Bill Vargas
50cc
upper bearings and lower bearings are all there? piston pins?
and what does the inside of the piston look like? pics?
and what does the inside of the piston look like? pics?
thurmma
150cc
There is a single score straight between the 2 exhaust ports that is deep enough that it won't hone out on the other cylinder
thurmma
150cc
All bearings are there as far as I can tell. Everything in the reciprocating assembly still feels nice and tight but, now that you mention it, I will take a better look just to double check.
I haven't taken the pistons off the rods yet. The retaining clips are all in place and in good shape.
49dimes
Damn I'm hungry
Mark I am curious as to what exactly is the cause my self. Others asked questions that where on my mind as well but this is really sounding like a problem that is not just associated with the 170. I have a friend who has the same tuning issues with a DLE 60 twin. Ran great for the first 5 or 6 gallons and then tuning issue began. Jody Hack had mentioned that some earlier DLE's had problems with cylinder "skirt" design and porting. Just saying here. I am wondering how much of the piston is being exposed at bottom dead center and once the piston cylinder breaks in piston slap is introduced and aggravated causing a weak induction path ( ie going lean) .
Alky6
150cc
FWIW, here are five pistons out of my 350cc 4-cyl boxer type outboard racing engine. Typically a lean and hot condition leads to sticking on the exhaust side of the piston where it is hotter. And that appears to be what happened in your case, IMHO.
In the pics:
The left three are stuck on the exhaust side. The middle one also burned the top of the piston. The right two were from items going through the engine. 2nd in from right resulted from the retainer breaking in one of the main crank bearings and going through the cylinder. The far right was a costly mistake when in a hurry and mounting the piston backwards so the ring gets hung up in the exhaust port....
In the pics:
The left three are stuck on the exhaust side. The middle one also burned the top of the piston. The right two were from items going through the engine. 2nd in from right resulted from the retainer breaking in one of the main crank bearings and going through the cylinder. The far right was a costly mistake when in a hurry and mounting the piston backwards so the ring gets hung up in the exhaust port....
49dimes
Damn I'm hungry
The owner of the DLE 60 to the best of my knowledge has not pulled the engine but I suspect if he did he would see some damage on one or both pistons. I know for a fact he had let another fly the engine extremely hard (high energy 3D) when it was brand new and he had no means of baffling. He had the engine in a EF91 (heavier plane higher load for engine) and reduced prop size from a 24x8 to 22x10 to get better acceleration. Maybe the common issue between the 170 and 60 is over revving when the engine unloads thusly going lean for a bit. From personal experience I learned about over revving
from unloading the prop and causing a temporary lean out damaging piston / cylinder. My engine told me It was not happy by simply locking up hard in flight and causing the spinner cone bolt to back all the way out. I watched the expensive aluminum cone torpedo to asphalt and my plane dead stick to dirt. I also had good baffling/cooling and no signs of heat stress on the cylinder. The scoring on my piston (3w85b2) was like the two on the left in @Alky6 photos.
from unloading the prop and causing a temporary lean out damaging piston / cylinder. My engine told me It was not happy by simply locking up hard in flight and causing the spinner cone bolt to back all the way out. I watched the expensive aluminum cone torpedo to asphalt and my plane dead stick to dirt. I also had good baffling/cooling and no signs of heat stress on the cylinder. The scoring on my piston (3w85b2) was like the two on the left in @Alky6 photos.
Bill Vargas
50cc
Judging the discoloration of the mating surface between the crankcase and that cylinder, the gasket was moving around and the cylinder bolts were not tight or they loosened up just enough for the gasket to lose its seal,,, the rest is history.
New top end and several cans of carb cleaner to get all that very fine metal bits out of the bearings and you should be fine.
New top end and several cans of carb cleaner to get all that very fine metal bits out of the bearings and you should be fine.
Bill Vargas
50cc
To help keep the Cylinder Base Gasket in place, use an automatic Spring Punch to make little dimples on the gasket mating surfaces. As the gasket is compressed during assembly, the gasket and sealant will squish into these dimples to help secure it into place. McMasters is a good source for the Automatic Spring Punch.
