2 stroke break in ?

TDean122 · Two Stroke Sniffer Joined: 13 Jul 2014 Karma :

Hi,
I'm rebuilding the top end of a aprilia rs 125 im changing the piston put and was wondering if it will need nroken in ive read people saying it didn't but I though it would if so what's the best way to break in a new 2 stroke piston ?

Thanks

Boxing · World Chat Champion Joined: 13 Mar 2012 Karma :

Start it up, let it tick over, do NOT rev it up. Only little blips to keep it started if they're needed. Leave it for about 10-15 minutes, let it get nice and warm, turn it off and leave it to cool down for 10-15 minutes. Repeat it another two times. Three heat cycles.

People say to run them in for 100 miles and what not, I just take it easy on them for the first 100 miles, and keep the engine running freely. Don't go up hills in sixth or anything like that, you don't want to put a high load on the engine.

People say to take them easy for 100 miles, some say not to bother at all. Personally I take it easy and not go out racing around the twisties for about 50 miles. Then I take the exhaust off and look up the port to see if everything is still all in good working order.

Remember, with a 2 stroke the longer you warm it up, the longer the topend lasts. If you go out guns blazing up the road on a cold engine, you'll begin to get a cold seizure.

People say to change the 2T to mineral oil and all this, which is a load on nonsense. Ran all my 2T's after a full engine rebuild in on their usual oil. First ride I'll let it run a little rich as well. About 25ML's more, but I premix all my 2 smokers.

Edit: Also keep an eye on your coolant levels. You want to make sure the head gasket is all good as well. Check for leaks around the coolant pipes as well when you're doing the heat cycles. Some people say to re-torque the topend nuts as well, but I haven't ever bothered with it.

TDean122 · Two Stroke Sniffer Joined: 13 Jul 2014 Karma :

TDean122 · Two Stroke Sniffer Joined: 13 Jul 2014 Karma :

Vincent · Banned Joined: 16 Oct 2006 Karma :

Standard oil pump setting should be fine. Have you checked it's set right and doesn't need bleeding or anything?

As above, keep revs under about 7K for the first 100 miles then work it up over another 100. Avoid labouring the engine and, if it's got one, keep an eye on the temp gauge.
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TDean122 · Two Stroke Sniffer Joined: 13 Jul 2014 Karma :

Vincent · Banned Joined: 16 Oct 2006 Karma :

I'm not sure about the RS but most I've done it's been a case of lining two marks up....one on the pump wheel and one on the body - with the throttle open and/or closed. Very straight forward once you know the settings.
To bleed all the air out of the oil lines, you usually hold the pump open manualy while the motor is ticking over. Bleeding the pump itself varies.
Aye, you could do with a workshop manual....maybe have a google.
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P.addy · *Formerly known as* P. Joined: 14 Feb 2008 Karma :

Don't let it idle. Run it in properly.

Start up, put helmet and gloves on, ride away. Wait till it says 65+ on temp gauge before giving it beans. Aim to keep under 7k rpm but don't worry if it tips above that.

My RS was run in like that but with random blasts to about 10/11k over a 200 mile period. Nothing went wrong and it ran fine.

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
as Paddy says DO NOT LET IT IDLE
No need to adjust oil pump, Just check theres plenty of 2t in the hose leading to the pump & no bubbles in it.
then, just warm it up & ride. dont go into the red-line. dont go over 7000rpm, although this is where the pv kicks in (7400rpm) for a few miles. how many? varies on who you ask.
i normally warm it up, ride it till i get bored of sub pv riding (not much more than 150miles tbh) then gradually increase the revs.
ie. 50miles at 7500rpm then let it cool down.
50 miles at 8500rpm & let it cool down. & again 50miles at 9500 rpm then ride it as per normal.
im not saying thats the "proper" way to do it, but i';ve been doing it this way for years & never had any problems following a re-build.

cheers,
GAZ

DJP · Crazy Courier Joined: 11 Dec 2011 Karma :

TDean122 · Two Stroke Sniffer Joined: 13 Jul 2014 Karma :

Thanks for the help guys il do that then thanks

stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

Yeah I don't agree or see what the Idling a new engine several times up to working temperature (heat cycling?) is doing for an engine or how it's helping to run them in?

These people that say heat cycle your motor X amount of times before you ride it, have never really explained why they say that, and what the heat cycling is supposed to achieve?

I can understand starting a freshly build motor and letting it run while you check for leaks etc, or on a 4stroke engine letting it run until the stat opens, to check the cooling system is working and again no leaks are occurring. Then I could also understand that you want to re-torque the head bolts etc, in case they need it etc.

But all that pony about sitting at 2000rpm, 4000rpm or whatever it is for 20-30mins to run in a new camshaft? What is that all about?