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Two engine questions/problems

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cbreaker

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Howdy.

I'm posting this in regards to two engines my friends are having trouble with. One is a Force .26 and the other is a Novarossi SBK-21 short stroke.

The Force .26. Weird issue. Basically, the engine runs okay, and at about 240 degrees. But, when you open the throttle completely for about three seconds, the engine suddenly boggs down and will stall within seconds.

Now, from what I've heard, this usually means that the HSN is too lean and is not providing enough gas at full throttle. This does not appear to be the case however, because we can richen it up to hell and the problem still persists, except now the engine runs like ass because it's way too rich.

We tried leaning out the HSN, and richening it, and the same problems occur. We are stumped. Any ideas?

Okay then the SBK-21. The engine was running okay, at about 230 degrees. The idle was a little high, but the engine seemed to have a ton of power (you could pretty much pop a wheelie when you wanted to.)

However, there is almost no smoke coming from the pipe. You can see a little bit, but it's not like other engines I see with a nice steady stream of smoke when you nail the gas.

The engine isn't too hot; we never had it over 250. But it's kinda weird with so little smoke... is this indicitive of short stroke engines?

So anyways, then we ran out of gas. We filled up the tank, and we had problems with the engine. Basically, the engine would run fine at idle, and you could rev it up on the box like there was no tomorrow. Then you plop it on the ground. A little over 1/2 throttle and the engine simply dies. Poof, stall.

I couldn't tell by the sound whether it was too rich or too lean. The engine would never get very hot, 200 at most. We tried leaning and richening. Very very small increments, but eventually turning the dial a lot in each direction. The problem still continued no matter what we did. We couldn't seem to make the engine run without stalling.

The SBK-21 has a LSN, HSN, idle screw, and MSN. We never touched the MSN, and the position seems to be about "flush" with the body of the carb.

Any ideas on the Novarossi?

At this point the only engine that runs reliably is my good old B01; the thing is a tank. Too rich? It doesn't care, it'll push right through it. Too lean? It'll run itself into a meltdown if I let it. So it's super easy to tune, and therefore I don't really have a lot of experience with tuning. I richen or lean depending on if it's cold or hot outside and the engine temps change. Other then that it just runs like a champ.

Also, lastly, how do you set carb settings to factory defaults? I read somewhere that you can "strip" the needle or carb if you turn a needle in too far, but it seems difficult to know when the needle is all the way in.

I appreciate your help ahead of time.
 
the .26 doesn't have a msn el .in imo when the .26 force has around a gallon or more it starts loseing compression and just keeps getting harder to tune

just a bad design
 
Originally posted by El Pirata
Aww, a detail...

Buy a new better carb then you have a msn.

better yet a better mill ????thats has a better carb
 
These aren't my engines, and although I have heard mixed reviews about the Force .26, it's not my engine so I am not the one to replace it.

This one has less then a gallon through it. Can a bum glowplug cause the engine to fade out and die at full throttle?

I'm actually more concerned about the Novarossi SBK .21 at this point, since my friend would like to be able to race the thing on on Sundays with me and it's not really good when you stall out after applying 1/2 throttle.

Oddly enough, the engine dies just the same whether you smack the throttle open or open it gradually.

I have heard that you should not touch the MSN on the nova carbs. Truthfully, I don't really know what the MSN does.

From my own research:

HSN: Controls maximum fuel to the engine.
LSN: Restricts the flow of gas to the engine at idle speeds
Idle: Holds throttle open a little bit to keep engine running at idle

MSN: Midrange needle - does?

Anyone have experience with a Novarossi short stroke?
 
Originally posted by cbreaker
Can a bum glowplug cause the engine to fade out and die at full throttle?

MSN: Midrange needle - does?
Yes absofreakinglutely a bad glow plug can cause it to die at full throttle.


MSN regulates the fuel to air mixture at middle range of the rpms.
 
My Ofna .25 did the same thing no matter what the settings were until after I had a Gallon through it! It just woke up and and ran fantastic and still does with about 2 1/2 gallons through it now. I posted this problem last year on RCU and allot of other members said the same thing "that it took allot longer to break it in then some engines do".
 
I had a similar problem with a Rossi not so long ago....found it to be one of two things...i changed both so I'm not sure which was the cure. I decreased the amount of fuel tubing that was stuck down in the pipe....and changed the spring on the fuel tank lid. My thinking was that it was possibly building too much pressure in the fuel tank and blowing the lid open at WOT causing the engine to lose its prime. Or it could be a possible partially blocked fuel filter. Ran into that once (filter in the tank was dirty) and as rpm's rose the the fuel couldnt keep up.

Seems to me though that you've tried richening and leaning the settings with no change so it must be something else. even saw something similar to this where a guys car ran fine until half a tank was gone then it would die. Found a small hole in the tank than when the fuel level got under the hole it lost its prime and died. fill it up and it ran strong again till half a tank was gone.



Just my thoughts....hope they help

Saggy

One more thing I would check is the exhaust seal...if its blown it can have similar results.

Saggy
 
Hmm, I didn't think about the exhaust. I thought that the engine would keep on running even with no pipe you just wouldn't have any power. But it sounds resonable. We'll check it out.

His engine doesn't show much of a sign of an air leak; the seals are all nice and dry. The fuel tank lid is a little more difficult to detect, since you kinda end up spilling a little bit of fuel around when you gas up.

The engine seemed to be running good today fortunately. It kept doing the stalling thing, until we replaced the glowplug. Then some form of magic happened and it started running a lot better, no stalls. The thing is, I put the same plug that wasn't working on his into my engine, and it ran fine.

So I guess it's entirely possible that his engine just didn't like the glowplug. Maybe it wasn't the kind that the engine is setup for. I think it was an OS8 plug, but I'm not sure (we don't remember where we got it.)

His engine was running at about 230 and had a good amount of power, but there just wasn't a lot of smoke blowing out the pipe still. Richening the engine more seemed to rob way too much power, so I guess this is normal for his engine. Meanwhile, my GS B01 billows out the smoke something fierce at 265 degrees.

Unfortunately, during the races he was blessed by both a dogbone breaking AND a front CV breaking, so it didn't matter much today!

The help has been most appreciated, and if anyone has anything to add, please do so.
 
Last edited:
The new plug was a different type, I believe it was a McCoy plug.

The old one that was in his is now in my engine and works fine.

Odd. Picky little buggers.
 
not meaning to squat on your thread cb. but ryhton and i had a similer thing happen with ryhtos rb. ws711. today it whould not run worth a poop. i thought it had an air leak.but none to be found.pulled the carb all is good.checked the head that was good.back plate good.no leaks...so we put his other fule tank on. that wasn't the problem.fule lines good.now we are wtf at this point.this thing ran great last weekend..when you start it idels good but when you give it gas it fumbles all over its self.try to addjust hsn and lsn nothing.works... and i do know how to tune a mill.i have never seen this happen befor.when we were playing with the hsn turned it in so far that it was scary.but it was still blowing fule out the stinger... ???????
 
Originally posted by zandor22
not meaning to squat on your thread cb. but ryhton and i had a similer thing happen with ryhtos rb. ws711. today it whould not run worth a poop. i thought it had an air leak.but none to be found.pulled the carb all is good.checked the head that was good.back plate good.no leaks...so we put his other fule tank on. that wasn't the problem.fule lines good.now we are wtf at this point.this thing ran great last weekend..when you start it idels good but when you give it gas it fumbles all over its self.try to addjust hsn and lsn nothing.works... and i do know how to tune a mill.i have never seen this happen befor.when we were playing with the hsn turned it in so far that it was scary.but it was still blowing fule out the stinger... ???????

Well zandor I found the problem and it isn't good. Popped the back plate off and looked at the rod and noticed the brass bushing for the crank was all egg shaped and causing things to be all messed up. I ordered some parts and they will be here in about a week so I will have to run my good WS7 11 mill this weekend and park the other buggie till parts come in. Not a cheap fix either.
 
Well, I just had the same problem on a friends Khosho Super Ten with an OS CVX Power engine. I just couldn't fix the problem. I decided to disassemble the engine and I saw that some parts in it where dead so he had to change the engine. Just try to have a look and do the same as me but be careful when you do something in the engine; if it's not dead and you do something wrong, you will kill it very fast.
 
The Novarossi engine seems to be running fine now, for some reason. Maybe it still wasn't completely broken in, who knows. But there's still not a lot of smoke. Maybe this is normal for Short Strokes?

The Force .26, well, we're going to try and get it running better with more tuning, and maybe in the process of burning more fuel the problem will go away.

We'll see. If not, then we'll pull it apart. I have a little experience doing so now, because my B01 decided to chew up a bearing on me. Chomp. I don't know how six balls from the bearing could have escaped/disintegrated with no damage to the piston, sleeve, conrod, or shaft. Where did they go? It's so weird. Anyways at least now I have a baseline knowhow on how to take apart an engine without breaking it.
 
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