Just got done doing a rebuild on my 721 carb. I couldnt find a complete kit online so i ordered all new rings, gaskets, needle ect. by part. Runs much better now. Afterwards i too had problems with adjustments. Non-governed idle is fine, but governed is too high by 100-150rpms. It wont adjust down, but since its not that bad i have left it. High is now adjusted to 3700 since it drops to 3500-3600 with blades on. These arent perfect but ok for me. I would clean the carb/jets, replace all rings/gaskets and see how it does and check for vaccum leak. How high is your idle?

 

You can look up Kaw. parts here: http://kmcb2c.econnect.partsandwarr...ion=CATALOGB2B&chID=350998&elementType=1&historyDepth=-1&CHANGENUMBEROFITEMS=63

Service manual here: http://www.mymowerparts.com/pdf/Kawasaki-Service-and-Repair-Manuals/

 

Mine was running 3600 with the blades on from new. I want to say it was set at 3750 so what you are set at is fine. I never had any trouble. Back then I was thinking a lot of manufacturers set Kawis to 3600-3750 with the blades on. Seems like a rep told me one time they could be ran at 4000 no load without an issue. But it has been a long time.

That spring loaded screw on the carb that stops the throttle butterfly... I have messed with that twice. Once I adjusted it to get through a cut. Tightened it a little which stopped the surging/hunting that was going on so I could cut and investigate later. Afterwards I realized that was seeming to hold my low idle speed up in the 3k range so after dealing with the problems I found I decided to back it back down so it would slow down to idle. But the engine will die as I adjust it back out before it reaches idle.

I had been not caring cause I didn't have time to try to sort it out. But now that I'm realizing it's hard to start back after warming up if I shut it off... well that's enough motivation to make time.

I just can't figure out what to try next. I figured maybe taking the carb out and cleaning it. But the service manual is not much help there. Dunno if I need to have gaskets ready first. Dunno how to get access under the capped jets, etc.

 

Look, the spring loaded screw ya messed with is the "idle speed screw" and has no bearing on surging etc. just the idle speed.
You need to pop the carb off and go thru /clean it. A can of carb /choke cleaner spray and blow gun should do it.
NOTE : the jets are different on left and right ! Do not get them mixed up!

IDK where ya get the manual isn't helpful. If ya take the time to read it...

I would get all the gaskets and an inlet needle ahead of time.

 

BigFish is right. The screw is only an idle adjustment, but is considered "non-governed" in the way you set the screw via the manual. The "governed" idle screw is at the bottom of the throttle plate, but like I said adjusting according to the manual did nothing for me. I agree there is nothing in the manual as far as cleaning the carb, other than maybe the bowl. However, do a youtube search for cleaning a double barrel Nikki carb and a few videos will help. They may be off a Briggs, but similar enough to give you an idea of what your looking at. I would clean the carb, order any parts that need replaced, rebolt and then follow the manual's directions for setting idles. If you don't want the hassle I would order a new carb for about $300. Don't take it to a dealer as that's all mine will do is put on a new carb and charge you mark-up and $60 to bolt it on.

 

I agree there is nothing in the manual as far as cleaning the carb, other than maybe the bowl.

Actually there's a p.29 that covers it. How detailed does a manual have to be as far as cleaning goes ???
Complete disassembly is fully covered , including removing the "capped jets".
You shouldn't have to remove the throttle or choke shafts unless the seals are shot or they have excessive play.
I generally won't soak in carb /parts cleaner unless a carb is really gunked up with bad gas/varnish residue

Tip: To remove the jets, use a " hollow ground " straight blade screwdriver/bit. Get ya an el-cheapo 4 way screwdriver from china freight. The straight blades are hollow ground. ( google it)

Dunno how to get access under the capped jets,

Then, you, bud, did not take the time to read the manual, as it is clearly spelled out... sheesh !

The bottom line is, you generally need some understanding of the inner workings of a carb, before ya start tearing into one, right?

Right.

 

Thanks, I didn't have access to any of my manuals, all on PDF on an old computer that I haven't fixed yet. All I had was a chapter from a similar manual on my phone that had much less detail.

Those are more helpful for sure. I also have what they call the late model carb which was another point of confusion. I figured that out trying to find an exploded parts diagram of the carb to go along with the crappy manual pages I had.

I will tear into it here soon when I have time I guess and see what all I find.

As far as the low idle screw on the carb I understand what that does. It just won't run if I try to back it out to slow the idle speed down. I want to say it dies out before it gets to 2200 RPM. And yes I did adjust it in before as a crutch to get some cutting done. Adjusting it in created a "stop" just enough to settle out the surging/hunting RPM problem I had. Settles out the surge but it won't idle down and is stubborn to crank back after warm... if any of that points to any other problem besides a dirty carb....

As far as the 11,000 posts that comes from posting as a professional on here back when I was the big fish and you were still a minnow. I sold my lawn and landscape business years ago. Now I just have my 3 properties that I have to cut and very little time to do so.

 

Yeah if I had to guess I would guess one of the pilots is plugged up with gunk from the ethanol damage.

I say that cause when I try to slow the idle it's like it starts to starve one cylinder.

I think the coils and the valve clearance is OK because I can get it to crank hot by jiggling the throttle butterfly with my finger. Don't think it would do that if it were valve clearance. And it will start and idle at a lower RPM when cold without sounding like one cylinder is not hitting, leading me to believe that the coils are not the issue.

Could be wrong but I guess I will go into the carb and see what I got going on there first.

 

Sounde like the best next step. One thing, coils often are fine cold but act up when hot. Let us know what u find.

 

Revisiting this... and adding some info...

The Kawasaki engine I have is the FH721V-CS26. I never could figure out what the deal was on that, but I have still yet to find it listed anywhere for parts or a manual, and nobody has had any answers on that so far?

After looking around several times I finally found a listing for FH721V-CS instead of AS or BS. More looking and I finally found listings for FH721V-CS21 and FH721V-CS27... but no CS26.

I just went ahead to diagrams on both and looked at the carb, and it looks a lot like mine. It appears I was not loosing my mind without taking it off with no parts and tearing into it. Mine has a 3 screw cover on the top the fuel hose connects to, and just past the engine side pair of screws are raised areas on the carb with expansion caps in them, or welch plugs or whatever you want to call these metal caps. But these are pressed in over my pilots like I feared.

This is why I was saying I don't see any instructions in the manual other than removing the pilot screws and jets... no mention of getting to them to do so. Wasn't looking at a correct repair manual for my version.

Looks like these have to be carefully drilled or punched as to not hit anything under, then use a pick in the hole to try to pry them out. And then I think these will have to be replaced at $7 each unless I can figure out something else.

Looking in the correct manual it is found on 2-18 and 2-19. These other manuals the fuel system is chapter 3.

I am tempted to just take the carb off, soak it and try to blow back through it and see how that goes. But I am not usually lucky enough to get to half-do anything like this. I usually will be the unlucky one that has to break one completely down to clear it out.

I'm just glad I have been able to figure out how to get it started and it has been running OK for me as far as mowing. Otherwise I would have been screwed. I just happened to be sick and unable to sleep is the only way I even found time to find the info I needed and parts that look right.

 

Looks like these have to be carefully drilled or punched as to not hit anything under, then use a pick in the hole to try to pry them out. And then I think these will have to be replaced at $7 each unless I can figure out something else.

Look, it ain't no big deal to drill a small hole in em' and pry/pop em' out. Unless yer a caveman ya ain't likely to mess the screws up. I use a specially ground adjustable reamer blade (chisel) fer poppin' welch plugs etc. But a drill will work fine. Pay attention to the manual.
Ya don't gotta replace the plugs, they're mostly fer tamper proofin'.
You should replace the "tower" O rings as well as the bowl seal. Lube the pilot screw O rings with a dab of grease, also the main jet O rings. Don't mix up the mains.

Have fun.

 

Guys I've had a string of issues over time and little time to address, so I have kind of a daisy chained mess on my hands.

I started having a run issue which turned out to be several things, all fuel ethanol content related. Water in fuel, damaged fuel lines, fuel filter, fuel pump. Blah blah.

I kinda had to to best I could and make do in order to get some mowing done, so I replaced stuff, switched to Rec90 fuel and have just been calling it good so long as it starts, runs OK and I can get the mowing done. But I need to get it fixed back right.

I tried to adjust things back to get it idling at the right speed and found that I can't. If I keep adjusting it down it dies. So it idles too high after warm up, and doesn't want to restart when hot. So I figured maybe go all the way through the adjustments.

I did all the adjustments again, and I still can't get the idle down without killing it and on top of it, now it's hunting up and down sometimes randomly.

Do you think I have plugged up jets? If so, what do I need to order before I pull the carb off and how do I gain access to the ports and passages?

Or am I off in left field here and need to be looking at something else?

Try adjusting the valves. Kawasaki says every 300 hours. That may be your non start issue after a warm engine.
Try adjusting the valves

 

Try adjusting the valves

This may help too.
Before you tear it off you might try hot soaking it in a heavy solution of sea foam (1 can in 1 gallon of gas). I did this by just emptying one tank and running it through the system for 10 minutes and letting it sit overnight. It deff helped, but I did have to pull it off and clean it. I did not have to remove the welch caps to fix my issues though. Search Nikki carb cleaning on youtube if you do, helpful. If hot soaking helps at least you know it's a gunk/carb issue. If it's all too much headache a new carb is $300.

 

Guys I've had a string of issues over time and little time to address, so I have kind of a daisy chained mess on my hands.

I started having a run issue which turned out to be several things, all fuel ethanol content related. Water in fuel, damaged fuel lines, fuel filter, fuel pump. Blah blah.

I kinda had to to best I could and make do in order to get some mowing done, so I replaced stuff, switched to Rec90 fuel and have just been calling it good so long as it starts, runs OK and I can get the mowing done. But I need to get it fixed back right.

I tried to adjust things back to get it idling at the right speed and found that I can't. If I keep adjusting it down it dies. So it idles too high after warm up, and doesn't want to restart when hot. So I figured maybe go all the way through the adjustments.

I did all the adjustments again, and I still can't get the idle down without killing it and on top of it, now it's hunting up and down sometimes randomly.

Do you think I have plugged up jets? If so, what do I need to order before I pull the carb off and how do I gain access to the ports and passages?

Or am I off in left field here and need to be looking at something else?

How much is a new carb?

 

Last I looked it was $300 or so for my FH721.

 

Would it be less trouble, and get your machine back up to par? Its a tuff decision but sometimes its better all around to just slap a new part/ carb on, and go. Let us know what you decide to do. Sometimes those jets are never right again, and damage really easy trying to clean them.

 

That was my plan C. Fortunately, plan b worked. $300 isn't chump change, but won't break the bank either.