View Full Version : Pistons.....

03-06-2009, 06:55 AM
Hey all,

Im riding a 2006 model rs125 fp version.

Looking to change my piston and was looking through a website.

i need help clearing a few qns i have

1. it seems like the wiseco piston has different grades like 53.95 or 53.97. which one shld i be getting and is there any diff between the 2?

2. my rs is my main mode of transport however i do go down to the track once in awhile. shld i be lookin at flat head single ring pistons. would it improve the bikes response not forgeting the lifespan of the piston.

would appreciate ur help regarding this matter.

Cheers and thanks!

03-06-2009, 07:23 AM
you tell us the difference, then ask us what is the differecnce.

there clearly two different sizes. measure your barrel with a vernier caliper, find out what size your barrel is, then buy the appropiate piston. if your barrel is 53.99 theres no point in getting a 53.95is there. you get the size thats closest to the size of the barrel to prevent any possible piston slap, or blow by.

by gettign a tighter piston you may increase the compression ratio.

if you get a flat top, you will need a flat top head like a vhm head. or performance will be worse than it was before.

03-06-2009, 09:13 AM
Thanks for the reply..

Yeah i understand that u need to change the cylinder head. but how about the lifespan as i use my bike for daily commuting....


03-06-2009, 09:36 AM
With a Wiseco you DO NOT want the closest fitting piston. A wiseco needs .0025-.003"(.0065-.0762mm) of clearance. Forged pistons grow more from heat than cast pistons. If your just daily driving the bike skip the wiseco. The other issue with wisecos is cold seizure. If you flog the bike before its fully warmed you can seize the motor very easily with a wiseco. A standard cast piston will be a better choice and cost 1/4 the money.

03-06-2009, 10:02 AM
ie a vertex race piston.

03-06-2009, 10:31 AM
Thanks once again.

Well i live in a warm climate country, the lowest the temp goes is like 26C and i give my bike like 5 to 10 mins to warm up usually. so it shldnt be an issue.

so wad you r saying is that i shld just get an original aprilia piston?

03-06-2009, 10:48 AM
Stock piston = good as new. Wiseco = trouble? Maybe, why take a chance?

03-06-2009, 10:54 AM
note taken......

was just thinking of upgrading something as i already have a 34mm carb, vforce and a arrow exhaust.

beside i need a new piston so was thinkin of getting something to improve the response of the bike

Anyway putting the piston aside. any recommendations to improve my bike's performance?


03-06-2009, 05:08 PM
16T front sprocket? Prestreched HD chain Non o-ring.
When replacing the piston, set the squish .6mm? or buy a performance head [will need high octane fuel]

03-06-2009, 07:25 PM
set the squish too .6 on a road bike? not a chance.

you want 1.00mm min even that usualy requires machining of the cylinder head.

03-07-2009, 04:02 AM
.6mm on a road bike... lol

03-07-2009, 10:47 AM
.6mm on a road bike... lol

THere you go again. Instead of posting to help the situation, you come here to start trouble.

03-07-2009, 04:12 PM
thanks for the replies guy.....

that y i was thinking of change the piston to a flat head.

was wondering what the lifespan of one is ie: the wiseco one.....


03-08-2009, 01:38 PM
Some say the Wiseco last far longer under racing conditions than a cast piston. They are more prone to cold siezure too. Setting the correct piston clearance is critical when installing a Wiseco. Carefull selection of the correct size is important as the cylinder is near impossable to resize with Nicasil coating.

Also you mention 1 ring piston. Not recommended for street use as your compression will fall off rapidly as the ring wears. If you dont mind rering every season then its ok to use. Also be interesting if someone has done dyno testing for [performance gains with singlke versus dual ring setups.

03-08-2009, 05:27 PM
lol its funny you American talking about 2 stroke pistons when you lot have never had 2 stroke. The wiseco is the best of the best. Just go by the aprilia/rotax manuel to find out the piston size you need.

Insure you always warm up your engine until 50'c while blipping the throttle. In the cold weather though, your engine might seem warm but not all the coolent is warm, just take your time :)


03-08-2009, 05:47 PM
Dont have or know two strokes? Currently Im driving a Derbi GPR with a Wiseco piston.

Also cut back your signature it takes up way to much room. Its annoying every time you post in thread.

03-08-2009, 05:52 PM
lol its funny you American talking about 2 stroke pistons when you lot have never had 2 stroke.

Dude, they've had loads of 2 strokes. moto x, snowmobiles, 2 stroke road bikes even back since the 70s, RD's, KH's, RZ's, RS50s, etc

End of the day, Wiseco, Vertex, ProX are all quality and you wont notice a difference on the road

03-08-2009, 06:36 PM
no offence intended, but i get the impression that a high number of posts doesnt necessarily mean alot of experience or knowledge? i have just seized a bike, and spent two weeks off the road, with a bill for nearly 300/$425 to get my barrel repaired and replated and get a new piston. i will always listen to advice, but only if its from a good source, so next time i decide to ride out on a cold evening, i will warm up the bike PROPERLY and tape up part of the radiator, advice i should have listened to.
my advice? spend your money on some new gear, some better gloves, good boots and a helmet that fits and offers proper protection, after all, you cannot put a price on your head.

03-08-2009, 06:46 PM
Thats a bit off topic but i agree. too many people on forums guess things or post up incorrect information. Thats why i try to only post up advice / info that i have tried myself, or know to be 100% factual. If im not sure, then i say so.

03-08-2009, 07:51 PM
yes, i am sorry for my un thoughtout out speech.