Carb info

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carbs are usuall the same.
both typically (Zens) have a walbro WT-603 on them the 4 bolt zens have the WT-813. the CYs have the WT-668.


they are all very similar and preform very similarly. with the 813 being the exception as it has an accelorator pump, but doesn't flow quite as much fuel on the topend as the 668 or 603s.
 
it give you an extra squirt of gas which can help the low end a bit. but the 813 can cause folks to flood out their motors quickly also. every time you squeeze the throtle, you get a shot of gas. if the motor isnt running and you give it 5 plus squeezes, you on the virge of flooding the motor out.

im running one 813 on my ESP 27.2. while i do notice a bit more low end grunt, i also notice a smidge less top rpm also. probably go back to a 668 on it soon.
 
so while we are on the topic of carbs, doesn't anyone have any solid info on what carbs are better for certain applications, and what the differences in performance are??? at just a quick look i find:

wt-499- alcohol carb (self explanitory)
wt-257
wt-603
wt-813
wt-668
wt-644
wt-771

that doesn't include the various barrel carbs that i don't think anyone uses in rc stuff.

so any input???
 
wt-499- alcohol carb (self explanitory)
wt-257- no choke carb. most boat guys run this one and like it alot
wt-603- stock zen 2bolt carbs. heard of some haveing needle floating issues. but hey... it happens to all of them.
wt-813- stock zen 4bolt carbs have
wt-668-stock cy carb and HPI Baja carb
wt-644
wt-771- i hear this is the 813 without the accelator pump setup
Click to expand...

the 771 and 813 are said to be the same except the accel pump on the 813.
i run an 813 on my ESP 27.2 i like it but have heard the 813/771 doesn't flow as much fuel full open as the 668 does. From the way my motor run with the 668, i think i can agree to that. i seem to get more top rpm from the 668 than the 813 but get a bit more bang out of the low from the 813s pump. not ran a 771 but know alot of the boat guys also like this carb as do many of the Onroad guys.

603. decent carby i ve used a few. didnt notice needle walking issues on any but others have mentioned it. seems to be a bit less topend than the 668s. similar to the 771/813. but its hard to really say for sure. a dyno is the only real way to know for sure, and i m hopeing to get this tested out soon.

i had a 254 on my Berg/Boss 23cc reed motor. they were tapped for the reed valve. but i really liked the way the carb ran. wonder if it could be used via the normal pulse circut?

not tried a 644. nor heard much about it.

now the 668 has been my carb of choice. i am Still running the 668 that came on my original rtr HPI Baja 5b. the carb is now 4ish years old and working as it did when new.



in part of my carb seeking quest, i have to call Walbro. I ll try to do it this week, and see if i can chat with tech support, and find a few possible carbs they offer that could work for our needs. im especially interested in seeing if they have a barrel carb that could work, or can suggest a GOOD model for the Reed Case Motors.

the 668s have been nice, but i think their could be better suited carbs available.
 
nice 1 guys thx ur all ur info and time on this, 1 question wil i need to retune the carb if its not been done befor hand????

by the way i'll get an 688 and go from there will repor back an d wat happens when i get it soon minted
 
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