Muffler

[Rivco]

No, I did not have a fire when the breather gasket failed. Luckily most of the oil shot out to the side and went to the bottom of the engine compartment. It could have been much worse. When I took my 425 to the local Kohler Service Center they informed me that the gasket failure was a known service issue and fixed it at Kohler's expense per Service Bulletin #273.

Back to the muffler issue, I hope to have time to take the muffler off this weekend and take a look at it and the pipe it attaches to. My 425 also seems to run very hot and I would bet, as you suggested, that the cause is the poor design of the muffler and muffler placement. Keep us informed of the progress of the dual exhaust system. Do you plan on insulating the stainless steel tubing that remains inside the engine compartment? I'm no expert, but it seems to me that it would get hot also, and would need to be insulated.

If you would like to do away with the problem ..... install dual exhaust...see attached photo showing the new dual exhaust exiting out the right and left side of engine cover/hood.



go to a stainless steel braided fuel line, re-route the fuel line, lower the heat shield ( yes I said lower the heat shield), and relocate the fuel filter closer to the fuel tank . PT's two into one 90 degree sq/ tube exhaust manifold needs to be re-engineered period!!!-

 

[Clarke]

If you would like to do away with the problem ..... install dual exhaust...see attached photo showing the new dual exhaust exiting out the right and left side of engine cover/hood.



go to a stainless steel braided fuel line, re-route the fuel line, lower the heat shield ( yes I said lower the heat shield), and relocate the fuel filter closer to the fuel tank . PT's sq/ tube exhaust manifold needs to be re-engineered period!!!-

Does your machine seem to run a lot cooler with the exhaust opened up. When I replaced the muffler we drilled and tapped to check the back pressure on the system. If I remember correctly it was in the neighborhood 18 to 20 inches. I think that is high but still within Kohlers specs. I am also looking at a westach cylinder head temp. gauge. With the temp gauge installed it would be easy to see if the mod. did any good.

sg

 

[Rivco]

All I can say is that making these changes to my 18 Hp 180 helps with keeping the engine compartment cooler and pretty much doing away with popping and run on when shutting off the engine.

I don't have the hydraulic cooler fan so these changes were a big improvement.

I don't know how well these changes would work on the 422 or 425!!

 

[Marks481]

Wow, nice job. I keep toying around with the idea of dual mufflers, but cutting another hole and adding a trim plate on the opposite side of the engine canopy is a pretty big job.

How about some more pictures of your exhaust header inside the engine compartment?

 

[Rivco]

Wow, nice job. I keep toying around with the idea of dual mufflers, but cutting another hole and adding a trim plate on the opposite side of the engine canopy is a pretty big job.

How about some more pictures of your exhaust header inside the engine compartment?

If I get a chance I'll to post a few pictures this week. The mufflers are just
3" american made glasspacks ( the shortest ones I could find ) with 3" Super trap tips welded into the end of the glasspacks. The glasspacks have a
1-3/4" inlet & outlet. I used black pipe & fittings to do the conversion.

Without a welder and plasma cutter it will be kind of a pain in the backside modifying the engine hood.

 

[ponytug]

Dear Folks,

Just a minor point, but if the Kohler doesn't require premium gas, don't use premium! You aren't doing the engine a favor.

Premium gas will heat the muffler more. In fact it will heat alot of things more. Premium has a longer ignition/burn time, which is why it doesn't knock, aka pre-ignition. A longer burn means that it is hotter (sometime much hotter) as it leaves the exhaust valves and into the the headers/muffler. The added heat is a problem for everything downstream; exhaust valve, header, muffler. It can warp cylinder heads, erode headers, crack welds, warp and wear out mufflers. (That's CAN. As in it has for some people on some engines with certain driving styles in some locations.)

The Kohler (and the Robin) engine is designed for 87RM octane, and if it is knocking, you have other problems which should be addressed first. (Timing, tuning, carbon removal...)

Now, if you have souped up your engine with a turbocharger, fuel injection, higher compression, alloy pistons and crankshaft, with nikasil coatings, sodium filled valves, and ceramic lined headers, you are probably up to 80HP, and you may need premium, but the discussion probably belongs over on www.enginecoversions.com/hotrodtractors ... But photos would be welcome!

All the best,

Peter

I have 217 hours on my PT425 purchased in April 2004. I am just now noticing the same muffler problem as Clarke. I got the last Kohler 25hp PT made and it has the same configuration as Clarke's (and Fourteen"s), metal gas tank in hood and insulated muffler between the engine and battery. The last few times I have used my 425 I have noticed a small amount of smoke coming from the engine compartment and when I check, it is the muffler insulation that is smoldering. I called Terry Estep at PT and he told me to check for a crack in the pipe leading into the muffler and if it is cracked, send it to him for rewelding. He said that if not cracked, send him the muffler and he would check it out to see if it is okay or needs replacement. When I told him I had read about some of the muffler problems on TBN, he became quiet and did not say anything for about 30 seconds. Then he restated to check for a crack in the pipe and call him back. I will do that but I think I will also take my machine in to a Kohler Service Center.
I use BP premium gas, change the air filter frequently, clean and oil the prefilter frequently.
I know this thread has been dead for 2 years now, but if anyone has new info about this problem, please post.
PS - I also had the Kohler breather cover gasket failure and had that problem fixed at my local Kohler Service Center.
Danny in North Dakota.

 

[Rivco]

If you would like to do away with the problem ..... install dual exhaust...see attached photo showing the new dual exhaust exiting out the right and left side of engine cover/hood.

lower the heat shield ( yes I said lower the heat shield),

OK- I guess I should explain why I said to lower the heat shield. The heat shield on my 180 as installed from the factory did not do a very good job of trapping or capturing the air being blown in from the engine fan / flywheel. I lowered the shield 2" to trap more of that incoming air and force it up around the exhaust pipes and elbows to help with more cooling ability. I had to notch the shield some to fit around the pump when I lowered it.