Exhaust glowing red - issues..

[jpdodd]

Here's the problem:
After about 1-2 minutes of idling, the exhaust starts to glow red - starting at the point where the exhaust pipes enter the muffler and then proceeding to make the entire muffler and pipes red (if I let it get that far)

Here's the engine info:
2005 Kohler CV730s (CV 730-0040)

Here's what I've tried so far:
Brand new carb.
New spark plugs
Changed muffler
switched out plastic diverter inbetween the carb and the main engine (not sure what it's called)
Checked the shear pin under the flywheel. - perfect condition.
Reset the magnet parts outside the flywheel (sorry, not a technician so I can't remember what they're called)
Checked for fuel/ oil in exhaust ( a friend smelled it and didn't detect odor of either)

Other info:
I bought the tractor off an older gentleman who had used it for years. The only thing he changed recently was the carb. After he changed it, he only ran it briefly, so never noticed the muffler issue. I can't image that he ran it for years with the muffler getting that hot.

The mower starts great, idles great, runs smooth, but occasionally will have a backfire out the exhaust when shutting down.

I've exhausted my friend help, online video help, and am turning to you

I really think it still has something to do with the carb... but the only screw that we can adjust (beside the idle screw) is on top of the carb... but didn't seem to help when we adjusted it. Maybe we're adjusting incorrectly? - I've never worked with this kind of carb before (without L and H screws).

The only other thing I've seen mention online was the exhaust valve clearance, but I see no way to adjust them on this engine.

Any ideas?

 

[semimechanicman]

this video might help

 

[Scrubcadet10]

It is running extremely LEAN.. too much air, or not enough fuel.
i would remove the carburetor and thoroughly clean it (even though you replaced it, sometimes i have had to clean the CCP carbs) and replace the intake gaskets
4,3&,2 are gaskets i would replace.

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If the previous owner replaced the carb with a "Will Fit CCP carb" it is not uncommon for the jets to be too small for the engine size.
There is also no adjustment for the valves on this engine since it uses Hydraulic Lifters.

 

[jpdodd]

this video might help

Watched that one. Thanks though!

 

[jpdodd]

It is running extremely LEAN.. too much air, or not enough fuel.
i would remove the carburetor and thoroughly clean it (even though you replaced it, sometimes i have had to clean the CCP carbs) and replace the intake gaskets
4,3&,2 are gaskets i would replace.

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.

www.partstree.com

If the previous owner replaced the carb with a "Will Fit CCP carb" it is not uncommon for the jets to be too small for the engine size.
There is also no adjustment for the valves on this engine since it uses Hydraulic Lifters.

I was thinking there was too much air ( lean) but with all new gaskets and such couldn't figure out where it was getting in ( or how to adjust the carb). Does the horizontal screw in the picture adjust the fuel/air mixture? Didn't seem to have much affect when we turned it while running at low RPM.

Just talked to my brother and he mentioned that I should adjust the screw at high RPM. Does that sound right?

 

[bertsmobile1]

Quick & dirty test for lean running is to turn the choke on just slightly
If the muffler stops glowing red then it is a too lean problem.
Other trick is to restrict the air passing through the filter .
Things line covering 2/3 with glad wrap or a brown paper bag with a small hole in it .
Start the engine and it will probably blow some black smoke so you then cut more holes till it just stops smoking.
If the engine runs fine & muffler does not become red then you have confirmed too lean running .
There is this little grey band between just too lean but makes the muffler glow red and lean enough to cause the engine to surge .
Your engine could be in that band

 

[jpdodd]

Quick & dirty test for lean running is to turn the choke on just slightly
If the muffler stops glowing red then it is a too lean problem.
Other trick is to restrict the air passing through the filter .
Things line covering 2/3 with glad wrap or a brown paper bag with a small hole in it .
Start the engine and it will probably blow some black smoke so you then cut more holes till it just stops smoking.
If the engine runs fine & muffler does not become red then you have confirmed too lean running .
There is this little grey band between just too lean but makes the muffler glow red and lean enough to cause the engine to surge .
Your engine could be in that band

Pulling the choke more than just a little causes it to die out. Haven't tried just a small amount. I'll try that tomorrow and see. Thanks!

 

[jpdodd]

Pulling the choke more than just a little causes it to die out. Haven't tried just a small amount. I'll try that tomorrow and see. Thanks!

Ok. So I started it up this morning. Pulling choke a little had no effect on heat. Pulling a little more causes engine to run rough.

I also noticed that when I put the air filter on, it causes the muffler to get red hot faster...I was thinking the air filter would help restrict air flow some...

 

[jpdodd]

I was thinking there was too much air ( lean) but with all new gaskets and such couldn't figure out where it was getting in ( or how to adjust the carb). Does the horizontal screw in the picture adjust the fuel/air mixture? Didn't seem to have much affect when we turned it while running at low RPM.

Just talked to my brother and he mentioned that I should adjust the screw at high RPM. Does that sound right?

I also tried adjusting the horizontal screw on the top of the carb while at high RPM. Turned it all the way in and out with no change in engine performance...something strikes me as weird there...if that is a fuel mix adjustment...then it should cause it to run lean or rich affecting performance right?

 

[StarTech]

I got a good idea that OP didn't buy the OEM carburetor since it is nearly $500 retail; PN 24 853 102-S. So it is very likely just a will fit after market that has a problem internally or is simply the wrong carburetor for that 23 hp engine.