4stroker Posted October 21, 2007 Report Share Posted October 21, 2007 i bought another rz top end yesterday (stock) and want to get it ported for a 7mm crank will i be able to get away with not using a spacer and taking up the extra stroke with some custom domes? does anyone on here run standard cyls with a 7mm crank? thanks, mark Quote Link to comment Share on other sites More sharing options...
2strokespirit Posted October 21, 2007 Report Share Posted October 21, 2007 i bought another rz top end yesterday (stock) and want to get it ported for a 7mm crank will i be able to get away with not using a spacer and taking up the extra stroke with some custom domes? does anyone on here run standard cyls with a 7mm crank? thanks, mark What pistons are you going to use? 795s? I dont think the domes will be the problem, how far is the 795 pistons top ring form the top of the piston? Quote Link to comment Share on other sites More sharing options...
NYUK Posted October 21, 2007 Report Share Posted October 21, 2007 cases need to be trenched. Quote Link to comment Share on other sites More sharing options...
fastbanshee8 Posted October 21, 2007 Report Share Posted October 21, 2007 The 7mm crank isn't a drop-in, like the 4mm crank is. You will have to get your cases trenched, so that the crank journals don't hit the bottom of your cases. As far as cylinders go, I think you can run up to a 10mm stroker on the stock cylinders, but I don't know what all is involved, other than trenching the cases for damned sure. Quote Link to comment Share on other sites More sharing options...
4stroker Posted October 22, 2007 Author Report Share Posted October 22, 2007 yup yup i know i need to get the cases trenched, no biggy never handled a set of 795s but that is prolly what i will use as i want to use the longer rods the standard wisecos top ring is about 5mm below the top of the piston i believe, can anyone tell me what the 795 is? Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted October 22, 2007 Report Share Posted October 22, 2007 if youre gonna go 7, you might as well go 10mm. it will be almost identical costs.. Quote Link to comment Share on other sites More sharing options...
4stroker Posted October 22, 2007 Author Report Share Posted October 22, 2007 if youre gonna go 7, you might as well go 10mm. it will be almost identical costs.. i doubt it i checked the port timings today with the 7mm crank and the transfer may already be too high, so it will be even worse with the 10mil also with the 10mil the top ring will almost certainly be above the deck at TDC without a spacer plate, and a spacer plate will make the transfer timings even worse is there anyone on here running a 7mil on stock cyls prolly wont help me anyway, as i think rz transfers are higher from standard than a banshee Quote Link to comment Share on other sites More sharing options...
4stroker Posted October 22, 2007 Author Report Share Posted October 22, 2007 i just measured up a standard wiseco pro lite piston and it seems from the edge of the piston to the top of the first ring land is 3.5mm, which means the top of the ring is going to be flush with the deck at TDC looks like i will have to run at least a 1mm spacer under the barrels to make it reliable Quote Link to comment Share on other sites More sharing options...
Jhughes7 Posted October 22, 2007 Report Share Posted October 22, 2007 i doubt it i checked the port timings today with the 7mm crank and the transfer may already be too high, so it will be even worse with the 10mil also with the 10mil the top ring will almost certainly be above the deck at TDC without a spacer plate, and a spacer plate will make the transfer timings even worse is there anyone on here running a 7mil on stock cyls prolly wont help me anyway, as i think rz transfers are higher from standard than a banshee Dont waste your time with a spacer plate do it right the first time and save yourself the headache, and like loco said 7 or 10, the crank cost the same. Quote Link to comment Share on other sites More sharing options...
4stroker Posted October 22, 2007 Author Report Share Posted October 22, 2007 didnt u read what i just wrote? if the extra stroke is gonna push the piston out of the barrel, then your gonna need a plate.... no two ways about it! and the plate may just raise the ports too high that it will make the powerband unridable... so who gives two hoots and a holler if the 10mil crank cost the same! if it aint gonna work it aint gonna be worth a pinch of shit! Quote Link to comment Share on other sites More sharing options...
dajogejr Posted October 22, 2007 Report Share Posted October 22, 2007 Did you read what they wrote? The crank costs the same, you're going to have to get it ported correctly for the 4, 7 or 10 mil crank. If you're gonna go bigger than 4, go 10 and get the porting to match the crank.... Any of those cranks the porting is going to be off, and to match the porting to a 4 vs. a 7 or 10 is the same price...so why not go 10? Quote Link to comment Share on other sites More sharing options...
RZBansheeMan Posted October 22, 2007 Report Share Posted October 22, 2007 Hey Mark, what cylinder castings do you have at the moment ? If they are the "1UA" cylinders, those already have a lot of port duration from the factory vs "48H" and "31K" , if you are interested I can send you some port maps. As far as the spacer plates, I cannot speak from experience, but we all know that with a 4 mil, the pistons are 2mm above the deck height and with the cut domes they are very common and reliable, so I probably would try to keep that my target area. A 7 mil would obviously be 3.5 mm above the deck height, so maybe just a thicker base gasket (unsure of the thickness's available) might keep you close to the +2 deck height target. I would think that a spacer plate would be needed for the 10 mil though. Mike Quote Link to comment Share on other sites More sharing options...
2strokespirit Posted October 22, 2007 Report Share Posted October 22, 2007 i just measured up a standard wiseco pro lite piston and it seems from the edge of the piston to the top of the first ring land is 3.5mm, which means the top of the ring is going to be flush with the deck at TDC looks like i will have to run at least a 1mm spacer under the barrels to make it reliable [/quotU U are 100% right, go with the 7mm. You will have to use a space rplate or just a thicker gasket, I dont like using to much of a thick gasket, because sometimes they just like to squeeze out under the jugs and blow, but for that I use plibond and "glue" it to the jugs and casing, i know this sound weird but it works great. Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted October 22, 2007 Report Share Posted October 22, 2007 ok well now youre not making any sense. if you have to run a 1mm spacer plate anyway then why not run a thicker one to accommodate the 10mm crank? thats just stupid not to. crank prices are the same as well as trenching. with either motor you really need to be running at least 39mm carbs, straight cut gears, lockup, big air filters and a good solid clutch. it doesnt make any sense to build a 7mm at this point. there have been many guys that built 10mm out of stock cylinders than ran very well.. honestly, i dont think you have any clue as to what youre doing is you think you cant build a 10mm. the spacer plate will raise the cylinders back up to get your port timing back to where you need it. Quote Link to comment Share on other sites More sharing options...
blowit Posted October 22, 2007 Report Share Posted October 22, 2007 ok well now youre not making any sense. if you have to run a 1mm spacer plate anyway then why not run a thicker one to accommodate the 10mm crank? thats just stupid not to. crank prices are the same as well as trenching. with either motor you really need to be running at least 39mm carbs, straight cut gears, lockup, big air filters and a good solid clutch. it doesnt make any sense to build a 7mm at this point. there have been many guys that built 10mm out of stock cylinders than ran very well.. honestly, i dont think you have any clue as to what youre doing is you think you cant build a 10mm. the spacer plate will raise the cylinders back up to get your port timing back to where you need it. And I think you missed the day that they taught port timing 101. Raising the cylinders will increase port timing thus make things worse. He has a very valid reason for considering 7mm vs 10mm. You are obviously bogging on someone that has sense enough to "check" port timing and verify that indeed, target numbers are out the window and optimal flow will not be seen. There are a bunch of banshees that run big cranks but many have "stroker" sleeves that have a taller barrel that the head locks in to and have relocated ports for the big stroke. A big waste of time compared to a PV cheetah though. 4stroker, yes the 4mm is as big as you can go with optimal port timing. The 7mm can be done but you have to stack base gaskets and further increase timing to get it done. Worth it though but I would not even do a 10mm on a stock cylinder anymore. Just not enough blow down and not worth it. Brandon Quote Link to comment Share on other sites More sharing options...
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