Please help with engine noise

[Andreas]

Hi Everyone,

Last night with running my HSP .18cxp nitro ofroad/onroad truggy after putting the engine back together it was making a weird noise. Its not something a can discribe, its not your normal high pitched sound, its more a deeper sound. The RPM's also dont get high enough for second gear to engage.

I've tried leaning out the HSN to get the RPM's up but no luck, it gets to a certain point and stays there, throttle response seems to be all good and low RPM's sound fine but mid to high RPM's have this weird sound to it.

What could this be? I'm clueless at this stage, please help guys :\

EDIT : Almost forgot, at first i had trouble starting it, when it did start it was reving quite high and could not kill it by closing the exhaust, i had to pinch the fuel line, its actually still like that, i can kill it with closing the exhaust now but it takes a while

 

[RC/Racer]

was the engine overheated @ all.. did you try setting your LSN... change out your glow plug..

 

[sv250]

It should kill when plugging. If it doesn't then you have an exhaust leak prolly at the block to header gasket.

That might be your noise also. Lack of pressure will also keep the fuel from flowing to the carb causing a lean condition at upper rpm despite needle settings.

 

[synnyzter]

It should kill when plugging. If it doesn't then you have an exhaust leak prolly at the block to header gasket.

That might be your noise also. Lack of pressure will also keep the fuel from flowing to the carb causing a lean condition at upper rpm despite needle settings.

This also explains the failure to shift. An exhaust leak would actually increase torque in the lower rpm's but kill your top end thus not a high enough rpm to shift.

But, technically the pressure from tank to Carb isn't actually what keeps the fuel flowing, its the difference in atmospheric pressure between the intake and the inside of the Carb (venturi-effect) It simply just needs to be sealed

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[Rolex]

It should kill when plugging. If it doesn't then you have an exhaust leak prolly at the block to header gasket.

That might be your noise also. Lack of pressure will also keep the fuel from flowing to the carb causing a lean condition at upper rpm despite needle settings.

That would be my thought, also.

 

[Andreas]

Wow, thanks guys, this actually makes a lot of sense to me now that you mentioned it, the engine might have overheaten once or twice... i think.

I dnt remember having a head gasket? Or even shims, any suggestions on that?

ill have a look at the exhaust gasket. Ill let you guys know how it goes.

 

[Racer 1966]

But, technically the pressure from tank to Carb isn't actually what keeps the fuel flowing, its the difference in atmospheric pressure between the intake and the inside of the Carb (venturi-effect)

No,really it's the pressure. These are not true carburetors,no real venturi in there just more of an air valve. That's why they lean out and most won't run without the pipe to tank line on it.

 

[synnyzter]

No,really it's the pressure. These are not true carburetors,no real venturi in there just more of an air valve. That's why they lean out and most won't run without the pipe to tank line on it.

Not real carbs? A mechanical device that regulates fuel and air....a carb plain and simple.

Sorry bud but you are indeed wrong, unless you want to argue science anyhow The line from the pipe to tank does contribute to a properly running engine but it aids in regulating fuel (lamens terms).

While the pressure yes indeed helps keep the fuel flowing but....it alone cannot provide enough fuel to the Carb hence the need to prime. The venturi effect is in fact involved as the fuel inlet takes in fuel, the fuel funnels in speeding up causing a vacuum or (less than atmospheric pressure) which is less than that outside the Carb pulling more fuel in (venturi effect). Just because you can't see it doesn't mean its not there

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[Rolex]

It's not a motor, it's an ENGINE.

 

[synnyzter]

You are correct . Since you mentioned it...why are they called "motorcycles" and not "enginecycles"....yes yes. I've actually wondered this before lol.

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[Alexander_0_1]

I've only had this happen once, the tubing from the pipe to tank fell off and it seemed like my engine had more power, I was running richer than normal cause the HSN had vibrated loose, but when I cracked the throttle I was almost instantly ballooning up my trencher x MT tires

 

[synnyzter]

Yep as I said without that back pressure from the pipe the bottom end is insane but its not safe for the engine, the top end also suffers just as much as the bottom end increases. That even happened on my quad once, header busted it got loud but man it was gnarly acceleration but it had the top end of a moped lol

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[STANG1981]

It's a late reply on me but I always carry a temperature gauge and traxxas makes 1 and any cheap 20 dollar kind would also help to watch the heat once u get running right... U should be between 210F to 220F degrees and those gauges that wrap around the heatsink for on board readings are off and not as accurate and the best is a separate 1 that u can just monitor as u need... This way u will always keep Ur nitro eng cool to a point and prolong that beast...

 

[synnyzter]

210-220 is way too cool....you want around 260 or your losing a ton of performance.... if your running 210 your engine is crazy rich

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[STANG1981]

That's what I run all my eng blocks without pushing it to much I heard about higher like u run but I had bad luck and I live in FL so I can't run like that so climate and outside temps will be retuned and I hate playing with needles it's a pain but cool if u can that's lucky it sucks 4 me..

---------- Post added at 10:02 PM ---------- Previous post was at 9:56 PM ----------

I also hv a saying if ain't smoking or at least a little at idle or when I'm going from a dead start then it's to lean for me or I'm not doing something right...

 

[sv250]

210-220 is way too cool....you want around 260 or your losing a ton of performance.... if your running 210 your engine is crazy rich

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Bullshit! Throw the temp gun in the trash. Use it for break in and rough tune, then its smoke and performance. Fuel also plays a big factor in temps. Saying that it needs to run 270 is BUllshit.

The best performing modded engines out there are running in the low 200's

Talk to the real experts like Robin from ERCM. watch the video of the worlds fastest nitro truck running just over 200 deg.

Take a look at Clockwork's site. Look at the temp readings after each run and find 1 in the dozens of vids that runs at 270.

And it is pressure. Pull the line and its just a steady pour. Nothing increases with rpm. There is no diaphrams, springs, or secondaies in these carbs, Theyre just a valve.

Always somebody thats an expert at race cars or motorcycles or boats snowmobiles whatever that thinks taht makes them a nitro engine guru.

You could be the top engineer at NASA for all I care. That doesn't mean poop with these engines.

 

[synnyzter]

Bullshit! Throw the temp gun in the trash. Use it for break in and rough tune, then its smoke and performance. Fuel also plays a big factor in temps. Saying that it needs to run 270 is BUllshit.

The best performing modded engines out there are running in the low 200's

Talk to the real experts like Robin from ERCM. watch the video of the worlds fastest nitro truck running just over 200 deg.

Take a look at Clockwork's site. Look at the temp readings after each run and find 1 in the dozens of vids that runs at 270.

And it is pressure. Pull the line and its just a steady pour. Nothing increases with rpm. There is no diaphrams, springs, or secondaies in these carbs, Theyre just a valve.

Always somebody thats an expert at race cars or motorcycles or boats snowmobiles whatever that thinks taht makes them a nitro engine guru.

You could be the top engineer at NASA for all I care. That doesn't mean poop with these engines.

Don't recall anyone in this thread with a highly modded engine trying to be a pro anything...

Second I don't think you need to act rude and cuss at people, that doesn't help his engine noise now does it? This is a friendly community so try to keep it that way, k?

his engine manual will clearly state the optimal engine temp just as any internal combustion engine runs best withing a certain temp range. 260 is just a generic but safe rule of thumb. Snowmobiles, motorcycles, NASA? Lol anyhow... I bash and race nitros and no I don't know everything I based that from both my experience and many other similar threads in this forum, not from what NASA taught me....?

So back to helping the guy...

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[sv250]

Back to helping the guy, He needs to check for leaks. He said he took it apart. I think he has an exhaust leak. So do others here. Check the gaskets, fuel line, and maybe the backplate.

Yes this is a freindly forum, but its not G rated. If words like Bullshit offend you that much, than you need to get a life. Notice there are no word censors....Hmmmm I'm Guessing thats because the grown ups here dont have virgin ears.

I'm rude because I see this same advice screwing people up all the time. If the temp theory was correct, you wouldnt need a temp gun. We could just put one of those pop uot things that come in the Thanksgiving day turkey on it. Just lean the needles til the button pops out lol.

Too many new guys have their engines tuned perfect at 220 deg, read some temp tune BS and start monkeying with their tune til they screw it up or melt it down. Its dangerous/bad advice.

 

[synnyzter]

OK no virgin ears...then you're a jerk. Did I stay within the lines of the rules?

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---------- Post added at 2:28 AM ---------- Previous post was at 2:23 AM ----------

"Throw away the temp gun."

" If the temp theory was correct you wouldn't need the temp gun...."

Are you arguing with your inner self?
I also don't recall saying it wasn't a leak....dude share whatever you are smoking please!

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[Alexander_0_1]

Oh, ass: donkey, burro, jack/Jenny....all other names for ass, ok ill shut up now