48chebbie

My Feedback: (58)

well,how should i start this,i have heard so many great things about this .54,but to be quite honest,i am not real pleased,period!i got a brand new one of these out of the box recently,bolted it on a light .40 size low wing,and tsarted through the normal process. i run an o.s.f plug,on 20/20 byrons ys blend 4-stroke fuel,ran about 4 12oz. tanks through it on the ground,then started tuning,well,between the fuel absolutely slobbering out around the highspeed needle,to the inability to lean it out at idle,to the extremely POOR transition,i am not in the least pleased. now before i get jumped,yes,i have slightly enlarged the airbleed in the back of the carb:no change. TT gives you 3 extra o-rings for the highspeed needle,tried all 3:no change. and,with a gallon of fuel through the engine,it is no better.NOW,think i am just not having luck with ONE bad engine out of the bunch?well guess what?i bought another .54 2 weeks ago,'cause i thought i got one bad apple.......i have now gone through this rigamarore twice in a row,and have 2 junk,low powered,messy,slobbering 4-strokes for my trouble! guess the prices on those YS's don't look so bad after all. does this sound familar to anyone? any ideas?

Jazzy

Yes, this has happened before. More than once; though I've not yet heard of the HS needle leaking so badly.
Do a search. There is a cure. (The problem isn't the airbleed. It is the opening in the hardened steel throttle barrel. Provided of course the timing is correct and the valves are gapped properly.)

CurtD

My Feedback: (1)

The problem IS the airbleed, at least with the two TT .54's I have. You have to drill out the airbleed hole to 3/32" to get it large enough to be able to lean the idle sufficiently. My theory is that this carb was designed to run on no nitro type fuel and just doesn't get enough air with the fuels we typically run here in the states.

The OTHER big problem that's easily resolved is improper cam timing. If you take the cam housing side cover off and look in with a flashlight, you'll see a small dot on one of the camshaft gear teeth. Put the crankshaft at Top Dead Center by lining up the inscribed line on the prop drive washer with the casting line on top of the crankcase. The dot on the gear tooth should be directly under the valve lifter, centered, or exactly 180 deg opposite the valve lifter.

I've found several TT .54's with the cam gear set one tooth off from proper timing. The engine will run but will exhibit the symptoms you describe. At certain throttle settings it will spit fuel back out the carburetor, which may be the source of the raw fuel you're seeing. If not, you can use automotive gasket sealer (the Permatex black stuff seems to be impervious to fuel) to carefully seal both sides of the banjo fitting. I also cut a short piece of fuel tubing that slides onto the high speed needle and is compressed between the top of the needle and the housing to seal the threads. The O-ring on the needle valve doesn't seem to do a very good job for some reason - probably clearances.

Once you get past the carb problems the little TT .54 seems to be a nice, reliable sport engine. It ain't a YS in the power department but it'll pull a 5 lb .40 size plane with reasonable authority. Just don't expect 3D performance.

HarryC

My Feedback: (1)

A friend and I have 4 of these engines, great at top end power but utterly hopeless at getting near to an idle. I tried drilling out the airbleed but it was no help. In the end I bought the twin needle carb for an ASP52 and with a tiny amount of turning down the length of the inlet pipe on the TT, it fitted fine and the engine now idles well. Good engine, crap carb.

Harry

Jazzy

Let me guess: Setting the needle for full throttle is easy. But, when you start throttling down it loads up and dies.

If this is the case and the timing is correct and the valves are adjusted properly, then this is the cure:

Remove carb from engine. While looking at the inlet of the carb rotate the carb barrel with the throttle arm toward the idle position until a tiny opening between the carb housing and the hardened steel throttle barrel remains. Mark the hardened steel throttle barrel at the center of the crescent wth some form of scribing tool and remove it. With a round needle file or similar dremel attachment carefully file/grind off the sharp edge of the crescent at your mark. In essence you're beveling the hole drilled through the throttle barrel.
It doesn't take much to take too much off the edge! Just take off a little bit at a time until your engine transitions properly.

I have drilled out the airbleed hole to 3/32". It didn't work. After making the adjustments to the barrel more than half of the enlarged airbleed hole is now covered by the screw.

The problem was too much vacuum within the carb resulting in too much fuel and not enough air.

BTW, I tried to find the thread where this info was listed but, couldn't find it. I'm not sure where it is now... it's around here somewhere... anyone seen my marbles? I seem to have lost them...

48chebbie

My Feedback: (58)

well,i took the side cover off to look at the cam gear,and with the piston at TDC,the marks on the hub(which is an arrow)lined up with the casting mark on the housing,the dot on the cam gear is at the 5 o'clock position,the tallest tip of the valve lifter is at the 2 o'clock position. so is this right,or,is this engine way the hell out of time? fixed the leaky needle,fished around the shop and found a fatter o-ring,with the same i.d.,and thickness. any ideas????

HarryC

My Feedback: (1)

If the piston is at tdc on every second rev the the inlet will be opening and the exhaust valve will be closing. They should be equally opening and closing so if you look at the rocker arms from the side, they should be parallel or so very close to parallel as makes no difference. If, at tdc, the two rocker arms are at quite different angles then the timing is out. I suffered this problem with a brand new TT91 that had not been assembled correctly at the factory.

H

mikenlapaz

Did TT get this carb problem resolved during the last 5 years?

Is this the same engine or a new improved version? http://www3.towerhobbies.com/cgi-bin...?&I=LXKG11&P=0

bigedmustafa

My Feedback: (2)

All current Thunder Tiger 4-stroke engines now come with dual needle valve carbs and no longer use an air-bleed type carburator, despite what Ace Hobby's website still says. If you pull up .pdfs of the current 4-stroke manuals, they'll show low-speed needles in the parts diagrams.