Hi Guys,

Wonder if anyone can help........ i tried to break in my new ABC Fourstroke engine today, and the instructions sate run it in like a 2 stroke, as full speed for 2 - 3 Minutes then let it cool down.........

It started but the only way it will keep going is to richen it up (kinda smokey) until it was about 1-1 1/2 turns from closed !!!!!!! is that running it too rich ? i ran 1 tank throu it but the engine got HOT !!!!!!!! so i allowed it to cool down. The engine makes kinda of a clicking noise (is that normal) when u turn it by hand......

So i kinda didnt wana ruin it so i came home for the day !!!!!!!, any help would be appreciated........

Thx

After you start it, close the needle until the engine is running as fast as it
will go. Then open the needle until the engine just begins to slow down a bit.
You will hear it. That type of engine is much tighter when new, and will get
quite hot, until you get some runs on it. Only run it for a few minutes at a time
then let it cool off. If you had a tach, you could richen (slow down) the engine
about 3-400 rpms, and it would be plenty rich enough to not overheat.

Dave.

The clicking is normal.

Dragonheart - What make of engine is it? I know of no 4 strokes that are ringless. All of Saito's aac and abc engines have rings. I don't believe a ringless 4 stroke with conventional valves and breathing will work, because of inadequate bottom end lube. So even though I agree with the instructions (I use that proceedure for all engines except the old iron stuff) be real carefull to not over heat that ring. Make sure it is seated good before really leaning on the engine.

Denis

Hi,

Its an Old SC 65FS ABC........... i got it new from a guy who brought it about 10 years ago...........

I think that's a Magnum engine over here and it will have a ring I bet. You didn't hurt it running it rich. You don't have to worry about ABC pinch and running too rich with a ringed engine. But sence you did run it you have probable given the ring and the cylinder enough time to get acquainted. So you can probably do the thermal cycling now that they call for for the rest of it.

Denis

Mine is ringed not ABC

Enjoy,

Jim

Only the new OS .70FS is ABC (ringless) as far as I know.

FBD.

Wrong! OS FS20 are ringless.

Jens Eirik

Only the new OS .70FS is ABC(ringless)???

Both OS FS70 II and OS FS70 Ultimate are ringed.

Jens Eirik

Jens

I believe you but now I'm going to have to get off my butt and go look at my old OS FS20 to confirm it. How about the FS26 or do I have to look at that myself too.

Denis

I don't believe I see a ring listed here for the new OS .70 FS (Ultimate)....

http://www.gpmd.com/cgi-bin/wgpprt100p?&I=OSMG0875

I thought I read right here on RCU, that the new .70 FS had an ABC piston/liner
(ringless) and an airbleed carb....listed as improvements.

Are you sure about that, Motorboy ?

FBD.

Well my OS FS20 DOES have a ring according to the parts list that came with the engine as does my OS FS26 and 30. So I still know of no conventional model 4 stroke that does not have a ring. YS 4 strokes could get by without a ring because they use crankcase induction but they also have rings.

Denis

Flyboy

ABC is not ringless necessarily. Many ABCs are ringed engines. I don't know about the OS70 ultimate but if it's ringless I would sure like to know how they lube the bottom end. Cause I don't think they use crankcase induction.

Denis

See at parts in PDF file:

http://www.os-engines.co.jp/english/...e/sinindex.htm

It was older OS FS20 where had piston without ring. Not know about newer FS20...

Jens Eirik

The new "FL" 70 is the ringless OS.

http://www.osengines.com/engines/osmg0876.html

"The FL-70 is the first engine from O.S. to incorporate a ringless piston/liner assembly, which reduces maintenance."

FBD,

Looks like (from your link) the OS 70 uses the same ring as the .91FX.....

Gary

submikester has it....[sm=thumbup.gif]

The FL-70 is the first engine from O.S. to incorporate a ringless piston/liner
assembly, which reduces maintenance.

I never wrote about OS 70FL.

Buy the [8D] and see better between 70FL and 70FS..

Before You wrote about OS 70FS was ringless and the new engine OS 70FL are without ring. Read better next time.

Jens Eirik

OK, even though Motorboy is wrong on all counts....

....he wins the Nit-Picking Contest. I said the "new OS 70 FS".
"FS" meaning four stroke".....

FBD.

Well now I have to say I know of one conventional 4 stroke that is ringless, the OS 70FL. I see in the graphic that they connect the crankcase to the muffler. I guess that's how they oil the bottom end. I doubt it's to vent the case to the exhaust. On a ringless ABC I would doubt the blow by pressure would be enough to win over exhaust pressure. I'm not sure I like the idea of oil out of the muffler for lube. If they are still relying on blow by to lube the bottom that would take a pretty loose fit piston even considering the two oil groves. It'll be interesting to see how these work out.

Denis

The OS "parts listings" for their "individual motors" are all screwed up

Why would they list the 91FX ring under the OS 70 along with other parts, for other motors unless they were interchangeable?

If you check the actual manuals, these appear to be correct and list the "actual" parts for that motor.

....so I goofed.....

Anybody run one of these "FL's" yet?

Gary

I just got off of the phone with the OS Engine Techs at Hobbico, they said there are two reasons for the line from the crankcase to the muffler, for a cleaner installation, all the oil comes out in one place, and to stabilize tank pressure taking advantage of the positive crankcase pressure on the intake stroke and and the even greater crankcase pressure during the combustion stroke. The ABC setup is not immune from blowby, therefore lower end lube is accomplished just like a ringed engine. The cylinder is a mildly tapered bore not as extreme as a two stroke tapered bore yet still has a noticeable pinch at the top. In the instructions under Engine Construction it says "the cylinder bore is a little tapered" I could not copy and paste it or I would have.