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rd350lc piston with 107 rod?
Posted: Fri Jul 08, 2011 4:32 pm
by bigmuff
Not sure if anyone has managed to do this but i want to run a rd350lc piston in my SR175 barrel without having to re-rod the crank. Crank is a 60mm mec with 107mm rod. I have had a reed block made in work and wondered is it just a case of top and tailing barrel, and if so how much off each end? Barrel is runnig 180 ex timing, 130 transfer and 145 inlet at present with a 62mm Asso piston. Just need to get boost port cut if I can use the rd350 piston. Can anyone help?
Re: rd350lc piston with 107 rod?
Posted: Fri Jul 08, 2011 5:22 pm
by Powolotti
exhaust and transfer timing stay the same if you take the difference in compression height from the bottom of the cylinder, i.e Lambretta 39mm and RD 350 36mm...so 3mm off bottom and you´re fine.
Re: rd350lc piston with 107 rod?
Posted: Fri Jul 08, 2011 8:30 pm
by soullad
before you have any maching done to cylinder just recheck your timing after you take out your cylinder to 64mm. The port entry angles on those SR barrels can be abit hit and miss and the port timings may alter slightly. Worth giving the barrel abit of a tune whilst your at it?
Re: rd350lc piston with 107 rod?
Posted: Fri Jul 08, 2011 9:31 pm
by bigmuff
soullad wrote:before you have any maching done to cylinder just recheck your timing after you take out your cylinder to 64mm. The port entry angles on those SR barrels can be abit hit and miss and the port timings may alter slightly. Worth giving the barrel abit of a tune whilst your at it?
Geoff Stephens at Allstyles did the ports a few years ago. Will get him to do the boost port and any extra work to the ex/inlet if required.
Cheers both for the replies. Best i get the top end stripped this weekend and get the ball rolling.
Re: rd350lc piston with 107 rod?
Posted: Sat Jul 09, 2011 7:48 am
by bigmuff
Powolotti wrote:exhaust and transfer timing stay the same if you take the difference in compression height from the bottom of the cylinder, i.e Lambretta 39mm and RD 350 36mm...so 3mm off bottom and you´re fine.
If I were to use a 58mm crank instead of a 60mm would the amount you machine off the bottom remain the same?
Re: rd350lc piston with 107 rod?
Posted: Sun Jul 17, 2011 1:22 pm
by grimspeed
bigmuff wrote:Powolotti wrote:exhaust and transfer timing stay the same if you take the difference in compression height from the bottom of the cylinder, i.e Lambretta 39mm and RD 350 36mm...so 3mm off bottom and you´re fine.
If I were to use a 58mm crank instead of a 60mm would the amount you machine off the bottom remain the same?
no you need to take another 1mm off !
Re: rd350lc piston with 107 rod?
Posted: Sun Jul 17, 2011 5:15 pm
by bigmuff
grimspeed wrote:bigmuff wrote:Powolotti wrote:exhaust and transfer timing stay the same if you take the difference in compression height from the bottom of the cylinder, i.e Lambretta 39mm and RD 350 36mm...so 3mm off bottom and you´re fine.
If I were to use a 58mm crank instead of a 60mm would the amount you machine off the bottom remain the same?
no you need to take another 1mm off !
Cheers, i think i've got my head around it now. waiting for piston to turn up, then get barrel bored and measure up before any machining/porting is done. Thanks again for all the info.