5ivet won't idle?

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LukeOR

LukeOR

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Ok guys, maybe someone out there can help me out. I have two 5iveT engines that are both having similar problems. I can only get them to run while giving them about half throttle, as soon as I let off, they quit. I have tried new diaphragms, swapped carbs (including 2 brand new ones), reset factory needle settings, changed fuel, pressure tested the engine for air leaks, spark good, changed filter and fuel lines, air filter good, I am running out of ideas, as you know there is not much to these engines but I can't seem to figure it out. I have looked in forums but so far have not found anything that seemed to help. I'm still not convinced its not a fuel problem and I am looking at swapping in a whole new tank, fuel, and lines to see if that helps. Both engines appear to be ok (IMO) but maybe they are toast? They both have compression and show only minor wear marks on the piston/cylinders. I have always kept filters changed every run and they have never sucked dirt or sand. It could be they just need more tuning? In the past I have reset factory needle settings and always had them start first or second pull. Both engines have only maybe 3-4 tanks ran through them. Also when I checked the engine for leaks I did not check the manifold, it looks fine but I don't have another to swap out yet, so that is a possible fault. Surely someone out there has had a similar problem? It must be something so simple I have overlooked? Any advice would be much appreciated, thanks guys!

here's a link to the video,
 
Had this problem a few days ago on my 5ive T. My son reset needles back to factory and adjusted idle screw. It worked fine after that. ( he was the one that messed with the needles in the first place...lol)
 
Carb is a Walbro 668, w/throttle shaft bearings. (the sand like to eat the aluminum around those shafts). The first time I bought one, I stuck it on, and it ran tits right out of the box. I recently bought another and upon install same problem. I reset needles to factory specs, and same thing. I will try the idle screw/low needle when I get home and let you know if I have any luck. thanks!

here's a video I made a while back, when she was running good....
 
Have you checked to make sure your throttle servo and linkage are set up properly ??
I feel something is off there judging from the video.

I recommend you double check the above.

Then I would crank up the idle screw, go around 4-6 full turns.
And crank it back on.

If the idle is still low, then obviously give it a couple more turns.

If the idle is already high, turn it back till you hear it idle smooth....

It’s no way you got 2 engines with the same issues. It’s going to be something so silly LOL.
 
It has got to be something silly as I have swapped just about every part out including engines. Anyway I just got home and Im about to go have at it once more. Curious as to why you think linkage might be an issue? It seems good to me, full throttle and the throttle stop tab just hits opposite side of where the linkage connects. And when I give it break there is no throttle shaft movement, at rest there is about an 1/8" of play before the throttle shaft will start to move. The idle screw is something I haven't really messed with yet, I always thought I could get it running then set the idle, but many times Ive been wrong before....lol. When I do have it running it really feels like it wants to die, not like it just slowly sputters out from too low of idle. I'll go give it a try and give you all the update, thanks again all.
 
You guys hit that nail on the head, I feel like such an idiot. I went over and (just for good measure) returned needles to factory 1 1/4 low, 1 1/2 high, but right away i noticed the idle screw was barely making contact. I cranked her in about max, backed her off a little bit, primed it and first pull she idled ( I actually had forgotten to choke it as well), a few minutes later I had the needles roughed in and was so excited I threw it in the truck for a quick trip over to the bash pit and get some final tuning in. Idle screw.......how on earth I was able to overlook that I have no idea. But thanks guys. On a side note, I have learned a lot about the walbro 668's, and even have a few spares now....... lol.

Speaking of carbs, does anyone run much in the sand? I went through two carbs fairly quickly due to sand eating out the throttle shafts. I have since purchased the ones with the bearings installed, I was wondering how long these type will last? I have not had problems with it yet.

Thanks all!
 
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