XT 675 choke stays on

Hey all, I have a Kohler PH-XT675-2044 4407316528 engine on a walk behind mower. It starts & runs great when cold, but as it warms up, the choke never comes off & it misses & blows black smoke till it quits. If I open the choke by hand it's perfect, but the choke device on the muffler will close the choke again when I let go of the linkage.
If I heat the device on the muffler with a heat gun, it will respond by moving full clockwise & opening the choke, so I know it works. It's like the muffler isn't getting hot enough. Sorry for the long post, but any ideas??? Thanks Lots!!!
Roger

 

Sounds like something physical happened to the muffler. Have you owned the mower long enough to spot any changes? Is the exhaust louder? Can you look at another identical machine at a dealer?

 

Thanks, the unit belongs to my neighbor, so I'm not real familiar with it, but it sounds the same as it always has any time I'm outside & she is using it (until it slowly started to run like this). There is no physical damage to the muffler & there doesn't seem to be any exhaust leaks. I tied the choke open & cut some long grass with it & it seems to have lots of power, so I don't think the muffler is plugged... Thanks Again!!!

 

sounds like either the choke stat is bad or the muffler possibly rotted out some causing it to not get as hot even though the choke stat moves when heated they typically fail by moving less over time and eventually your choke will no longer open all the way.
really do not see a way to adjust tension of the stat unfortunately there is a you tube video where one guy reversed the linkage so the shorter movement would open the choke also read where some would drill holes in the muffler right below the stat so it would get hotter and move further, maybe could mark the plastic end hole location and pop it off the end of the rod and reposition it or solder a new end on with multiple holes so you would have some adjustment on it so there is probably ways of fixing it without actually buying parts if you want to tinker with it. you could also put a manual choke on it.

 

Look at manual at this website:https://www.manua.ls/kohler/xt675/manual?p=22

 

Thanks Beelz, unfortunately that's not the system that's on this unit. The system I have bolts horizontally to the top of the muffler& instead of using the vacuum choke break, the throttle linkage / governor performs this function. I'm still trying & and thinking of ordering a new bimetal spring assy. It's ~ $4o.oo CDN but I want to avoid drilling holes in the muffler if I can. The part # has been superseded, so I'm hoping it has been changed to address this issue??? I'll let you know... Thanks again!!!

 

Unless the choke assembly is part of the mower and not the engine, you have to find out how Kohler handles revisions since the model number by itself is not sufficient to identify the engine components. Having to drill holes in the muffler sound like you have a replacement choke from a different revision than choke used with the revision of the muffler currently on engine.

 

I don't like the system they used on these. It works in theory but not so well in application, as you've experienced. I think the properties of the coil change over time and it responds differently after use than when new. I think I would be tempted to just disconnect it and put a choke cable on it. Seen too many that just didn't work right.