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Joined: Apr 2015
Posts: 325 Likes: 1
Apprentice level 4
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Well done mate.
Been keeping an eye on this thread - Ive just finished stripping down one of these engines. Just logged in to offer a replacement carb for you (I have several).
If youre thinking of getting into fixing up mowers remember:
Keep It Simple!
Fix the easiest problems first - 90% of the problems I fix on a daily basis are carby blockages or just old fuel.
If the engine wont rev or surges (revs up then down) in your case now I would strongly suspect just a blocked air filter. They have a foam pre filter on them try cleaning out that first (I just wash them in the old petrol I drain from the tank) and smack the paper filter on the ground to loosen up the crap (If you have an air compressor handy give it a good blow out), dry the pre filter, reinstall and see what difference that makes - I'm positive that'll fix your engine. The Air filter doesn't need to be changed EVERY service but does need to be cleaned out thoroughly.
Good luck with the mower!
Pete
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Joined: Jan 2009
Posts: 6,926 Likes: 10
Pushrod Honda preferrer
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I think the need to clean the carburetor a second time, suggests you did not take that Honda video seriously enough insydney. It's a bit like repairing a mechanical clock: rather routine if you do it the right way, and one disaster after another if you don't.
It is easy to miss the foam prefilter that Honda air cleaners nearly always have. If you look after the prefilter, the paper filter is unlikely to need much attention unless the engine has run for a long time with smoky exhaust. That blue smoke contains a great deal of liquid oil, and the paper filter filters it out a lot more effectively than the prefilter does, so the result is a clogged paper filter. When they contain dust, Honda endorses tapping the filter element on a hard surface, or blowing it out with very low air pressure from the inside outward, but of course that won't help with oily paper. I've been known to wash an oil-soaked Honda paper filter in petrol several times in succession, to remove oil, and it has worked, but in reality this operation is as likely to destroy the element as to clean it. So, the acid test is, does the paper filter look dry and completely clean (normally, either white or pink colour)? If it looks blackish after blowing it out, the odds of saving the filter element are not good.
In repairing engines, the best advantage you can have is experience. It sounds to me as if you have been learning rapidly from this project, and pretty much enjoying it, so all is going well.
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Joined: Mar 2015
Posts: 23
Novice
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it was completely my own stupidity and desire to get it done quickly... and as they say "more haste less speed" i didnt consider the lower retaining part of the main jet actually had a central hole, and took more care cleaning the other part of the jet (the long part with about 15 holes) that explains why after a few mins enough petrol managed to pass through, but not continually. now i have cleaned it properly all is well ;0
to answer your Q re' the airfilter, to be honest it doesnt look too bad, definitely not blue/black or oil soaked. thats why i was wondering if i had bent the choke lever a little whilst coaxing it off last time. tomorrow if i get time i'll knock it out to see if anything shakes loose...
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Joined: Jan 2009
Posts: 6,926 Likes: 10
Pushrod Honda preferrer
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What you are calling the lower part of the main jet (the part with the thread on the outside, and the screwdriver slot in the bottom) is actually the main jet. The long tube that goes directly above it, with the multitude of holes around the outside, is conventionally called the emulsion tube or emulsifier, though Americans (and Honda) tend to call it the nozzle. So, you had cleaned the emulsifier but not the main jet. You may still not have cleaned the idle jet, a black plastic object which slides down vertically into place just to the right of the idle mixture adjustment (pilot screw, in Honda-speak) and directly below the idle speed screw. The plastic idle jet has to be handled delicately, and the metering hole in the bottom of it is only 0.3 mm (12 thousandths of an inch) in diameter, so you need a fairly special object to clean it. If your engine idles perfectly it may be safer to leave it alone.
If the air filter is dry, and is not caked with dirt on the outside, it is probably good to go. Tapping it on the bench to knock loose dirt out will do no harm, but in general that method only removes caked dirt.
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Joined: Mar 2015
Posts: 23
Novice
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yes it was the main jet i failed to clean properly the first time, i had concentrated on the emulsifier. i steered clear of the idle jet this time as it sounded very delicate thats on the to-do list
the airfilter looks ok, definitely not caked up with crap, so i will tap it out and try it again, results to follow
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Joined: Jan 2009
Posts: 6,926 Likes: 10
Pushrod Honda preferrer
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Thanks for the report, insydney. Please check that the choke is closing completely, take a look at the spark plug, and inspect the state of the engine oil. Note that the oil should stay clean for years (Honda says change it every 100 hours' use) on that engine, unless the piston rings are worn, but it seems that chonda users are even worse than Briggs users for failing to change it when it's dirty. It does not have an oil filter, and the engine will wear rapidly and severely running with dirty oil.
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Joined: Mar 2015
Posts: 23
Novice
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well without the filter it runs quie well, although erratic with the filter and the filter cover in place it just dies, as soon as i lift the cover it improves immediately. so it looks as if the filter is stuffed after all the choke moves from stop to stop so it appears to be ok although i'll remove the air filter body later so i can see down the throat and confirm that i changed the oil when i first got it and it was pretty dark but i didnt take particular notice at the time it has a new plug which was the first thing i replaced using an NGK BP6RES which is what it was running when i acquired it it is not burning oil from the look of the exhaust, can you suggest a good threads you can recommend on here to: 1. show how to tune this particular engine ? and 2. that cover checking valve clearances ? cheers grumpy you're a genius 
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Joined: Jan 2009
Posts: 6,926 Likes: 10
Pushrod Honda preferrer
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If it makes a noticeable difference when you remove the air filter cover, the filter is badly obstructed and needs to be serviced, which may well mean replacement in the case of a chonda. However most properly serviced chondas run as well as Hondas, which means start first pull and never miss a shot, ever. (They do sound rather inferior to Hondas due to oddball muffler design, but they don't misfire.) Hence you still have problems to find and fix. I think the chondas called 40, 400 and 4000 are all copies of the GXV120, which is advertised as 4 hp. You can learn quite a lot about them from these threads: https://www.outdoorking-forum.com.au/forum/u...p;Words=gxv120&Search=true#Post53596https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=58437&page=2With regard to tuning the engine, the best procedure for most adjustments is to follow the Honda owner manual, here: http://engines.honda.com/parts-and-support/owners-manuals/gxv120However valve clearance is not covered in the owner manual. Here is the page from the workshop manual:
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