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frankd_nm
02-02-2009, 08:30 PM
Looking at the stock top end parts sent me into sticker shock. About $1300-$1400 for the top end. That's going to put a strain on my racing budget. Other than the big bore kit are there any aftermarket kits at a better price?

I'm probably looking at running between 21-35, 7 lap races this year (not to mention a few trackdays). What are my chances or making it through the year without a top end rebuild?

Now might be a good time to suggest that AF1 stock a few sets of rings too.:rolleyes:

HONDARACER
02-02-2009, 09:54 PM
I have a Mitaka cylinder I bought from the UK as a spare to make a BBK from. I can tell you the Rotax parts are far superoir in quality and finish. I also have a spare Rotax barrel and piston and I dont know how many miles were on the motor, but I cannot believe what beautifull condition the piston and cylinder are. 2 thing you can do to monitor your engine are do a compression test and if you have access to a fibre optic scope you can inspect the cylinder for damage. Scopes sell very cheap these days so it may be a worthwhile tool for a race bike toolbox.

the brit
02-03-2009, 10:10 AM
AF1 list a Polini 153 cc (http://www.af1racing.com/store/Scripts/prodView.asp?idproduct=6715) kit - the complete top end with barrel, piston, head, gaskets and hardware for $649.99. If you want to stay 12Xcc, i'd guess it'd be the same or slightly cheaper for a smaller kit based on my experience with the 50/72cc stuff.

odie_trackie
02-03-2009, 12:31 PM
I was looking at the cost for a top end for these engines and had the same reaction.

I did some digging and found Polini entire top ends for less than the cost of just the OEM piston. This was from Polini UK (so you Brits are covered) and I contacted Polini USA and they said they can get the 09 RS125 parts in the US.

So, FrankD, this might help you recover from that nasty case of sticker-shock. :)

motopix
02-03-2009, 03:07 PM
Can't you just replate the cylinder if it's damaged? If it's not damaged I don't even know why you would need to touch it when doing a top end. To me, top end means piston/ring/pin/clips/gaskets.

HONDARACER
02-03-2009, 05:02 PM
Cost to replate would be $250.00 I am really amazed how durable the stock barrels are. As long as the motor gets piston changes when needed and it never gets run without oil, the original jug should last for a long time.

Steve / AF1 Racing
02-03-2009, 07:13 PM
Cost to replate would be $250.00 I am really amazed how durable the stock barrels are. As long as the motor gets piston changes when needed and it never gets run without oil, the original jug should last for a long time.

You are 100% right.

The standard cylinders are honeable and re-plateable several times before needing to be replaced. I've used Millenium 3 times now, and each time the cylinders come back in truly impressive condition. We also use Millenium for all of our 1060cc big bore kits.

Additionally, the spare pistons that we've sourced from Pro-X (http://www.af1racing.com/store/Scripts/prodView.asp?idProduct=7004) , and the aftermarket gasket set (http://www.af1racing.com/store/Scripts/prodView.asp?idproduct=6908)should make the top end change pretty reasonably priced.

frankd_nm
02-03-2009, 07:49 PM
Thanks guys, all this is good to know. I'd love to have at least the piston, rings and pin on hand just in case. The cylinder and head on hand would just make that more comfortable.

It's rare that I place 1st in any of my races, so it's critical that I don't miss a race if I want to do well in the overall points. I came in second overall last year in the lightweight superbike class (running my Suzuki SM) and I think I missed 2 race weekends that year. I just have to get out there and run consistently this year and I should be ok.

HONDARACER
02-03-2009, 09:03 PM
Also I have heard Honda CR125 piston rings are the same as the stock Aprilias. Should be pretty reasonably priced. The rings are 54mm x 1.16mm thick x 2.2mm wide.

Steve / AF1 Racing
02-03-2009, 09:07 PM
Also I have heard Honda CR125 piston rings are the same as the stock Aprilias. Should be pretty reasonably priced. The rings are 54mm x 1.16mm wide x 2.2mm thick.

Might want to research that a bit though.

I addition to the obvious issue of ring end gap, there is ring chamfer, locating pin positioning, and probably something else I don't remember/comprehend.

I tried running down a similar theory for an RS50 customer some time ago with an unusual big bore kit. Though the specs matched and we got a good ring end gap, the engine never made good compression. That top end lasted all of 4 hours.

HONDARACER
02-03-2009, 09:35 PM
Just the piston rings are the same. Not the pistons themselves. And yes I would definatly compare them very carefully before sticking them in.

HONDARACER
02-04-2009, 09:34 AM
I was looking on the Wiseco catalouge and a lot of the 125cc pistons they make all use the same piston rings. THey are only 1mm thick so they are to thin for the stock RS.

odie_trackie
02-04-2009, 01:34 PM
This is all great info. I'm very happy that AF1 is coming up with alternatives for the RS125.

Thanks AF1!

PJ ENGINEERING
02-04-2009, 06:18 PM
Also I have heard Honda CR125 piston rings are the same as the stock Aprilias. Should be pretty reasonably priced. The rings are 54mm x 1.16mm thick x 2.2mm wide.

No you heard the mitaka piston use the same ring as the CR125 The CR ring also fits the Vertex piston and the wiseco piston BUT NOT THE GEN APRILIA PISTON :)

HONDARACER
02-04-2009, 06:33 PM
No you heard the mitaka piston use the same ring as the CR125 The CR ring also fits the Vertex piston and the wiseco piston BUT NOT THE GEN APRILIA PISTON :)

SO what exactly is the difference between the stock rings [Rotax] and the aftermarkets? I measured the stockers and they are 1.16mm. I also have a set of rings that were packaged in a Mitaka wrapper [clear celephane] that measure exactly the same as the stock Rotax rings.

PJ ENGINEERING
02-04-2009, 06:43 PM
SO what exactly is the difference between the stock rings [Rotax] and the aftermarkets? I measured the stockers and they are 1.16mm. I also have a set of rings that were packaged in a Mitaka wrapper [clear celephane] that measure exactly the same as the stock Rotax rings.

The stock ring is 1.20 mm thick and the mitaka/ vertex / wiseco/ CR125 is 1.00 thick The end.

Mitaka dont make rings and "Riken" do and they should be in a Riken packet

By the way still waiting for the tank and helicopter to come by :rambo:

Socket
02-11-2009, 01:44 PM
do not buy the wiseco piston online, make sure you talk to someone that isn't an idiot.

I'll explain later.

my topend rebuild that I ordered cost me 400 including barrell...