Hopefully can get a final answer, go gx series, gx2, gx2plus crankshaft interchangeable, only gx2 crankshaft available at d moment

I have to agree with Rex and Craig. The newer GO engines (Champion etc) are extremely tight - too tight. Crazy hard to get started even on on a run in bench with plenty of pre heating (Competition Heat and hot air gun in liberal amounts).
This may be a design feature for longevity, but the rod and crank pin take such a hammering during run in that any positives in having an engine this tight are surely negated.


Yes. The crankshafts are interchangeable. The only difference being various coatings and the epoxy ramp in the later versions.

A rhetorical question I asked in a different thread: "I wonder if the strain on the conrod is higher during the first couple runs, when the pinch is still tight but the engine barely gets above idle, or when the engine is revving at tens of thousands of RPMs after break-in?"

If your engine has a weak conrod, surely it's better to find out before you've gone through the trouble to break-in the engine properly.

It's not a matter of the engine having a "weak" rod. Any rod placed under that much strain with millimetres of very, very tight pinch to push through for the first couple of gallons of it's life won't like it - particularly the first 10 tanks or so.

The rods are designed to take the stresses of the high revolutions when moving in a nicely fitting sleeve without issues, but the stresses and strains on rods, and particularly wrist pins and wrist pin mounting recesses in the cast pistons on a new motor this tight are extreme.
It's not uncommon on engines this tight that have been run in mounted in the car with less than precise temperature control over the early tanks to have significant wrist pin slop after a gallon. We have seen this time and time again with super tight new engines.

You can easily change the rod after run-in (highly recommended in the large majority of the tight fitting Taiwanese produced engines), but you can't repair the worn out wrist pin mounting areas in the piston.
A nice firm fit for engine longevity is one thing, but crazy tight tolerances that cause significant internal wear and tear before the engine is a couple of gallons old is something else.
Like Rex stated - they are just too tight now days.

Thanks, i'll make my purchase soon

Fair enough. Also, perhaps they are simply meant to run hot.

I haven't noticed significant over-tightness on my .18 engines from GO.

The GO .18 engine is a sport engine with a pullstart from what I can see on their website, for that reason they cannot be a tight fit from new because the cord would break if the motor jammed during run-in startups.

Yes they will need to be run hot to get the sleeve to expand and help relieve the stress on the piston and rod, unfortunately that means less lubrication because of the leaner setting to get the heat up.

We appreciate (Rex Shane and I) you want to defend the brand but we are just giving our constructive opinion from years of experience running .21 race engines and having owned a few generations of GOs.

I'm not defending the brand. I have no allegiance to the brand at all. I've run two of their engines and I have a couple spares of the one I still use. The main attraction for me is the engine costs $45, so if my girlfriend's nephews fry it, it's painless to replace it. I'm just speculating as to the reasons why they designed their engines the way they did.

Put a baby-sock over the heatsink if you want it to run hotter during break-in without leaning the fuel mixture too much. That's like the first thing anyone tells a nitro noob about running in cold weather, and it applies equally-well here. Does it fix the problem that their race engines are too tight out of the box? No, but if it helps the break-in process go more smoothly, then roll with it.

I think a sock for temps is a non-issue, since high pinch generally means high temps anyway. It sure did on the Caster Grenade (rebadged GX 5-port) I had a few years ago. That thing always ran hot.. 290-310 hot... I never preheated, but it quickly got plenty hot after starting.. Always. Was a good engine though. One of the best idlers I've ever had too...

These need more than a baby sock, beer can holder, tin foil or anything else you might have.
I think between us we have run in literally hundreds and hundreds of engines, so "noob advice" doesn't really apply here.
If you got your hands on one of the newer (say) Champion engines, you would see exactly what we are talking about. It's hard to get across just how tight these engines are.
Why they make the tolerances so tight on these is anyone's guess - but the end result is customers don't want to go there twice. Which is a shame.
We have imported GO Engines since around 2008. Through all the generations of engines - Pro Series and early Gen 5, GXR 5.5 and GXII-5RHO we have never struck engines as tight as these latest batches.

If you have Rex's expertise and can hand lap the piston / sleeve set before run-in that's cool - but not everyone has the know how to do that safely.
It just seems extreme that you need to go to those lengths, when most other brands bed in nicely with no such issues.
Anyway, we are flogging a dead horse here. That's the way they are for whatever reason, and that's that.

That's also why you don't see them on our website any more.

when i had the GO based MG66 it was hitting the 124C temp.. so more than 250F and by the end of the 6 - 10tanks.. the engine came to life.. and i never had a issue with it.. total beast and a joy.. as with many or any engines.. a good run in is a fun race engine.. in end result.. with these engines them having tight tolerences between the sleeve and piston will only give a long life engine once its bedded in.. and cycled for 10tanks = 1L of good fuel.. ive just run in a Soar RS21 and its on its 14th tank.. and the tightness is only on right at the top.. so very close to ready.. great prices of the GO engines.. shame people dont take the time to show their potential.. as they have few and far between flaws now days..

IŽve owned a few Champion and UDP engines, what IŽve found is that preheating the engines a little hotter (say 110-120 C) absolutely loosens the engine during break in. Next time give a try and go straight to 110C with a heat gun, youŽll see the engine will start at first try and the break in will be much easier this way.
Before you ask, I have over 5 gallons on the first champion I broke in using this method, havenŽt changed anything on it yet, not a single issue with the con rod, bearings are in great shape and crank pin shows normal wear.

If anyone is having a hard time breaking in these engines just go a little hotter than usual with preheating and problem solved.

yeah the extra heating does make that extra for a easy start and run in.. im swinging between investing in the ty l.ed os or just grab 2 go engines with a 2072 pipe.. would be fun to have choices of the two.. how was the cera udp engine ?? from bottom to top..? and what differences are there between the engine 2years ago and now.. ??

You had the MG66, try out the Godzilla & 2072, plenty of grunt & good fuel economy.

All go engines are good, gx, gx2, gx2+, udp, champion, cera, i bought an italian mill n re-sell it. For the price n performance, u need 1 to race against italian/japanese mill to tell d myth. Just patience with break in, heat is needed at least 10tanks.