pictsidhe
Well-Known Member
We have gone to TiPis group: Small-4-stroke-engines groups.io Group
I'll try and gin up a picture from the illustrated parts breakdowns to illustrate Scott's point.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
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? LOLI'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.
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.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.
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)Filling an oil filter before fitting can cause pump priming problems.
Aluminium would give higher stiffness to weight. Should be a much better thermal expansion match, too...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.
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.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
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.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."
That chain redrive is horrific. I'd be amazed if he hasn't broken his crank.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.
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.That chain redrive is horrific. I'd be amazed if he hasn't broken his crank.
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?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.
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.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.
A much heavier cover plate would do it. It is a pretty shabby design, though.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