I recently acquired an older supertigre engine.....a S-90.The needle valve assembly is different than the newer G engines.The hi-speed needle is just a straight needle with the L on the end...like the Higley needles.Actually ,it doesn't have a needle...I need one.I am wondering if the newer parts fit the older engines.I think it is made in Italy and the newer ones are made in China,maybe.
So should i change out the carb, if the new ones fit, or should i keep the orig. and look for the older style hi speed needle.And does anyone know where i can find the older style?

Thanks,Dave

I'm guessing your S-90 has the dished cylinder head and round spraybar. If it is the round spraybar, it probably does use the needle with the bent leg on the end and these can be found on Ebay. I found a few listings but I think the one you want is this: http://www.ebay.com/itm/2-Super-Tigr...item4cff7acd9e

Your S90 will probably take the long one. Make sure you have the little brass clamp nut for the needle valve.

If your S90 has the square cast head and milled spraybar, you'll probably need the other needle valve like this: http://www.ebay.com/itm/NEEDLE-VALVE...item4843159e92

The G2300 and S90K (non dished head) use the same spraybar and needle valve, I'm pretty sure. I couldn't find just the needle valve for the S90K/G2300.

Hope this helps.

Thank you for the info.My cylinder head is NOT dished but is square.I haven't taken out the spraybar, yet, and looked but it has the little brass nut that tightens on the needle....so i expect that the long needles are the ones that work with this. That auction ,you sent,has 2 needles...do both work on the same engine?

Do yuou know if all the G parts interchange on the older S engines?

thanks Dave

You have an S90K engine if it has a square sand-cast head. I have an S90K as well, and my engine has the carb/spraybar arrangement that the G2300 does. Mine does not have a retaining nut on the needle valve, so perhaps your engine is newer than mine is. I'm not an ST expert, but I've rifled through enough threads to have a good idea. I do not know which needle will fit your engine, the listing said ST, MVVS, Como I think. They may all use the same thread/taper. If it were me, I'd use the spraybar setup from the G2300. I have an S29 with the bent needle and retaining nut and my needle valve spews fuel like mad when running over 1/2 throttle. My S90K needle valve does not do this. The S29 made a mess on my test stand with the leaky needle valve. But for $7 plus postage, its worth trying the bent needles.

Many parts from the G90 do NOT interchange with the S90/S90K engines. The cylinder liner is the same between the G90 and S90, however the piston, ring, and conrods are different. The S90/S90K have a removable front housing that can be rotated to fire the engine clockwise. The G90 is a 1-piece crankcase. The cylinder head and backplates are the same I think, and the carbs are really similar. The S90K has a milled spraybar, the new G90's have a round spraybar. The S90K is undoubtedly a stronger engine than the G90 based on what other G90 owners have said. My S90K has about a gallon on it, and turns an APC 13x6 at over 13,500rpm on just 5% nitro. On FAI fuel it loses about 800rpm but has a much snappier exhaust note.

The S series engines are designed for low nitro. Don't use more than 5% or you will have issues. My S90K is somewhat intolerant of nitro - had a hard time getting it to run reliably on 5% nitro. It now tolerates it but just barely.

Great info....yes my st has a top cylinder head more like the G series but the front housing has 4 screws and is removable.Says "made in italy" on the side of engine.
and has the big S. So then ...looks like my best bet is to change the whole needle valve assembly to me.But yes 7 bucks is a cheap fix if it works.

thx,dave

I can't get the back plate off this S-90.Any ideas on getting this off without tearing up the thing?
I've been cleaning up this engine...inside and out.Would like to see if there is much rust inside.

Dave

If the screws wont come out, heat the crankcase with a heat gun or hair dryer. On my example, they are flathead screws and the backplate uses a paper gasket. Use a screwdriver that fits the groove as tight as possible and carefully knock them loose. A razor blade works well to break the backplate loose from the engine. Again, get it good and warm as most glow fuel has a little castor in it and its this oil that hardens over time and makes it a pain to get stuff apart (and getting stuck rings loose).

Try the $7 needle valve first, and if that doesnt work well, swap out the spraybar. The ST carbs are some of the best on the market if you learn the tricks to get them tuned just right. I'm a big fan of the ST carb.