Long Rod/Long Stroke?

[servetakid]

Im going to be having some minor porting work done to my Rapido Classic and potentially some skimming of the barrel so i can get the squish perfect. I am just wondering while, i go to that effort wold it be worth fitting a longer stroke crank or long rod to a crank. How much real world difference would this make? Is it good bang for my money? Do spanish cases need machining for a 60mm crank? Soes a longer rod make much difference compared to a crank?

cheers,

jordan

[servetakid]

Basically, the question is. is this a worthwhile modification? And would would you go for a long rod or long stroke crank?

[servetakid]

Is it a worthwhile upgrade then?

[servetakid]

I am getting porting work done, so was thinking of doing this at the same time. For a 60mm crank do you need to machine cases?

[RICSPEED]

60mm will go in without machining .. any bigger and the rod end will rub on the case

as eden said 60mm crank needs to be done at same time as poting work as the longer stroke throws port timings out

[corrado]

Using a 110 rod allows you [or your tuner] to play around with various thickness packers to adjust port timings, as in using a 2.5mm packer would equate to taking 0.5mm of the base of the cylinder. Using a 115/116 rod usually means using a different piston with the gudgeon pin closer to the crown, though if you read what Darryl, Dan and Sean are doing they're using a 9mm packer with a standard piston and 116 rod.
Read the thread on the RB250 on the dyno pages.

I used a 25mm sanding drum to remove about 0.5mm from the back of the casing when I fitted a 60mm crank to be on the safe side.

[Adam_Winstone]

Many of the newer 60mm stroke cranks use a rod with a slimmed-down big end, these commonly clear without needing work to the cases but there are still many 60mm stroke cranks that will contact with the casing and need material to be removed. I know of a number of instances where people have blindly followed the advice that they don't need to modify the casings only to find that their crank does hit the casing. Modifying the casing when it is empty is one thing but stripping it down to modify it when you've only just built it is a real pain in the ****! (NECK)

Adam

[servetakid]

Just to get my head round this, with a 60mm crank i will up the CC to a 230, and alter the port timmings. With a longer rod, i will just alter the port timings?

The general reasult if done right will give more torque at the expense of some revvy-ness? but should pull taller gearing?

[servetakid]

Im purely after more grunt and a similar revvy-ness.

[tea5ive]

If using a long rod less thrust into the cylinder wall this creates less friction and the rod is kept more upright in the cylinder, every bit helps