What would you do? By twowheeler (Read 1,533 times)

[twowheeler]

If you had ro run your 50 or 150 at 8000 rpm's all the time, would you switch to synthetic even though its not recommended?

If not what brand/weight would you trust your motor to?

[Bashan]

8K is not that high for RPMs. My GY6s will hit 9K or even a bit above at WOT. My Pegasus, which is the GY6 "B" engine will top out at 9,700. By the way, the CF Moto engine that is called the "B" is not a GY6 at all but the term seems to be gaining traction.

Anyway, your 8K RPM is well within safe parameters. What is your concern? The heat from WOT, or the mechanical stress? I did experiment a little with Mobile 1 synthetic diesel oil in my naked GY6 bike. I tried it because diesel oil is formulated to stand up to the rigors of a diesel engine which include high temperatures. You can read that thread right here. The argument against running synthetics is that the tolerances are too loose in a GY6 and the slippery molecules of synthetic oil slip past the rings. I did not notice that I was burning oil while I was using Mobile 1, in fact the bike ran great. Member Oot Scoot, who is a dealer on the west coast, uses this oil for all of their SYM engines. If your concerns are heat and mechanical stress Mobile 1 synthetic diesel would cover both. Just keep an eyeball on your oil levels.

[twowheeler]

You suggest the diesel vs the 4T synthetic Mobile One has?

I have a BN139QMB and every motor spec ive read for these ZNEN 50's is the max HP peaks out at 8000 rpm vs the regular QMB139 at 7500

With all due respect many folks here including the great and powerful Alley insist you should be nowhere near 8000 rpms. Ever.

[twowheeler]

Interesting response to this on another forum...

2.hidemyass.com/ip-3/encoded/Oi8vdGhlc2Nvb3RlcnByb2Zlc3Nvci5wcm9ib2FyZHMuY29tL3RocmVhZC8zMjg2L2NyYWNrcy1tZQ%3D%3D

[Bashan]

Well, that's what my tach reads. It's the same tach for all of my bikes, I swap it around. It could be off I suppose, I don't have anything to check it against. Those are the highest RPMs I saw on the tach, not what I normally run.

This is the oil I was talking about:

[kz1000st]

I'm very conservative in my use of revs Rich. I know there is more available on anything. Heck! Kawasaki 250 Ninjas red line at about 14,000. After breaking the valve springs on my 150 when it was new, I'm shy about using full throttle. Like I said over there 8,000 is 133 revs per second. I can't even belch that fast.
And as I said to Jack. Oil is oil. Even the cheapest crap is SM, Mobil 1 is even SN. That is worlds better than the SE we ran 40 years ago.

[Bashan]

Yeah, I only said that about topping out at 9K to make the point that he wasn't roasting his engine at that lower RPM. Certainly lower RPMs that meet your performance expectations is prudent.

To prove to myself that I wasn't going senile...yet, I did a quick search and came up with a couple threads. This guy says he is popping 9,500. Mac says in this thread that he hit 10,250 with a modified GY6 and 8,500 is a routine redline. I can hit 9K with my GY6s, they are winding tight and I don't do it for very long, but unless my Tiny Tach is wrong, it happens.

Dec 7, 2013 16:07:47 GMT -6 kz1000st said:

I can't even belch that fast.

[tvnacman]

Can we get a governor on my wifes nagging ?

John

[jct842]

I don't think a person could find oil today that is actually bad.

As far as max rpms go I believe the stroke length is the biggest factor on our little engines with the 50cc taking top honors. You look at model airplane engines specs and the smaller and shorter stroke engines again take top honors for high rpms./ A stroker should not be able to get the rpms a stock engine can. There is a max piston speed in feet per sec. for a standard construction of piston/cyl. john

[twowheeler]

[glow=red,2,300] There is a max piston speed in feet per sec. for a standard construction of piston/cyl. john

English please?
Read more: www.scooterdoc.proboards.com/index.cgi?board=talk&action=display&thread=9034#ixzz2mqOG7VEl
[/glow]

[jct842]

The longer the stroke the further the piston travels (both up and down combined) There is a limit to how fast the piston is moving and the shorter stroke engines do not travel as far so they can rotate faster. It has something to do with friction and self destruction when speeds become high enough.

The way I figure it a 150cc at 9,000rpm is 3375 feet per min. where a 50cc at 9,000 is only 2452 feet per min. and would have to turn over 12,000 to have the same piston speeds as a 150cc. Some of the chome bores and expensive engines can go a whole lot faster than that.

hotrodenginetech.com/calculating-piston-speed/
www.wiseco.com/Calculators.aspx

[Alleyoop]

People, very simple the 4 strokes motors produce their max horsepower anywhere from around 7200-7500 rpms. Now why in the world would you want to run them at 8K+?? At 8K the motor is screaming and if you cannot hear the difference you deserve the blowup. You are not doing nothing for your performance as a matter of fact you will loos power also depending on the quality of the valve springs you could get valve float and KABOOM the piston will hit the valves. Not only that but the crank rod can break and or let loose and come out your motor case. Can you imagine the heat been generated on the crank bearings!!
Yes the motors will crank high rpms but at what price, there is a reason they mark the tachs RED starting at 8K(RED DANGER) first thing you learned when you where small RED MEANS DANGER but then again maybe you didn't learn anything.
Alleyoop

[mike6736]

If you want speed and power get a bigger scoot.. why push a little motor to the max?

Magoo

[LUKE]

Dec 8, 2013 0:51:45 GMT -6 mike6736 said:

If you want speed and power get a bigger scoot.. why push a little motor to the max?

Magoo

Exactly!!!! i hate when people buy a 50cc then install a BBK on it,
BBK will only ruin your scooter, plus you need to re-jet and all that stupidity... my goodness! im about to sleep and u got my blood boiling...
a 250cc japanese scooter is the best to ride around town. 50cc chinese is only good for doing errands like going to walmart when your mommy ask you to buy a loaf of bread.
but anyhow, to each his own. whichever fits your lifestyle right?!!!

[twowheeler]

50cc chinese is only good for doing errands like going to walmart when your mommy ask you to buy a loaf of bread.