Ported Avenger 85

Gordy

Gordy

Active Member
I recently ported my first engine. It's an Avenger 85. I swapped the piston for the CDH110 piston using the top 2 rings only as the gap in the bottom was in the middle of the open portion of the transfers for a few degrees of the rotation. It came out really nice and has great torque and runs really good. I haven't opened her up yet but 40mph is effortless on a 36T sprocket. I just swapped on a PZ19 from the BoFeng and it runs incredibly well. I also modified a genuine MZ65. Next is a CNC head and a custom clutch.
 

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Got the carb tuned properly last night. Unfortunately the air filter that came with the carb doesn't fit so I have to order a more low profile filter. However the bike is ready to rip as soon as weather gets better.
 
LandSpeedRecord said:
Looks awesome!
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Thanks! It is pretty awesome. I put a new aor filter on and I've been doing a few that I here and there. I decided to rework the front motor mount but I have to wait for Monday for that. The new one is steel, but I have to wait until Monday to be able to cut my pieces out on a cnc plasma table. The new hoop is a split shaft collar. Kinda bummed because it's been really nice and I've had the bike torn apart to redo some things.
 
Gordy said:
Thanks! It is pretty awesome. I put a new aor filter on and I've been doing a few that I here and there. I decided to rework the front motor mount but I have to wait for Monday for that. The new one is steel, but I have to wait until Monday to be able to cut my pieces out on a cnc plasma table. The new hoop is a split shaft collar. Kinda bummed because it's been really nice and I've had the bike torn apart to redo some things.
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It will come back together soon. I have been wanting to do a build with one of those. Or maybe the Iron Maiden with the Minerelli type cylinder.
 
LandSpeedRecord said:
It will come back together soon. I have been wanting to do a build with one of those. Or maybe the Iron Maiden with the Minerelli type cylinder.
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The avenger is a fun one to build. I won't run a stock piston, it has the ring gap right in the center of the intake port. That's just asking for high rpm ring snag. Mine has a CDH110 piston and is gonna get a LD100 cnc head. It should be close to done then until I pull the case apart. And I have a clutch I'm building for it but I'm waiting on springs.

I'm porting a jug for another guy as soon as the jug comes in Wednesday and I'll be using an MS380 piston. The 380 piston has ring gaps in the right spots.
 
Gordy said:
The avenger is a fun one to build. I won't run a stock piston, it has the ring gap right in the center of the intake port. That's just asking for high rpm ring snag. Mine has a CDH110 piston and is gonna get a LD100 cnc head. It should be close to done then until I pull the case apart. And I have a clutch I'm building for it but I'm waiting on springs.

I'm porting a jug for another guy as soon as the jug comes in Wednesday and I'll be using an MS380 piston. The 380 piston has ring gaps in the right spots.
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WOW thanks for the heads up on the Avenger 85! Absolutely wrong to have a ring gap passing over a port. I would feel like I may have a catastrophic failure every time I ride if I knew the ring gap was passing over a port.
 
LandSpeedRecord said:
WOW thanks for the heads up on the Avenger 85! Absolutely wrong to have a ring gap passing over a port. I would feel like I may have a catastrophic failure every time I ride if I knew the ring gap was passing over a port.
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Yeah, that's why I changed the piston in mine. While I had it apart I figured I'd port it. I can go more on the exhaust if I want, and I might if I pull it apart again.

If you go with the CDH110 piston use the top 2 rings only and drop the jug to have no base gasket and just use Permetex Motoseal for a base. Then optimize squish. Should be pretty decent there, but if you want to port it it'll be way more powerful.
 
Makes sense. Normally I would give that a try. But I am in a situation I have never been in for a motorized bike. I am living a little over 60 miles from the nearest town. I would normally not even consider that distance being 120 round trip. But it could be an interesting challenge. Run the larger capacity tank frame and a seatpost tank should give me close to the range. I could also carry a few ounces of oil measured out to mix a half gallon part way back. Anyway I'm just playing with ideas on what would do that distance the best. Probably a Harbor Freight 4 stroke actually but I have a love for the little two strokes.
 
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