Trying to match a Walbro carb to my converted Ryobi motor. Was told to keep venturi size to between 9-11mm.
My problem is I can't find venturi specs on any of the Walbro carb sites. All I find is part numbers.
I have tried "Googling" specific carb models with no results.
Can some one point in the right direction please.

Check here for a list of Zama and Walbro in the 11mm venture range: http://www.rcuniverse.com/forum/Walb...2371019/tm.htm

Check this site for carb info by number that shows in the parts breakdown the venturi size: http://wem.walbro.com/walbro/product...m=WT%2D628%2D1

Good luck,

Richard

if you have a pile of carburetors, grab a caliper and go measure the venturi, they made them in divisions of 1/64" so they aren't too hard to tell apart.

The is a number inside the venturi on Walbro carbs. The number is in 64ths, so a 24 would be 24/64 or 3/8 inch. Convert to metric for mm.

Regards, Richard

The Ryobi comes with a "20".

They run a lot better with a "24"

And run even a little better than that with a "28"

Also check the walbro site. They list all their carbs and the specs. IT is tedious to search through.

This may help, here is the list of Wt carbs with accelorator pumps, and hi and low needles and no primers. I compiled this from other's work and take no credit. It at least tell you the venturi size on the most desireable carbs. I am sure there are more.

6.5 mm with fuel pump return spring (4 stroke)
WT 366-1
WT 456-1

7.95mm
WT 37-1
WT 424-1

9.53mm

WT 35-1
WT 38-1
WT 204-1
WT 357-1
WT 367-1
WT 381-1
WT 385-1
WT 417-1
WT 449-1
WT 450-1

11.11 mm
WT 29-1
WT 356-1
WT 358-1
WT 464-1
WT 516-1
WT 517-1
WT 527-1
WT 613-1

12.7 mm
Wt 513-1
Wt 537-1

13.49mm
Wt 171-1
Wt 172-1
Wt 228-1
Wt 285-1
WT 529-1
Wt 451-1
Wt 480-1
Wt 540-1
Wt 542-1
Wt 555-1
Wt 610-1

I went with the Wt-247-1. Got it running but wasn't able to spend alot of time with it tonight. Too late.
I think the fuel pump is weak. Had to prime it a couple of times to get it running.
Can someone give me an initial needle adjustment for the high and low needles.
Carb is real clean but I don't think it's been run in awhile. Tabs in fuel pump diaphragm are pretty stiff.
Needle tips look okay. One was shiny on the tip. Idled okay but wouldn't rev up. I'm swinging a 16X6 prop.
Plan on spending time running motor,if I don't go flying. Good forecast,and very little wind!
I love these windless fall days here in Oregon.

Thanks for all your help,Dennis

starting settings are 1.5 turns out from stop on both needles.

where in Oregon are you? I'll be flying in McMinnville on saturday with my ultra stick lite with a Mac 32 on it...

I live in Eugene. Do you fly right next to the Spruce Goose?
I'll give the 11/2 turns a try.


Dennis

Check the black rubber diaphram under the stamped steel cover on the opposite side of the carb from the fuel pump. It must be very supple and flexible or the carb won't work right. If the fuel pump diaphram is stiff, the other (regulator) diapram probably is no good. You should put a rebuild kit in the carb.

AV8TOR

And use the tan teflon pump diaphram that should come in the kit. The blue one will also work, but the tan is preferred for ethanol "contaminated" gasoline. Regards, Richard.

no, I fly at the other field in Mac, too many trees by the museum.

Man, "contaminated" is a nice word for the gasoline we have these days....

Oh for the days when we had "real" gas and I could run 13:1 compression hot rod engines on the street!!

AV8TOR

Spent more time today and got engine running pretty good.Smells like it's running hot. took a non-contact temp gauge to cylinder fins. Running around 180-200 dergees.
At first motor would only pop occasional while starter was held to it. Wore my starter battery down and got the starter pretty warm.
Then,all the sudden it took off and starting running. Started easily ever since then.Must of dislodged something in the carb? Haven't kitted the carb yet.
According to Walbro you tune idle and then high end. Sorta different from glow 2-cycle. My temporary throttle was sloppy so I couldn't get a good idle. Have revamped it since then.
I'm using an older metal cased CH CDI unit for spark. I hear a tick noise coming from the box as spark fires. Is this normal. I also get a jolt while touching spark plug boot at times. Is this normal? Wish I had one of those metal boots. Boot is definitely pushed on all the way.
Is this leakage going to possibly produce interference in the radio system?
Well, making progress thanks to all your support.
You guys are the greatest!!

Thanks again,Dennis

The tick is NOT normal and will destroy the CDI. You should NOT get a shock. More knowledgable people can help you out to fix the problem, but I would not try to fly with this going on, interference can and likely will happen.

Good luck.

Sincerely, Richard

You can buy the metal boot from Valley View and install it on your plug wire

Thanks for the warning. I'm still only bench testing the motor.

Just got thru talking to Jody at Valley View. New metal boot is on the way.


Thanks

What RPM's you getting for idle and WOT. I've got a Ryobi that I converted last year. I haven't put it on anything yet. I ran it the other day. I hadn't run it since last year. I've got a WT-324 and S/S ignition. I get about 2100-2200 rpm at idle and about 7200-7300 WOT on a Zinger 18X6 prop. Fast transition is good but if I advance the throttle slow as soon as it comes off idle the motor will stammer and act like it will quit. Once I get past that all is fine. Have you had this happen with yours? I got the carb from Ebay so I may need to put a kit in it. I noticed that a gasket or whatever it is is a blue plastic material. I've never seen a Walbro carb with that. Maybe that's the problem. I would like to get it all tuned up so I can put it something like a Giant Big Stick. Next thing to do is make an aluminum muffler for it. I'm running the original muffler with some of the internal baffling removed and a 1/2" ID outlet. I probably make a muffler unless I can find an aluminum at a reasonable price. I don't really want to pay around $35 for ones I have seen.

Yours is doing what mine is doing

What carb. # are you using? Do you fly yours on a plane? If I was sure that it wouldn't quit, I wouldn't hesitate to put it on something. It sure does start easy. Even when hot, it will start in 2 or 3 flips and purr like a kitten. I hope I can get the little hitch out of it.

Right now I cannot remember the number as I did this engine in 1998

It runs solid and doesn't quit unless you turn it off.

I bench tested the engine again today at the local flying field. Thought I'd give the neighbors some slack.Motor started easier than last time,I just wasn't advancing the throttle enough. CDi worked fine but it does have a tick coming from the box itself. Was able to hold an idle around 2200-2500rpms. WOT was around 6500-7000 with 18X6 MAS prop. I was following Walbro's tuning directions. Set low end first and then high end.If I leaned out the high end it ran faster but starting smelling hot. 1 turn open on HS needle was really fast but no 4-cycling was present. I need to hook up a servo so I can better control over throttle.
Will keep at it. Hoping to install motor on Balsa USA 108" 1/4 scale.

Mine will not four cycle on the ground but it does a little on a down run in the air

I was told this was caused by less wind pressure on prop while engine is idling in the air than when on the ground.
Hope this makes sense,it did to me when someone explained to me.
I have another gasser "Homelite" that 4-cycle all the time at idle while flying.
The Homelite was already set up and installed on a plane,82" PT-19, when I got it.