Crazyatvspazz Posted December 14, 2009 Report Share Posted December 14, 2009 i got a question ...most likley a noob question but whatever... i have a stock motor. i want to install a set of weisco prolite pistons just for the hell of it. my machine has less than forty hours on her... i mean the paint hasn't even rubbed off my clutch cover! will i have to bore it over or can i just throw a set of std size pistons in it? if i check the compression and thats good i should be able to just put them in right? what should my compression be on a bone stock motor? thanks in advance Quote Link to comment Share on other sites More sharing options...
T_Shee Posted December 14, 2009 Report Share Posted December 14, 2009 i know its probably not what you want to hear but the only true way of knowing if you need a bore is gonna be to take it to a shop and have it checked thoroughly. most likely you would be ok to just throw pistons in but for peace of mind id recommend going .010 over. if your gonna spend the 200 bucks on pistons you dont wanna find out the hard way your cylinder was out of round and bust a skirt or something. Quote Link to comment Share on other sites More sharing options...
shanYE west Posted December 14, 2009 Report Share Posted December 14, 2009 The bore will have to be corrected even if you install std bore wiseco's.. The forged pistons require a looser tolerance over the casted pistons.. You wouldn't notice any difference by switching to the wiseco's anyways.. Stay with the stockers until you need a bore or rebuild. Quote Link to comment Share on other sites More sharing options...
GrMeyer Posted December 14, 2009 Report Share Posted December 14, 2009 If your wanting to get a set of new pistons... Then get a port job while your at it and do a 1 over on bore for a fresh run of the new pistons. then you will have a long life of the top end and a shit load of more power. Quote Link to comment Share on other sites More sharing options...
rocketracing Posted December 14, 2009 Report Share Posted December 14, 2009 i got a question ...most likley a noob question but whatever... i have a stock motor. i want to install a set of weisco prolite pistons just for the hell of it. my machine has less than forty hours on her... i mean the paint hasn't even rubbed off my clutch cover! will i have to bore it over or can i just throw a set of std size pistons in it? if i check the compression and thats good i should be able to just put them in right? what should my compression be on a bone stock motor? thanks in advance if it only has fortyhours on it you should probably run it a while longer or maybe hone it a little because the wiseco pistons will swell a little where as the stock cast pistons will not. you can mike the cylinders and see how much clearance you have because you may have enough. the wiseco specs call for 3 thousandths clearance Quote Link to comment Share on other sites More sharing options...
Crazyatvspazz Posted December 14, 2009 Author Report Share Posted December 14, 2009 if it only has fortyhours on it you should probably run it a while longer or maybe hone it a little because the wiseco pistons will swell a little where as the stock cast pistons will not. you can mike the cylinders and see how much clearance you have because you may have enough. the wiseco specs call for 3 thousandths clearance well i want to put a cool head on it 21cc probrably... still want to use pump gas i figured if i have the head off may as well put some pistons in it. Ill prob just take it to my dealer and have him bore it over .10. thanks for advice!!!! Quote Link to comment Share on other sites More sharing options...
shanYE west Posted December 14, 2009 Report Share Posted December 14, 2009 well i want to put a cool head on it 21cc probrably... still want to use pump gas i figured if i have the head off may as well put some pistons in it. Ill prob just take it to my dealer and have him bore it over .10. thanks for advice!!!! Why switch the pistons if there is nothing wrong with them? Quote Link to comment Share on other sites More sharing options...
papa_smurf49319 Posted December 14, 2009 Report Share Posted December 14, 2009 First off, you probably know but you will have to pull the cylinders off to get the pistons of the con rod, but thats no biggie. Second somebody will correct me if i am wrong but i think wiseco starts the pistons off at .020 over, as stated early if there is no excessive clearences and the cylinders arnt really glazed then save your money! Cody Quote Link to comment Share on other sites More sharing options...
Crazyatvspazz Posted December 14, 2009 Author Report Share Posted December 14, 2009 yhea lol ive re-built couple baster/cr motors i know what iam doing there... i just wasent sure if i could just throw a set of std size pistons it it but it does make good sence to just have it checked and if necesary bored out .10 over. and yes there is a standard size weisco piston kit http://cgi.ebay.com/ebaymotors/Wiseco-Piston-Top-End-Kit-Yamaha-Banshee-350-Std_W0QQcmdZViewItemQQhashZitem5ad5324671QQitemZ390123898481QQptZMotorsQ5fATVQ5fPartsQ5fAccessories If i can keep stock bore i will if not ill go over anybody know of a good place to do the machine work? Thanks Quote Link to comment Share on other sites More sharing options...
Crazyatvspazz Posted December 14, 2009 Author Report Share Posted December 14, 2009 will swaping the stockers add HP? and will i need to re-jet? Quote Link to comment Share on other sites More sharing options...
papa_smurf49319 Posted December 14, 2009 Report Share Posted December 14, 2009 i know wiseco makes 64mm pistons, but i dont think they make .010 over, i think they start at .020 over, and i hope you dont have to bore it .100 over after 40 hours lol. Just swapping pistons will give you a minimal gain, nothing that you would feel if your current engine is in good running order and has good compression. Cody Quote Link to comment Share on other sites More sharing options...
blowit Posted December 14, 2009 Report Share Posted December 14, 2009 will swaping the stockers add HP? and will i need to re-jet? No and No. I would highly recommend leaving the stockers in. Just no reason for Wisecos. Forged pistons also are a softer material (less silica) thus they will wear more. It is not uncommon to get a couple hundred hours or more from stock pistons. B Quote Link to comment Share on other sites More sharing options...
papa_smurf49319 Posted December 14, 2009 Report Share Posted December 14, 2009 No and No. I would highly recommend leaving the stockers in. Just no reason for Wisecos. Forged pistons also are a softer material (less silica) thus they will wear more. It is not uncommon to get a couple hundred hours or more from stock pistons. B Ill agree with you on the horsepower side, but forged pistons vs cast wearing faster, i dont know if i could totally agree with that. I know you guys do alot of r&d and you really know your stuff, but i just dont see how a forged piston will wear faster than a cast. I know that a forged piston will tend to swell, therefor you might have a little more clearance when you fire the engine up cold. I will have to do a little more reasearch but in my experience (with cast pistons, hypereutetics, forged pistons in small and big block chevys, there is no inclination of wear more so with one or the other.) never noticed any loss of hours on my personal banshee either. Elaborate a little for me, im sure you have your reasons, just curious as to why you stated they above. Thanks Again Cody Quote Link to comment Share on other sites More sharing options...
blowit Posted December 14, 2009 Report Share Posted December 14, 2009 Ill agree with you on the horsepower side, but forged pistons vs cast wearing faster, i dont know if i could totally agree with that. I know you guys do alot of r&d and you really know your stuff, but i just dont see how a forged piston will wear faster than a cast. I know that a forged piston will tend to swell, therefor you might have a little more clearance when you fire the engine up cold. I will have to do a little more reasearch but in my experience (with cast pistons, hypereutetics, forged pistons in small and big block chevys, there is no inclination of wear more so with one or the other.) never noticed any loss of hours on my personal banshee either. Elaborate a little for me, im sure you have your reasons, just curious as to why you stated they above. Thanks Again Cody Without writing a novel, most casted pistons are a hypereutectic variety with a high level of silica with will result in undisolved solids in the grain structure. This silica improves scuff resistance while also being harder than Al but does give up some ductility. These levels of silca are not found in forging alloys. Also, comparing forging to cast, a cast piston will have a tighter, more uniform grain structure while the forged piston grain is "stretched" into form so it is constantly under stress. Forging is actually a good thing for many structural applications but the down side in a high delta T situation is irregular expansion during heating. This can cause increase scuffing and requires additional clearance that further accelerates wear. I am NOT dogging the forged piston and they are usually preferred for HO applications but they are not the best for all situations. A forged piston can last a long time as well. However, you may see in increase in skirt heating from increase blow by, irregular ring wear, etc. All things that we accept in the quest for performance. Hypereutectic pistons have evolved greatly with new alloying and do much better in a high mileage engine such as a car. Brandon Quote Link to comment Share on other sites More sharing options...
GrMeyer Posted December 15, 2009 Report Share Posted December 15, 2009 Learn something new everyday!!! Quote Link to comment Share on other sites More sharing options...
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