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Post by katt on May 20, 2018 17:28:26 GMT -5
I am working in delivery and i tend to spin engine to 7000k or even 8000k most of the times to get speed up to 40MPH right now its adjusted for perfect acceleration/speed ratio however i am concerned if i run at this high RPM day like 6 hours will be bad for the engine?
When i go to 8000+ rpm i can hear engine sound wired so i usually don't go in the red zone maybe for a second or so.
On one side i like that engine does not go faster it stops me from driving fast like idiot, i don't want a bigger bore kit.
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Post by humanshield on May 20, 2018 18:15:59 GMT -5
4 stroke.....
You can probably do 7,000 all day long. 8,000+ starts to put a bit of stress on the motor imo.
But it also depends on the balance of the engine and the reciprocating weight and how far out of balance the rotating mass of the crank vs rod & piston is for example.
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Post by Happypancake! on May 20, 2018 18:43:20 GMT -5
It should always be a WOT. It’s a scooter.
I run consistently at 9700 rpm w no issues.
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Post by katt on May 20, 2018 23:37:44 GMT -5
It should always be a WOT. It’s a scooter. I run consistently at 9700 rpm w no issues. And you have Chinese gy6 engine or made by honda?
I feel like today i might have overheated going 10 minutes at 8000rpm consistently then on the light it slowly died and would not start, i cranked with kickstand and wide open throttle and started in about 2 minutes then engine it made some noise.
I think for short periods of time in the city going past 8k is okay, but for consistent driving i keeping mine at 7000 at least until i get a temp sensor.
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Post by katt on May 28, 2018 5:32:14 GMT -5
What i noticed is my oil is getting low i had full dipstick two weeks ago now i have about 60% left perhaps has to do with spinning engine very fast, i know with cars you tend to burn oil even on new cars when RPM go past 4500, perhaps scooters are same.
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Post by diynuke on May 28, 2018 7:17:22 GMT -5
stock they can handle allot xD 7000rpm is kind of for what they are made for and if its overheating all the time your air fuel mixture could be a bit on the lean side.
All stock engines tend to run lean for the least emissions and fuel consumption.
and if it is consuming oil i would suggest checking the crank case breather (on top of the valve cover) my scoot had the same. turned out the hose was sandwiched between the frame and the buddy.
and high speed? these scoots really aren't fast.. but yeah longest running engine is one that has time to warm up and rev's at 7000rpm and have it run hard once in a while. and if it keeps revving a bit high just trow in some heavier roller weight's
Aslong as they have oil and a correctly tuned carb you won't see one break down fast.
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Post by Happypancake! on May 28, 2018 11:14:10 GMT -5
What i noticed is my oil is getting low i had full dipstick two weeks ago now i have about 60% left perhaps has to do with spinning engine very fast, i know with cars you tend to burn oil even on new cars when RPM go past 4500, perhaps scooters are same. Honda GET motor. |
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Post by GrumpyUnk on May 28, 2018 12:17:56 GMT -5
happypancake forgot to mention that he has never had a valve float problem, and can run all day wide open, because he has a 2T engine. No oil to check in the crankcase, either. But he does burn oil, all the time.
I am not sure if a 2T can really handle WOT all the time as well as a 4T engine. The 2T is firing on every rotation, never giving the engine the 1/2 time off that a 4T engine gets. The 4T fires every other revolution, though it fires the spark plug on every rotation.
I have read the engines were designed for a top rpm of 7900 in the 'specifications' section of a 138QMB engine manual. The peak torque and hp developed right around there, so higher rpms are not producing max torque or hp.
If you are burning oil, check the viscosity you are using, and look for leakage from the crankshaft seals on either end of the crankshaft. Do not forget to look where the crankcase vapors are being vented from the tube on the rocker arm/cam cover. Look for oily smear at the end of the tube. You can also add a length of hose, pointing it UP to allow more vent 'length' before the liquid will work its way out the end. Gravity will tend to return any liquid to the engine, and the length may keep the pulses from pushing all the way to the end, carrying lube droplets. Look for oil on the filter cover seal and the drain plug seal. You can also have leakage at the cam cover, due to looseness or a flattened O-ring gasket. The 'base gasket' at the bottom of the cylinder can also seep oil. Use some GUNK engine degreaser or brake cleaner to rinse off the engine if it is oily, and then check regularly to determine where it is seeping from. If the rings have gone, you'll get oil consumption that may lead to blue smoke out the tailpipe. Valve stem seals can also allow consumption if they have hardened due to age & heat and no longer seal. You would most likely notice a puff of smoke when you first accelerate after riding for a while, and sitting at a stoplight if the valve stem seals are on their way out.
tom
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Post by katt on May 29, 2018 18:23:54 GMT -5
I have read the engines were designed for a top rpm of 7900 in the 'specifications' section of a 138QMB engine manual. The peak torque and hp developed right around there, so higher rpms are not producing max torque or hp. My engine does not go above 7000rpm until it gets to 35mph mark.
I hit about 35mph on 7000rpm, 40mph on 8000rpm and if i really want to go faster for a very short time i hit 8500-9000rpm and i get to 45mph.
I used 10w-40 but i want to go with 20w-50 since its summer now.
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