Trouble with my new engine....

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nitromad

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Hi guys,

I tried to start my brand new sts .28 up for the first time tonight and ran into some trouble.

It would start, run for 2-3 seconds and die. Over and over and I couldn't get it to stay running. It happened at idle and also with a little bit of throttle open. It would start, run for 2 seconds and stop. Even leaving the glow starter attached made no difference.

I tried factory setting, a bit leaner, a bit richer everything.

I'm using new 5% nitro (just for running in purposes), a brand new OS A5 glowplug, and a fully charged glow starter indicating a healthy plug with its needle.

Before I ever used it I stripped the threading in the cooling head by screwing a glowplug in to tight. I have subsequently installed a replacement and all my compression is back.

Does anyone know why this is happening? Its driving me insane (no pun intended).

Cheers

Chris
 
Why 5%? 20% would make it easier to run. Running 5% with a cold plug would be a pain. Either try a hot plug or higher nitro.
 
olds97_lss said:
Why 5%? 20% would make it easier to run. Running 5% with a cold plug would be a pain. Either try a hot plug or higher nitro.
Agreed. One of the major benefits of nitromethane in glow engine fuel is that it helps the engine run smoothly at idle. If you intend to run 30% eventually then there should be no harm in performing break-in with 30%, providing the head is shimmed accordingly.
 
I'm using 5% as I was told it softer on the engine during run in and also assisted lubrication as it has a higher oil content. My friend did the same thing with the same engine and plug on his and had no problem.

I plan on running 15% through it during regular use, as I like open spaces with ramps more than tracks and like to keep temperatures down as much as possible as I am often operating flat out for extended periods.

I beginning to get concerned as the first engine I was supplied with from Kyosho was faulty, and now this one refuses to run.

I will take your advice and try running some 15% through it. Are there any other ideas?
 
An engine of that size isn't designed for 15% nitro. It's more suitable to use 20-30% with 10-12% oil in it. Generally it's a good idea to use a hot plug, such as a OS A3 during break in.
 
I agree with the folks here...... I don't think you will get your temps up running only 5% nitro. In order to break the mill in properly you would need to get your temps to around 220. I have never broken anything in on less than 20%. I am still a rookie tuner, but it would seem to me that the nitro content is too low, and that is why you can't keep it running. What are you temps reading? I am curious as I just think there is too much oil in the 5% to get the temps up. Take care and good luck.

Tom
 
I took your advice and ran a higher nitro fuel (15%) instead but still no luck. Then I noticed that the pull start unit was soaked in fuel and that there was fuel leaking from behind the backplate. I took the backplate off and there was fuel everywhere. So this leads me to believe that engine has a faulty seal and would explain why its starts but never for longer than 2-3 seconds.

If this is the case I cannot believe my luck - the Kyosho engine that came with my buggy was faulty and lasted about 10 tanks, then I purchased a new STS engine and as soon as I put the glow plug in, the threading in the head button stripped like butter, and now that I've replaced that it looks as though the engine is faulty after all. Is there any other explanation as to why there would be fuel leaking through the backplate and into the pull start? :doh:
 
First, I actually got cooler temperatures as I went up in nitro percentage. I ran 20 and then switched to 30. With my OS RG, I got more consistent tuning, and obviously more power by making the switch.

Second, I don't know about fuel leaking through the pullstart, but you said you removed the backplate and found fuel. That should be no surprise, since fuel is sucked into the cranckase before it goes up into the engine through the ports. By removing the backplate, you just allowed all of the unburnt fuel to dump out.

Third, a starter box makes life soooooo much easier. You don't have to worry about leaky pullstarts, pullstart strings breaking, or one way bearings going out on you. Plus, you don't have to get arm pump yanking away on that handle.

Fourth, (since for whatever reason I numbered all the others), your engine could likely be dying for two reasons. One is that the HSN/LSN is too rich to stay running and flooding the engine out. The other is that the HSN/LSN is too lean and the engine is dying because it isn't getting enough fuel to stay running. The easiest way to tell is the sound that the car is making when it dies.

If the engine blubbers and dies, too rich is likely the issue. If the car is getting flooded, where it becomes difficult to spin the flywheel, that is likely the hsn being too rich. If the car starts each time, but blubbers to death when you give it gas, that is likely the LSN being too rich.

If the engine cuts out instantly, without blubbering it is likely too lean. Start by richening the LSN if this is happening instantly from idle, or if it happens the second that you let off the gas. If it is happening once the engine gets to high revs (without letting off the gas) it is likely the HSN being too lean.

My procedure for breaking in an engine is to:

1.) Find and mark bottom dead center first. Do this by removing the glow plug and resting a long object like an antenna tube on top of the piston. Rotate the flywheel until the engine at its lowest point, and then scratch an index mark on the flywheel so you can identify this position quickly. Each time you shut the car off, immediately put the engine in this position(for the life of the engine not just break in). This keeps the piston out of the tapered upper portion of the cylinder as it cools, allowing it to contract fully, and not get stretched out.
2.) Set all needles, including the idle gap to manufacturer specifications.
3.) Test glow ignitor on a working glow plug outside of the car. I have seen many people cuss at their engine for not starting, when it was simply a dead ignitor battery.
4.) Cover exhaust and attempt to start car w/o ignitor. This sucks fuel to the engine. If your fuel lines are clear and you can see it getting sucked towards the engine, stop right before the fuel reaches the carburetor.
5.) Attach ignitor to engine and attempt to start car. Keep trying until car starts, or engine becomes difficult to turn over (from flooding). Manufacturer's break in settings are almost always way too rich.
6.) Once it floods, lean the HSN 1/8th turn. Remove glow plug, attempt to start engine to blow out any unburnt fuel. Re-install the glow plug.
7.) Repeat steps 5 & 6 until the engine starts.
8.) Once engine is running, remove the glow ignitor, and the car should at least idle. If not, try leaning the HSN another 1/8th turn.
9.) After getting the car to idle, set it on the ground and attempt to drive it. It will likely be extremely sluggish, and blowing out lots of smoke, and probably spitting alot of unburnt fuel out.
10.) Using an infared temperature gauge keep leaning the engine until you achieve temperatures between 200-230 F (measured at the glow plug). Cooler and you need to lean the HSN, hotter and you need to richen the HSN.
11.) Once the temperatures are in range, run the car in 30 second intervals, bringing it in each time and pinching the fuel line. The car should die between 5-7 seconds after pinching and holding the line. If it dies in less time, richen the LSN 1/8th turn. If it takes longer to die, lean the LSN 1/8th turn. Repeat this process until the engine pinches within this timeframe.
12.) Once the engine is in the right temperature range, and the LSN is set according to the above pinch test, you are ready to heat cycle it. Run the car in 3 minute intervals of varying throttle (not more than half) and then shut the car off. Return the engine to bottom dead center, and allow it to cool fully until it reaches outside air temperatures. Repeat this until you have done 30-45 minutes of drive time (not counting cool down time).
13.) Once you have run 30-45 minutes of heat cycling, adjust the engine for performance tuning. Go to 230-250 F, with the engine pinching out in 3-5 seconds. Also, make sure your idle is adjusted as high as possible without making the car move. This will allow for less lag time when accelerating from a standing start. Make sure that you always restore your engine to bottom dead center after running as well.
 
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Hi - thanks for your reply, I appreciate the advice.

I suspect something else more serious is wrong than needle settings. There just shouldn't be fuel leaking through the pullstart - especially on a brand new engine that has never been taken apart.

I'll do my best to explain what it is doing:

The engine is keen to start, but won't stay running. It runs for 2 seconds then pop, it stops dead.The engine does gurgle a little before it stalls (I can hear it starting to go as the revs stop - but it is not really obvious). In the mean time fuel is leaking out from the back of the engine and pull start. This is why I think it is a seal problem. When I give it throttle, it revs then hesitates then revs again over and over and will not settle into a steady idle. As soon as I bring the the revs down it hesitates then pop, stalls again.

I'm concerned about trying again in case I am damaging the engine. I don't really know what to do next...is there anyway to visually tell if the engine has a seal problem?
 
Well I tried pretty much everything and had no luck. Luckily STS have been very understanding and I have sent the engine to local stockist to be repaired/replaced under warranty, so will keep you informed.

Thanks again for the detailed advice guys, I appreciate it!
 
ok ....i have an engine question for kx250ryder...........my savage still has the stock engine s25.......this thing is runing at 280 & sometimes hoter but has the blue-grey smoke comming from the exhaust getting oil on the truck......i think the ideal running temp arta be around 240-255......I'm running 20percent......how do i get the temp down ? I'm running a cold plug (MC9)......do i need a hotter plug ? fuel change to higher nitro content ? do i open or close the low & high end needles ???
 
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speedticket75 said:
ok ....i have an engine question for kx250ryder...........my savage still has the stock engine s25.......this thing is runing at 280 & sometimes hoter but has the blue-grey smoke comming from the exhaust getting oil on the truck......i think the ideal running temp arta be around 240-255......I'm running 20percent......how do i get the temp down ? I'm running a cold plug (MC9)......do i need a hotter plug ? fuel change to higher nitro content ? do i open or close the low & high end needles ???

I was having a similar problem with my CRT and I found that fatening up the low end a bit did the trick for me.

Tom
 
speedticket75 said:
ok ....i have an engine question for kx250ryder...........my savage still has the stock engine s25.......this thing is runing at 280 & sometimes hoter but has the blue-grey smoke comming from the exhaust getting oil on the truck......i think the ideal running temp arta be around 240-255......I'm running 20percent......how do i get the temp down ? I'm running a cold plug (MC9)......do i need a hotter plug ? fuel change to higher nitro content ? do i open or close the low & high end needles ???

I am not sure about plugs. I ran McCoy MC-8 plugs for all my non-OS engines, and OS 8's for my OS engines (OS uses a different size plug). I never had much luck with the MC-8s lasting, so it was probably the wrong plug for my application. The OS 8's work great in my RG, and that is all I have ran lately. I hope someone else can chime in and offer you some advice on plug selection for your engine/fuel/weather conditions.

If you are still managing to see plenty of smoke at temps of 280 or more, chances are that you have a really lean top end, and are compensating by having a really rich bottom end.

First try the pinch test. Run your truck (after warmed up) for about 30-45 seconds varying throttle, and immediately bring it in. Pinch your fuel line right at the carb nipple. Hold the fuel line until the engine dies. If takes between 3-5 seconds, you are in range. If it takes less time, richen the LSN (counter-clockwise). If it takes more time lean the LSN (clockwise). Keep repeating this with 30-45 seconds of runtime in between until the pinch test shows results in the right range.

While doing that keep an eye on the temperature. If the temperatures are above the 230-250 range, adjust the HSN richer (counter-clockwise) and vice versa (leaner - clockwise) if they are below the 230-250 range.

This will work on pretty much every big block .21 or above engine (I have no idea about small block .12-.20 engines). You may be able to squeeze out better performance by tweaking it here or there, but I have yet to see any engine not run well using the temperature/pinch test method for tuning.

Some may be able to tune by ear, but I am way too procedure oriented to bother with that. I like a given set of steps to success; science, not art for me. To each his own though, I don't mean that as an attack on any other's tuning methods.

EDIT: when adjusting needles, think hours on the clock (1/12th turn at a time). Really small adjustments are necessary. 1/4 turn can be the difference between an engine that is too rich, and one that is lean enough to blow up.
 
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Nitromad, before you drop that new or repaired mill back into your rig, you need to get some RTV sealant and seal up the backplate and carb. throat. May also want to make sure you have no air leaks in the fuel tank or fuel lines.

The way it sounds, you may have had an air leak and it may have been caused by either a worn back plate gasket or the back plate was loose.
 
Thanks for the information.....Ill try the pinch test this weekend & see what it does......
 
I'm suprised no one metioned it before monkey wrench !who is "dead on" i always rtv seal all my engines when new/or taken apart since airleaks will cause these type of problems.
 
Monkey wrench - I will definately do that. I always suspected an airleak until I found the pullstart unit drenched in fuel which indicated to me a seal problem. There was literally raw fuel dribbling from the back of the engine.

I plan to use new fuel hosing, but can you tell me how to check a fuel tank for airleaks? Also, I have no idea how to rtv seal my engine - any tips would be a big help. Thanks mate.
 
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rtv sealing a nitro engine is fairly easy.....take the carb off the engine & apply a small bead of rtv on the carb's neck where it meets the carb's main body & set it aside......next remove the exhaust header & gasket......apply a thin layer of rtv on the exhaust gasket & set it aside.....allow both peices to cure then put it back togather.....if you have the rubber coupler that holds the header & pipe togather you can rtv that too but thats up to you.....
 
finnaly found the heating problem on my engine......the fuel filter had a crack in the housing but i didnt find out till i cleaned the filter and put it back togather. when i tried to tighten the filters housing it kept slipping & wouldnt get tight........
 
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