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-   -   Another engine problem thread! (https://www.rctech.net/forum/nitro-off-road/226532-another-engine-problem-thread.html)

Toltol 06-12-2008 11:33 AM

Another engine problem thread!
Hi guys, sorry for posting another engine question but I just want to make sure that I have the problem diagnosed correctly.

I have a new buggy and the shop that I purchased it from put 2 tanks of fuel through it for me. When I brought it home it started after some time and I ran it easy for about 5 minutes.

Now when I start the engine it cuts out after a few seconds and is then really hard to start (and hard to pull cord), there is also some fuel/oil coming out of exhaust when i turn it up. Also, if I try to increase throttle when its started it cuts out.

Would I be correct to say that its flooding? And should I try to lean it out with the low end screw, if so whats the correct procedure.

Thanks for any help.

slaytanic 06-12-2008 12:09 PM

It's way rich and not broke in yet.

Toltol 06-12-2008 01:27 PM

Okay, I fiddled around with the high speed screw a bit and I got it started. Put 2 tanks through it driving at mid-high pace. I then had to give up trying to start it on the 3rd tank (hand covered in blisters!). It seems to be kicking but seldom starting, and when it does start is stalls after about 10 seconds even with the glow starter on it. And if I try giving it some throttle during those 10 seconds it stalls.

Any ideas? Thanks again.

jaylude22 06-12-2008 01:33 PM


And if I try giving it some throttle during those 10 seconds it stalls.
During those 10 seconds, does it spit out raw fuel from the pipe? If so, you're probably still too rich.

Toltol 06-12-2008 02:21 PM


Originally Posted by jaylude22 (Post 4533053)
During those 10 seconds, does it spit out raw fuel from the pipe?

Cant say that it does. Maybe a little bit of oily residue. The pull start does get very hard to pull. Which needle should I use to lean it out? And but how much should I turn it?

slaytanic 06-12-2008 02:39 PM

Pull the plug out and turn it upside down. Pull it a few times to clear fuel. Also put the pug on your glowstarter to dry it out. You will prolyy hear it sizzle. Then I would lean it out on the hi speed needle maybe 3 hours. If it gets hard to pull stop right away or you could break the rope or vaporlock your engine damaging the rod.

desertbird 06-12-2008 02:50 PM

Watch all 24 of these if you have not already.


Should give you a better understanding of HSN (high speed needle), LSN (low speed needle) and the Idle Screw.

Here's how I get it straight.

HSN, how it runs on the throttle. want smoke and 220 - 250 degrees

LSN, how it comes off idle. want quick crisp response

Idle screw, how fast the engine idles.

I'm still new, so others should chime in if I am missing something. But, those videos helped me get it figured out quickly. Good luck, its fun tuning.

Jesse 06-12-2008 11:53 PM

If you want information on how to properly break in your nitro engine and or tune an engine properly, go here:


feel free to ask any of those guys questions in relation to.

Toltol 06-18-2008 05:02 AM

Hello again. After a few days away I decided to give it another go. This time I leaned the HSN half a turn and vola! It started on the first pull. Idled fine but seemed a little high on revs (high pitched sound also). It was very responsive to throttle and had a light stream of smoke. However, whenever I gave it more than half throttle it would die down and eventually stop (traveled very fast even on half throttle). Could the HSN be leaned too much?

Turbine_au 06-18-2008 06:38 AM

Sounds slightly too lean on the LSN for run in and possibly a slightly high idle screw.

When you go more than half throttle, does it suddenly cut out or does it start to bog down and eventually die? If it's a quick cut, it's too lean. If it bogs down over time and then stalls, it's rich. Your best bet is to watch the youtube videos to get an idea of the sound the engine should be making. Tuning a nitro car is all in the sound.

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