Finally got the Mack Mag built!

[FurryOnTheInside]

Will I have to break the engine in again? And I can still use the same piston and rings right in the new cylinder right?

When you do the break in it's the cylinder that you're wearing in to seal well against the cast iron rings, so yes it will need another break in (1 gallon at 24:1 synthetic, and high load not low speed!). Yes use the same piston and rings.

I don’t think it would have anything to do with the carb issues, but maybe... I just noticed my chain has been slightly rubbing the back wheel?

I can't see how that could be related to the carb issues.

 

[Kpi890]

When you do the break in it's the cylinder that you're wearing in to seal well against the cast iron rings, so yes it will need another break in (1 gallon at 24:1 synthetic, and high load not low speed!). Yes use the same piston and rings.


I can't see how that could be related to the carb issues.

And I guess I never mentioned it but I’m running 32:1 right now fuel mixed with opti-2 oil. Would this be causing the carb issues? Should I be running a different mix or type of oil?

 

[FurryOnTheInside]

And I guess I never mentioned it but I’m running 32:1 right now fuel mixed with opti-2 oil. Would this be causing the carb issues? Should I be running a different mix or type of oil?

No, but sometimes people believe the instructions that say to use 10:1 or 16:1 in their fuel mix and then the air filter will become gummed up much more quickly when the carb coughs fuel back out into it.

32:1 has slightly more gasoline in it than 24:1 so that should theoretically make it run a little richer when you switch from the break in ratio to the running ratio. Whether it is noticeable in reality, I'm not so sure.

32:1 with decent synthetic is a perfectly decent running fuel mix ratio, after breaking in with 1 gallon of 24:1, climbing and accelerating. (If you baby it, it'll just take 2 gallons to wear in.)

 

[Kpi890]

No, but sometimes people believe the instructions that say to use 10:1 or 16:1 in their fuel mix and then the air filter will become gummed up much more quickly when the carb coughs fuel back out into it.

32:1 has slightly more gasoline in it than 24:1 so that should theoretically make it run a little richer when you switch from the break in ratio to the running ratio. Whether it is noticeable in reality, I'm not so sure.

32:1 with decent synthetic is a perfectly decent running fuel mix ratio, after breaking in with 1 gallon of 24:1, climbing and accelerating. (If you baby it, it'll just take 2 gallons to wear in.)

Okay thanks! And you don’t think a eeed valve would help at all with the gas out the carb situation? Even if I don’t modify the piston or ports? Or works it hinder my current setup?

 

[FurryOnTheInside]

Okay thanks! And you don’t think a eeed valve would help at all with the gas out the carb situation? Even if I don’t modify the piston or ports? Or works it hinder my current setup?

If you don't use a windowed piston (or large notch and lowering of the port for the same effect) to increase the duration then the reed valve will be a restriction hindering the flow of the intake and make the bike slower (even though it will reduce noise and will virtually entirely prevent the reversion).
The piston ported engine breathes in short gasps, the reed valve engine takes longer slower breaths. What you're proposing would result in short slow breaths so the engine couldn't take in as much volume as it really wants to.

 

[Kpi890]

As of right now I think I’ve got it as fast as it’s going to be with the low end power I really like. It tops out at 33 but has a whole bunch of low end power probably due to the extended intake and running the bike without the stock exhaust cap. I am running a 44 tooth sprocket and thought it would go faster than 33 but I guess not. I ordered a 36 tooth sprocket I am going to try on there and see what top speeds that will get me along with the MZ expansion chamber. I wouldn’t mind sacrificing a little of the low end to get the bike up to 40mph so that I would at least keep up around town on 35mph I ride between neighborhoods and such. This is all running the stock NT carb jetted to 68, still seems like it’s four stroking at WOT both at a 67 and 68 jet but I’m nervous to jet any leaner for now. What should I expect different once I put the MZ 65 pipe on there?

 

[FurryOnTheInside]

As of right now I think I’ve got it as fast as it’s going to be with the low end power I really like. It tops out at 33 but has a whole bunch of low end power probably due to the extended intake and running the bike without the stock exhaust cap. I am running a 44 tooth sprocket and thought it would go faster than 33 but I guess not. I ordered a 36 tooth sprocket I am going to try on there and see what top speeds that will get me along with the MZ expansion chamber. I wouldn’t mind sacrificing a little of the low end to get the bike up to 40mph so that I would at least keep up around town on 35mph I ride between neighborhoods and such. This is all running the stock NT carb jetted to 68, still seems like it’s four stroking at WOT both at a 67 and 68 jet but I’m nervous to jet any leaner for now. What should I expect different once I put the MZ 65 pipe on there?

You should really be using the muffler cap. You can easily make some changes to the internals of the muffler so that the cap doesn't restrict it too much. Exactly what and how depends on which of the at least two types of muffler you have. If you have one tube inside with a bunch of holes in it and one threaded hole at the end for the cap bolt, you can make a big hole next to that thread hole. Also with both types of muffler you can shorten the internal stinger (the little pipe in the cap), just saw a bit off the inside and try it out.
It is difficult to set up a carb when you have an important part of the muffler missing lol.

Idk about the MZ65 pipe. I know that you can get at least 8000rpm and 37.27mph out of the stock pipe (with the cap on) and stock jet in the NTTC carb. An offset magnet key will help smoothness at high rpm probably make it faster too, at the expense of bottom end.

 

[Kpi890]

Got the two intake studs JB welded into place now so shouldn’t have any more issues with the one side stripped. It didn’t have any air leaks but I knew in the future I will eventually be taking the intake manifold off so now it’s good to go. Went ahead and JB’d both of them in there for peace of mind.

And here’s a few pictures of my plug running WOT, pulling clutch and killing engine at the same time. It’s still four stroking quite a bit and that’s a 67 jet in the NT carb right now. I’m also 4 stroking quite a bit at the low end as well and sometimes the throttle response is lagging up if I give it some throttle and let off and go to give it throttle again. Could the cylinder be flooded or something? Doesn’t seem like it would be after riding it so much, but I’m kinda stumped and not super eager to jet leaner but that sure seems like that’s what it wants. I’m running a B8HS plug 32:1 opti-2 mix?

 

[Kpi890]

Man the frustration level is at 100 now. The carb is running rich all the time and I cannot figure out what is going on. It’s having issues idling and it’s 4 stroking at all rpm ranges. The c clip is at the highest setting and the jet is a 67. Would it have anything to do with the air filter being on the side of the bike and as I ride the air passing by it itsnt allowing enough air in? I’m lost here. The throttle response is garbage it takes a second or two to get past the 4 stroking and then it’ll finally rev up.

 

[FurryOnTheInside]

You should really be using the muffler cap. You can easily make some changes to the internals of the muffler so that the cap doesn't restrict it too much. Exactly what and how depends on which of the at least two types of muffler you have. If you have one tube inside with a bunch of holes in it and one threaded hole at the end for the cap bolt, you can make a big hole next to that thread hole. Also with both types of muffler you can shorten the internal stinger (the little pipe in the cap), just saw a bit off the inside and try it out.
It is difficult to set up a carb when you have an important part of the muffler missing lol.

Idk about the MZ65 pipe. I know that you can get at least 8000rpm and 37.27mph out of the stock pipe (with the cap on) and stock jet in the NTTC carb. An offset magnet key will help smoothness at high rpm probably make it faster too, at the expense of bottom end.