View Full Version : Breaking in 2 stroke - Am i doing something wrong?!?

profqwerty - n/a
1-Dec-07, 01:45 PM
I'm trying to break in the EC25PS. I have followed the manual, with 30:1 ratio, varying the throttle, under load, mineral oil.

The exhaust is VERY smokey - adjusting the air screw makes some difference, but not enough. The engine is warmed up (when started there's huge amounts).

There is also a small amount of oily goo coming out of the exhaust joint and splattering off the fan.

Plug is biscuit brown, no oil inside cylinder when cold.

Idling @2000rpm is just about ok for a minute, but it will quickly drop revs eventually dieing.

Varying the throttle will keep it going though. if the throttle is opened, sometimes it picks up slowly, sometimes it makes that deep chugging noise and drops revs.

I was also adjusting the blade pitch - 45 degrees and it will go too fast, so it's at 50 degrees now. I thought that might be the problem with the not picking up quickly. doesn't explain the smoke though.

I'm new to breaking in engines, so any help please give freely http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

It's 9 x 3z blades, 550mm duct. I'm pretty sure the max rpm is 4500rpm for the blades.



tonybroad - n/a
1-Dec-07, 03:20 PM
i'm not familiar with your engine but most 2 strokes are smokey and chokey and don't always pick up well until they are well and truly up to temperature

it's also not unnusual for a 2 stroke exhaust flange to be oily, in fact i'd say it's a good sign overall

check your choke is operating properly, that can often give a chugging feel, cause engines to die slowly and produce excessive smoke

but get everything well warmed up before changing things


profqwerty - n/a
1-Dec-07, 03:41 PM
Thanks. I will check the choke tomorrow, then leave it going for a while!

hovmart - n/a
1-Dec-07, 08:19 PM
you need to de pitch till you are getting 6500 rpm at the engine, the smoke should get better as it warms up

hovmart - n/a
1-Dec-07, 08:21 PM
you should be able to go to 40:1 to help stop the smoke

Mart366 - n/a
2-Dec-07, 07:45 AM
If its a new engine, or been completely rebuilt, chances are it will smoke like a good un for a while. Its due to all the internal surfaces of the engine having a protective coat of lubricant added during the assembly process.

My 447 produced huge amounts of smoke on its first proper outing, once that was burnt off (by running the engine) its runs clear.

you always will get some smoke at startup, thats the nature of 2 strokes, but once the engine is running it will disapear.

Are you using mineral 2 stroke or synthetic? mineral oils are always smokey, and produce a lot of ash. Synthetic on the other hand tends to burn cleaner and not have so much smoke


profqwerty - n/a
2-Dec-07, 10:05 AM
It's direct drive to the fan, fan's limit is 5800rpm, so the engine limit would have to be likewise. but yeah, 50degrees is too much at the moment.

The normal mixture is 40:1, but for break in the thing says use 30:1.

I'm using mineral oil; it recommends for break in:)

It's new, so i guess would take a while to burn off the coating then?

be back with some results later i hope!

Burtythepilot - n/a
2-Dec-07, 02:29 PM
<font color="royalblue">The problem with synthetic oil is that it is so dam good at lubing, nothing can ever 'bed in', hence sometimes the reason why some manufacturers say to use mineral to start with for however many hours till all the high spots have worn off and when everything seems sweet, go to the leaner mix of synthetic oil and let it rip. That's NOT 'rest in peace', by the way, that normaly happens around the final lap of the world champs.

I can't see that you are doing anything wrong... Your neighbours might though... ha ha.[/COLOR] http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

profqwerty - n/a
2-Dec-07, 03:57 PM
argh! not been able to do it today. lots of other stuff came up...have to wait till next weekend now http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

actually thinking about it...it has to be left to cool between running...so what if i did like 15 mins of running each evening, then it would cool off over the next day and do it again? or does the whole lot have to be done in one block?

Hornet - n/a
2-Dec-07, 11:18 PM
The Robin engine manual is very vague when it comes to running in. Mine just states to to run on 30:1 and take it easy on the engine for the first hour. If you have already done a few runs letting it warm up then cool down then I would give it some longer run time. Just keep varying the throttle up and down and let it run through the rev range, but do it slow and easy. No quick jabs of full throttle just nice n easy up and down. Once you have it running on the recommended amout of oil there will not be much smoke during running, only usually during idle or after a long idle and on a cold start on choke.