FR730V Carb Whistling/Surging

Hello, my Husqvarna ZTR has 150 hours on it. All of a sudden I'm noticing the FR730V engine surging when not mowing. It will also pop. Very shortly after the problem started, I started hearing a whistling sound. I thought best to just shoot a video...

https://youtu.be/2nGh_v18QV4

I've done a lot of searching and reading and I'm not sure what to do next. Runs pretty good while under load but I think I still hear the whistling. I've removed and cleaned the carb, the jets, etc...also i pried off the aluminum caps off of the top of the carb and I can see through the pilot jet.

Any ideas on where to go next?

Thanks!
Adam

Surging is always caused by a lean condition as evidenced by applying choke (enriching the fuel/air mix).
Could be from debris in carb (something you missed) or a leaking gasket (the whistling you hear) or possibly just an EPA issue.

The gaskets look great. I just can’t figure this out. I’ll take it apart again and clean it again I suppose.

After watching your video
Maybe head gaskets, do a compression check

does sound rather like an air leak.
Try getting a trigger pack of WD 40 or similar.
Start the engine & saturate the manifold and outside of the carb with the WD 40.
If you get a change in engine speed or clouds of white smoke you have an air leak.
From there is is a case of soaking small areas to find the leak.

Check the top of the manifold as a lot of Kwakas have a port for the fuel tank vent in the inlet or manifold.

Considering you do not have an engine guard in place, you may have turned the rear into something very solid thereby cracking the intake of carb base. It may be a good idea to add a fairly long piece of hose to the breather snout before you begin spraying WD-40 around the carb / manifold to keep the spray from going down the throat.

Good luck,

Max

That is why I always make the effort to specify a trigger pack so you can control the spray and of course spraying anything volatile around a running engine is never a good idea wooof wooof, where have my eyebrows gone.

bert,

How many times have we set the eyebrows, mustache, beard on fire when the slightest breeze came by just about the time we pulled the trigger on the spray can? lol

During one extremely hot summer night at the race track, was taken out going into a corner while a bunch of folks that apparently had no idea how to roll thru a corner decided to bunch up. I lifted while waving a hand out the side curtain to no avail. Needless to say, I was spun and the next two decided to give me mouth to mouth association.

Broke the base of the brand new, ultra light (possibly a bit outside the rules) 500 CFM Holley Twice barrel. Got the old girl fired up and didn't think she would rev high enough to make it back to the pits and the tool trailer. Wouldn't idle, didn't want to rev. First thought, broke the intake or carb somewhere. Couldn't see it under the intense work light and the heat from those 750 watt halogen bulbs while in a 4 layer fire suit is nice and cozy.

After checking all the strain reliefs in the wiring circuits also, came to the conclusion to spray some ether around the carb base and along the intake. Well Sir, the side of the car I was on when I took this action had the breeze (although hotter than a three p*t*red Billy Goat freakin' in a forrest fire) said to me upon the first rev and pop out of the base "Hello beard, eyebrows and beard, I came to remove you for the evening." Boy did it ever! I'm just glad I made sure I had the tall breather in place when I sprayed that ether considering the needle and seat weren't jee hawing as well and a bit of gasoline decided to join the fray of fire in the pits.

Fire suit came in handy putting out the fire. Would have been nice had I not removed the firesock on the head. lol

Ever since then, even using a spray can with a tube, I make sure nothing can get down the intake other than where I'd like it. So, good of you to always point out to the others that may still have their eyebrows to maybe preserve them until old age. lol

Have a great one my friend from downunda!

Max

I fixed it! I was idling the machine and inspecting it with a flashlight and noticed what looked like to be a gap in the manifold connection to the engine. Sure enough the bolt holding the manifold on the left side top was loose. After removing all four bolts and removing the manifold I could see that the manifold gasket was damaged. I ran to a local dealer who had the gaskets in stock, replace the manifold and everything works great again. No surging no whistling. Apparently the bolt worked loose and blew the gasket out.

Thanks for the help everyone.

Spyshot,

Glad you're up and running.

Max