I have a HPI Trophy 3.5 with the stock engine and have trouble priming it.

However, I noticed that once I remove the fuel line from the HSN, fuel immediately flows and drips down. Once I reattach it to the HSN, fuel stops flowing again.

I'm in the process of removing my carb and cleaning it. Any tips or ideas on what to do?

You may need to check your tank lid to make sure it is sealed and that your exhaust gaskets are in good condition so that your system is building enough pressure to pump fuel

Thank you.

Yes, I did all that and it all looks fine. I checked the fuel tank and it's $8 so I might order it. I'm surprised because I only put a gallon through the engine

The car is almost brand new and ran perfectly. In fact, I also made a YT video of me starting and running it.

As of yet, it has become very difficult to tune and of course the priming.

Hope tank cures your problem,I'm sure someone one on here can offer you some more advice on your issue, good luck!

take pressure line from pipe and blow in it. if you cant force fuel into carb using this method then open the throttle and then blow in the pressure line. if fuel flows into the carb at this point your idle gap is to tight or LSN is set to lean.

Also yet taking the fuel line off the carb and blow through the pressure line. If fuel comes out of the fuel line, take out the HSN assembly, fully disassemble and clean it.

If no fuel came out when you blew the problem is between the lines... tank, filter whatever else is btwn.

could also be that your needles are way to lean. richen everything up a tad and see if it helps. the carbs on these things basically work like taps and if the taps are closed to much it might be difficult for fuel to get into the carb in the first place.

Thanks for the replies everyone.

I basically took out the carb, soaked it in dishwasher liquid water for 30 min and cleaned it thoroughly using a toothbrush. I then dried it out using compressed air and kept it out in the open for 5 hours to dry further. I then ran some ARO through the carb.

I put everything back together and voila! Fuel flows through like a charm. Basically, my HSN was clogged - it wasn't allowing fuel to enter.

I'm a complete nitro n00b. Any tips to stop fuel clogging in the future? Thank you!

Dr G

Probaby you are using a fuel with a high content castor oil, castor oil will dry up....

I'm a nitro n00b and the only fuel I have ever used is Traaxas 20%. It worked flawlessly for me - lots of power and easy to tone.

I think cleaning the carb is part of the maintenance routine - at least for me. From now on, I'll clean out the carb and fuel tank after every 1/2 gallon through.

I also noticed my needles are much more easier to tune after a super clean carb. Note to self- If your engine is struggling to keep a tune, take out the carb and clean it.

DrG

Are you running a fuel filter? Contaminates can accumulate in the bottom of the tank from refueling and stuff falling in. Any particulate will not go over well when it gets to the carb.
I've never had to clean a carburetor due to foreign contaminates.

I'm guilty of not using a fuel filter I'll add one soon.

Nevertheless, I did some Googling and found that the fuel I use - Traxxas Top Fuel 0 has high castor oil content which causes it to gum up.

I also Googled 'clogged hsn' and came up with numerous posts describing my exact problem! Someone also said it is a fairly common problem among nitro engines - clogged fuel lines and even the fuel tank.

What type of fuel do you use?

DrG

Just make sure to run your fuel tank and fuel lines empty at the end of your last run. That way there's no fuel left to gum up in the hsn.

Great tips here, a fuel filter is definitely a must IMO. The little Dubro inline ones work fine for me. Traxxas Top Fuel is good stuff, it doesn't gum up too badly, but it still can. As said above, run it totally out of fuel when you plan to let it sit for longer than a few weeks. Capping off your engine for storage is also a good idea. Basically it's a set of rubber caps that cover the fuel inlet, carb venturi, and pipe stinger. That along with after run oil helps a lot to stop the gummy crud and will also keep the internals from corroding from long storage times. Nitro fuel can cause extreme corrosion if left to sit in an engine. You can also find vacuum line caps at most auto parts stores that work well for plugging up the engine. For cleaning, denatured alcohol works really well at dissolving gummed up fuel.

UPDATE:

Thank you for the tips everyone. Here are some updates - I'm having the following issues with my engine:

- very difficult to prime
- glow plug burns immediately as soon as I hit WOT
- very erratic idle
- idle sounds very different. Not sure what it is, but it's not what it used to me. I only put 1 gallon through the engine.

Is it time for a rebuild? This is a HPI nitro star F3.5 engine.

Would it be economical to have it rebuilt? Or should I just get a better engine like Werks of Novarossi?

Thank you!

DrGladwin