2005 RX1 MCX rear mount

[Radioactivenewf]

Tried contacting them but they don't make those caps anymore, also don't have any old stock. Guess finding them used would be out of the question....

 

[RED]

I fixed a mcx with a big front mount turbo in the mountain once, it ran kinda like yours. There is 2 lines hooked to the intercooler. They were backwards, tell me how/where the lines going on yours.

 

[rxrider]

RED - you're correct on this, if they are backwards the sled won't work.
I have Pictures in rxrider's turbo garage thread, somewhere in the start of the thread, back when I ran a rear Mount MCX.
Link in my signature.

 

[Helgy]

RED - you're correct on this, if they are backwards the sled won't work.
I have Pictures in rxrider's turbo garage thread, somewhere in the start of the thread, back when I ran a rear Mount MCX.
Link in my signature.

What exactly is the difference between the two? Also, my sled has been running out of gas under boost so I checked my fuel pressure and it was less than 1lb at idle. I turned the regulator in all the way and I still only had a hair over 2lb. Is this normal?

 

[mbarryracing]

One line pressurizes the float bowls thru the vent T's, the other pressurizes the backside of the slide diaphrams so they are equalized with the throat of the carb under boost and open as intended.
I don't think 1psi would be enough to adaquately push the fuel into the float bowls and keep them filled. I thought ideally idle should be 4 psi and then maintain 1:1 rise above boost pressure. If you can't get more then 2 psi, I question wether your getting adaquate pressure rise with boost then. But then again not sure what regulator and pump you have, that maybe the setup.

 

[Helgy]

One line pressurizes the float bowls thru the vent T's, the other pressurizes the backside of the slide diaphrams so they are equalized with the throat of the carb under boost and open as intended.
I don't think 1psi would be enough to adaquately push the fuel into the float bowls and keep them filled. I thought ideally idle should be 4 psi and then maintain 1:1 rise above boost pressure. If you can't get more then 2 psi, I question wether your getting adaquate pressure rise with boost then. But then again not sure what regulator and pump you have, that maybe the setup.

I have an MCX, with the stock fuel pump and an electric one on a solenoid and pressure switch. I threaded the regulator adjustment in until it made the highest pressure I could get, just over 2lb, there was a lot of thread still sticking out and turning it more did not make any difference, so I backed it out till it was just past where it made 2lb.

 

[mbarryracing]

So the electric pump will only make 2 psi? Might be the electric fuel pump is failing and can't produce more then that.

 

[Helgy]

So the electric pump will only make 2 psi? Might be the electric fuel pump is failing and can't produce more then that.

I was referring to the stock fuel pump, at idle. I have read elsewhere that at idle 4-5lb fuel pressure is what you want, but I can only get 2lb. I hooked up a fuel pressure gauge yesterday, but its impossible to read it riding under boost, I need to find a sucker to go for a ride with me I guess....

 

[rxrider]

2005 RX-1?
There is no way you can run a turbo kit on the Stock fuel pump.
The MCX-press kits for the RX-1 came With a high output Bosch inline fuel pump.
MCX used a Malpassi 1:1 rising rate fuel pressure regulator.
My fuel pump and FPR is from 2006 and are still working as good as New.
Set fuel pressure at idle to 4-5 lbs as mbarryracing says.
I have mine set at 4.5 lbs.
I had to go Down on the mains to 127.5
Get hold of a fuel pressure meter, T it in after the FPR, check fuel pressure at idle and at full boost.
Fuel pressure at idle = 4-5
Fuel pressure at 10 lbs = 14-15
You get the drill.

 

[Helgy]

Jan - My sled is a 2003, it has the stock pump and the Bosch. I have the MCXpress installation instructions. I replaced my blown engine, with the shim installed as per MCX instructions, it worked great before it broke the crank - now it runs out of gas under boost. I can only get 2lb fuel pressure from the stock fuel pump, the regulator adjustment threads in all the way with just my fingers and I can not get more than 2lb of fuel pressure at idle. I checked all of the fittings for leaks and its tight. Hoses are in the right places. Is it possible that my stock fuel pump has failed? The nearest Yamaha dealer that works on these sleds is Prince George Yamaha, and it is an 8 hour drive one way for me.

 

[mbarryracing]

Stock pump is not a high pressure pump, it is a pulse diaphram pump like what is used on 2 strokes and is NOT capable of producing more than 1-2 lbs nor flow enough for higher HP.
Reason for an electric pump to produce EFI type pressures, it is intended to by-pass the stock pump all together. The stock pump should not feed the electric pump, because it cannot flow enough to supply it.
Set the regulator to the electric pump

 

[Helgy]

Stock pump is not a high pressure pump, it is a pulse diaphram pump like what is used on 2 strokes and is NOT capable of producing more than 1-2 lbs nor flow enough for higher HP.
Reason for an electric pump to produce EFI type pressures, it is intended to by-pass the stock pump all together. The stock pump should not feed the electric pump, because it cannot flow enough to supply it.
Set the regulator to the electric pump

So, should my electric pump be on all the time? Right now it is on a pressure regulated solenoid, and only comes on with boost. Should I get rid of the solenoid and have it on all the time? The electric pump has its own separate fuel supply.

 

[mbarryracing]

Helgy,
Technically it doesn't HAVE to be on all the time, but having it switched with boost is probably causing its own issues.
First, you aren't setting the fuel pressure regulator to accomodate the high pressure pump when the pump isn't even on... so how do you know what pressure the electric pump is giving you when it finally does turn on.
Second and more importantly, seeing that the electric pump must be plumbed into the fuel system in parallel with the stock pump for both to be able to deliver fuel (especially if there isn't a check valve between the two) then the high pressure pump is just bleeding off all it's pressure backwards thru the stock pump diaphrams and back to the fuel tank thru the pickup, short circuiting itself by taking the path of least resistance instead of going thru the regulator to the float bowls. Hence no fuel flow and running out of fuel when the fuel flow is needed most when the boost comes up. If you don't have a check valve to control flow then I really think that's your problem, if your electric pump is even turning on at all...
The Full Power Performance RX1 setups actually use just the electric pump 100% and use the mechanical fuel shut-off valve to turn off the line from the stock pump to prevent that short circuiting. This way if the electric pump fails, you can open the valve and limp home on the stock pump. It's one or the other, though... not both at same time for the reason i just explained.
You could accomplish the same thing with 2 one-way check valves so the electric pump can't short circuit backwards by over-powering thru the stock pump.

 

[Helgy]

So, should my electric pump be on all the time? Right now it is on a pressure regulated solenoid, and only comes on with boost. Should I get rid of the solenoid and have it on all the time?

Helgy,
Technically it doesn't HAVE to be on all the time, but having it switched with boost is probably causing its own issues.
First, you aren't setting the fuel pressure regulator to accomodate the high pressure pump when the pump isn't even on... so how do you know what pressure the electric pump is giving you when it finally does turn on.
Second and more importantly, seeing that the electric pump must be plumbed into the fuel system in parallel with the stock pump for both to be able to deliver fuel (especially if there isn't a check valve between the two) then the high pressure pump is just bleeding off all it's pressure backwards thru the stock pump diaphrams and back to the fuel tank thru the pickup, short circuiting itself by taking the path of least resistance instead of going thru the regulator to the float bowls. Hence no fuel flow and running out of fuel when the fuel flow is needed most when the boost comes up. If you don't have a check valve to control flow then I really think that's your problem, if your electric pump is even turning on at all...
The Full Power Performance RX1 setups actually use just the electric pump 100% and use the mechanical fuel shut-off valve to turn off the line from the stock pump to prevent that short circuiting. This way if the electric pump fails, you can open the valve and limp home on the stock pump. It's one or the other, though... not both at same time for the reason i just explained.
You could accomplish the same thing with 2 one-way check valves so the electric pump can't short circuit backwards by over-powering thru the stock pump.

Great info, mine has check valves - I need to check them. I have a solenoid switched on by boost pressure that powers the Bosch pump, and it also turns on a light on the dash to show power to the pump. All of this stuff looks old, I would like to get rid of it. So, if I put a valve on the fuel supply to the original stock pump, I can run the Bosch pump through the regulator and get the results I want, and have the old one as a spare? Will the engine start properly, or do I have to have the pump turn on before I start it? I have noticed that the sled has been increasingly hard to start, even after 15 minutes or so, I think the stock pump is not doing its job.

 

[mbarryracing]

Are you sure the electric pump is even turning on? Or that it's flowing correctly?
I wouldn't trust the power light alone to tell you the pump is operating correctly. You need to jumper power to the electric pump to check and then set the regulator with it to ensure it's pressurizing.
If the float needles and seats in the carbs are in good shape, then they shouldn't leak or overflow with the electric pump 100% of the time as long as the regulator base fuel pressure is not set any higher then 4.5 lbs. If you install a manual shut-off valve to replace the check valve, then put it AFTER the stock pump (on outlet line) so you can block it off from the high fuel pressure keeping it from getting pressurized so you don;t worry about blowing out a diaphram.
IMO that i'd run the electric pump all the time, run it off a relay that powers up with the head light. That way it only kicks on when the engine is running, and not during cranking / starting.
The sled should start with the fuel that is sitting in the full float bowls from when you shut it off last.
If it happens to run dry on fuel during extended cranking, etc , you can manually open the valve so the stock pump fills the carbs during cranking.