|
|
Post by paydem on Dec 3, 2017 14:48:07 GMT -5
After unhooking my oil pump I came up with a couple of questions. Is it better for the engine to coast with oil pump or without it?
For example, I ride at full speed, then let off the gas. The CVT still spins the engine at a certain RPM (higher than idle, of course), but if I don't give any gas, the engine does not receive the lubrication it needs, right? On a geared moped it's easy - you just pull in the clutch and the RPM drops, the engine braking is out of the way. But what about the scooters?
In my eyes, the oil pump supplies more oil when you're coasting and throttle is shut RATHER than when the oil pump is unhooked and you're running premix. I 95% certain that I'm making no sense with my words whatsoever...
It would be interesting so hear out your opinions about this topic.
|
|
|
|
Post by 'O'Verse on Dec 3, 2017 15:10:29 GMT -5
Your thinking the cylinder is possibly going dry upon coasting? My guess is if the piston is pumping than liquid is being sucked down into the cylinder. Question is... do rpms ever drop lower than idle speed while coasting? I don't think they do. As long as your bike is producing rpms then proper lubrication should match. Whether it's enough is another question. Like down a mountain just coasting may be a different story. If that makes sense. I would trust pre mix over oil pump any day.  |
|
|
|
Post by tiny on Dec 3, 2017 15:10:47 GMT -5
Even coasting or at idle you're still getting both fuel and oil. i dont see it as a problem my self as i tend to do it also or go low throttle. But im no expert others here may have different opinions.
|
|
|
|
Post by oldgeek on Dec 3, 2017 17:52:30 GMT -5
After unhooking my oil pump I came up with a couple of questions. Is it better for the engine to coast with oil pump or without it? For example, I ride at full speed, then let off the gas. The CVT still spins the engine at a certain RPM (higher than idle, of course), but if I don't give any gas, the engine does not receive the lubrication it needs, right? On a geared moped it's easy - you just pull in the clutch and the RPM drops, the engine braking is out of the way. But what about the scooters? In my eyes, the oil pump supplies more oil when you're coasting and throttle is shut RATHER than when the oil pump is unhooked and you're running premix. I 95% certain that I'm making no sense with my words whatsoever... It would be interesting so hear out your opinions about this topic. I completely understand the angle you are working, and it is a good question. Here are a couple thoughts I have on your theory. 1) At "idle" is the oil being pumped into the carb really going much further than where it is pumped into the carb? There is some velocity through the carb with the slide shut, but is there enough velocity to move to oil into the motor? The oil is not really diluted with gas yet at that point, but some raw gas is coming in at idle for sure to help get the job done. 2) It is common to have to up jet when going to premix, due to the gas/oil mixture being slightly thicker than just gas. I dont know if the pilot jet is always made bigger, but the MJ is usually a couple points larger. No matter what, at idle with premix there is always going to be oil getting to the motor if it is running. 3) I think oil injection was developed primarily to eliminate the chore of carefully mixing your gas and oil. Lets face it, no one really likes having to measure gas and oil when refueling. But for some the benefits of premix such as knowing exactly what your ratio is, and then being able to tweak it easily makes the process worthwhile. I could go on and on with MY theories, but I am pretty sick, and I think the cough medicine is making me ramble a bit.Lol! I have several 2T scooters, and some of them are still oil injected, and some are premix. I just have to keep careful track of which ones are which! BTW wrong or right, I have a habit of goosing the throttle a bit after a WOT run to help lubricate and cool the motor a bit |
|
|
|
Post by ryan_ott on Dec 3, 2017 18:15:06 GMT -5
You’ll get all sorts of opinions on this question but here is mine:
I’m premix, all of my bikes are always premix. I don’t like to coast, say down hill, with the throttle completely closed. Higher rpm, very low throttle opening to me equals lack of lube. I prefer to crack the throttle just slightly when I’m running down hills, just enough to notice the temp drop. A little full throttle goose is always mandatory after a full throttle run.
|
|
|
|
Post by AtariGuy on Dec 3, 2017 19:13:33 GMT -5
I'm understanding what you're saying. With engine braking (coasting down from wot) an oil pump still runs in speed with the engines rpm - even with the throttle closed. It's still supplying gobs of oil to keep things well lubricated.
While premixing and engine braking, the engine draws a very very strong vacuum signal through the closed carb still drawing fuel to maintain ignition. In that sense, you're still getting a dose of oil per stroke, but not quite to the degree of an injector as you're relying solely on the pilot jet to feed premix.
I'd recommend, for premixers, blipping the throttle (like ryan stated just before me) during decel to still give a bump shot of oil to the crank/cyl. Some high end premixers will even run pig rich in early/mid throttle carb tuning just for that reason, blipping to oil the engine while coasting down.
Do you need to? Depends if you've got a crazy build and are protecting a few thousand dollar investment. If its a stock/mild sport build, you shouldn't need to, but it wouldn't hurt to blip.
|
|
|
|
Post by AtariGuy on Dec 3, 2017 19:19:32 GMT -5
I'll add this too, i know there are coasting gears for gy6 (50-150's) where it lets the rear wheel free-wheel instead of engine braking. I haven't found one for a minarelli yet, but i can't say i've looked for one though. But if there is one, it would disengage the rear wheel from the driveline if the wheel was spinning faster than the engine - allowing the engine to return immediately to idle. Benefit? Maybe for hypermiling - but you wouldn't ride a 2 stroke for that... 49ccscoot.proboards.com/thread/19957/gy6-final-coasting-gear |
|
|
|
Post by benji on Dec 3, 2017 19:59:07 GMT -5
When running down a hill on a 2t motor, letting go of the throttle and engine braking down the hill can spike cylinder temps cuz the fuel cools down the cylinder walls and rings. The oil is for lubrication, not cooling. I've heard of long down hill runs causing heat spikes and possible seizures.
Personally, I go full throttle down every hill. But only cuz of the added speed 😁
|
|
|
|
Post by paydem on Dec 5, 2017 9:28:46 GMT -5
Although I hate mixing gas everytime I fill up, I still run premix. In my case I have stock oil pump with 10k km's on it and no matter what anyone says, I don't trust it. I sound too much paranoid, but even in my area we had cases when stock oil pumps let out and seized perfectly running engines.
I thought that I would be eaten alive for questioning a such thing, thankfully it didn't happen. I never go idle down a hill, but i have a lot of hill's in my area so it was interesting to see what your opinions would be.
|
|
