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02-03-2021, 03:08 AM
Senior Member
I just got a 150 high comp and I'd like to get more info about exhaust "systems" that work well with these engines. The one I got has the two stroke looking muffler with a lot of small holes for the exhaust, it attatches to the cylinder with a 45 degree curved pipe, pretty cool looking but might require a big cutout in the cowl and that decidedly non scale look. I have found straight pipes to work well and sound great on smaller Saito engines, they don't seem any louder either. So maybe I could just use a flex pipe in place of the stock muffler? I see that Saito sells 90 degree angle manifolds to transition to their flex pipe but isn't that too aggressive? Note that I bought a Seagull Yak-11 Reno Air Racer for this engine and the exit from the round cowl would be a nice small hole if I could use a pipe type exhaust. Obviously if I fly this like its full scale counterpart it will be wide open swinging a high pitch prop a lot of the time so if the type of pipe has any effect on performance or heat build up that would be a consideration too.
I originally bought this for a WWI bipe but decided a potentially high strung powerhouse would be happier in something fast and clean.
I originally bought this for a WWI bipe but decided a potentially high strung powerhouse would be happier in something fast and clean.
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husafreak (02-03-2021)
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husafreak (02-03-2021)
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husafreak (02-03-2021)
02-03-2021, 12:11 PM
02-03-2021, 04:03 PM
The RCS system is pricey but looks really nice and I did get a great deal on the engine so the total isn’t outrageous. 🤔
I went “surfing” to find out why Saito switched from high compression to lower on this 150 engine which basically brought me to an earlier discussion on this thread. I know one solution is lower nitro and I have gotten a couple of gallons of 5% VP Racing fuel for it. But back in the discussion someone had put a .015 shim under the cylinder and readjusted the valves to lower the compression. They all seemed to agree it was an easier running engine with lower compression. But really now, if I just avoid running it lean by dropping the rpm 300 from peak and use low nitro is that also a good final solution? That’s what the high comp engine was made for isn’t it? Or is lower comp “always” better for this engine. Obviously I’d rather run it stock as designed if it’s not a flaw.
I went “surfing” to find out why Saito switched from high compression to lower on this 150 engine which basically brought me to an earlier discussion on this thread. I know one solution is lower nitro and I have gotten a couple of gallons of 5% VP Racing fuel for it. But back in the discussion someone had put a .015 shim under the cylinder and readjusted the valves to lower the compression. They all seemed to agree it was an easier running engine with lower compression. But really now, if I just avoid running it lean by dropping the rpm 300 from peak and use low nitro is that also a good final solution? That’s what the high comp engine was made for isn’t it? Or is lower comp “always” better for this engine. Obviously I’d rather run it stock as designed if it’s not a flaw.
02-03-2021, 04:30 PM
Saito's original marketplace was Asia and Europe were 0% nitro (FAI) fuel use was commonplace. Lower compression ratios of later releases was to cater to a wider marketplace, namely the US market where we are all nitro junkies. Many engine manufacturers did the same.
As I mentioned in our PM's 5% nitro will tame the beast until it breaks in fully, then 15% max nitro can be safely used. A shim to reduce compression is an option however when you want all the power back you'll be looking into buying 30% nitro fuel or removing the shim.
As I mentioned in our PM's 5% nitro will tame the beast until it breaks in fully, then 15% max nitro can be safely used. A shim to reduce compression is an option however when you want all the power back you'll be looking into buying 30% nitro fuel or removing the shim.
Last edited by Glowgeek; 02-03-2021 at 04:33 PM.
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husafreak (02-03-2021)
02-03-2021, 07:25 PM
I have never used more than 15% "nitro"(methane) in a Saito since 1979. I have run everything from 15% down to FAI with good results. The main reasons I lowered CR were for better idle and part throttle and lower vibration levels. Perhaps lugging a larger prop at lower RPM without detonation. Once in place, I never returned to running without the shims. Engine durability is also improved at lower CR levels.
Rather than strain the guts out of a light duty Saito, when more power is desired, I simply used a larger Saito . At times, a similar sized YS when a larger Saito would not fit.
The YS 140 series has brought me to the disposal of several Saito 150, replaced easily with YS 140 series.
Rather than strain the guts out of a light duty Saito, when more power is desired, I simply used a larger Saito . At times, a similar sized YS when a larger Saito would not fit.
The YS 140 series has brought me to the disposal of several Saito 150, replaced easily with YS 140 series.
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husafreak (02-03-2021)
02-03-2021, 10:45 PM
OK, thanks. Horses for courses. I guess I'll try it stock first and if I'm not happy for the reasons mentioned I'll try a shim. Power output won't be an issue. Sport plane.
Next is props. Some here in the past have recommended heavier fiber props instead of wood for the high compression engines. I do like APC props. I used to get them for my Japanese modeler friends when I was stationed in Japan in the late 80's. They were considered an advantage by pattern flyers at that time, just about everyone ran YS 60 or the brand new YS 120 then. Now that was different, we all payed dearly for 30% nitro fuel to be competitive.
Next is props. Some here in the past have recommended heavier fiber props instead of wood for the high compression engines. I do like APC props. I used to get them for my Japanese modeler friends when I was stationed in Japan in the late 80's. They were considered an advantage by pattern flyers at that time, just about everyone ran YS 60 or the brand new YS 120 then. Now that was different, we all payed dearly for 30% nitro fuel to be competitive.
02-04-2021, 01:16 AM
ps i still hate those hard boiled grey graupner props you like
pps Jim you still out there ? and what's the latest adventure.
There's riskier things than an apc prop strike!!
02-04-2021, 02:59 AM
Senior Member
And if the rears are shielded, oil still flows right through them, they, (the shields) could save the day if a bearing breaks up.
The grey Graupners are getting real scarce, the back side of the Xoars gets a groove worn around it and won't stay tight.
The grey Graupners are getting real scarce, the back side of the Xoars gets a groove worn around it and won't stay tight.
02-04-2021, 04:08 AM
Bearings breaking up at less than 12K rpm? Not something I worry about unless I'm running 2 strokes at 17K plus rpm. They make high performance bearings with plastic retainers for that purpose. I have seen shields and seals pop off of bearings for no apparent reason so out they come.
I don't think anyone would disagree that the religious use of ARO is the best thing one can do to prevent an engine from rusting internally. If internal bearing shields or seals are left in place they impede the distribution of the ARO throughout the engine case at the end of the day's flying session. Eventually the factory bearing grease will get washed out and replaced with corrosive combustion byproducts in shielded or sealed bearings. Better to have the ability to quickly and effectively flush out those corrosive elements with ARO than to have them trapped in the bearings.
Last edited by Glowgeek; 02-04-2021 at 04:48 AM.
02-04-2021, 11:09 AM
O/K. May need some expert help here. Another member sent me his Saito 50 to go through and it arrived today in pieces. Some missing bits, such as one white plastic piston pin protector and the intake/cylinder O-ring backer, but still have the cam cover bolted on and crank installed so not a full assessment.
Problem I can see so far is this must be a very early gen as it does not match any of the manuals I can find. Specifically the LS needle is external with the metal throttle arm retained with a nylock nut. Carb has a mounting boss, no choke and inlet has a 90 degree turn away from the back of the engine so no way to reverse orient like more modern installations.
I can post some pics later if required, but hope someone has some info on parts availability, (if newer bits are compatible) and/or economics of repair. Compression feels good, but as stated still have to finish dismantling so no guarantee more won't be found.
Would also be nice to find some documentation, but nothing so far matches.
Problem I can see so far is this must be a very early gen as it does not match any of the manuals I can find. Specifically the LS needle is external with the metal throttle arm retained with a nylock nut. Carb has a mounting boss, no choke and inlet has a 90 degree turn away from the back of the engine so no way to reverse orient like more modern installations.
I can post some pics later if required, but hope someone has some info on parts availability, (if newer bits are compatible) and/or economics of repair. Compression feels good, but as stated still have to finish dismantling so no guarantee more won't be found.
Would also be nice to find some documentation, but nothing so far matches.
02-04-2021, 07:12 PM
I once had an odd (to me) thing happen with a main bearing. YS 90 heli engine, would have been 30% nitro, 2011. walking out to the flight line with it idling and it stops suddenly, case is cracked, find half a ball imbedded in the case at the crack, wedged between the case and the rod, the other half of the ball is rattling around free.
02-05-2021, 03:10 AM
Senior Member
O/K. May need some expert help here. Another member sent me his Saito 50 to go through and it arrived today in pieces. Some missing bits, such as one white plastic piston pin protector and the intake/cylinder O-ring backer, but still have the cam cover bolted on and crank installed so not a full assessment.
Problem I can see so far is this must be a very early gen as it does not match any of the manuals I can find. Specifically the LS needle is external with the metal throttle arm retained with a nylock nut. Carb has a mounting boss, no choke and inlet has a 90 degree turn away from the back of the engine so no way to reverse orient like more modern installations.
I can post some pics later if required, but hope someone has some info on parts availability, (if newer bits are compatible) and/or economics of repair. Compression feels good, but as stated still have to finish dismantling so no guarantee more won't be found.
Would also be nice to find some documentation, but nothing so far matches.
Problem I can see so far is this must be a very early gen as it does not match any of the manuals I can find. Specifically the LS needle is external with the metal throttle arm retained with a nylock nut. Carb has a mounting boss, no choke and inlet has a 90 degree turn away from the back of the engine so no way to reverse orient like more modern installations.
I can post some pics later if required, but hope someone has some info on parts availability, (if newer bits are compatible) and/or economics of repair. Compression feels good, but as stated still have to finish dismantling so no guarantee more won't be found.
Would also be nice to find some documentation, but nothing so far matches.
Cougar, is that carb attached with a single screw like the early 40's and 45's? Thanks, Dave
Similar to this 45, me thinks. I have personally never seen a 50 like, you may have a rare treasure.
Last edited by 1200SportsterRider; 02-05-2021 at 03:21 AM. Reason: Add content.
02-05-2021, 03:55 AM
Interesting, I've only seen the the 40, 45 and earliest 56 engines with the single lug back plate and 90° inlet carb. All of the 45S and 50 engines I've seen have had the later (2 screw) mounted carbs. Could be a treasure, could be someone swapped in a back plate and carb from a 45?, could be someone swapped in a 50 case to a 45? Some pics would help.
Last edited by Glowgeek; 02-05-2021 at 04:03 AM.
02-05-2021, 05:14 AM
02-05-2021, 06:18 AM
All my radials run 15/15% with castor and like it a lot.
no glo driver, easy starts and get you out of trouble.
Best yet.
No Dead SticksIMHO