irenaslavo

I think I don’t have luck with boats.. every time I try to improve my boat it get worth…. I bought new Zenoah 26cc, I install it and run it with no problem then I decided to make some modification then I changed the carburetor to 257, Installed clutch and Walbro water pump, change all cooling tubes , water pickups and new fuel take with screw cap instead to Sullivan Tank.

Today I give it a try, engine start after 3 pulls thanks to advise from stoddy and Paul M whom they direct me how to start engine in absence of primer bulb. But the engine lost power completely and what ever throttle I put the boat move 5 mph, I played a lot with carburetor needles but no way, I checked fuel tank and I closed the return fuel tube but no success also,

1- I made plus fitting exactly as Justaddwata post ( http://www.rcuniverse.com/forum/m_61...anchor/tm.htm# ) and I manage to do it perfectly.

2- I used Tygon tube ( length 16’) to connect pulse fitting to water pump.
3- The engine ideal very good.
4- Water mump and new water pickups working excellent because water came out outlets as fountain.
5- I played ignorance with carburetor needles because I don’t have factory setting. But I start with 1 ½ for H and 1 ¼ for L.

long time I read post about pulse fitting and carburetor setting also about ventilation of screw cap fuel tanks but I can’t remember where and I don’t know what happen… can anyone help me please? I’m really depressed

martno1fan

hi try 2 on the low 1 on high,heres a link to the settings for your carb,scroll down .
[link]http://bonzisports.com/carbs.html[/link]

irenaslavo

Thanks martno1fan for your replay but do you think 2 for L is not much, in the engine manual they mentioed 1 + or - 1/4

irenaslavo

I read the link, I think it was better to order WT 813 instead of WT 257

martno1fan

the 257 is a good carb its what most use in fact,try the settings it says on the website that should get you started and running .Also does your tank have a vent in the cap? make sure its not blocked.

irenaslavo

Thanks martno1fan , I will try this setting… for tank…yes my tank have vent and I will check it, also the tank have return tube but I close it... Shall I open it to make good ventilation

irenaslavo

I read that water pump should close to engine but I don’t know if 16” is long distance or good distance? Any advise ?

fun4ej

My Feedback: (1)

I think I've read that the water pump should be no more than 4" away from the motor...and use a tubing that is fairly stiff so that the vacuum pulse is not decreased from the tubing wall flexing.

stoddy

needle settings for 257 carb are 2turns on low needle and 1 turn on high should run ok on that setting.
also if the motor is revving and the boat is only doing 5mph move your strut or stinger up lifting the prop out of the water or try a different prop
had the same problem myself with my apache thought it was the clutch bought a new one still did the same.
changed the 3 blade prop for a 2 blade and of it went so i shouldjust have a look at those before you go buying carbs
the 257 is a good carb

irenaslavo

Thanks gentlemen, I tuned carburetor 2 turns for low and one turn for H... engine working perfectly but I didn’t try full throttle because I was worry since I read posts about carburetor starvation at high speed with water pump fittings in the carburetor. Shall I open L needle a bit to permit more fuel OR no problem.

Also I would like to know if there is big difference between stock Zenoah carburetor, WT 257 and WT 813 and why better to replace stock carburetor by 257 or 813

stoddy

no starvation at full throttle run same setup in my apache
give it some throttle and enjoy..

stuch

the 644 stock carb is bomb proof and has the same bore as the 257 and 813. only difference is a choke and primer bulb. i hate the 257 its a son of a gun to tune and hold a tune. i use a 644 on all my fully modded pum260's as well as my stock ones. i remove the choke and fill the holes with quick set JB WELD. its bacally a 257 thats easy to tune and hold a tune. i got 5 257's in a box want to buy them..LOL..

dicko

I heard the opposite of that, I've been told by a reliable modifier and read that the 257 holds a better tune than the 644 as the needles & o rings are better in it. from what I understand the 257 will perform for many years where the 644 will degrade over time as the o rings degrade. I have both, but am yet to run the 257, so far the 644 has held up fine, but I wouldn't say it has had much use yet. time will tell for me.

MrMikeG

257's are the easiest to tune, that is why everybody uses them. 644's suck, they last about one year then they are junk, they go out of tune and you can never get them back. For $25 brand new the 257 is the best improvement you can buy for your engine.
The settings are 2 on the low and 1 on the high, you might have to lean the high needle a little depending on your altitude but that is it. Remember both the high and low circuits are open at wide open throttle so basically your 3 turns out total, the same as your running 1.5 on both needles! Don't worry about being too lean on the top end, these engines produce the most power when the carb is set slightly rich.

irenaslavo

Thanks very much gentlemen …. In France they are selling stock Zenoah with 644 and replace carburetor after 3 weeks because I was thinking it will gives better performance accordingly I can’t judge about durability of 644… the problem I faced because I tuned 257 same as 644 but thanks to martno1fan and stoddy , I tuned 257 and engine working good.

I heard from French racers whom they are using top end racing engines and sometimes they practicing with stock Zenoah that WT 813 is better than 644 -257, it gives better acceleration and they are using them on stock and modified engines, also they are using champion RZ7C plugs and they never use NGK normal or Iridium spark plugs although I read many post recommended NGK.

I’m think to order WT 813 and give a try.

dicko

the 813 is the same as the 257, except with a bulb primer.

stuch

doesn't the 813 have an acllerator pump in it also???

stuch

257's suck i like the 644's so take that to the bank....

build4less

I second the 644 over the 257!!

webdr

257 all the way. 1 on the high 2 1/2 on the low. Report back and let us know how well it runs

dicko

yes it does.

irenaslavo

I’m a little confused, 1 on the high 2 1/2 on the low or 1 on the high 2 on the low, and I believe opinions regarding durability not performance… I replaced 644 with 257 because I through 257 gives better acceleration and now I’m thinking about 813 because I saw many racers using them and tune at 1 ½ Low and 1 1/4 high then how 257 and 813 are them?

dicko

have a look at this link Mart posted at the top of this thread.

http://bonzisports.com/carbs.html

it shows the differences between each of the carbys. at the bottom of the page it shows the baseline needle settings for each carb. the settings will change slightly as the engine runs in & also on alititude, air pressure & humidity.

BB Modss

@ 2550' above sea level we run 2 on the low and 7/8 after break in on the high. wt-257. Mopartybob has one of my thinned and modified 257's on his mild mod zen and has yet to complain about tune issues.

irenaslavo

O.K, I will try different setting with 2 and 2 ½ for low and 1 and 7/8 for high and I will update.