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TOPIC: carb settings on 257 walbro

carb settings on 257 walbro 5 years 6 months ago #4366

hi guys i cant seem to get my 257wt walbo carb to stay tuned or set it right .
was running verry lean if set on factory settings. L=2 H=1, tryed difrent settings still verry lean. runs at half throtal sam as full. then if held on full takes long time to get up on the pipe tryed lots of settings but it seems to de tune its self .
motor is a new 26 zenouh with a full mod jug and pisten boster ports etc, , will run fast full revs at end of straite after some times if it dosentit just runns like half to 3/4 then will burst to full till i back of for corner then dose same again
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Re:carb settings on 257 walbro 5 years 6 months ago #4367

  • marc
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It should run with those settings (2L - 1H) You can go a little richer on high to start out if you want to be on the safe side. You should check for air leaks at carb manifold, fuel lines, cylinder base. If all else fails try a stock carb to rule out the carburetor. Did this engine ever run ok in the past or is it new?
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Re:carb settings on 257 walbro 5 years 6 months ago #4368

hi marc ,motor was brand new stock .then got mod jug and pisten put on it . so its still running in its clocked up 1,1/2 hour running time and used 5 tanks. running at about 18to 1 fuel/oil ratio..
was thinking would fuel hose lenth cause this also.or to rich oil mix. im now also going to try diffrent prop. it was running a 7015-2 propshop going to try a 6717-3,

wen it did get on the pipe for a cupple half runns it realy opended up. tiny tac reading if 17580 at some stage.

but now tiny tac is stuck on 19999 and cant seem to re set it at all. but you can see and hear motor it not skreeming as it should or dose when it opens up.

will look into those other things also. may try difrent carbs i have a 318wt also a walbro terminator,pumper carb i think thats what its called .
also ive just moved the pipe back one inch to 12,1/2 inch to see if that helps.
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Re:carb settings on 257 walbro 5 years 6 months ago #4369

  • lohring
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I assume you are running near sea level. You can try up to 2 1/2 turns open on the low needle. Be sure to check the carb diaphragms, especially the pressure regulator diaphragm. Replace it if it is a little wrinkled. While you're doing that, be sure the fuel filter screen isn't dirty.

Your pipe and prop need to be changed for a modified engine. I run closer to 12 inches from the face of the cylinder along the pipe to the high point on that style of pipe. A 70 mm prop won't let the engine rev enough. I've run props as small as a 6717 cut down to 61 millimeters.

Good luck

Lohring Miller
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Re:carb settings on 257 walbro 5 years 6 months ago #4371

  • marc
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I agree with what Lohring has suggested also...since you've gone from stock to modified, some things will change, such as prop selection and pipe settings. Strut depth probably also.

You can refer to this article by Carlo C. for carb needle settings for the popular carbs: http://www.modelgasboats.com/Magazine_Content/Tech_Articles/Starting_Your_Engines.html

If you are trying the 813, it will tune similar to the 644.

Keep us posted.
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Re:carb settings on 257 walbro 5 years 6 months ago #4374

HI guys , well when i ran it i had pipe set at 11,1/2 have moved it to 12,1/2 . gess ill try it at 12.

also the props 7015 7016 were what boaters segested me to use on my mod. ive just been given a 6717- 3blade to try . is this 6717 prop better to try in 2 blade or 3 blade . or what other props could you sujest for me to try out . also is it better to have the strut higher or lower . what hight dose what . as some say high is faster some say low is faster. i did try diffrent stut hights but dident make to much dif in speed but when up hihger it did make boat a bit looser with the 7015-2, prop on the boat .

sorry for adding so menny pics of boat but i like it lots..haha when it gets up to good speed it realy flys and flat out into the wind no probs dosent lift or trys to flip at all . i know races probly dont clase this boat but im finding it a great ride . just want to get this full mod motor dialed in:woohoo: .....

ive also added a pic of my mates boats and mine at owe lake we run at . its great a lake one min drive from my home and me and 2 of my mates are the only guys ever down there using it .its just the right size for boats of this size not to smale and not to big with sand beach all the way around it ..
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Last Edit: 5 years 6 months ago by seahawkwa.
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Re:carb settings on 257 walbro 5 years 6 months ago #4375

more pics
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best carb to use 5 years 6 months ago #4405

can ennyone tell me what carby is the better carb. i have 3 difrent carbs all new just trying to see what carb would be better to use .

i have all walbro carbs.. tw 257 stock no mod , wt318 stock no mod , and a walbro pumper carb i think some people call it a terminator or pumper carb has choke removed . i was told this carb realy pumps fuel in . not shore on it at all.

all carbs are new . just trying to find out what people think is the best one to stick with to tune in this motor of mine . motor is 26 zeno, full mod jug intake exaust , ports eye browed etc etc... piston lightened to 22g about flat top piston, releved ring shaved piston wall, 2 boster ports,

idd like just to know what people think is the best carb to set boat up with .
ive had boat running ok on the 257 . and better now the carb had the dirt removed from the mesh filters..but somone sead that the motor might runn leen at full revs with that carb because of the mods that have been done..
i take on all info good or bad on enny of those carbs. :silly:
Last Edit: 5 years 6 months ago by seahawkwa. Reason: moved to new thread
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Re:carb settings on 257 walbro 5 years 6 months ago #4408

  • marc
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Any good mod Zenoah should run great with a good 257 properly adjusted. It is by far the most popular carburetor for gas boats.

What number is your pumper carb? Also are you certain about the WT-318 number? Are you sure it's not WT-813? The 813 is a pumper carb sold with the Zenoah performance kit. It is also a good carb. You can read about it in this article Scott did.

http://www.modelgasboats.com/Magazine_Content/Product_Reviews/Zenoah_Racing_Kit.html
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Re:carb settings on 257 walbro 5 years 6 months ago #4411

hi marc , mate you are right i did get the numbers rong its a 813 ;) ,
then numbers on that other carb i got told was a pumper carb .

L7
WT285. is this a good carb. when thay say a pumper carb is that just because its got a acelorator pump in it . or is that diffrent again. to the 813.....

thanks for all your help .
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