Crankshaft question

[Daggs]

So, I recently bought a project Lambretta with it came a brand new crankshaft. I'm not sure of the make, but the box is marked Ricambio Rapido and the crank looks the dogs' danglers.
However, it has a 110mm conrod. As we know Innocenti rods were all 107mm (except the TV 175 which i think was 113mm?)
If i use this in an engine I guess I will have to use a three mm packer plate? If I do, what is the likely effect on the engine regarding performance?

[holty]

hi, i think compession height of the piston dictates the length of rod, i would guess its a jap rod for a jap piston at a rough guess, im sure someone more knowledgable than me will help you work out which piston you need, or have you already got your piston, in which case you will need to use a packer as you suggested.

[dave wheeler]

the likely effect is it will vibrate less and give you a tad more tourque, tv rod is 116mm btw

[Grumpy225]

If I do, what is the likely effect on the engine regarding performance?

It depends on what you are trying to achieve performance wise and what the port timings are. Generally speaking though, it's a good thing.

[thebassmasta]

how does it affect port timing?????

[Grumpy225]

By changing the length of the rod, the the position of the piston in the cylinder has now moved (in this case up by 3mm) for any given point in the crank rotation. Just plug the numbers into the port timing calc and see for yourself. Change the rod length from 107 to 110 to 116 and watch the numbers move.

http://lambretta-images.com/archive/porttiming.php

[Daggs]

I don't have any other engine parts yet. In fact the engine isn't stripped. I may not use it in this application, but would be interested to know of a good application for the future.

[kevspeed]

110mm rod,possibly a Piaggio 'ape',rod,using larger small end Bearing to suit the 'Suzuki' 225 conversion,with the 'TS250 piston.

[thebassmasta]

By changing the length of the rod, the the position of the piston in the cylinder has now moved (in this case up by 3mm) for any given point in the crank rotation. Just plug the numbers into the port timing calc and see for yourself. Change the rod length from 107 to 110 to 116 and watch the numbers move.

http://lambretta-images.com/archive/porttiming.php

but your jacking the cylinder up by using a packer plate so in theory your not affecting port timings

[Grumpy225]

By changing the length of the rod, the the position of the piston in the cylinder has now moved (in this case up by 3mm) for any given point in the crank rotation. Just plug the numbers into the port timing calc and see for yourself. Change the rod length from 107 to 110 to 116 and watch the numbers move.

http://lambretta-images.com/archive/porttiming.php

but you're jacking the cylinder up by using a packer plate so in theory you're not affecting port timings

the port timings change because the piston is now in a different part of the stroke (as in going from BDC to TDC) depending on the length of the rod. In other words, if the piston is at BDC on a crank with a 110 rod, that piston will be sitting 3mm higher than one with a 107mm rod.

Go to the link, plug in the numbers and hit calc. You will see what I am talking about.