Type A Type B

INTP_ty

Active Member
Local time
7:33 AM
Joined
Sep 25, 2017
Messages
491
Does anyone know if the bore is the same for the EBay Chinese “80cc” A & B engines? I think I might have damaged my piston...

My rod says FM80. I damaged the jug though, so I’ve been using a spare jug I had laying around. But that one came off a motor with a ZL rod.

I ended up using my damaged jug though (small corner piece broke off -who cares lol) but now I’m getting this ringing noise from the head.

Sounds like an empty spray paint can.



Theory: ? Bore is smaller on the ZL rod & I ended up shimming my piston down???


Idk what’s going on but it does not sound right.



Are all the wrist pins the same?
 
Does anyone know if the bore is the same for the EBay Chinese “80cc” A & B engines? I think I might have damaged my piston...

My rod says FM80. I damaged the jug though, so I’ve been using a spare jug I had laying around. But that one came off a motor with a ZL rod.

I ended up using my damaged jug though (small corner piece broke off -who cares lol) but now I’m getting this ringing noise from the head.

Sounds like an empty spray paint can.



Theory: ? Bore is smaller on the ZL rod & I ended up shimming my piston down???


Idk what’s going on but it does not sound right.



Are all the wrist pins the same?
The bore is the same on both, one sit's higher due to wrist pin location.sounding like a spray can cant be good best to open it up and see what's going on.
 
The bore is the same on both, one sit's higher due to wrist pin location.sounding like a spray can cant be good best to open it up and see what's going on.

I just did. No scoring or anything. Pings like a fresh can of Primer & boy does she ring at WOT

Oh yea, the bottom of the head -one of the corners is chipped off. Idk if that’s what’s causing the noise? I think it’s on the right side. Like those ports on either side. Yea one has a chipped corner -missing chunk
 
Aside from the wrist pin, are the barrel pieces (the thing with rollers that sits in the rod) universal? Cuz i probably mixed those up lol
 
Aside from the wrist pin, are the barrel pieces (the thing with rollers that sits in the rod) universal? Cuz i probably mixed those up lol
Yes they are the same. you could be bouncing the piston off the head or the chiped port is catching the rings not sure but doesn't sound good sorry.
 
Measure your squish gap by squashing some 1.2mm soft (rosin cored) solder between the piston and head. You need more than 0.5mm gap (mine's minimal at 0.55mm)

(Insert a piece of solder, bent into inverted V shape so the base of V is in the spark plug hole, turn the engine over once to squash the solder, pull it out through the spark plug hole and measure the thickness with your vernier caliper)

If you are fairly sure that the piston has sufficient clearance, then I would insert chunks of heater hose (or whatever) between every two fins on the head to damp the ringing. You can do this with the cylinder too. That should eliminate the possibility of the the sound coming from the fins, just to narrow down the possibilities.

The roller bearings for the wrist pin are standard, the same for both A and B pistons.
 
If the rings would catch, they would have snapped.

It actually hurts my ears. This is my 2nd kit btw.

Loudest around the cylinder...
 
If the rings would catch, they would have snapped.

It actually hurts my ears. This is my 2nd kit btw.

Loudest around the cylinder...
Maybe. I would eliminate the other possibilities I mentioned above, then you can see if it's necessary to remove the cylinder and check the rings for marks. :)
 
It’s apart in front of me rn

It’s an aluminum ping noise. Just put your ear close to it. It really is painful to hear
 
Back
Top