How to tune a Zenoah engine

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One guy says bubble not full means to lean because the bubble should stay full , the other gentleman was thought it was to rich because it sucked to much fuel , or lean because it didn’t suck all the fuel out of it . I admit my 6.8 hp 260 PUM Does not have a primer bulb in my rc boat but The bubble is befor the carb not after so rich or lean either way it should be full you want to make sure your fuel delivery can Handel all the fuel the motor can use and some the adjustments on the carb cut the fuel down but it could be argued either way that it’s half full because it sucked to much out of the bubble being to rich or it’s to lean cuz it’s not sucking enough to keep it full either would be wrong cuz if the tank is full the bulb should be full weather your flooding or starving it .....THATS STRICKLY A THOUGHT I don't KNOW THAT TO BE FACT BUT SOME ONE NEEDS TO ANSWER THE MANS QUESTION WITH REASONING OR A LINK TO EXPLAIN WHY CUZ ITS GOT 3 of us wondering now as I said I don’t run a primer bulb but your trucks would drown with my carb and settings
Ps those tuning instructions are copy and pasted from performance. Unlimited word for word .
 
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I’ll find a boat forum it’s clear the guy that asked the question never got his answer nor did I what I did learn was when you guys don’t know the answer you say what is it. Exactly your asking . Be it 10 years old or a day people will search the web and when it brings them here this thread will only leave them confused as it did me . When you have two opposing answers and it’s left in the air who is the reader to take for correct answer . So for you horse commenters go back and read the whole thread and give all those that are lead to this thread a definitive answer rather then a smart remark and it will prove this forum useful rather then smart mouths
Ps If you search the web TODAY for tuning a 2stroke or zenoah this is one of the top web results that’s how i got here and wasted my time signing up for this forum as will every new person that just got there first gas boat or truck will all want to know how to tune there carb in ten more years from now or next week
 
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Armyof1 said:
I’ll find a boat forum it’s clear the guy that asked the question never got his answer nor did I what I did learn was when you guys don’t know the answer you say what is it. Exactly your asking . Be it 10 years old or a day people will search the web and when it brings them here this thread will only leave them confused as it did me . When you have two opposing answers and it’s left in the air who is the reader to take for correct answer . So for you horse commenters go back and read the whole thread and give all those that are lead to this thread a definitive answer rather then a smart remark and it will prove this forum useful rather then smart mouths
Ps If you search the web TODAY for tuning a 2stroke or zenoah this is one of the top web results that’s how i got here and wasted my time signing up for this forum as will every new person that just got there first gas boat or truck will all want to know how to tune there carb in ten more years from now or next week
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First off, F off and go back to your internet searches. The guys from 10yrs ago aren't even on the site anymore. Your direpectful tone will not be tolerated here. There is a group of good guys here that would have been itching to answer your questions but now, I seriously doubt it. So good luck with your searches elsewhere. Secondly, F off.
 
tbh there's a million'n'one ways to tune an engine ?as everyone will have there own little tips/tricks/do's/don't's/by ear/by smoke ect ect ect.. ? ...go to vid seems to b obr's tuning vid on u tube ?..jus tune so its running ok...then leave it?.....no clue about the bubble?.6 bubbles...2 bubbles.......long as it's got fuel in it....run it?..ita not a Aston Martin v12?
evssv said:
tbh there's a million'n'one ways to tune an engine ?as everyone will have there own little tips/tricks/do's/don't's/by ear/by smoke ect ect ect.. ? ...go to vid seems to b obr's tuning vid on u tube ?
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??:ROFLMAO:
 
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If you would have bothered to use the forum search function you would have seen, weve been over the primer bulb function, or it should be called the air purge bulb, just recently. And to note, in the carb rebuild thread I've recently updated with a fix for a half full primer bulb, or at least the most recent issue that I came across and help to find the root issue Gotta love when dr google shows you things that have little to no bearing on what your actually after.
 
Brian m taylor said:
Hi i have set my ow and high screws as it states. But when I try to start fuel c9mes out the caberator and the exhurst. Does that mean the diapham is bad ???
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double check yer needles mate, wind all the way in but so they bottom out gently, don't force em tight or you may damage the tip of the needle or seat,
then wind out the 1 5/8 low and 1 7/8 high, thats for an 1107 carb, 668 carb is 1 1/4 low and 1 1/2 high,
you aint trying to start with the choke on are you ?
starting should be choke on, one or two pulls maybe three till you hear a pop from the engine,
choke off then it should run after teo or three more pulls,
fuel out the carb and exhaust means its flooded,
take the filter off, tip car towards the carb so any raw fuel drains out, let the filter dry out then refit, tip any raw fuel out the exhaust side as well,
take the plug out and pull it over a few times to expell any excess fuel, fit a fresh pug or make sure the original ones dried out properly,
also check for spark as well, then do the above start procedure (y),
if it does the same thing and floods badly , then start to look at the carb diaphram etc,
 
My idle screw has no effect on idle revs for some reason. Is it OK to use radio throttle trim instead?
 
Seandonato73 said:
Means your trim is set too high. The servo shouldn't be in control of the idle speed.
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Trim is neutral, maybe I have to move it back or forward a notch on the servo horn
Also isn't it doing the same thing? You're just opening up the butterfly a bit. As long end points are set?
 
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No, you should be relying on the carb idle screw for idle rpm adjustment. It has to do with consistency. When set right there should be no tension from the servo on the carb at idle speeds. Get the carb to idle properly with the carb then set trim and epa.
 
I have to have it fully in like this and tune idle with L jet. Is that OK?

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So the basics is get the engine to run. Put the car on a box or whatever with the wheels off the ground. Let it worm up. Doesn't really matter how high the idle (screw) us set, just so it will stay running. Run your low jet in slowly till the engine picks up rpm. Note this position. Run the low jet put till the engine rpm drops off. Note this position and go in between the low rpm and high rpm. Your not setting idle with the low screw. Now turn your idle screw to get your idle where you want it. You may have to play with the low screw a little, but truthfully you shouldn't be far off base settings. Then proceeded to hook up the linkage and set trim and epa. Then you can start running and tweaking the high screw. Don't be surprised if you need ro go back and tweak the low screw after a high adjustment.
 
Seandonato73 said:
So the basics is get the engine to run. Put the car on a box or whatever with the wheels off the ground. Let it worm up. Doesn't really matter how high the idle (screw) us set, just so it will stay running. Run your low jet in slowly till the engine picks up rpm. Note this position. Run the low jet put till the engine rpm drops off. Note this position and go in between the low rpm and high rpm. Your not setting idle with the low screw. Now turn your idle screw to get your idle where you want it. You may have to play with the low screw a little, but truthfully you shouldn't be far off base settings. Then proceeded to hook up the linkage and set trim and epa. Then you can start running and tweaking the high screw. Don't be surprised if you need ro go back and tweak the low screw after a high adjustment.
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Cheers, I think I'll have to to adjust the linkages. I understand what your saying but the idle screw has no effect on rpm at all. This is the problem. It is screwed all the way in and there is still no charge.
 
It's not the tune, pretty sure the linkage isn't letting the carb close completely so the idle screw has no effect. Just finished watching F1 quali so out Tothe shed
 
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