High compression engine ping?

[lazylightning@mail.r]

This action is also another reason why you don't over rev a 2-stroke

As the cranshaft rotates through 360 degrees, the needle rollers will reverse direction as the connecting rod angle changes with respect to the rotation of the crank pin.
The needle rollers can spin only so fast before they can't reverse their spin motion over the crankpin surface, momentarily coming to a rotational stop whilst still sliding.
This puts microscopic flat spots on the hardening layer and over time the hardening starts to break up - impact of continual detonation will also cause this layer to break up.

So how do some of these small two strokers do 16,000 rpm's, with 15,000 as a sustainable rpm?

 

[lazylightning@mail.r]

Thanks alot Fabian for the info about the performance connecting rod replacement. It looks interesting, but I think the real issuebeing the bearings and ignition timing problem.....I will have to go for the heart of the problem. My budget is so incredibly limited, so I will try to repair the old connecting rod and crankshaft. I work in a hangar that has a welding shop and and machining shop. If we can get that crank apart, I can ask them to take off the damaged layers in the connecting rod and on the crank bearing surface. They're all pretty hip about my ride, so the main welder, a little granny that acts like a young girl, already offered to make my expansion pipe for free. The funny things is, that she welds so darn good(and is highly respected for that) that she even welded two pieces of 1 mm stainless sheet for me(as a test on my metal for the pipe), using a 2 mm stainless electrode - on a normal welder - no argon or torch welding. She said nobody else can do that, it's just that she has great experience packed in her hands. I gave her the pieces to see if she could do it. Next, I was planning to cut and bend all the pieces for the pipe, but now it looks like I'll have to tap the collective resources of our factory for more urgent matters. With the rod and crank surfaces remachined(will cost me nothing if do-able), then I'll just have to find performance needle bearings or cage and bearings to fit the new size. I know, I should think ahead and find them before machining. Does anybody know names of a good super performance bearing? SKF, was one I saw mentioned?

 

[lazylightning@mail.r]

So could this incorrect timing of the standard kit cdi have also caused me to be unable to reach a higher speed? Before the bearings cashed out of course...

 

[lazylightning@mail.r]

Anybody got a link for those bearings and double lip seals for the 66cc/F-80. I lost that thread and cant find it...

 

[Fabian]

The quality of the needle roller bearings, the weight of the needle roller bearings and the bearing carrier weight determines how fast an engine can be revved (with regards to what the bearings can take) plus all sorts of exotic surface coatings are applied to high performance bearings.

When you purchase a complete replacement engine (including electrics) for $70 - $100, you're not getting worlds best technology; you're not getting a titanium bearing carrier; you're not getting the best metallurgy for the needle rollers; you're not getting the best case hardening process for the needle rollers; you're not getting cutting edge surface coating technology and you are not paying serious money for the needle roller bearings.


The standard CDI may only have a small effect on your top speed figures, as when i went from the standard CDI to the Jaguar CDI, i didn't notice any meaningful increase in peak power (on my completely standard engine) but it seemed to run with a less aggressive level of vibration. In some ways the engine felt like it had less power but the speedo does not lie.

At the end of the day, the only difference between my current engine and the 7 previous engines is the Jaguar CDI and reed valve intake.
My current engine has more than 10 times the distance on it than each of the previous engines - i'm inclined to believe that the ignition curve has a heck of a lot to do with it.

 

[lazylightning@mail.r]

Oh yeah! For sure with the Jaguar cdi. I'm still going to try to find a proper two stroke moped cdi here in Russia because of the long distance shipping and all. But I would get one of the Jaguar cdi's for sure. I think it's proven it's importance.

BTW, I paid about $270 for my engine kit.

 

[Fabian]

I paid $250 for my engine kit in Australia

 

[FelipeCobu]

Hi Fabian,

Both my engines came without a "caged" bearing. Instead it comes with needles between the rod and the pin (big end of the rod), someone here at the forum told me its more reliable then the bearings perhaps it can be a be a cheap solution. If my memory serves me well they are 2.5 x 10 mm (diameter x length) rollers.

 

[Fabian]

The non caged, otherwise known as a crowded roller bearing assembly is the best solution, especially given that the standard CDI uses a 4-stroke igntion curve which causes detonation and hammers the connecting rod bearings.
I happen to know that bicycle engines manufactured at the Nantong Jali factory in China are assembled with a crowded needle roller bearing setup.

From what i understand, most manufacturers have converted to this method.

 

[lazylightning@mail.r]

The non caged, otherwise known as a crowded roller bearing assembly is the best solution, especially given that the standard CDI uses a 4-stroke igntion curve which causes detonation and hammers the connecting rod bearings.
I happen to know that bicycle engines manufactured at the Nantong Jali factory in China are assembled with a crowded needle roller bearing setup.

From what i understand, most manufacturers have converted to this method.

I think mine is crowded roller too. I was getting alot of power and getting the max out of it with a stock cdi though.