SCALE QUITS PULLING HALFWAY DOWN THE STRAIGHT

[SayMikey]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

 

[Duck899]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

Sounds like its lean or too much prop....unloads in the corners but sags in the straights?....

 

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Mikey,

are you running the stock carb?? If so give the knob a squeeze with some dykes or a pair of pliers. I found what happens to them is the o-ring isn't thick enough to keep it from vibrating out of it's original setting which will actually cause the knob to spin itself in and out. That will give you a major headache!

It kept happening to me at the Manteca races so my friend Roy and I started the motor and hooked up the water jug hose to the engine and started up the engine.

We discovered two important things. 1st, the needle was spinning itself in and leaning out the motor. Secondly no matter how hard and how tight we made the pipes bracket and coupler, the pipe kept sliding back about a 1/2 inch. We'd kill the motor and it would slide right back into the place that we started it out at. We never would have known the pipe was moving had we've not tested it this way. Weird!

 

[Mark Bullard]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

Mike,

I think that you have your stinger to restricted. Are the pipes stock? Have you drilled them out? What is the Dia. of the stinger. Do you run the exhaust out the transom by way of tubing? And if so what size? Have you run this setup before and if you have what has changed. Maybe a new motor?

Mark

 

[Don Ferrette]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

Mike- you might try restricting the water a touch & richening it up. I'm thinking head temp might be too cold & by the time you get it lean enough to make some heat & clear out you're too lean on the top end. A .450" stinger bushing might also be worth trying as you may need a tick more fuel pressure at upper rpm band. Back when I was running the 67 greenheads they seemed real happy running pipes with a stinger diameter around .450-.455" in the scale hulls. B)

 

[SayMikey]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

Mike,

I think that you have your stinger to restricted. Are the pipes stock? Have you drilled them out? What is the Dia. of the stinger. Do you run the exhaust out the transom by way of tubing? And if so what size? Have you run this setup before and if you have what has changed. Maybe a new motor?

Mark

I have a os needle its been rich and lean,head at .010 motor is god put my backup in it. transon exhaust 3/4 inch no restriction. I have a black ab pipe used the .410 and the .450 stinger no difference. I will try it with out the cowl this weekend. As far as prop load ive went all the way down to ax452 and up to a x460 motor feel warm pipe is near 400 degrees

 

[Don Ferrette]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

Mike,

I think that you have your stinger to restricted. Are the pipes stock? Have you drilled them out? What is the Dia. of the stinger. Do you run the exhaust out the transom by way of tubing? And if so what size? Have you run this setup before and if you have what has changed. Maybe a new motor?

Mark

I have a os needle its been rich and lean,head at .010 motor is god put my backup in it. transon exhaust 3/4 inch no restriction. I have a black ab pipe used the .410 and the .450 stinger no difference. I will try it with out the cowl this weekend. As far as prop load ive went all the way down to ax452 and up to a x460 motor feel warm pipe is near 400 degrees

.010" on head clearance??? Wow, I always ran .013"-.015" on the 67 greens with 60%. h34r:

 

[Mark Anderson]

Does it slow down or just go over the hill and stop pulling. If it stops pulling I would think it iis under propped. The boat ride may also suffer when it stops pulling. You need more load or more rpm.

 

[Mark Bullard]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

Mike,

I think that you have your stinger to restricted. Are the pipes stock? Have you drilled them out? What is the Dia. of the stinger. Do you run the exhaust out the transom by way of tubing? And if so what size? Have you run this setup before and if you have what has changed. Maybe a new motor?

Mark

I have a os needle its been rich and lean,head at .010 motor is god put my backup in it. transon exhaust 3/4 inch no restriction. I have a black ab pipe used the .410 and the .450 stinger no difference. I will try it with out the cowl this weekend. As far as prop load ive went all the way down to ax452 and up to a x460 motor feel warm pipe is near 400 degrees

Mike,

What is the inside stinger dia. I had to drill the inside stinger out ot keep the pipe from building heat. What I found was the pipe was very restrictive on my motors. Now I am not saying that this is what they do on all motors just mine. I move so much fuel thru a motor that I think that the fuel was burning a little in the pipe. When you said that the pipe temp was about 400 degrees it sound a lot like the problem that I had. I did get the pipe to work but it just would not turn up the RPM's so I went to another pipe. I drilled the stinger out to about 0.450.

Mark

 

[SayMikey]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

Mike,

I think that you have your stinger to restricted. Are the pipes stock? Have you drilled them out? What is the Dia. of the stinger. Do you run the exhaust out the transom by way of tubing? And if so what size? Have you run this setup before and if you have what has changed. Maybe a new motor?

Mark

I have a os needle its been rich and lean,head at .010 motor is god put my backup in it. transon exhaust 3/4 inch no restriction. I have a black ab pipe used the .410 and the .450 stinger no difference. I will try it with out the cowl this weekend. As far as prop load ive went all the way down to ax452 and up to a x460 motor feel warm pipe is near 400 degrees

WHEN I COME OFF THE CORNER JUST BEFORE MID TRACK THE MOTORFLATTENS OUT RPM SOUNDS DOWN MY REAL CONCERN IS THE PIPE HEAT AND IF I SOLVE THAT MAYBE I CAN GET THE MOTOR TO PULL FARTHER DOWN THE STRAIGHT.....MARK ANDERSON DO YOU THINK MORE PITCH IS IN ORDER I TRIED A X457X3 4.0 PITCH TOUNGUE CUT OFF....ANOTHER THING WHEN IT SLOWS DOWN IF I LET OUT IT WONT GET BACK UP.

Mike,

What is the inside stinger dia. I had to drill the inside stinger out ot keep the pipe from building heat. What I found was the pipe was very restrictive on my motors. Now I am not saying that this is what they do on all motors just mine. I move so much fuel thru a motor that I think that the fuel was burning a little in the pipe. When you said that the pipe temp was about 400 degrees it sound a lot like the problem that I had. I did get the pipe to work but it just would not turn up the RPM's so I went to another pipe. I drilled the stinger out to about 0.450.

Mark

 

[Duck899]

What does the plug look like after a run? Is there anything left of the element? What does the top of the piston look like?

 

[Mark Bullard]

mY CMB 67 AB BLACK PIPE 82U55 RUNS LIKE A BULLET ROUND THE CORNER BUT SLOWS HALFWAY DOWN THE STRAIGHT. TRIED PIPE AT 11 1/4 12 TRIED A AB PAROBOLIC SAME RESULTS..LARGE FUEL LINES X457 HAD A 1457X3 SAME RESULTS MOTOR COMES IN WARM BUT THE PIPE IS WAY HOT?/"?/???

Mike,

I think that you have your stinger to restricted. Are the pipes stock? Have you drilled them out? What is the Dia. of the stinger. Do you run the exhaust out the transom by way of tubing? And if so what size? Have you run this setup before and if you have what has changed. Maybe a new motor?

Mark

I have a os needle its been rich and lean,head at .010 motor is god put my backup in it. transon exhaust 3/4 inch no restriction. I have a black ab pipe used the .410 and the .450 stinger no difference. I will try it with out the cowl this weekend. As far as prop load ive went all the way down to ax452 and up to a x460 motor feel warm pipe is near 400 degrees

WHEN I COME OFF THE CORNER JUST BEFORE MID TRACK THE MOTORFLATTENS OUT RPM SOUNDS DOWN MY REAL CONCERN IS THE PIPE HEAT AND IF I SOLVE THAT MAYBE I CAN GET THE MOTOR TO PULL FARTHER DOWN THE STRAIGHT.....MARK ANDERSON DO YOU THINK MORE PITCH IS IN ORDER I TRIED A X457X3 4.0 PITCH TOUNGUE CUT OFF....ANOTHER THING WHEN IT SLOWS DOWN IF I LET OUT IT WONT GET BACK UP.

Mike,

What is the inside stinger dia. I had to drill the inside stinger out ot keep the pipe from building heat. What I found was the pipe was very restrictive on my motors. Now I am not saying that this is what they do on all motors just mine. I move so much fuel thru a motor that I think that the fuel was burning a little in the pipe. When you said that the pipe temp was about 400 degrees it sound a lot like the problem that I had. I did get the pipe to work but it just would not turn up the RPM's so I went to another pipe. I drilled the stinger out to about 0.450.

Mark

Mike,

I think that you are have the same problem that I had with the pipes. When I got the heating problems solved and tried to get the motors to turn up they just would not do it. The pipes held them back. Now I bet the pipes would work just fine on a MAC but the CMB do not have the same timing numbers that the MAC has. I think that the pipe does not have enough volume. I think that I would try a Mac 11cc or 13cc muffled pipe. And drill the internal stinger the same as the external stinger. And this should be about 0.43 to 0.45.

Mark

 

[Don Ferrette]

The black AB67 pipe has a stock stinger i.d. of .470" & the internal stinger is bigger than that. More often than not they need to be reduced to up the fuel pressure up top. However, I'm now wondering if there is not enough load on the motor....... :blink:

 

[Joe Warren]

Raise the head to .014-.016 & Increase the pipe volume W/ Different pipe. Mac 11-13 or a 84 parobolic Drill out to 23/64 All the way thru........Length is Good. Mike,If you have a 13cc or can get one Just put it on the boat @ 12 for a few laps around the pond & find the range on the needle window to see if you can get a handle on the heat. Then you can sneak back up on the 50,000rpm set up.