Hi

I don't have pics after that....but I have opened a couple of times recently and yes...oil is very clear an nice....Anyway I use a Molsyn 150k oil mixed with castor (15% + 3%) with this engine....
The problem with the picture I showed of the cam is not that the oil is dark, but that there is not enough oil....it was almost "dry".

The oil that comes from the vent is also clear.
Since I lost my muffler during one flight, I haven't been able to fly again...I don't have much time neither because I'm currently writing my Thesis for my Engineering degree...
Maybe next month when I find a solution for my muffler and the work is done =)

Saludos,

Jorge

new graupners? do tell

Graupner G-sonic have been out for a a few years. I only have one and haven't run it.

https://shop.graupner.de/webuerp/ser...RTN=1318.28.25

I have used both graupner on my engine.... unfortunately haven't had a tach at hand to follow the performance....but so far the best prop for the engine looks like is the 13x7, I think it revs around 10K. A friend of mine has a 46fx in a super chipmunk...he had a 11x6 with the square tips...he changed to the sonic type and man what a difference!...
Props are much more efficient and lightweight, they may have less load, but the engines perform better. I though that the old style would perform better on the 4 stroke because of the lower RPMS, but the props showed me that I was wrong.

I would say that they are very similar to the APC, but, the graupners are much thinner on the hub and much much lighter...but not as stiff. I'm very happy so far.... I think they are the best alternative here, where you can see a 13x6 APC for 20 EUROS!!! 20!!!! hahaha I just laught!

We have the same problem here. Graupner G-sonic is over twice the price of APC.

Hi,

I bought my TT-75s in England for 129 Pound.

I use an APC 12x7 or 12x8 depending on flying style. This engine wants to rev.

After break in, I checked the engine and found the camshaft sintered bearings "wet". So, I do not see a need for any modifications.

Actually, I am disapointed about the engine because of these sintered bearings. ItĀ“s a very cheap solution. I expected ball bearings. Anyway.

Can the sintered bearings be removed and replaced by standard ball race bearings? I wonder if they are a "standard" size.

Anyone considered this?

I bought mine in england for the exact price too...

Bushing bearings on camshaft is not only on thunder tiger.... I've heard Saito uses bushings there...remember the cam rotates half the speed of the engine.

The Bushings I think are not easy to remove if they can be remover at all...you'll have to mill the crankcase and the cover to accomodate the bearings....but I would bother neither.

I've tried the 12x7 and yes, the engine does rev more....but I don't see the point running the engine with a prop that a 75 2 stroke usually spins.... I would load the engine more.

Bushing bearings have been around a long time and do a great job as long as they are lubed properly.

When you say these motors like to rev, what rpm's are you talking about?

You are falling victim to the confusion most folks experience with glow four-strokes. You are assuming (my guess - no offense intended) that the four-stroke glow engine will produce more torque than an equivalent sized glow two-stroke engine. In most instances, the two-stroke engine actually has "more torque" when allowed to spin the same prop as a four-stroke glow engine running at its best prop size for power production.

No, you're not crazy. What is confusing most folks is that when trying to choose a two-stroke glow engine displacement size equivalent, they must increase the four-stroke glow engine's displacement by a factor of 1/3rd more displacement, just to stay even in power production. Now and then there are a few exceptional engine models in both two and four-stroke designs that might tip the scale slightly in the opposite direction, but these are aberrations and do not upset the relationship significantly that I have described.


Ed Cregger

No offense taken Ed

What I mean is actually is that the engine is in it's high power range with a higher load....
What I've seen is that if you take an engine...and put a smaller prop from what it is capable of turning...the engine revs up...and you say wow this thing likes to rev!... and that it revs good, it doesn't mean that it is at it's best. I know for sure that my tower 75 has far more power and torque than my TT 75, with many props on it.... If I put a 11x7 on my tower 75 it spins at 15000rpms....if I put it on my TT...it will over rev also... they will develope good power, but it won't be the optimum.

I'm still lerning, and thank you also for the input.... I hope that the thread doesn't get out of whack.

Saludos,

Jorge

I've heard of people removing cam bushings from smaller OS four strokes and installing bearings. I intend to try it, they do look like they are pressed in. I didn't pay that close attention to the F-75S when I had it, as long as you can get a tool behind them to remove them, they should come out. I doubt they are cast in place. As long as oil is available, I would not worry about cam wear.

GKA, yes the bearings are pressed in. Not much space to work in but if you are creative you can get them out.

These pics are of my new never run 75s

Rear Bearing seal drilled a .040" hole and installed at 12 o'clock

If you can see the cam gear alignment dot it is slightly before 12 o'clock. That is were it was when I took it apart. Does anyone else find their timing marks the same or different?

I hope to get it together tomorrow and get ready to run it.

With the piston at TDC the timing mark must align with the pushrods.
clean work!

Waiting for the results of your tests =)

The push rods would make it at 12 o'clock. Mine came from the factory at 11:30 or 40. If I go one more tooth it takes me past 12 o'clock. I think I will try it this way and if it runs poorly I will readjust it.

the push rods are not vertical to the cam... and the important thing is that the dot is aligned to the pushrods, not to an imaginary vertical line.... so it won't be at 12 o'clock but a little bit earlier.

So in this picture the piston is at TDC. The cams is not aligned properly?

It looks like yes.

The manual shows a better diagram of it, take a look at it.

I finally got to run in my 75s today.  I left the timing marks as I last posted.  I used an APC 11x8 prop and 30% cool power heli fuel.  First tank was slobbering rich but I couldn't get it below 5K rpm.  It ran about 7K.  let it cool. 2nd tank.  Ran it about 8.5K. Cool down.  3rd tank 9.8K. Cool down. 4th tank 10.9K.  Idles as low as 2200 and accelerates with no hesitation.  I will pull the cam cover and check for lubrication later this evening and post results.  I am ready to fly it.  I just need to put it in an airframe and should be able to fly by Friday.   Estradajae  thanks for your input on the cam lube.  I had a few drops coming out the front brg during the runs but not excessive.

Opened the cam plate and everything looks great.  I checked the valve lash and need to adjust the valves.  how often are you guys adjusting the valves?  and how much run time till they stabilize?

That is good news, I hope you like the engine as much as I do.

I did adjust the valves a couple of times and after a gallon or so, I didnĀ“t have to do it again...the times I disassembled it IĀ“ve adjusted them as well.

I hope I can fly again, this time I will tack my engine.

IĀ“m still waiting for a response from Thunder Tiger Europe. A guy here in Germany answered, and after 2 emails it seems that he didnĀ“t understand the problem at all...

At the end he said somethin like...if I understand well the problem...the burr in the intake manifold is causing lubrication problems....[:@]

Keep us posted on how it goes.

saludos,

Jorge

Jorge, I will really be surprised if you get a response from TTE or anyone from TT.  If they haven't responded by now they are not going to.  The only way you will be able to get anything is to call them as they are trying to ignore you.

I am going to put a 12X8 prop on it and see how that runs on a Hangar 9 40 size Super Stick.  I pick one up used from one of my club members for $50 US.  I am thinking of mounting the motor sideways.

You are right on it....but it looks that the people just don't read what you say!! and I did it in english and german....

Anyway...

I don't know if your muffler has a baffle or not, mine had, and since it had an aditional threaded hole opposed to where the nipple is, I think I got a bug hehe...I had starting difficulties with this muffler. I installed the engine at 225 deg. with the muffler just pointing down... when I primmed the engine, it seems that too much fuel got accumulated in the muffler, because of the baffle, it may get enough fuel to run the engine for a minute or so backwards (it was crazy how long it could run backwards)....and without a starter was always hard to start in that position.... when cold, I could start it with a back flip on the spinner.... It really likes to kick, but the prop stays there and tight.

Since I lost the muffler, I bought an ASP muffler from Just Engines, and I'll test it this week, I hope that I don't have any more start difficulties (I like hand start, actually chicken stick or backflips)... I hope also that the engine can breath a little better and sound a little louder!! it is hard to hear when another plane is around...is too quiet!

You should no have problems to start it since you have access to the carb to prime the engine easily.

Look here for spare parts:
http://www.tiger.com.tw/product/9802.html

Hi Friends,

It's my first post here at RC Universe. This is the best TT 75S thread i've found! Since this is a new motor, there aren't nice reviews or other infos about it.

So, here comes:

What to do with the breather nipple? Until this TT engine, I had only used OS, and the breather nipple is conected to another nipple at the inlet pipe. Leave it open?
Next step is make the bearing's hole modification. <<<<thanks for this tip!

Rom,
Brazil
Just learning english!