Poulan Pro 4620AV Runs when choked but give it throttle and it dies

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rhfarms

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I have a poulan pro 4620av saw that I have recently put a new piston in. The compression with the old piston was 130 psi, I can start the saw and it runs fine with the choke all the way on but put it to half choke and try and give it throttle and it falls on its face and dies. Where do I need to look?
 
The fact that you have to put the choke on and try to make it very rich says that it must have an air leak somewhere downstream. What did you seal the engine with? As a quick test on those engines you can put your thumb and index finger over the intake and exhaust ports and connect a vacuum pump to the impulse nipple. If it's leaking you should be able to tell.
 
Sounds like a air leak to me, Did you seal everything up good when you replaced the piston? the fact the piston needed replacing my mean you have a bad seal. what caused the problem in the first place? (replacing the piston)
 
The fact that you have to put the choke on and try to make it very rich says that it must have an air leak somewhere downstream. What did you seal the engine with? As a quick test on those engines you can put your thumb and index finger over the intake and exhaust ports and connect a vacuum pump to the impulse nipple. If it's leaking you should be able to tell.
ya beet me too it lol!
 
I think I may need to take the engine back out and seal up the bottom end (crankcase) with some rtv. I think maybe my air leak could be coming from there? The muffler and carb seem to be sealed up good. Thanks for the quick replies guys.
 
I think I may need to take the engine back out and seal up the bottom end (crankcase) with some rtv. I think maybe my air leak could be coming from there? The muffler and carb seem to be sealed up good. Thanks for the quick replies guys.
RTV is not the best choice there as it is not fuel resistant. The proper sealant is something like Yamabond4, available at Yamaha parts counters or the equivalent from Honda or Threebond.
 
Is there anything I could pick up at an autoparts store? I dont have any real good small engine places around.
 
I have found stihl's version and will use that. I would assume it is an air leak as I reassembled with no new gasket where the crankcase fits back together around the bearings/seals. This is my first time working on small engines and I am not very familiar. Thanks for all the help guys. And to Austin1 the reason for replacing the piston was slight scoring on the exhaust side but the crankcase walls looked and felt to be ok.
 
I have found stihl's version and will use that. I would assume it is an air leak as I reassembled with no new gasket where the crankcase fits back together around the bearings/seals. This is my first time working on small engines and I am not very familiar. Thanks for all the help guys. And to Austin1 the reason for replacing the piston was slight scoring on the exhaust side but the crankcase walls looked and felt to be ok.

I think Austin1's point is what caused the 'slight scoring' of the piston. An air leak is a likely cause of piston scoring. A pressure/vacuum test would be a good idea.
 
I had used a touch of ether after winter, which I now know is a dumb idea in these small engines, I really don't like ether at all but the thing just was really hard starting. Could the fabric gasket on the backside of the carb be replaced with the gasket maker? Just want to cover all my bases just so I don't have to tear it apart again. Thanks for all your help guys.
 
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