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HPI RS4 Starting Trouble

HPI RS4 Starting Trouble

Old 02-10-2015, 07:47 AM
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Questions?? HPI RS4 Starting Trouble

Im new to nitro and im having trouble getting my evo3 started. I get it to rev up for a split second then shuts off. Ive been adjusted the needles and cant seem to dial it in to stay running. So can anyone diagnose which needle I should adjust when having the problem of it reving up for a split second. Thanks guys.
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Old 02-10-2015, 04:27 PM
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Originally Posted by Spleen View Post
Im new to nitro and im having trouble getting my evo3 started. I get it to rev up for a split second then shuts off. Ive been adjusted the needles and cant seem to dial it in to stay running. So can anyone diagnose which needle I should adjust when having the problem of it reving up for a split second. Thanks guys.
First... Determine if it stalled because it is too rich. This is often easy to note if the second time you try it starts again then stalls. Or.. If you remove the plug and fuel sprays out. A good mix isnt wet and there shouldnt be visible signs of fuel when turning over without a plug

Then there's the engine itself, it may have shagged bearings, worn conrod, no compression. This isnt something you can tune to.

So... to get a safe idle...

First set your IDLE gap to 1mm not more.
Then set your servo trims and install rubber band to carby from top needle to keep it closed.
Then richen the top needle HSN two WHOLE turns counter (it will make sense later)
Remove and check your plug is healthy
While plug remove turn oiver engine to clear any floods

Now... * Without ANY throttle applied!

1) Replace plug
2) Try to start it
3) If it starts and then stalls shortly after close clockwise LSN 1/4 turn, remove plug, turn over to clear flood and go back to 1)
4) If it starts and it revs higher and higher, richen the LSN slightly until idle is stable, no mater if its high. Then you can lower the idle screw

Repeat these steps until you get an idle without any throttle. The reason for richening the top needle HSN is to ensure there is ample fuel pressure. Once you have an idle, try using throttle in very tiny increments adjusting the HSN top needle until it revs but is still a little rich. The final tune of the top needle should be done when up to operating temps and under load on track/street/car park.

Also check all fuel and pressure lines for air leaks.

let us know how you went.
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Old 02-12-2015, 09:22 AM
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Originally Posted by Spleen View Post
Im new to nitro and im having trouble getting my evo3 started. I get it to rev up for a split second then shuts off. Ive been adjusted the needles and cant seem to dial it in to stay running. So can anyone diagnose which needle I should adjust when having the problem of it reving up for a split second. Thanks guys.

-Anytime there are issues starting, I say start with factory settings.
(USUALLY its about 3 turns out on the top, and flush on the bottom.)

-The next thing is to look at the lines. (I would remove the fuel tube and check for holes, You can generally blow thru the line and see if you can feel any air coming out anyplace along the line)- Or just start with fresh lines.

-Remove the servo arm for the throttle and return the endpoints to 0. close the Carb so that only 2mm of gap exist in the Neutral position and attach the servo horn and test the throw of the servo. when you Stab the brake, it should not entirely close the carb, but rather allow for a small gap. Then once the servo throw is adequate, re-attach the servo horn to the servo with the screw. Its also a good idea to check and make sure the throttle return spring is attached as well and working.

-Another tip racers use is getting a heat-Gun or Hair dryer and pre-heat the motor before starting. Trying to start a cold motor can be very hard on the mechanics and by heating up the motor is allows the metal to expand slightly allowing for smoother pulls.


Questions for you...
-Did you break in the motor as recommended? they suggest 3-5 tanks, I tend to go a bit more- 7-10 for break in.

-Do you leave Fuel in it when you are done running or is the tank dry?

-Has it ever been over temp- IE over 220-250?



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Old 02-12-2015, 06:52 PM
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I think I had one of those ages ago. Does it have the fuel tank with the primer button? If so, mine did the same thing so I swapped out tanks for one with no primer and it fixed the problem.
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Old 02-14-2015, 04:54 PM
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Yea it has the primer on the tank. I got it used so I assume it has been broken in and I leave the fuel in there cause I have never ran it yet
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Old 02-14-2015, 05:05 PM
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Im confused with the rubber band around the carb. Is that to keep the carb open at 1mm or to completely close the carb just to drain the excess fuel. Also when I have flooded the engine, take the glow plug off and flip over all the fuel comes out of the exhaust. Thanks again guys for all the help.
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