Ld100's

On the same stroke a longer rod has less angularity and more dwell as it passes through tdc and bdc, if the long rod had a low holed piston it would allow for the piston to have more twist in the bore showing thrust side wear much quicker than a high hole would.
There are three types of engine over square, square and under square, over square will be long rod less angularity and stroke longer than the bore's dia, square could have ether long or short rod and a stroke equal to the bore then under square is shorter stroke than the bore's dia.
Over sq is for torque, sq is good all around and under sq is for higher rpm usually though higher angularity can also pose a problem with piston wear.
 
Bore (47mm) and stroke (40mm) being the same: The PK80, short rod (85mm) low hole piston vs. the Zeda80, long rod (89mm) high hole piston. Any real advantage of one over the other?
 
Go to page three of the PDF below and start from the title CRANK SHAFT...i think this may help answer your questions as this PDF is all about the differences of the PK80 vs Zeda 80 vs GT-5...it willl download to your downloads for off line use for better reading puposes...DAMIEN
 

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That's the document I'm pulling the specs from. I was just composing a reply relating to the difference in performance between the 66/80 cc engines and the LD100. Just hang on a tick ;-)
 
Cisco said:
Bore (47mm) and stroke (40mm) being the same: The PK80, short rod (85mm) low hole piston vs. the Zeda80, long rod (89mm) high hole piston. Any real advantage of one over the other?
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Not really they are so close to being the same, slight angularity difference and the thrust side wear slightly higher with the low hole piston but this is mostly done to get the piston height correct (or close) with the different setups.
 
The YD100s and the LD100s are more under square than the 66/80 cc engines, but I've heard that the YD100 has better low end torque yet lesser high RPM performance. If an under square engine generates better torque at higher RPMs, then why don't these 50mm bore engines perform better?
 
Cisco said:
The YD100s and the LD100s are more under square than the 66/80 cc engines, but I've heard that the YD100 has better low end torque yet lesser high RPM performance. If an under square engine generates better torque at higher RPMs, then why don't these 50mm bore engines perform better?
Click to expand...
If you want torque, get a steel sleeve 100. Way more torque than a 66 and a yd 100. Steel sleeve has better compression, at least how I set them up.
 
Cisco said:
The YD100s and the LD100s are more under square than the 66/80 cc engines, but I've heard that the YD100 has better low end torque yet lesser high RPM performance. If an under square engine generates better torque at higher RPMs, then why don't these 50mm bore engines perform better?
Click to expand...
The low end torque gain comes from displacement but it falls off or flattens out sooner having to deal with the compression over a larger area. This takes away from it being able to rev higher.
 
Everybody wants the Big Bore engines (I want more power!). Are they really better? I'm intrigued by this new LD100 engine. @Karl Snarl , what steel sleeve engine are you talking about. There is a lot of discrepancy in quality.
 
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