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Topaz

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The moderators are actively discussing the situation, and Admin has been providing tools for us to be more "granular" in how we moderate threads. The goal is for a private off-HBA discussion to not be necessary, and that you guys can have a constructive discussion on any HBA-appropriate topic to whatever degree you want, here, on HBA. If that hasn't been possible because threads are being hijacked, then we owe you folks an apology. It's always a fine line between keeping a thread constructively on-topic and clamping down too hard, limiting discussion. We're going to screw that up sometimes. Other times, such as lately, one or more of the moderators (that'd be me, this time) will be "away" for some period of time for outside reasons, and the remaining ones have to pull double-duty to keep an eye on the entire forum. To the extent I've contributed to that with my recent absence, I apologize to both you and them.

Back on the point, if someone is disrupting the flow of conversation in a thread, hijacking it, or just continually injecting unwanted commentary - especially in the opinion of the OP - please report those posts as WSimpso1 mentioned earlier. We will jump in and keep the thread running how you want.
 

soupercooper

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I found this very important unofficial Technical Advisory for the kohler v-twin engine, not 100% certain its for all v-twin models though. as it mentions the CH730 model but Im sure it reflects more models including maybe EFI versons (ECH series) perhaps worth a look though.

The cover in the valley between the cylinders is a serious design and construction flaw on these Kohlers.
Under that flimsy cover is a 3-sided "U-shaped" oil passage such that the oil pump feeds oil straight up to the bottom of the U and it flows around the sides and goes down various passages to oil everything inside the engine. The rest of the area (inside the U) under that cover is the crankcase breather with a flap valve, a mist separator ("horse hair") element, a drainback passage. A HUNDRED TIMES I have seen CH-730s where the gasket under that cover leaks pressurized motor oil back into the breather system and then you really don't have much oil pressure. The solution is to drill and tap for tiny studs and nuts straight down through the cover into the "walls" that separate your pressure oil from your oil-return areas. This will clamp the flimsy cover (with the shoddily-placed original bolts) down on to the very narrow and ultra-critical gasket areas that always invisibly leak internally. Other than that they are good tough engines. The factory redline on that unit is 3750 rpm, by the way.
FYI: fill oil filter with oil and let sit for 10 mins before install
 

karmarepair

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I found this very important unofficial Technical Advisory for the Kohler v-twin engine, not 100% certain its for all v-twin models though, as it mentions the CH730 model, but I'm sure it reflects more models, including maybe EFI versions (ECH series), perhaps worth a look though:

"The cover in the valley between the cylinders is a serious design and construction flaw on these Kohlers.
Under that flimsy cover is a 3-sided "U-shaped" oil passage such that the oil pump feeds oil straight up to the bottom of the U and it flows around the sides and goes down various passages to oil everything inside the engine. The rest of the area (inside the U) under that cover is the crankcase breather with a flap valve, a mist separator ("horse hair") element, a drainback passage. A HUNDRED TIMES I have seen CH-730s where the gasket under that cover leaks pressurized motor oil back into the breather system and then you really don't have much oil pressure. The solution is to drill and tap for tiny studs and nuts straight down through the cover into the "walls" that separate your pressure oil from your oil-return areas. This will clamp the flimsy cover (with the shoddily-placed original bolts) down on to the very narrow and ultra-critical gasket areas that always invisibly leak internally. Other than that they are good tough engines. The factory redline on that unit is 3750 rpm, by the way."

FYI: fill oil filter with oil and let sit for 10 mins before install
I'll try and gin up a picture from the illustrated parts breakdowns to illustrate Scott's point.

ALL the 749cc Kohler V-twins use the same block and closure cover. The point this story makes supports the argument AGAINST driving the prop from the Shaft/PTO end on the engine, the usual place for mowers, tractors and wood chippers and my initial first choice. The prop loads are going to get reacted by the bolted Closure Plate, as opposed to the flywheel end, where everything is a part of the block casting. Yeah, the journal bearing on the shaft end of the crank is longer, but the journal bearing on the flywheel end is in a stiffer part of the block, and is larger in diameter. Engineer Spacek in Czechoslovakia chose the flywheel end drive when he was using this "brand K" (apparently Kohler came after him for using their engines in an aviation application), and he's a pretty sharp designer.
 

soupercooper

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I'll try and gin up a picture from the illustrated parts breakdowns to illustrate Scott's point. (reply to soupercooper tech advisory)

(new subject) ALL the 749cc Kohler V-twins use the same block and closure cover. The point this story makes supports the argument AGAINST driving the prop from the Shaft/PTO end on the engine, the usual place for mowers, tractors and wood chippers and my initial first choice. The prop loads are going to get reacted by the bolted Closure Plate, as opposed to the flywheel end, where everything is a part of the block casting. Yeah, the journal bearing on the shaft end of the crank is longer, but the journal bearing on the flywheel end is in a stiffer part of the block, and is larger in diameter. Engineer Spacek in Czechoslovakia chose the flywheel end drive when he was using this "brand K" (apparently Kohler came after him for using their engines in an aviation application), and he's a pretty sharp designer.
your reply based on my last statement may confuse some readers as its a different subject than what I posted? I believe you combined two different subjects in one statement and it confused me as well as others? LOL
thanks for the help locating a diagram of crankcase breather issue, that will help clarify the advisory statement.
 

soupercooper

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here is initial effort to show crankcase breather and its weak design to sealing surfaces in center of the area, as noted in advisory to add more studs or fasteners to center area to eliminate oil passages by-passing to crankcase breather.
 

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karmarepair

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here is my first and only effort to show crankcase breather and its weak design to sealing surfaces in center of the area, as noted in advisory to add more studs or fasteners to center area to eliminate oil passages by-passing to crankcase breather.
Looks great, and my initial response WAS a little garbled, since I thought the sealing in questions was being done by the Closure Plate. My bad.

I'm wondering if replacing that breather cover with something stiffer, like a chunk of Cold Rolled Steel, would help, IN ADDITION to some more fasteners, and possibly a dowel pin or two, although there is not much meat there for adding fasteners - the existing fasteners work into bossings alongside the sealing surface. Or maybe adding a clamping plate on top of what seems likely to be a sheet metal stamping.
 

karmarepair

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pictsidhe

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Looks great, and my initial response WAS a little garbled, since I thought the sealing in questions was being done by the Closure Plate. My bad.

I'm wondering if replacing that breather cover with something stiffer, like a chunk of Cold Rolled Steel, would help, IN ADDITION to some more fasteners, and possibly a dowel pin or two, although there is not much meat there for adding fasteners - the existing fasteners work into bossings alongside the sealing surface. Or maybe adding a clamping plate on top of what seems likely to be a sheet metal stamping.
Aluminium would give higher stiffness to weight. Should be a much better thermal expansion match, too...
 

TiPi

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If you use the engine upright in an aircraft, I would block the original breather off and add 2 smaller breathers to the rocker covers, Y-piece, small check valve and into a breather can.
I don't think the Kohler engines have an oil supply for the rockers (the B&S don't), so the top end might not be lubricated properly and getting the blowby out through the rocker covers would at least move some oil mist up there for the lubrication of the rocker gear.
From the manual:
1602637102046.png
 

soupercooper

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If you use the engine upright in an aircraft, I would block the original breather off and add 2 smaller breathers to the rocker covers, Y-piece, small check valve and into a breather can.
I don't think the Kohler engines have an oil supply for the rockers (the B&S don't), so the top end might not be lubricated properly and getting the blow-by out through the rocker covers would at least move some oil mist up there for the lubrication of the rocker gear.
From the manual:
View attachment 103040
Great Info TiPi, I went to your website on your engine project BTW, very well done. I will be following your progress for sure, a pioneer, the best type IMO.

back to subject on hand:
TiPi is correct there is no oil supply to rockers. I like your idea of misting valve train with oil by rerouting the crankcase vent to rocker covers and add a catch can. i will heavily consider that great idea.

I plan on converting to roller lifter and rocker valve train, Kohler command and small block chevy share same valve train parts to certain extent. There is a you tube video on this I will share as he best explains better than I can with plain words. actually I'm linking two you tube videos one discusses the rocker arms and the other discusses the roller lifters. spacing on the lifter tie bars is different on Kohler than chevy so roller lifters wont interchange but roller rockers (1.5 ratio) will as discussed in the videos. also as you may know you need to switch to a roller cam as well and Im going with heavy duty push rods and better valve springs for this set up.

One of the video he mentions he gets these engines up to 10,000 rpms (not with stock flywheel! etc etc) for lawn tractor pull competition wow. obviously you cant do some of these performance mods that will sacrifice reliability for aircraft application. I feel its best to limit to 35 to 40hp range for reliability and avoid certain mods and use mods that improve flow (light porting), reduce friction (roller valve train) and not increase heat or stress. this subject could go on and on to the right approach and I cant truly cover it all here, everyone has to do there own research. these engines capable of up to over 100hp with mods BUT only for engines that never leave the ground. Viewer discretion advised...LOL
 

soupercooper

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Soupercooper is 100% right on this. Straight out of the service manual (here by the way - http://www.kohlerengines.com/engines/onlinecatalog/pdf/sm_24_690_06.pdf)
"
2. Place new filter in shallow pan with open end up. Fill
with new oil until oil reaches bottom of threads. Allow
2 minutes for oil to be absorbed by filter material."
I'm not the one who wrote this article but thanks for the feedback and additional info on the subject. That article actually written by a GAL, looks like she has seen or built or repaired hundreds of these engines, maybe she works for kohler? or is a Kohler repair shop? it was a comment posted on you tube from a video of a guy with a kohler in an air trike (not air trike enterprises) and he used a CHAIN DRIVE for his redrive! Im sure some of ya must of seen this? here is the you tube link, it was also posted on Dan Johnson you tube channel. Id Like to see what the guys have to say about this chain redrive, looks sketchy to me but I AM A JACK OFF ALL TRADES...MASTER OF NONE.

 

pictsidhe

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I'm not the one who wrote this article but thanks for the feedback and additional info on the subject. That article actually written by a GAL, looks like she has seen or built or repaired hundreds of these engines, maybe she works for kohler? or is a Kohler repair shop? it was a comment posted on you tube from a video of a guy with a kohler in an air trike (not air trike enterprises) and he used a CHAIN DRIVE for his redrive! Im sure some of ya must of seen this? here is the you tube link, it was also posted on Dan Johnson you tube channel. Id Like to see what the guys have to say about this chain redrive, looks sketchy to me but I AM A JACK OFF ALL TRADES...MASTER OF NONE.

That chain redrive is horrific. I'd be amazed if he hasn't broken his crank.
 

soupercooper

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That chain redrive is horrific. I'd be amazed if he hasn't broken his crank.
I hear ya...he's been trying to sell the trike. and i dont think he has too many hours on it to find out its a time bomb.
 

soupercooper

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If you use the engine upright in an aircraft, I would block the original breather off and add 2 smaller breathers to the rocker covers, Y-piece, small check valve and into a breather can.
I don't think the Kohler engines have an oil supply for the rockers (the B&S don't), so the top end might not be lubricated properly and getting the blow-by out through the rocker covers would at least move some oil mist up there for the lubrication of the rocker gear.
TiPi: I see your B & S uses a diaphragm pulse fuel pump just like the Kohler but Kohler places the pump right on top of Rocker cover where B& S is mounted off to the side but pulls the pulse (plumbs) from the rocker cover as well , my question is, if we incorporate your breather location idea to rocker cover will it hamper with the pulse pump function? are you still going to use the pulse pump or go to an electric fuel pump?, or perhaps use both for redundancy?
 

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TiPi

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The pulse pump works on the suction in the crankcase, opposite to some 2 stroke engines. The crankcase is vented through a reed valve (located in the breather/oil separator assy). If you vent the crankcase through the rocker covers, you will need to add the check valve I mentioned after the Y-connection, to ensure that there is a vacuum in the crank case for the fuel pump.
In my case, I will use the blowby to move the oil from the crank case to the oil tank and I don't know yet if the remaining vacuum is going to be enough for the fuel pump. I have 3 options if it doesn't work (BTW, the vacuum is very small, much smaller than the 2-strokes):
gravity feed (preference with the heads-down engine)
electric (I have a brushless Micro pump that weighs 30g and draws under 100mA)
pulse pump ex 2 stroke (maybe with a spring)
 

soupercooper

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update on crankcase breather and its weak design to sealing surfaces in center of the area, as noted in advisory to add more studs or fasteners to center area to eliminate oil passages by-passing to crankcase breather.
attached image of breather cover for kohler command engine, its made of cast aluminum but i found another comment of this problem on another you tube video, I posted link of you tube video below.

I believe the gasket shown in the photo is an attempt to fix the problem?, im not sure yet, but truly this needs to be closely looked at for a solution as you see in comment below it pump all the oil out of engine. maybe they added those traces of RTV to gasket as shown in photo to solve problem? but do we want to take a chance here? i would think to maybe add studs or fasteners to center of plate like mentioned on prior advisory posting? Update: Im finding many comments now on the plate warping as well, so adding fasteners would be a must for me or machining a thicker plate or to be honest forget kohler all together!!! I'm seeing several of complaints about kohler engines on you tube as I research this more and more.
maybe I/we should stick with Briggs like fellow member TiPi



comment from you tube:
Just an FYI if someone comes across this. This engine family has or had a service bulletin where the high pressure oil galley will blow the gasket out there at the breather and drain the oil out within seconds, literally. Just had this happen on my old z-turn mower while I was using it. By the times I got it back to the carport as fast as I could, (less than 30 seconds) the oil quit spraying out while I was trying to see where it was coming from and that was it, crankcase was bone dry. There is supposedly an updated kit that comes with a new style gasket and breather to help address this problem.

 

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TiPi

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PPD: piss poor design we would call that. Having the full pressure oil gallery right next to the breather with widely spaced hold-down bolts. There is not much you can do short of welding the oil gallery canal closed or drill & tap another small bolt (M4/M5) at the indicated location to apply a bit more pressure in the centre:
1602674697571.png
 

pictsidhe

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PPD: piss poor design we would call that. Having the full pressure oil gallery right next to the breather with widely spaced hold-down bolts. There is not much you can do short of welding the oil gallery canal closed or drill & tap another small bolt (M4/M5) at the indicated location to apply a bit more pressure in the centre:
View attachment 103072
A much heavier cover plate would do it. It is a pretty shabby design, though.
 
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