ZMN80 Rod longer than ZL40 rod ?

[Jayraye39]

My motor had a ZL40 crank/ rod. I only had to use 1 base and 1 head gasket for piston/ head clearance. I just finished installing a balanced crank that is a ZMN80 rod. But now I have to use 2 base gaskets and 2 head gaskets for piston/head clearance. Also my squish is only 0.5mm. with the doubled gaskets. almost need a 3rd base gasket. What am I missing? Measuring the stroke I get 42mm. nothing else changed. same motor and piston. Im baffled

 

[Jayraye39]

Is this possibly a stoker crank that I just happened upon?

 

[Nickt919]

ZL40 is 40mm stroke

 

[GW's Motorized]

Measure the length of the old rod vs the new rod.

 

[Nickt919]

Zl40 rod is 115mm

The 2 rods can have the same length and different pin locations

 

[Jayraye39]

ZL40 is 40mm stroke

yes both rods are supposed to be 40mm stroke

 

[Jayraye39]

Zl40 rod is 115mm

The 2 rods can have the same length and different pin locations

the pin looks to be in the same spot. Is it possible for the crank itself to be smaller in dia?

 

[GW's Motorized]

the pin looks to be in the same spot. Is it possible for the crank itself to be smaller in dia?

Do you still have the old crank?

 

[Nickt919]

Crank Geometries

Figure 1: Image showing connecting rod length Figure 2: Image showing stroke (Stroke is also difference of piston height at TDC minus BDC) -------------------------------------------------------------------------------------------------- Below is a collective table of many of the common crank...

smolikperformance.com

115mm is overall length
Smolik measures center to center on the pins

 

[Jayraye39]

hard to measure while in the case so i used a piece of hard wire. the rods look to be the same and the dia. of the crank to be the same. cant really get a good measurement on the pin hole but from top of the roller bearing to top of crank wheel is also the same. Their is 2mm somewhere and i cant find it. im using a high hole piston so a low hole piston will only make it worse