f16man

Wow that's pretty big gap, between the bowman ring and closed gap that outa wake her up, do you have something to break the glaze in the cylinder?

1QwkSport2.5r

The funny thing is, is the engine ran fine and turned the same rpm with the softer compression and .012" gap stock ring that it did a year ago when it had stronger compression. It was so strong, it would whack your finger flipping it if you didn't get out of the way quick enough. I checked the liner for corrosion or pitting and none was present.

I do have a type of honing brush made of a hard plastic bristle with some sort of ultra fine abrasive embedded in it that I used to break the glaze in the cylinder. It added a nice cross hatch to the bore. With the Bowman ring installed, it's got it's "pop" back that it had last year and it hasn't even been run yet. It should run at least as good as it did before. I use a Jettstream muffler on it (.90 size red).

FlyerInOKC

My Feedback: (6)

I have the opportunity to purchase a ST .75 with little or no time on it, what are these engines worth now days?

aspeed

I got my fairly used one for $20 at a swap meet. It works ok.

1QwkSport2.5r

I paid $85/shipped for an old S90K that was run a few times on the bench. I'd think $60-75 for a very nice lightly used engine to be reasonable. It takes a fair bit of running to seat the ring in an ST, so if the ring is completely silver in color, it's got at least a couple hours worth of time on it. A black ring is new or nearly new.

Charley

My Feedback: (2)

I haven't torn a ST down in many years. I seem to remember that some of them had pinned rings. What about the S 90?

CR

1QwkSport2.5r

All of my SuperTigres have pinned rings. S29, S45, G51, and S90K. I don't know of any off-hand that don't have pinned rings. I just installed a Frank Bowman ring into my S90K. It's amazing how much better it feels when flipping it over.

the pope

I would imagine they would all have pins . Remember its not a 4st with no openings in the liner . The ring would catch in the exhaust port etc otherwise . I have a mag that shows the ST positions of the pins , there not all the same . Cheers the pope

1QwkSport2.5r

Not all ringed 2-strokes have pinned rings. ST engines may all be pinned, but there are other brands that don't use pinned rings.

the pope

Hi there Tim , I was talking about the ST's but its been along time since I looked at that mag . But if Im wrong the pope is willing to be re-educated ! Cheers

1QwkSport2.5r

The reason I commented as I did was only in relation to your comment about a 4-stroke and snagging a ring in an open port.

I dont know if ALL ST ringed engines are pinned, but I'd hazard a guess that most are.

I think it would be good information for folks to have that info about piston ring pin locations. Maybe over on RCG in the "manuals" sticky.

I aint mad mad atcha and I wasn't trying to disprove you. You're a good ol' chap in my book!

tony0707

do use only the largest fuel tubing and tank hardware available for the ST 3000 ,so you will have no fuel drawing problems
The fuel tubing and tank hardware , for 60 and 90 size ,will not do the job , to feed the big glo engines that are 1.80 or larger
My old ST 3000 ( 1. 80 ) and my Moki 1.80 Need the larger fuel lines to perform as they should ,and they DO !!
Hope that info helps get her done
Enjoy

1QwkSport2.5r

Is the ID of the large tubing the same size, smaller, or larger than the ID of the fuel inlet on the carburetor?

tony0707

The power of the ST 60 and the 75 , comes up short for there size , from handling both
Very average over all performance from these two
My 51 and my old 3000 are real work horses ,and better than they SB ,as the best glo engines are
Like to own a G 90 as it is a light powerful engine ,i think in a 60 engine case ,that somehow i have not yet given a try
The 2300 is interesting to me after this thread
Flying two cycle glo for 23 years , more than most
The OS 75 AX has animal power in this size ,and best for a 60 size airframe ,that i know of
I flew a 75 ASP ( ABC ) with an OS 7D carb for years , on a 60 size airframe , until i bought the 75AX and experienced its performance
The 75 ASPs carb is a copy of the OS 7D carb ,a good carb that will hold up well ,( wore one out after about 200 flights ) but never as good a the OS 7D carb ( that i have 4 of - not for sale )
OSs claim to fame , is they make the best ( air leak free carb ) on the market with the best metal for the task ,which equals great reliability and performance
The 45 ,51 and the old 3000 are better glo engines than they SB ,and those that i have personnal experience handling ,a lot
Enjoy

tony0707

Found the power of the ST 60 and the 75 ,to come up short for there size
Very average over all performance from these two
My 51 and my old 3000 are real work horses ,and better than they SB
Flying two cycle glo for 23 years , more than most
The OS 75 has animal power in this size ,and best for a 60 size airframe ,that i know of

the pope

Its all good there Tim , you know you hold a special place in my heart ! Now back to all things ST . I have just spent 11/2 hrs looking through my mags and I am done ! If I come across it I'll post them for sure . For the Aussies out there it was in the Airborne magazine going back a few yrs so if anyone sees them . Cheers

1QwkSport2.5r

Awww shucks! LoL . You're good stuff Mike. Thanks for digging around for that magazine. You're a trooper.

FlyerInOKC

My Feedback: (6)

Average power is good for me, I build scale and I don't want rocket response.

tony0707

I do think the larger glo engines have bigger inlets ,on there carbs
Muffler pressure is needed as well
I used the regular size tubing for that
My larger engines ran great ,set up ,with the larger tubing

f16man

I have never seen a 2 stroke engine with out a anti rotation pin ,,, from glow engines to chain saws to go karts except an abc engine that has no ring,,,,I am 62 and been building and repairing engines my whole life.

f16man

[QUOTE=f16man;12161037]I have never seen a 2 stroke engine with out a anti rotation pin ,,, from glow engines to chain saws to go karts except an abc engine that has no ring,,,,I am 62 and been building and repairing engines my whole life.[/QU I f there is one how the heck do they keep the ring from rotating a tip into a port, and that is almost always a major catastrophe for the sleeve and piston at least....

1QwkSport2.5r

According to Frank Bowman's piston ring list, a bunch of the smaller Fox engines don't have pinned rings (.40 Schnürle, 45, 50, 59) as well as some Enyas (6002), and many others. I have a Fox .50 that doesn't have a pinned ring.

Charley

My Feedback: (2)

Well, the reason I asked is that you have to subtract the thickness of the pin from the measured end gap. So, the end gap of the old ring may not be the issue. Could be the old ring is just shot.

But the presence of the pin begs the question: How much allowance for the thickness of the pin must be included in the end gap of the new ring?

CR

1QwkSport2.5r

The factory ring as well as the Bowman ring overlap the pin as do all other ringed engines I've had apart including some trimmer and chainsaw engines. There is a notch on either end of the ring on the backside.

spaceworm

A workaround for engines without a pinned ring was a bridge across the port(s). Some hop-ups include removing the bridge when using a pinned ring to replace the stock one. Removing the bridge increases the flow; replacing the ring with a Bowman pinned ring increases the performance due to improved compression from better sealing rings and and reduced ring blow-by from smaller ring end gap.