replacing this incorrectly supplied carb with one of the 64* series carbs.

I know of only one person that has had success with the 677 carb and I am not quite sure for how long. As a general statement, if you use the 677 carb, you are taking a very big risk in ruining your motor.

Later,

[cbergen]

Actually Horizon was doing the replacing, maybe with Zenoah's OK. Contact your distributor in Oz to see if they can help you out.

[mickmurphy]

thanks john and chris for your replies i have gust got a 643 and a 644 the over day i will put the 643 on rite now and i will contact the people how sells them over here i have lost 1 motor i do not want to make it 2 not at $498AU a motor


thank mick :cool: