1200SportsterRider

You could also send one of the 50 sized velocity stacks, I'll just bore it out.

1200SportsterRider

Saito FG 100 connecting rod, interesting. At 16 to 1 gasoline to oil mix I don't see the need for the bushing.

$133.99, wow.

Glowgeek

I'm actually more surprised that the Saito FG-100cc twin doesn't use roller bearings.

Jesse Open

Usually requires a rather complex crankshaft assembly for a boxer twin







Or....make the stack from aluminum bar and make the vent connection with a tapped fitting. Done that too.

Glowgeek

OK, yet just about every other manufacturer of boxer twins 60cc and up are providing roller bearing rods on the crank assemblies. There's extra power to be had at 40:1 oil mix vs.16:1.

You know what I mean, 4 strokes already have a power deficit as compared to 2 strokes. I think Saito would sell a LOT more of their larger FG engines if they came equipped with roller rod bearings. I know several flyers that would love to have the 4 stroke boxer sound but won't buy a Saito JUST because of the plain bearing rods.

brickwoodward

Thank you very much, and I would, and will but I have to find them

Jesse Open

Split rods with caged rollers or built up two throw cranks are both fairly costly options.

They also take up more space, add mass...
Between that and the cost, the roller bearing holdouts would probably still walk away.

1200SportsterRider

Few would know the difference anyway, or care.

1200SportsterRider

QUOTE: You know what I mean, 4 strokes already have a power deficit as compared to 2 strokes. Only on paper, in the air where Flying Power matters, there is little difference.

It has long been known that retarded timing will burn up an engine, as will too far advanced timing.

Jesse Open

Hey Dave, hope the trip was a good one.


Perhaps Saito is also catering to a different customer base with the larger 4 stroke/cycle offerings (?). Seems unlikely there would be sufficient sale potential among the hobby buyers alone to justify developing the new, larger engines. The drone market has been pretty good lately to several companies with original roots in the hobby business. Deeper pockets there right now too. One market is shrinking while another is growing.
The customer with deepest pockets usually gets the most attention.

With the heating issue; Yes, both early and too late timing can raise temperatures. For some different reasons and in different ways.The differences of course are the areas affected.
Exhaust valves and seats see a lot of abuse from late firing. Slow burning from improper mixtures or even weak compression can drive up temperatures too. Happens with all fuels.


Still working on the Robinhood? Hope to get busy on mine real soon.

Glowgeek

2 stroke model engines make 40%-50% more horse power per CC than 4 strokes, that's why .90 cu in 4 strokes are recommended for many 60 size planes. I've flown many 60 sized planes on both 2 and 4 strokes. The realized difference in performance has everything to do with the airframe design as well as the rpm that the engine is designed to produce peak power at. Where a .62 4 stroke may fly a lightly wing loaded high wing 60 size plane fairly well it wont fly a 60 sized warbird worth a flip.

Yes, well known. I wasn't arguing that point on the other thread. I was merely stating that the timing on an Unmodified Saito FG engine can't be set retarded enough to cause a problem AND that the timing IS set advanced enough to burn the exhaust valve seat on the FG20 if the engine goes lean in flight. If however Saito had set the timing 28°-30° btdc the engine would just quit running if it leaned in flight, therefore no harm to the engine would occur, even with aluminum valve seats.

I'm not railing on Saito here, I love my FG engines. I set the timing as far retarded as the hall sensor bracket will allow on FG's and make sure they are set a little richer than my gas converted Saitos, which are set to 28°-30° btdc. So I lose a little power output, no big deal, better to have the engines around longer.

Cougar429

My Feedback: (3)

I would be interested in getting a few of my 125s fit with those stacks and love the idea of recirculating the vent ala' Surpass III. I have lots of pressure fittings so would tapping for those be possible without compromising the alloy?

Will have a boo through my spares.

Jesse Open

Yes sir, The Saito stacks are a bit thinner than the bar stock aluminum stacks I make. Still enough meat to carefully tap, and Red Loctite a fitting in place. Of course, you could also make a bar stock brass stack and solder a flanged connector in place.

The pre-carb recirc does not seem to affect carburetion in the least. The post-carb spot has been known to upset carburetion at times.

Jesse Open

Dave,

I was never intended to imply it was "easy" to get the timing retarded with the factory setup either.

Yet there are many home conversions made where yes, it is very easy to set the timing late, for whatever reason. The effects of too much advance were already noted and were not disputed!


The comment factual, accurate comment about late timing was added as a caution since some may have otherwise gone off thinking that late timing was somehow "safer".
Late timing does it's damage a bit more quietly.
By the time some reallize, the damage can be extensive.
Since folks had been discussing aluminum vs bronze seats, it was timely in that respect as well. Fact is, careful operation with correct mixture and timing and even aluminum seats can have a decent lifespan. (As well demonstrated by Arlyn with his Saito gasoline conversions).

Glowgeek

28°-30° btdc is not late timing. If someone modifies an engine and runs late timing, on purpose or not, it's on them.

Cougar429

My Feedback: (3)

Well, I went and grabbed the 150 I rebuilt for my friend back. Had to buy the airframe as well, but since it's a Goldberg Sukhoi 26, will forgive myself for not staying with bipes for now.

To replace it am awaiting a used 150. Should be here soon, but since international cannot guarantee how long that will take.

And this brings me to a couple of question. What would be an effective tank size with reserves for an average 9 minute flight? Mind you, both these will be heavy 3D so throttle usage will reflect that higher demand. To keep the weight down on the new build dropped the tank down to 12 oz. From past experience still had half a tank on average after that with the 125s so did not expect to need more. Unfortunately that was not a good match for the airframe, (30 CC gas) hence upping the cubes.

I have been running several different make 16/8 props on my 125s for years now, (their schedule shows 16/6) and that is also what Saito recommend for the 150, as well:

https://saito-engines.info/prop_sizes.html

In most of these I have looked at scale appearance in flight, not any honking around or vertical. Any thoughts on what would be best for 3D performance? Be advised, I normally run wood props for the first few flights, (in case things go south) and on this one, for appearances will likely end up 3-blaed. Not sure since have some nice Biela and other wood and C/F clubs.

kmeyers

All my bigger and small gas engines have roller bearings on press fit crank journals. Not very costly at all (just say-n).

Jesse Open

Yes, roller bearings have been very common in two stroke gassers for decades.
However:
Which four stroke, 50cc to 60cc boxer type twin cylinder engines do you have that are running roller bearing crankpins? (Just askin)

kmeyers

That would be ZERO on the four strokes, DLE, CCRC, RCGF and a 3W though all currently in my inventory.

Why not four strokes?

Glowgeek

IIRC, NGK uses roller bearings on their 4 strokes. They don't make twins yet.

RotoMotors makes 4 stroke boxer twins and singles with roller rod bearings. 85cc is the smallest 4 stroke boxer, so not within Gary's limitation of 50cc to 60cc. Still, it's smaller than the Saito 100cc boxer where the issue was first mentioned.

Jesse Open

Yes, Size matters.
Diminishing, returns run in close proportions to engine size.
Cost, complexity, even the availability of suitable mass produced bearings must be weighed against any potential benefits.
Obviously, at this point Saito has weighed the factors,made the choice, tooled up and built their 100cc, Boxer with a bronze lined,plain, journal bearing on the crankpin.

Linkan2

New Saito FG-50

Glowgeek

FG-50, cool. Should be perfect for planes rated for 35-40cc 2 strokes.

1200SportsterRider

I'm back from fishing and visiting and mighty glad of it. I'm a happy camper, I'm expecting the lil feller to arrive today. I needed a second 30 for the Minuette. This guy is NIB.


From 1999, whoda thought that?

FlyerInOKC

My Feedback: (6)

I am so jealous, nice find!