ST 35 Combat's sleeve orientation

[kevin king]

Anyone know the correct way to reinstall the sleeve on a ST 35 Combat engine? One side of the sleeve has 2 windows, the opposite side has one big window. When viewed from the engine case exhaust port. Thank you.

Kevin

[Massimo Rimoldi]

Hello.
In all 2S engines the highest window is the exhaust one, the lowest one (or ones) is the transfer window.
In your case the single window is the exhaust, the two coupled ones are the transfer ports.

Massimo

[kevin king]

Thanks Massimo!

[Paul Smith]

Very true. 
In all 2-stroke engines it is necessary to allow the hot compressed exhaust to leave the combustion chamber before the cool low pressure incoming charge can enter. 

[Motorman]

 I seem to recall ST made some sleeves where the exhaust and transfer opened at the same time. The one big window is the exhaust and the two angled windows are the transfer ports. Make sure you get the conrod with the chamfered side forward. The cut out in the back plate goes on the transfer side.

MM

[Massimo Rimoldi]

I seem to recall ST made some sleeves where the exhaust and transfer opened at the same time. The one big window is the exhaust and the two angled windows are the transfer ports. Make sure you get the conrod with the chamfered side forward. The cut out in the back plate goes on the transfer side.

MM

What you are talking about is the "Supertigre Transfer Ports" (Travasi SuperTigre) configuration which is the case with Kevin's sleeve.
Even in this case there is a small difference between the exhaust opening and the transfer ports, a few degrees but they are there. The engine MUST start unloading before putting fresh charge into the cylinder.

Massimo

[Howard Rush]

The side with the angled cut is the bypass side, opposite the exhaust.

[M Spencer]

" are 67 deg. BBDC to 67 deg. ATDC for both ports  ". https://sceptreflight.com/Model%20Engine%20Tests/Super%20Tigre%20G15.html  66 g-15 F.I. ,

"The exhaust and transfer periods occupy 137 degrees of crank angle . " https://sceptreflight.com/Model%20Engine%20Tests/ST%20G15-FI%20%282%29.html  71 G-15 F.I.

THO SOME ARE 138 /136 DEG, AND THE .35 IS 136/134 ALLEGDLY .

With the G-15 , the Goodyear was slightly revised . ( Theres two series ( runs ? ) of these ' red intake ' versions , that co-incided with the introduction of the G-15 R.C. , for radio pylon .)
the 21/29s , were know as ' simultaeneous ' in the later versions , and ' pipe timed ' . ( used for B T/R in NZ , the simultaeneous said to be marginally superior for that . ) ABC liners !

Was also a ' piped ' G-15 liner , most of these and many speed 29 cases were butchered with raised roof and liner top edge raised higher , over factory hight . The Flanged small port cases , 67 to 70 odd .
so the rarer G 15 F.I. case , but as per 67 RVD and ' pipe flanged ' RV 29 case from 67  on .



Like This . the top port lip ( and liner ) cut by ' the aces ' for piped use . Send me all your unbutcherd ones ! this is the prefered FAI T/R conversion to diesel , They then prefered the smaller Ex port .

As an aside .

If you want to authenticate it or otherwise , As the transfer top angle makes it awkward , visually . A flashlight or penlight ! at the cylinder top , makes observing the closeing more straightforward .

[Steve Helmick]

Howard's got it right. The hotrod ST's of that era had bevelled bypass ports and identical timing as the straight cut exhaust ports. Which reminds me about shipping the one out to Kev. Lots happening and not feeling all that good.    Steve