Running in a two-stroke engine?

[cambocambo]

Hi Guys

What is the procedure for running in a new piston?

Cheers

Cameron

[sidwyz]

I dont know bugger all about 2strokes, but im sure same principals apply to rings and bore, but im sure someone who know's will give there opinion.

This is just the way I think it should be done, and hold no responsibility what happen to your motor.

http://www.mototuneusa.com/break_in_secrets.htm

[FROSTY:Me]

dude theres fark all to it.its chrome bore so basicly youre only bedding in the rings. Take it a bit easy for the first tank of premix-- I usually run a mineral oil for first tankload but im oldschool

[Reckless]

dude theres fark all to it.its chrome bore so basicly youre only bedding in the rings. Take it a bit easy for the first tank of premix-- I usually run a mineral oil for first tankload but im oldschool

I've been doing it the mototune way for many years with many High performance 125cc 2 smoke Kart engines etc on Methanol, avgas and petrol. Don't take it to easy. I don't even start mine in the garage (well maybe for 30 secs max just to make sure it goes) then take it out and load the rings. Off and on throttle for a lap or so. Come back checkout water level etc, let it cool down then ride it like you own it, no constant throttle. Always had good ring seal, long lasting engines and fast ones to!

Read the mototune pages it really does work!

There are quite a few threads and posts on this in the Off road forum do a search!

Just my way each to their own??

[cambocambo]

Thanks there seems to be alot of different opinions on this.

[Henk]

Lots of opinions. New bike I'd do the whole run it let it cool, run it .... thing. Piston I used to do that one cycle, but then gave up and just rode the things, never had an issue, but then I don't ride that hard.

[McWild]

Do you have a manual?

Do you like to be sure?

[Reckless]

Do you have a manual?

Do you like to be sure?

The manual will tell you to go slow for ages which is the safest way for dummies not to screw things up. It'll tell you to idle it and warm it in the garage etc. Its not necessarily how to get the best ring seal and therefore compression and power. If it screws up mototune way its because you haven't checked the ring end gap or put hem on the piston wrongly or made some sort of cock up etc
But both ways work and last well one just gives a little omph, I believe!
I have done it for many years, never had a failure, no or very little blow by on the piston. But as I say each to their own I won't rabbit on any longer!

Btw take note of the change oil recommendations on his site! That helps to.

[McWild]

I think the mototune method is designed for maximum power but the lifespan of an engine run in that way is questionable.

What kind of bike is being run in?

I think for a performance application like dirt bikes and race bikes the mototune method would be a realistic way to go, as its whole life will be spent in either on or off.

For a road bike however, despite how one may try, there's a lot more pissing about in the midrange. I think maximising the engine life is a greater concern than squeezing every last drop out of the little engine on a road bike.

[Spuds1234]

I think the mototune method is designed for maximum power but the lifespan of an engine run in that way is questionable

You only need to do the mototune thing for a wee bit, not to many k's. Couldnt you just take it easy after doing the mototune thing for the rest of the run in period.

Best of both worlds?

[Reckless]

McWild The tittle says its a 2 smoker and his sig says KX 125 hence my recommendations. The mototune way IMHO will not shorten the life of this engine at all. A single ring high revving 125 has to be done regularly anyway.

Spuds1234 if you read the Mototune way the first few minutes are the most important. Which is why I don't run mine in the garage go straight to the trial and run it there, where you can load the engine with off and on throttle application usually on a gravel road section. Out back of the sandpit is good for this about 20mins, then back to the car check the oil and water. Then a few good loops using on/off on/off with the odd cool down in between, change the oil. 2 hrs all done, ride it like you own it.

BTW: I don't mean thrash the snot out of it in the first 5 minutes (a little common sense needed here) but idling it around on constant 1/4 throttle or doing 3 warm up cycles in the garage does nothing good for a 2 stroke High performance engine IMHO. You need to push those rings through the oil premix and bed them to the bore asap. You'll have a strong engine with good low down power that you don't have to thrash the shit out of to make it go, so your engine in the long run will last better I reckon.
But as I say just my 2c your engine make your own choice!

[marsheng]

Basically, to bed in the rings you need high power to force the rings against the cylinder wall. In doing so, you generate a bit of extra heat with the friction.

On my dyno, I warm the bike up to running temperature, give it 2 3/4 power runs, let it cool for 4-5 minutes, 2 more at 7/8 power, cool again and the 2-3 at full power. Now it time to race. I do give race engines a slightly larger clearance when reboring.

Think about it, how many times do you have to slide a ring against a bore for it to bed in 500 - 600 times or as some books say 1000 km at 60 kph at 3000 rpm or 3 million times.

[gammaguy]

heat is the enemy of a new engine,until the parts inside have become stressed in the right way and thermally stable

keep from gassing it too hard to start with then progressively work it harder after it starts to loosen up.listen to it and get the feel of it.

vary the throttle openings and dont lug it or thrash it,keep it in the torque band,not the power band.(there is a difference)

let it cool down after a while,and read the plug while its there.just to be sure nothing horrible is going on

and also never add extra oil.it will run leaner and therefore hotter.thats the last thing you want

i have run in hundreds of 2T engines this way,and NEVER had a problem.

good luck

[cambocambo]

Thanks for all the replies, yesterday i fitted a new piston and new head etc i warmed the bike up and let it idle for 5 mins then took it for about about a 3 kilometer ride in first gear. Then I let it cool and later in the afternoon did it again and gave it a good run. it runs mint!! I am really stoked with it.

[cambocambo]

I am stoked because I was able to strip the top end and put it back together to have it run mint... not bad for a computer guy and my first time working on a bike.