Bottom end failure - 2018 EC300

[blitz11]

I did a similar thing with my daughter's KTM 200 exc. However, i knew what the problem was (coolant being blown into the exhaust stream.) I build a fixture, pressurized the cylinder cooling passages with air, and submerged the cylinder. Cylinder was porous. Coated the offending area 12 years ago with JB weld, and it's been fine since.

Good luck with the bubbles! I hope that it it located in a small area, and that you can fix it with an epoxy, bead of weld, etc.

[5valve]

Prior to drowning the engine, I released coolant and did one dry test again, this time it held 1.8 bar like a champ, so skipped drowning and began the assembly.

Only variables from leaky to pressure keeper was drain bolt and radiator cap reposition.

This kind of confirms, that coolant, at least now with fresh gaskets and seals but with cold crankcases, is not leaking inside. Nothing porous.

I used proper torque values all round, so possible negligence from factory is now ruled out.

Will see how it holds in future riding hrs.

[Sc28]

Perfecto entonces,ojala y no te de mas problemas y sea un problema de juntas.
Yo he vuelto a abrir el motor, rodamientos del crankshaft y la biela tienen sobre 250km.
Como se puede ver,el lado del encendido vuelve a tener oxido(el lado derecho no,por eso no puse foto).
He pedido informacion a Rieju,que son los que tienen ahora motor y chasis de las gasgas 2018(moto identica bajo nombre de Rieju) y me han dicho que puede ser:

-desvaporizadores del cilindro obstruidos,que de ser asi se crea condensacion de agua en la camara de combustion.(en mi caso no)
-el salto del crankshaft,debe estar entre 0 y 0,02,si es mas Podria provocar deterioro de los rodamientos (la biela tiene 250km y en teoria el crankshaft quedo alineado, pero no me fio y voy a llevarlo a comprobar, puede que este sea el problema)

[5valve]

That rust doesn't seem bad, could even be 2 stroke oil residue, since crankshaft and crank area seem rust free, but it is low km's after your last service. On my old bike, left bearing was also coloured that way and never failed.

My cylinder bottom breather was clogged, since it is only 0,5mm. I remember on '08 model it was way bigger breather, so I already increased size to 1,5mm, for which I got some oposition here.

From factory mine crank offset was 0,05 left and 0,04 right. By the book 0,05 is max allowable, but this is data for 2006 model. I have had it fixed to 0,02, which should now be OK.

Maybe even crankcases assembly affects left bearing, as you must either heat the bearing or use a pulling tool from outside. Any sort of hitting affects its life. Right bearing is more durable because crank fits through cold.

My way is to first fit gearbox into right case, heat the left bearing inner race with heat gun (not flame gun) and slide crank into left case and then easily put everything together, torque to spec and do a few hammer hits to the left crank side, to ease the crank bearing tension from assembly.

[5valve]

Some update for my bike, not yet solved but could be in the process.

To refresh some memory, bike has a total of 72 hrs, 2018 GP 300.

From new it seems to have run too hot. Upon first head removal, due to water mixing, lines were in cylinder. @ 65 hrs.

Since then did 7 hrs and...replaced piston twice, main bearings twice (failure stator side once), conrod once.
Corrosion in crank area.

Finaly did a fluid compression test, since gauge showed everything being fine.
Calculated uncorrected compression ratio of almost 16:1 ....19.8cc.

Ordered new head, measured it (1.9 squish, 0.5mm base gasket, 1.25mm pistom to cylinder deck - in short everything stock) - again 20cc.
currently in the process of cutting chamber, to approx 24cc.

[(F5)]

Ouch! Pull that squish down to 1mm while you are there, but 13.5:1 is a far better place to be. Surprised it didn't detonate itself to bits.

[5valve]

Euro enduro riders have different squish understanding. They like it higher, at best 2.2mm, for soft power delivery, not so snappy for instant response, but tractable to the last rotation. Less strain on engine parts also. VHM uses 1.9 on all models and manages only compression for power delivery.
It also may be a fuel thing, 95 octane here being like 89 or similar in US. Newer GG rated for 98 because of generally higher comp for EC (13.8) and GP (14.1) models.

Damage damage...It did force the pressure to bypass orings into oil and crank area, so everything rusted inside, what killed LHS bearing.
My further head manipulation, squish to 1.5, while reducing some comp (by eye...) must have increased overall force, increased heat and stress further.

Currently bottom and top end are new, and wont even start it untill 13:1 is reached. Squish will put at 2.1 to be as stock as possible for possible future unwanted events elimination, No 1. being cylinder vertical lines.

[(F5)]

A close squish cant hurt the engine until it clips the piston to head at top revs. That won't happen at 1mm. I used to run a roadrace 50 at 0.5mm and it would clean but not hit the area, unless you reused gaskets.
There is no localised pressure, it's like a balloon when you poke it.

But I also recommend you face the squish angle parallel to the piston. It is wedge shaped.
Gas mixture is not burnt in that area, just wasted. Also the closer the piston gets to cool better to the relatively cold head. Make your squish about 50% area or a little less. I cut my chamber a bit square (obviously not very square) to get the volume right.

Any smoothing of the powerband is done with the right needle. My 300 is like a pussycat at low throttle applications and we get a lot of muddy areas here.

[5valve]

Cheers to that.
Every tuner I've talked to here, confirm their findings from road racing, having small squish is beneficial for response, but they all propagate big squish for slow terrain and engine longevitiy. Maybe if small squish is combined with high compression, it is a cracker, while having bigger chamber on small squish, its really more of a lugger.
Can't really cofirm, having 1.5 squish and 12.7:1 fluid measured compresson bike being low end monster, no matter the needle type or gearing. It would just stall rapidly below certain rpms, and those weren't idle low. '08 model.

'18 GP and '19 onward heads are more in the 30% squish area design, very narrow band, nothing to do about it. When piston is pressed into band, if fits the angle perfectly.

[(F5)]

Ahh, yes I haven't opened a 18, just 07s and earlier.

That solder looks like a wedge from here.