O.s. 21tm

[Scrogg]

Just orderd it! I was really torn between the RB 523 and the TM....stilll don't know which is actually better. I wanted the RB but I had to go with the cheaper of the two. RB adveritises no warranty either.
I just killed my 3.3 yesterday.:microwave
Sloppy crank bearing sent the glow plug element thru a perfect piston and sleeve. Bad thing is I knew the bearing was sloppy and kept running it
What do you guys think? I have never owned an O.S.
I'll update this thread when I get it.

 

[Captain Chaos]

your gonna like it=devil

 

[rckid91]

yeah os engines rule

 

[Tornsteel]

Just got mine broken in. I love it so far. It has more snap to it than my 3.3 had.

 

[marauder]

yeah os engines rule

I agree, OS engines have quite the reputation. We put an OS 18 CV-RX into a HPI MT-2 and it's just now getting broken in but it's simple to tune, starts with little effort (pull start), and looks pretty good too! It does drink nitro like it's going out of style though, time for a bigger tank.

 

[Scrogg]

What gearing do you guys run yours with? I ran 15/38 on my 3.3, the teeth are shot on the CB and all I have left are two 16 tooth CBs. I liked the quick acceleration I got out of the 15T CB. Should I buy another? All I use it for is racing.

 

[Tornsteel]

I'm just running the stock gears for now. I haven't researched it enough yet. I would like to find the best ratio for this .21 though.

 

[rckid91]

with the amount of torque u get from that .21 i dont think 1 tooth well hurt to bad

 

[Captain Chaos]

I just ran a 16/40 ratio with the TM at the track and it worked great.I normally ran a 15/40. With the 16 the engine runs cooler also.I think the .21 has more low end than the 3.3 for sure.

 

[Scrogg]

I was hoping to hear that, thanks guys. I like to have the torque/quick acceleration to be able to just blip the throttle and clear doubles.

 

[GH Racing]

yeah os engines rule

+1:yes:

 

[Scrogg]

Anybody running 30% nitro in these? I got my engine today.:yes:
I read the manual, it says 10-30%, but 20% is preferred. I just bought 30% Byrons last week for my Axial which blew up on the first tank.
I have 2 LC3 hot plugs, I am worried about running 30% and a hot plug in a small block... Should i get some LC4 plugs or a different plug? I have only used McCoy plugs in the past. I am thinking a MC-8 is in order? Should i just go get some 20%? It is approaching 90F down here already!

 

[Scrogg]

I put 6 tanks thru it today. Very smooth engine, super easy to tune. The factory needles where dead on for idling the first tank at 220F. When I started to drive it the temps fell to 160F, so I leaned it 2 clicks. Perfect, it ran 210 after that. It did not seem to mind the Byron's 30% fuel at all.
It was starting to wake up on tank #6, don't know if it is faster than the 3.3 was, but damn it is smoooooth. My 3.3 was a lightswitch in comparison.
I also installed a M2C racing 2-shoe clutch i had laying around. I was able to put the clutch springs/shoes on with just my fingers, I could not believe it.
I bought the 1.0 springs with the medium shoes. No clutch drag at idle finally, and the engagement was really smooth on it as well. I highly recommend these clutches if you are a Traxxas owner. It is a bit pricey but i finally have a proper working clutch.
Can't wait to put it on the track.

 

[CharliesTheMan]

I like what I'm hearing. When I get done with my brushless race Revo, I think I'm going to build a nitro with the OS 21 TM.

 

[Scrogg]

I got to run it some more today.... key word is some! It ate the tranny, stripped first gear down to nothing. I am going to loosen the slipper up some more, it's got to help.
She has about 2/3rds of a gallon now, still tight. It's running 235-260 blowing smoke and unburnt fuel, but hauling butt. The LC4 plug brought the temps down a measly 5 degrees on average. I am not sweating the temps due to the glow plugs have been perfect when I pull them.
WAY more power than the 3.3. It is not going to turn the RPMs the 3.3 can, but it's real close. All testing at this point is with 16/38 with close ratio tranny gears, it runs out of gear pretty quick on the straights. I want a little more topend speed but the reality is I probably don't need it! It could EASILY push a 17T clutchbell on my track conditions.

 

[Greyhound]

Scrogg
I just got big block installation for my kid revo 3.3 and still thinking about what engine to drop in, I have been holding my decision since it would need a new pipe. When I read this tread, I'm quite curtain that o.s. 21 tm would be a good choice. Do I need the bb installation kit and a new pipe for this engine? Thanks!

 

[Scrogg]

Nope and nope, it is direct drop-in. Matter of fact it fits in the chassis better than the Traxxas engines do. The best part was that the carb is no longer right up on the spur gear, plenty of room there now. The stock exhaust should be fine, but I am running a THS pipe.

 

[Greyhound]

Thanks Scrogg!

 

[Scrogg]

Glad this thread helped you. I got really irritated trying to find info on this engine before I purchased it. I found 100's of "It's great, buy one!" posts, but nothing to the effect of what I consider helpful information.:constipat I have to agree that what you hear about O.S. quality is true. They have earned their rep.

 

[Greyhound]

I just bought os .21tm and put roto start from HPI on, and hope to be able to install it over next weekend. I'll let you know how it goes if we have a chance to brake in and run it.