Abby’s Guide > Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) > Discussions > Inside an R-Tek engine

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jrtrebor

Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 539

Inside an R-Tek engine
Original Message Feb 15, 2012 6:05 pm

Well I got the bolt stud welded, new old flywheel on, air gap set, good spark. Put everything else back on the engine.
Still don't have the gov. vane so I just used the spring to keep the throttle at the idle position and used the idle screw
to bump up the idle up a little. Put the engine back in the housing and it start on the third pull.
Was idling and running well, then I heard a knock, couple seconds later heard another one then another one.
So I shut it down. Was one of those sounds you know isn't good, kind of a deep sounding clank.
It only made the sound maybe 3-4 times in about 20 maybe 30 seconds or run time.
Pull the engine back out and decided to take it apart to check the rod cap.
When I took the flywheel back off found that the new key I put in was sheared.
( could have had something to do with the knock)
Was really clean inside.

Intake port I believe

Exhaust port. The two ports on the side run down into the crankcase. Which is up in the photo.

Rod end on crank. You can see the roller bearings
Rod cap was tight.

Roller bearings in the cap. Most of them stayed in place when I lifted it off.

I decided to put in the old crank I had from another R-Tek. Same part numbers.
I put a few drops of oil on the crank journal so the bearings would stay in place.
There is enough space for one more bearing, but that's all that came out.
I guess once they all get spaced that's the way it should be.

A few photos of the difference between the two cranks. Same part numbers.
Top one is the older one out of a CCR2400
The ends of the counter weights are clipped off on the newer crank. (bottom photo)
and the casting itself is a lot rougher.

New crank on the left. If I remember to I'd like to weight them both.

Just for comparison. Honda 11Hp crank on top.

Key way slot on the replacement crank.
Things were going well until I cracked a ring. Hate when that happens. There is an alignment pin in the
piston ring groove for both rings. It keeps the end gap space of both of them aligned right above each other. Which normally you don't do.
Unfortunately I didn't see the pins at first, pushed on the ring when it was on top of the pin not aligned in the end gap and.... snap.

This message was modified Feb 15, 2012 by jrtrebor

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RedOctobyr

Location: Lowell area, MA
Joined: Nov 5, 2011
Points: 282

Re: Inside an R-Tek engine
Reply #19 Feb 16, 2012 3:34 pm

This is more of a question than a statement, but might you be better off with 1-too-few than 1-too-many? Being 1 short won't significantly increase the loading on the rest. But being over by 1 could conceivably pack them tightly enough that they are forced to rub against their neighbors. And since the adjacent bearing surfaces (one vs its neighbor) are rotating in opposite directions, that would seem to be a bad thing.

borat

Joined: Nov 10, 2007
Points: 2692

Re: Inside an R-Tek engine
Reply #20 Feb 16, 2012 4:28 pm

Too few or too many will lead to serious consequences. Having too few might allow a needle to skew. You don't take chances when dealing with something like this. The exact amount of needles is required.
I will wager that the number is 32.

jrtrebor

Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 539

Re: Inside an R-Tek engine
Reply #21 Feb 16, 2012 5:01 pm

I this case you could have to few bearings, but you couldn't have to many. It wouldn't be possible to fit more bearings in to the space that is provided, the rod caps wouldn't seat correctly.
On the other hand you could have to few, which could and would cause a problem. Especially on the down stroke. If there there is any slop or play in the in the rod connections somethings
not right. It will eventually hammer itself apart. Having said that though, having bearings I think is much better setup than machined aluminum crank rod ends. Could be wrong about that.

borat

Joined: Nov 10, 2007
Points: 2692

Re: Inside an R-Tek engine
Reply #22 Feb 16, 2012 6:35 pm

Two cycle engines cannot operate without roller/needle and ball bearings on cranks, connecting rods etc. Not enough oil in the system to run plain bearings.

jrtrebor

Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 539

Re: Inside an R-Tek engine
Reply #23 Feb 16, 2012 8:10 pm

32 bearings

mml4

Snow is good,
Deep snow is better!

Joined: Dec 31, 2003
Points: 544

Re: Inside an R-Tek engine
Reply #24 Feb 17, 2012 7:54 am

borat wrote:

Two cycle engines cannot operate without roller/needle and ball bearings on cranks, connecting rods etc. Not enough oil in the system to run plain bearings.

I think that depends on engine size. Many model airplane 2 strokes have plain bearings and they turn between twelve and 20 thousand rpm. Marc

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borat

Joined: Nov 10, 2007
Points: 2692

Re: Inside an R-Tek engine
Reply #25 Feb 17, 2012 9:05 am

mml4 wrote:

I think that depends on engine size. Many model airplane 2 strokes have plain bearings and they turn between twelve and 20 thousand rpm. Marc

I have to say, I didn't know that about model engines.

I know that any model engines my nephew owned had ball bearings for the crank. Don't recall seeing any bearing on the connecting rod/wrist pin. Understandable though. Can't imagine the tiny size of the bearings involved for those applications.

I assume that the type and amount of fuel/oil flowing through a model engine might be a bit more than a regular OPE two cycle engine. If I recall correctly, a lot of unspent fuel would splatter out of the exhaust of the (very few) model engines I've seen in action.

Nonetheless, there's a difference between a model airplane engine and an OPE engine. I've yet to see a plain bearing in a two cycle OPE, motorcycle. snowmobile or outboard engine.

trouts2

Location: Marlboro MA
Joined: Dec 8, 2007
Points: 1328

Re: Inside an R-Tek engine
Reply #26 Feb 18, 2012 10:08 am

The newer flywheel is thinner and might have been a change for higher revs rather than metal shaving for cost. Strange as you'd think they would have bumped the part number. Would the amount of metal lessened contribute to HP via an rpm change i.e. make it a bit easier to spin. ??

RedOctobyr

Location: Lowell area, MA
Joined: Nov 5, 2011
Points: 282

Re: Inside an R-Tek engine
Reply #27 Feb 18, 2012 11:22 am

My little R/C nitro glowplug engines turn around 25,000-30,000 RPM, as I recall. With itty-bitty brass/bronze bushings at either end of the connecting rod. I believe there are ball bearings supporting the crankshaft at either end, at least in mine. Mine were small .12 in^3 car engines. The castor oil in the model fuel is apparently enough. As I recall, the oil percentages are higher than for mixed-gas 2-strokes. Seems like around 8%-12% or so oil is common. So there is much more oil than for 2-stroke OPE. I think most of the mess that comes out of the exhaust is the oil. You can lean up the engines for more power (and less mess, I suppose), but the temperatures will climb significantly, and it's not good for the engine. You can tell when the car is running out of gas, and starts sucking in some air bubbles, because the RPMs will just scream for the last few seconds, if you give it full throttle.

trouts, I don't think the flywheel's mass would really affect HP output or rating. It would affect how quickly the engine could speed up or slow down. But in terms of steady-RPM power output (at stock speed, or a higher speed), I don't think it would make a meaningful difference. Once the flywheel is up to speed, a heavier flywheel shouldn't really sap additional power to maintain that speed. Now if one flywheel had much larger cooling vanes, let's say, that could make a difference, as it would be using more power to move the additional air around. So less of the engine's gross power output would be left to drive the rest of the machine.

This message was modified Feb 18, 2012 by RedOctobyr

borat

Joined: Nov 10, 2007
Points: 2692

Re: Inside an R-Tek engine
Reply #28 Feb 18, 2012 12:05 pm

I agree that the weight of the flywheel will not have an overall effect on horsepower but it will have effect on how the power is delivered.

A good example of flywheel weight variation and effect is the difference between a motocross race bike and an enduro race bike. Motocross machines have a lighter weight flywheel to allow for much quicker throttle response to deal with the quickly changing terrain/obstacles/layout of the race course. Some tuners actually change flywheel weight to match certain types of tracks (indoor vs. outdoor). An enduro race is all outdoors and over much more varied conditions from rocks to swamps etc. Tractability outweighs throttle response in an enduro race. The heavier flywheel helps to sustain engine torque and keep power manageable. Particularly in tight twisty woods trails where breaking the back wheel loose at a bad time will put you into a tree of off the trail. Been there, done that, it hurts.

On a piece of OPE, my preference would be for a heavier flywheel to sustain torque when the engine is subject to varying loads. As in a snow blower or even a lawnmower.

This message was modified Feb 18, 2012 by borat

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