jinma 224 with 2 hours

JohnS · Jan 17, 2005

I have never started mine using the decompression lever, either. But, I did assume it would provide some lubrication and it was probably a better way to go. That seems to be the core of this discussion. Does it or doesn't provide some lubrication at starter speeds?

Has anyone had their valve cover off, and cranked the engine over quickly, with decompression engaged? I believe that you would need to rig up something, like using vise grips, because the lever is part of the valve cover. If oil is getting to the top of the head, then it is most likely getting to other critical areas. Maybe you could do this test by shinning a good light in the oil fill hole. If you see new oil, answers the question. If no oil seen, doesn't answer it 100%, though.

Outside of the lubrication, I do believe there is some benefit just getting things turning when it is ultra cold out. Probably could be argued that it is more a battery issue, though.

Now, keep in mind, all these suggestions and tests are coming from someone who puts his tractor away for the winter! /forums/images/graemlins/crazy.gif

greg_g · Jan 17, 2005

(
Outside of the lubrication, I do believe there is some benefit just getting things turning when it is ultra cold out. Probably could be argued that it is more a battery issue, though.
Now, keep in mind, all these suggestions and tests are coming from someone who puts his tractor away for the winter! /forums/images/graemlins/crazy.gif
)
Things are beginning to be taken outa context here. John - it's unclear toward whom you're directing the "puts his tractor away for the winter" comment. So just in case, rest assured I use my tractors 365 days a year. When they're done for the day, they're parked either outside or in open front sheds.

My 2wd Yanmar with turfs was no good in mud and snow, so it was shedded a few months a year. But having said that - it had ThermoStart, which beats the **** outa glow plugs. The old Yanmar may have had lousy winter traction, it sure did start good in the cold. My KAMA doesn't even have glow plugs, and has not once failed to start. But sure I do remember - vividly - what comparatively hard starters those two Jinmas were in the cold.

Second, I've always maintained in these forums - that the primary benefit of the cold start decompression feature has been to save wear and tear on the starting system. I thought I was pretty clear in the past that upper cylinder lubrication was a fringe benefit of using the compression release for cold starts. If you've ever had to start a tractor with a hand crank, you'd be positively SOLD on the idea of using it for EVERY start. But with an electric starter, once the engine's been fired up for the day - using the decompression lever becomes optional in my book.

Harry, to say that using using the decompression feature can HARM an engine, purely flies in the face of millions of diesel engines - and motorcycle engines - and ATV engines -and airplane engines - that incorporate compression release in one form or another. What an absolute economic and engineering boondoggle it's been, for all those manufacturers have been wrong all these years.

//greg//

Harrygoodwrench · Jan 17, 2005

John,
Point well taken. Now I'm not trying to prove a point or anything like that. It really matters not to me how others prefer to start their engine. This however, is the way I view it. If you were to do the test for oil at the valve cover while cranking it would be inconclusive as the valve train is the last area to get oil pressure. The main areas that takes on wear during start-up are the areas of "high unit loading", main & rod bearings, camshaft bushings, cam lobes and lifters, etc.
Basically the cylinder walls need little lubrication except as splash lube and occasionally as oil cooling jets to "cool" the underside of piston and lube wrist-pins. The high unit loaded areas as I listed(bearings, lifters,etc) take on the most wear when starting as there is no oil pressure and metal to metal contact occurs.
Extensive cranking simulates the same conditions as low/or no oil pressure and accelerates wear. This using of decompression system only reproduces extended cranking.
If you want as little wear as possible the options are. Use only in ideal temperatures, use a pre-lube system, keep engine tuned(includes oil, etc), battery,charging, starting system up to specs etc,,,,,etc. These things are not always possible so we deal with it as best we can.
Like I said, it matters not to me how others start their tractors I just want to bring forth my opinion and the factual reasoning behind my opine.

Harrygoodwrench · Jan 17, 2005

Greg, you are free to believe what you want but that does not make it gospel.
Who died and left you the "self professed" expert on China tractors? I've turned wrenches professionally 30 years now and think I know just a little of what I say. And if I'm wrong I'll step up like a MAN and say so.
If you have nothing nice to say,,,,,,,,,,say nothing..............
Its well known you have a bad attitude toward Jinma's due to your bad experience with 2 of them, which I'm beginning to question. Stick to the subject and we can all get along.
Good day and no response is wanted.

Tractors4u · Jan 17, 2005

( But, I did assume it would provide some lubrication and it was probably a better way to go. )

You may be correct here John. I have never had a Chinese tractor but I have had more than my fair share of grey market tractors, particularly Yanmars, which had compression release levers. The Yanmars had oil pressure lights and each time I would pull the compression release and hit the starter, the oil pressure light would go out, indicating that the engine was getting oil. Am I misinterpreting something here?

Soundguy · Jan 17, 2005

( There is no way you are going to throw sufficient oil on cylinder walls at starter speed even with )

I may be way off base here.. but I always thought the premis of the decomp lever and no fuel during a pre-spinup was to get the oil pump pumping.. that way oil gets to the oil starved / drained down head.. not the cyl walls that are spalsh lubed?

We.. over in the yanmar forum.. also make use of our decomp levers. Most of our tractors don't have glow systems.. but have a cruder 'thermostart' option that burns a tad bit of fuel in the prcomb chamber to warm things up.. still not all units are thermostart equipped.

It is common practice to pull the decomp.. spin a few revs, and then release the decomp and move the throttle up.. that way fuel is no sprayed in during decomp. ( yanmar pumps have that 'all the way back setting' that effectively shuts the fuel down. ( a 2 handed job.. less if you have a foot throttle.. ) Many times a few revs of the starter and the oil light is already out.. or those with added on mechanical gauges are already seeing a few psi of oil pressure bobbing on the gauge...

Is it so different with the chineese units?

Soundguy

Soundguy · Jan 17, 2005

( The high unit loaded areas as I listed(bearings, lifters,etc) take on the most wear when starting as there is no oil pressure and metal to metal contact occurs )

Again.. with the decomp pulled.. seems like that high load is greatly relieved.. and as the oi pump is pumping.. seems like things like bearings are gonna get lube.. um.. faster than in a non-decomped situation here???

Soundguy · Jan 17, 2005

( If you've ever had to start a tractor with a hand crank, you'd be positively SOLD on the idea of using it for EVERY start. )

Amen to that. I've got a 2 cyl JD.. flywheel crank.. and without the decomp petcocks open.. it is a real bear to start.

At work we have one of those big chainsaws with a 6' bar ( sthil?) And unless you have arms like popeye.. you use the decomp button to start it..

Soundguy

Harrygoodwrench · Jan 17, 2005

Isn't the purpose of the decompression system to allow faster revolutions so it can provide the compression necessary to start??????? My point being is, the decompression systems main purpose is to allow the engine to start in the first place, If so equipped. Basically NO lubrication benefits take place during this practice only wear but at least engine runs hopefully and thats the main objective.
Wear DOES take place during this process thats all I'm saying

BTW, Tractors4U, I think what you experienced with the oil light going off while cranking is the oil light was only wired hot in "On" position and not cranking position. I've rebuilt many a engine in my professional career. Takes quite a while cranking to get oil pressure up. I've used a drill to drive oil pumps before starting to run up oil pressure and it takes a bit to get pressure up even using a mechanical gauge.
You guys make up whatever you want, as it is what you want to believe.

greg_g · Jan 17, 2005

( BTW, Tractors4U, I think what you experienced with the oil light going off while cranking is the oil light was only wired hot in "On" position and not cranking position. )
Dont' take my head off again Harry, but it actually does work the way T4U describes. SOP for Yanmar owners is to crank the starter and watch the oil pressure idiot light while holding the compression release open. Soon as the little red light goes out, let go of the compression release handle. Engine starts.

The Yanmar oil pressure idiot light is fed a constant 12v in both START and RUN. The sending unit is a diaphram switch, roughly calibrated so that 0 to ~6 PSI is ground. 12v through the idiot light to ground makes it glow.Complete circuit. At ~7 PSI and above, the there is enough oil pressure to push the diaphram away from ground. Open circuit.

Therefore, in START, the light remains ON till you crank the oil pressure up to ~7 PSI. With the engine running and the switch in RUN, the light remains off, till the oil pressure drops to 6 PSI. I know this from rewiring my own Yanmar.

//greg//