Air bubbles in the fuel line

[Waddo29]

I am running a newly built 29cc cy motor with a new RB Innovations Carburetor Heat Insulator Block w/ Diaphragm Filter, a new 990 carb, new ddm velocity stack, new dt1 air filter and all new gaskets. I am also running the Full-Force RC v2 High Flow Fuel Line Kit. I was stupid enough to initially connect the intake fuel line and return fuel line backwards and because the full force machined brass fuel fittings are so long, the return goes so deep into the fuel tank that it sucks gas and I did not realize the lines were backwards until the motor stopped running after about 3 minutes and the carb primer build would no longer prime. I got the lines hooked up correctly and the bulb primed back up right away. However, now I can run the motor until it gets to running temp, approx 180deg to 200deg, and then I start seeing air bubbles in the fuel line and the primer bulb runs out of gas and the engine dies and bulb will not prime again. Once the temp comes down, the primer bulb will again prime like normal and engine will run again until it reaches running temp, then same thing happens. Any ideas would be greatly appreciated.

 

[Z.hb71]

I am running a newly built 29cc cy motor with a new RB Innovations Carburetor Heat Insulator Block w/ Diaphragm Filter, a new 990 carb, new ddm velocity stack, new dt1 air filter and all new gaskets. I am also running the Full-Force RC v2 High Flow Fuel Line Kit. I was stupid enough to initially connect the intake fuel line and return fuel line backwards and because the full force machined brass fuel fittings are so long, the return goes so deep into the fuel tank that it sucks gas and I did not realize the lines were backwards until the motor stopped running after about 3 minutes and the carb primer build would no longer prime. I got the lines hooked up correctly and the bulb primed back up right away. However, now I can run the motor until it gets to running temp, approx 180deg to 200deg, and then I start seeing air bubbles in the fuel line and the primer bulb runs out of gas and the engine dies and bulb will not prime again. Once the temp comes down, the primer bulb will again prime like normal and engine will run again until it reaches running temp, then same thing happens. Any ideas would be greatly appreciated.

Vapor lock maybe or the insulator block is transferring too much heat to the carb. I think

 

[bigdipperfred]

How's your tank vent

 

[Z.hb71]

How's your tank vent

+1 good question

 

[Phill2]

I am running a newly built 29cc cy motor with a new RB Innovations Carburetor Heat Insulator Block w/ Diaphragm Filter, a new 990 carb, new ddm velocity stack, new dt1 air filter and all new gaskets. I am also running the Full-Force RC v2 High Flow Fuel Line Kit. I was stupid enough to initially connect the intake fuel line and return fuel line backwards and because the full force machined brass fuel fittings are so long, the return goes so deep into the fuel tank that it sucks gas and I did not realize the lines were backwards until the motor stopped running after about 3 minutes and the carb primer build would no longer prime. I got the lines hooked up correctly and the bulb primed back up right away. However, now I can run the motor until it gets to running temp, approx 180deg to 200deg, and then I start seeing air bubbles in the fuel line and the primer bulb runs out of gas and the engine dies and bulb will not prime again. Once the temp comes down, the primer bulb will again prime like normal and engine will run again until it reaches running temp, then same thing happens. Any ideas would be greatly appreciated.

You need to cut the return off so it only goes in just past the bottom of the grommet.

 

[DougStar]

Id double check for air leaks......but what you should do is try with old carb insulator block coz it may be a heat isssue then after that stilll same put rb back and cut return short see what happens

 

[Phill2]

Are you using the DDM silicone gaskets?

 

[Waddo29]

Vapor lock maybe or the insulator block is transferring too much heat to the carb. I think

I’m not sure what vapor lock is or what causes it so I don’t really know what to do to fix that issue, but I do have another isolator block I can change out and try. Thank you for your input

How's your tank vent

I am running a DDM aluminum aftermarket cap with the guts from my original Losi fuel cap. Up to this point I have never had an issue and I just had it all apart to clean it for the finish of this last rebuild and it all looked fine but I am no expert, is there anything in particular I need to look out for? Thank for your time to help me out.

You need to cut the return off so it only goes in just past the bottom of the grommet.

Thank you, I appreciate your advice and suggestion, this will be my first step of trouble shooting, fingers crossed maybe the last step as well...

 

[Top Dead Center]

Check out the comments with this video. An user talks about a teflon gasket or spacer that should have came with the heat sink.

 

[Phill2]

Check out the comments with this video. An user talks about a teflon gasket or spacer that should have came with the heat sink.

That's like the gaskets from DDM

 

[DougStar]

I’m not sure what vapor lock is

If you are getting vapor lock your car will starve cut out and when you open the fuel cap you ( car not running ) hear suck when the vacum pressure is released. Cap is blocked, should be able to blow air in not out . Hope this helps

Check out the comments with this video. An user talks about a teflon gasket or spacer that should have came with the heat sink.

Nah no mention of the teflon gasket

 

[Waddo29]

Id double check for air leaks......but what you should do is try with old carb insulator block coz it may be a heat isssue then after that stilll same put rb back and cut return short see what happens

Great advice, thank you. I think I will actually start by cutting the return to size just because I can’t see any reason why it is so long and if I ever get the fuel lines backwards again I don’t want to suck fuel into the carb without going thru the filter first. If problem persists I will try a another isolator block instead of the rb innovation heat sink block. This is the first time I have ever run one and the first time I have ever had this problem, hopefully just a coincidence. I am wondering if you have any tips on the best way (or how) to check for air leaks. Thank you for your time and help...

 

[DougStar]

Start the engine get a can of wd40 spray inlet mnifold if you rev drop you have a leak

 

[Waddo29]

Are you using the DDM silicone gaskets?

Yes, all gaskets (isolator, carburetor and velocity stack) are DDM

Start the engine get a can of wd40 spray inlet mnifold if you rev drop you have a leak
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Perfect, thank you

That's like the gaskets from DDM

Yes it did come with a plastic spacer which, unless I am mistaken, I did install it with the block. I will find out during all the trouble shooting suggestions I got from everyone if I messed up and did not get it on there

If you are getting vapor lock your car will starve cut out and when you open the fuel cap you ( car not running ) hear suck when the vacum pressure is released. Cap is blocked, should be able to blow air in not out . Hope this helps

Nah no mention of the teflon gasket

I am not hearing any pressure release or hiss when removing the gas cap, I will make sure to pay close attention next time. Thank you
I wanna thank everyone for all of the tips and suggestions, I have a solid trouble shooting plan to start with and I appreciate everyone’s help. I will let you all know what it turned out to be, or I will be back asking for more help:0?
Thank you

 

[Bill Mossor]

Sounds like vaper lock to me. Next time you are running & it dies, try lousing the gas cap & if it fires back up, then
that is your problem.

 

[Thrasher]

RB Innovations

Arent they the hucksters that sell "superchargers" for 2 stroke and nitro? If you have a problem with one of their products I am going out on a limp here and suspect that it doesn't work because it doesn't work. Feel me? You were had.

 

[Z.hb71]

Arent they the hucksters that sell "superchargers" for 2 stroke and nitro? If you have a problem with one of their products I am going out on a limp here and suspect that it doesn't work because it doesn't work. Feel me? You were had.

I don't see why this wouldn't work tho, it's a isolator block.

 

[Thrasher]

You are absolutely right but once a huckster. Just sayin'.

 

[Z.hb71]

You are absolutely right but once a huckster. Just sayin'.

I Honestly cannot believe people fall into the bullshit that is those "superchargers" ???

 

[Cupton79]

Did ur full force kit come with the fuel line clamps? My first one didn’t and mine did as you discribed.. l put the little clamps on... problem solved..