Brakes and rotor head travel (AC).

[Resasi]

Regarding forward travel on the rotor head, when my son and I were building our Hornet, I had noted that the mast was taller than the Benson I had been flying and it would be difficult to reach the rotor.

The rotor brake we had fabricated from a bicycle brake was not very robust, and so I did put in a negative 1degree with full forward stick to allow me to face into wind and, if needed, use that to assist in slowing/stopping the rotor by allowing a small amount of air into the top of the rotor. I was still very new and ignorant at the time, we never managed to get enough time on that machine to find out the negative aspect of that particular choice.

 

[Gyro jeff]

I pumped at least a pint of fluid through the brake system chasing the bubbles out, but still have zero pad movement from the button like pedal.
I think I will lose the pedal and install one of the Ninja master cylinders (has reservoir) with either a pedal, or maybe a lever next to the throttle...
I seriously considered losing the brakes, but the seat is high enough for "Fred Flintstone" braking to be not too effective....

I plan on move brake to left side with lever. did not like location heel brake . And my gryo looks like money pit but in poker terms i am pot committed.

 

[Aerofoam]

This is the master cylinder, I finally bled it completely by pumping the air from the cyl. back into the oil can tube, then while holding the pedal, pumped the air out of the tube, attached and then pumped while releasing the pedal. I also took out the rear bolt, so the pedal tilted whit the bleeder up hill.



This is the brake caliper, no brand names on this stuff...



The instruments are all working after I went through the connections:

 

[Aerofoam]

I ran the engine with the Mikuni clone carbs today, runs amazingly well. After warm up I ran it at about 5k rpms. for a few minutes.
I am at 3400ft. and it was about 85F out. The heads never went above 200F and the exhaust temps were hovering around 800 to 900F.

The vents and over flow were slobbering all over, so I had to keep shutting off the petcock to artificially lower the fuel level.
I am wondering if my fuel pump needs a regulator because the Bings were over flowing too (They had saturated floats).
Has anyone heard of a Rotax 503 having over pressure issues with the fuel pump?

 

[Abid]

This is the master cylinder, I finally bled it completely by pumping the air from the cyl. back into the oil can tube, then while holding the pedal, pumped the air out of the tube, attached and then pumped while releasing the pedal. I also took out the rear bolt, so the pedal tilted whit the bleeder up hill.

View attachment 1161131

This is the brake caliper, no brand names on this stuff...

View attachment 1161132

The instruments are all working after I went through the connections:

View attachment 1161133

That is not Matco brake system. Looks like old Hagar system. Good luck with it.

 

[Aerofoam]

That is not Matco brake system. Looks like old Hagar system. Good luck with it.

Thanks, it's working now. Actually the bleeding would be easy with 2 people, but it's a juggling act by myself....
I have a couple motorcycle master cylinders that would be better, but then I would need a hinged pedal, the shaft is not supported like this one.
A regular bicycle hand brake lever would work well and could be locked....

 

[Doug Riley]

IIR, EGT should max at 1100. This temp is typically reached, not at full throttle, but at cruise or cruise-climb RPM, especially when throttling back from full throttle.

The EGT readout is deeply affected by where the EGT probe is placed within the exhaust system. It's wise to cross-check the EGT by reading the color of the plugs. Chocolate-brown is ideal. Black is too cold/rich. Gray or white mean too lean/hot.

Given your density altitude and simultaneous low CHT and low EGT, it's a fair bet that you're running rich. See if the plugs bear that out. Be certain the timing is dialed in before messing with mixture. To check mixture via plug color, run the engine at the RPM you want to check, then shut it down immediately WITHOUT throttling down to idle.

Sorry, can't help with a Rotax pulse fuel pump generating excess fuel pressure.

 

[MikeBoyette]

IIR, EGT should max at 1100. This temp is typically reached, not at full throttle, but at cruise or cruise-climb RPM, especially when throttling back from full throttle.

The EGT readout is deeply affected by where the EGT probe is placed within the exhaust system. It's wise to cross-check the EGT by reading the color of the plugs. Chocolate-brown is ideal. Black is too cold/rich. Gray or white mean too lean/hot.

Given your density altitude and simultaneous low CHT and low EGT, it's a fair bet that you're running rich. See if the plugs bear that out. Be certain the timing is dialed in before messing with mixture. To check mixture via plug color, run the engine at the RPM you want to check, then shut it down immediately WITHOUT throttling down to idle.

Sorry, can't help with a Rotax pulse fuel pump generating excess fuel pressure.

If I remember the EGT location is supposed to be 100mm from the face of the piston.

 

[Aerofoam]

If I remember the EGT location is supposed to be 100mm from the face of the piston.

The EGT sensors are on the stock Rotax exhaust manifold and look to be about 3" from where the edge of the piston would be, I am assuming they knew where to put them!

I have adjusted the float 2 more times and have moved the bracket about 1/8" for increased total lift and the carbs are still over flowing.
I can control that by simply opening and closing the petcock to not allow them to get to full and it runs incredibly well, I am shocked at how much
thrust this little engine puts out, but as soon as I leave the petcock open too long, it overflows the carbs, bogs, and will choke itself off....
Could the reeds be causing a back resonance that is preventing the needle from fully closing?
I am having a hard time believing 2 brand new carbs are both faulty with the same problem as the Bings with heavy floats.....

 

[Vance]

I have adjusted the float 2 more times and have moved the bracket about 1/8" for increased total lift and the carbs are still over flowing.
I can control that by simply opening and closing the petcock to not allow them to get to full and it runs incredibly well, I am shocked at how much
thrust this little engine puts out, but as soon as I leave the petcock open too long, it overflows the carbs, bogs, and will choke itself off....
Could the reeds be causing a back resonance that is preventing the needle from fully closing?
I am having a hard time believing 2 brand new carbs are both faulty with the same problem as the Bings with heavy floats.....

If I was working on the challenge as you describe it I would replace the floats in the Bing carburetors if they were out of spec and replace the float needles.

If the problem persisted I would feed the carburetor by gravity taking the fuel pump out of the system to see if that is the source of the problem.

My experience with two stroke engines is that the fuel/air ratio is important and starting from scratch with a low quality carburetor not intended for the particular engine I am dealing with opens a whole range of challenges and a world of pain.

 

[Sv.grainne]

Have you weighed the floats?

 

[Aerofoam]

Have you weighed the floats?

I already weighed the bing floats and they are a bit heavy, I already dislike bing carbs from similar issues on Beamers and I don't want to spend $200 every 2 years for exorbitant crappy floats that only seem to last 1 to 2 years.
I replaced both carbs with new mikunis for the price of floats for one carb, but the new carbs are overflowing too which leads me to believe
it either:
A. Is just not adjusted high enough.
B. It's not the carbs and the pump is somehow over pressuring the carbs...

 

[Aerofoam]

If I was working on the challenge as you describe it I would replace the floats in the Bing carburetors if they were out of spec and replace the float needles.

If the problem persisted I would feed the carburetor by gravity taking the fuel pump out of the system to see if that is the source of the problem.

My experience with two stroke engines is that the fuel/air ratio is important and starting from scratch with a low quality carburetor not intended for the particular engine I am dealing with opens a whole range of challenges and a world of pain.

So, I did explain earlier that I was able to control the overflow by cycling the fuel petcock and the engine runs great.
it may be a bit rich because the EGTs were only around 950 after 4 minutes at 5k rpms, but I can't think about jetting until I stop
the gushing.....
This is completely a carb bowl over fill problem.
I would think if the pump was outputting too much, or if there was a feedback loop in the reed/pulse timing, someone else would have experienced this...
Maybe a call to a Rotax specialist is in order.....

 

[Sv.grainne]

I already weighed the bing floats and they are a bit heavy, I already dislike bing carbs from similar issues on Beamers and I don't want to spend $200 every 2 years for exorbitant crappy floats that only seem to last 1 to 2 years.
I replaced both carbs with new mikunis for the price of floats for one carb, but the new carbs are overflowing too which leads me to believe
it either:
A. Is just not adjusted high enough.
B. It's not the carbs and the pump is somehow over pressuring the

Sounds like they are adjusted to high, lower the float level.

 

[Abid]

I already weighed the bing floats and they are a bit heavy, I already dislike bing carbs from similar issues on Beamers and I don't want to spend $200 every 2 years for exorbitant crappy floats that only seem to last 1 to 2 years.
I replaced both carbs with new mikunis for the price of floats for one carb, but the new carbs are overflowing too which leads me to believe
it either:
A. Is just not adjusted high enough.
B. It's not the carbs and the pump is somehow over pressuring the carbs...

Replace heavy floats. The new ones are good and old ones (before 2015) were also good and lasted forever.

 

[Vance]

So, I did explain earlier that I was able to control the overflow by cycling the fuel petcock and the engine runs great.
it may be a bit rich because the EGTs were only around 950 after 4 minutes at 5k rpms, but I can't think about jetting until I stop
the gushing.....
This is completely a carb bowl over fill problem.
I would think if the pump was outputting too much, or if there was a feedback loop in the reed/pulse timing, someone else would have experienced this...
Maybe a call to a Rotax specialist is in order.....

When I am trying to diagnose a problem I try the easy things first.

If my floats are not working as designed I feel it is likely a problem with the floats, needle and seats or the fuel pressure.

Because the new carburetor float bowls are overflowing in the same way the original carburetor float bowls did I would I would try a gravity feed to the carburetors so I eliminate the fuel pump as a potential problem.

The carburetors in the picture in post 24 do not appear to me to be Mikuni carburetors.

I have had little success with off brand carburetors.

 

[Aerofoam]

When I am trying to diagnose a problem I try the easy things first.

If my floats are not working as designed I feel it is likely a problem with the floats, needle and seats or the fuel pressure.

Because the new carburetor float bowls are overflowing in the same way the original carburetor float bowls did I would I would try a gravity feed to the carburetors so I eliminate the fuel pump as a potential problem.

The carburetors in the picture in post 24 do not appear to me to be Mikuni carburetors.

I have had little success with off brand carburetors.

Cycling the petcock did in fact eliminate the pump from the equation, although with gravity feed, I could have some precision in the fuel pressure control.