Exh. ports Kohler 4hp

[Kelly 1,029]

I know it has been done but the search feature is not my friend tonight, the newer engine do not have tapped exh ports the orig. RJ engine has them, I know guys have tapped them but I can't remember all that is need to do so, any help would be great, I sold a engine and the port needs to be tapped for the exh to fit and look correct, for the guy, I forgot al about that issue till he set me a email about it, I just don't mess with the early tractor enough.

[GlenPettit 1,716]

Kelly:

I also couldn't find it on Red Square,

but try google; "Small Engine - tapping exhaust ports"

many entries there,   also try;  "Jacks Small Engine".

[clemedc 29]

Kelly

I recently tapped one of the lil blue K91 engines and the exhaust port is almost perfect size for a 1/2 pipe thread. Just stuff in a paper towel to keep the shavings out and use plenty of lube and slowly tap the threads backing up when it gets tight and start over until your happy with the depth. After taping the threads i used a short 1/2`` nipple then a 1/2 to 3/4 adapter.

[buckrancher 2,679]

the correct size is 3/4" pipe but you need to drill the hole bigger to tap it that size I have done this several times on a bridgeport mill  59/64" drill I may have posted a pic in the stainless RJ58 build

 

 

 

(I went and looked and I did not post a picture)

 

Brian

Edited March 25, 2013 by buckrancher

[formariz 11,987]

Kelly

 

I have done quite a few. Very easy but on an assembled engine need to be carefull with shavings. besides plugging hole with a paper towel i keep taking tap out and vacuuming shavings often. Kind of important to go in as deep as possible since hole in engine is a bit oversize for 1/2"tap. Going in deeper allows you to have higher percentage of thread on high part of taper so there is less chance of stripping threads when tightening nipple. On an engine without the valve this is really easy since you can see tap bottoming out through port. Of course important to go in perpendicular to opening. Here are some photos of a K90 I just did.

[wallfish 16,980]

Is using a 1/2" pipe going to cause too much back pressure or any engine problems besides a little less power? These aren't used for work and just putt around once in a while.

 

In the stable are 2 Clinton B1290s and 1 K91 that are tapped for 1/2" NPT, plus 1 K91 that is 3/4". I believe they are factory tapped threads and don't seem to have any issues running. I have a 1/2" NPT tap and need to do a K90 and a K91 but would they be better off being tapped for 3/4"?.

[formariz 11,987]

I use a 1/2" to 3/4" adapter right off the port . I don't think that one inch of lenght at 1/2" makes any difference since the engine was designed with a 1/2" port anyway.

[AMC RULES 37,127]

On an assembled engine...

any tips on how to ensure the tap stays square to the port as you're running it in?     

[rwilson 128]

tap it 1/2 and use a 1/2 to 3/4 street L or 45