SH Engines PT21AO-XGB .21 Competition Off-Road Buggy Nitro Engine

Engine has way more power than I thought. First two takes idle, 3rd and 4th powerband starting coming in. Once engine is up in temp, it really comes alive. Engine is fast with good quality materials.

Just won my first 20min A-main race easy tune! Can’t beat the price!

I'm in the break in stage. Motor had thrown a couple curve balls at me. I set carburetor needles to instruction settings, way way off. A base setting is flush on all 3 needles, rich setting but that is what you want for break in. After that tune to your own needs for the motor. Works great so far! Bubbles around glow plug are normal at a rich setting. I have the idle screw at .75mm. Good luck and let'er rip! I'll do another review after I win some races.

This engine has way more power than I expected! Great for those of us who are still learning to tune and won’t hurt the wallet.

Great motor for the price. There plenty of videos on-line that have reviews on these SH motors. The shipping was fast

Huge Powerhouse , Great Linear and Easy too Tune. It’s gonna definitely give those OS and FX boys a run for there Money. Don’t forget too add the head shim.

Very Strong Engine.With a Dynamite platinum 053 pipe it has great bottom end for a 8 port engine and very strong mid range and a screaming top end!

a few pointers, to start it it is wise to pre heat the block and head to about 200 degrees or so, especially when it is new and never ran. since I got mine broken in and I only have to heat it up to 175 degrees F on my very old Offna starter box.

If you are running 25 to 30 % nitro it is wise to add the included head shim to prevent engine damage.

once again when the engine is new, it is seriously tight, that's what you want and patience is needed with this. tuning is fairly easy and it is good to go with small adjustments on the high and low needles and only touch the mid jet to clean up the part throttle but go with very small steps at a time.

This engine is a very beginner tuner and budget-friendly. The downside of it is that it is VERY HIGH PINCH. I was on the same train as a previous review on here that was going to return theirs but I decided to give it another shot. After pre-heating the engine well over 90 it finally began to fire up. You just have to have a little bit of patience with this one. Another suggestion that I took from another review is to add in the second head shim and it provided way better compression result than with just the one. This high-pinch motor will eat away at your starter box rubber wheel at first, I have a Surestart and it's already eating away at it. However, keep at it and it will fire up for sure. Currently heat cycling and will be fine-tuning for racing.

Great motor! Good rpm range and responsive off the line. I’m in love the three needle carb make it easy to tune! I only had it for a week so far but as of now it a ripper! If you want a great motor for an affordable price this is it !

This monster rips! Screaming top end with plenty of torque for an 8 port. Took a lot of patience breaking this bad boy in as the pinch is tight! But once it was ready for the track it really came alive! Wasn’t real impressed with the stock carb, modified a Novarossi carb and threw on it, really woke the thing up! I’ve spent a ton of money on expensive engines and I am very impressed with this one from SH for the price it’s a steal!

Very tight pinch.! Burned through one starter wheel just to break in. Motor performance is phenomenal. Broke in w master basher vp fuel. Tuned ok on that. Currently I mix 350ml of vp 25 and 9 off-road with 150ml vp off-road master basher. Gives 10.5 oil percent with 23.5 nitro percent. Mix tunes well. piped with dynamite platinum exhaust. Twice the performance of my rtr. I backyard bash.

Normally shake my head at reviews where the person hasn't even used the product yet, but to anybody that buys this (or any slide carb SH for that matter), check the carb boot. Mine came with a hole in it, hiding in a crease of the accordion boot. Gotta pull the throttle wide open to see it.

Only found the hole in the carb boot when removing the engine from the break-in chassis after idling 6 tanks. Wouldn't be surprised if it was affecting the tune/behavior. Glad I caught it before actually putting it in the buggy since dirt getting past the boot would not be good.

The boot on mine is like a plasticy vinyl type of material. I've emailed SH Engines twice via their website but no response yet. Fortunately, I've got old engines to rob parts from. Grabbed the boot off my old Losi 8ight RTR Dynamite engine, which coincidentally is also made by SH. It's a normal stretchy rubbery silicone

I've only idled 6 tanks on the break-in chassis with plenty of heat applied to the crankcase (240°F). This engine comes with lots of pinch, and even though the instructions say that the carb settings out of the box should be good for the first start for break-in, mine would not fire until I leaned the low speed like 2 turns (about 4 turns from fully turned in). I could get a decent idle but would occasionally get some higher idle after several minutes. Perhaps some of this was the result of the carb boot hole, I don't know.

(10/18/2023) Update: I've been using this engine for actual driving for the past 3 weeks. Forgot to mention I've only ran it with the extra head shim installed. It's been great! Coming from running 2 Trackstar .21's right before this, this SH has a noticeably higher RPM scream, better bottom end pull, and a stable idle. The real question is how long this will last, as I'm only just nearing the 1 gallon mark (0.7 quart used for heated idle break-in).

I carefully set my idle gap (venturi removed, of course) to 0.6mm then put the larger venturi back in. Then just use low speed needle to set idle RPM. Have not touched mid needle. Running an old Jammin' JP-1 pipe (low end focused) with the manifold from a JP-3 exhaust. Bones Brew 30%/10% until I ran out, then Sidewinder off-road 30%/9%, no difference in power or behavior. Always preheating to at least 220°F.

Will update this review again if the piston and sleeve don't hold out till at least around 4 gallons, but so far so good, just gotta cover your bases and definitely check for carb boot holes out of the box.

I got mine and the Flywheel gets stuck bad at top dead center the pinch is so tight it cuts and destroys my ae starter box rubber wheel. Also, Neith the pinion diff gears, and the rubber starter box don't line up. I bought it 6 months ago and still can't get it to work instead I had to buy 3 starter box rubber wheels. It's getting expensive. I I'm not sure why the rubber wheel barley touches thee fly wheel and I'm trying to get it exchanged I destroyed my starter box rubber wheel trying to turn the Flywheel. I can't even turn the flywheel wheel with my hand the pinch is ridiculously tight and neither gear, flywheel, nor AE starter box rubber wheel. I can't afford to destroy another starter box rubber wheel. What should I do?????? The pinch just seems crazy tight i can barely move it with a wrench. Should I send it back for an exchange. I don't want a pull start engine. I've broken in tons of nitro engine before and never had a problem like this one.
Albert Fragione
5017 Landmark dr Pueblo Colorado 81008 (239) 331-0250