TEAM TWISTED NEVADA

hey everyone im having alot of trouble with my mac .67.. the motor is new, she was broke in with 6 tanks. im trying to tune her up but she just wont tune right. when the needle is at like 2 1/2 out she just pops like she is way to rich. when i start her up fuel starts poping out of the carb. i lean the needle and she kinda stops, but the needle is at almost 1 turn out. thats not good is it? im runinng 40% fuel and mc9 glow plugs. can someone help me on this. this is my 1st mac and alot of guyz said their hard to tune.

f16man

First measure the carb throat the one you want should be .510 dia. these are dump tube style carbs and if the dump tube is loose it will be getting fuel around the tube [not good] we also run a inflight mixture control from bvm but you will need a third channel, let me know what you got for carb size. Just so you know the other carb is about .550 dia.and have a problem with fuel draw, make sure you are using large fuel line, we run 65% nitro and .012 to .015 squish from piston to head, Ill explain that later.....

advanced builder

You also need to add some http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXS627
Any .67 that runs more than 25% Nitro needs OIL

Ron Olson

My Feedback: (1)

Which needle are you using? Andy usually sold the Kalistratov coarse needle with anything .45 and over. It has to be plumbed up correctly also, the line from the tank has to enter the bottom fitting, not the side. If that is the one then it should be much richer than 3-1/2 turns out.

TEAM TWISTED NEVADA

k so when i get to work tonight ill see what the carb is at. ill have to get some oil too. the needle i have is a third channel one, im not to sure about if its the Kalistratov coarse one. i just looked at it and the fuel line goes in the side and comes out the bottom to the motor. ill try and get some pics and put them up give me a couple of minutes. is my 40% to less do i need to go higher on the nitro?

Ron Olson

My Feedback: (1)

The 40% should be fine. The larger the engine the less nitro needed.

TEAM TWISTED NEVADA

should i go down in the nitro? heres a pic of the carb and the 3rd channel needle. i found a old post on i think is the same problem, could my rotor disc be out 180*? hope the pic works

TEAM TWISTED NEVADA

should i try and turn the fuel lines around and put the tank on the bottom and the out line on the side to the motor, and try to start her on the porch? ill put the needle at 3 1/2 turns out and see what happens? ill try and get some video so you guyz can see. let me know..

mike walker

Thats the way my k&b acted out of the box and I broke it in that way then found out the rotor was out 180

Sean Bowf

I don't think it is the root of your problem, but I think the MC9 is a bit cold for 40% nitro.

Sean

TEAM TWISTED NEVADA

should i go back with the mc 59?

toyotatruckin

sean Mc9 was my most used plug and almost always ran 40%

Ron Olson

My Feedback: (1)

I was going to say the same thing as Mike. I've run MC-9's in a lot of engines with different percentages of nitro and it seems to me to not be a sensitive plug like others brands I've tried but that's me.
Yes it is possible for the disc to be 180 off. Some engines are a real bear with disc rotors to put the backplate on correctly. It could be just slightly off and have the pin sticking through the intake opening.

TEAM TWISTED NEVADA

should i try and reverse the fuel lines first? if that dont work then i guess take out the motor and pull the backplate to check that disc. is their any other way?

f16man

This engine has a drum not a disc , notice the way the carb is mounted at an angle, the drum is used for a larger fuel /air charge due to this engines huge tranfer ports , kinda like how a tunnel ram intake manifold works on a big block automotive engine.On my mac there is only one way to put the drum timeing but go ahead and pull the rear cover off and lets take a look. Should have an o ring and not a gasket and keep the engine rear end pointed up when you disassemble the rearcover as there are needle bearings in the bottom end of the rod that could fall out, I work over a pan to catch small parts just in case..... You should probably pull the back plate so you get a better idea of how that engine is designed, what fuel are you running? MAC 67's do like nitro so 40% should be no problem at all and yes flip your fuel lines.....

f16man

If you want to just check your drum timeing you can look thru the ex. port and when turning the engine over in the normal direction when the piston comes down just past the ex port opening look thru the carb and the drum should be opening at that point.

TEAM TWISTED NEVADA

k well i think i looked at it right. i turnd and put the piston on the bottom and i looked threw the carb and the drum is not open. so i guess this means its time to take apart. should i not flip the fuel lines and just start working. flip the lines when im done.

rcguy1411

flip the lines firsr if it runs then you have fixed the problem KISS (keep it simple stupid) this will only take a few minutes to do before you pull the engine tear it apart rebuild the engine re install test and maby still end up scratching your head

Ron Olson

My Feedback: (1)

It could be 180 off then but swap those lines around anyway. The weird thing is that you'd think that they should be as you have them but for some reason they work better the other way around.

TEAM TWISTED NEVADA

ok ill let you guyz know, ill flip the fuel lines and give it a try. i would realy like for that to work, lol thats what im hopeing for anyway. i dont want to take apart this motor if i dont have to. ill get video of what it is doing and post it up so you can see for your selfs.

Sean Bowf

The OS #8 (hot plug) used to be my most run plug, and I run 40%...

Everyone ran the MC9 (a cold plug) in everything because it was cheap and durable. I don't think it is cheap any more, and I hear a lot of folks getting bad ones out of the wrapper. I did tests with a bunch of plugs on 40%. MC9, OS A5, OS#8, OD 89, etc, etc. The fastest out of all the plugs was the OS #8. It is not "durable" at this percentage, but it was the fastest (best for speed) plug out of the group I tested.

As I said though, I doubt it is causing his problem.

Sean

f16man

You are one of the few to get your hands on a MAC 67 these days as they are arguably the fastest in thier class, everone that owns a nitro powered boat should learn all they can about it and know how to break it down and put it back together, otherwise you are missing half of the hobby , It is not rocket science at all and there is a few things to do to it to make it more freindly for future starting and running......

TEAM TWISTED NEVADA

sweet i love that i have a mac, but its def not like any of my other nitro motors. its alittle more complicated i see. my K&B 67 isnt even this hard, thats the biggest motor i have. the rest are all .45 and smaller. thank you guyz for all the help so far. give me alittle bit and ill get that video in here.

TEAM TWISTED NEVADA

[&:]sorry guyz i would of had that video up, but the darn belt broke on me. im runing to hobby store to get another one. be back soon as i can so i can get this video in here for you guyz.

TEAM TWISTED NEVADA

k well my batts went dead in the darn camra. well i flipped the fuel lines and put the needle at 3 turns out. she still does the same thing, poping and spitting all over her self. when i was done i pulled th glow plug and the spring inside was messd up, does that mean anything? now does this mean that i need to take apart the motor and flip the drum? please let me know.