STS d30m, is it dead?

[Fourthbean]

I bought a Savage second hand, I did not hear the engine run before buying and according to him it had not run in 6-8 months. After attempting to get it started (made sure there was fuel to the carb and a glowing glow plug) I thought to check the compression. With the glowplug out there is no pinch at TDC, from what I have read this is synonymous for "rebuild your engine!". Just wanted to get a second opinion before I start looking at my options. New piston and sleeve for 50 bucks or buy an sts 28 for 120?

Thanks for any input, I am new to the nitro game.

 

[SMaxxin]

With the glow plug out there will be very little resistance (normal), how does it feel with the plug in?

 

[Fourthbean]

It does seem to have a good deal of compression with the plug installed. I must have read the other article wrong about the pinch, or maybe that was talking about a brand new (not broken in) engine.

Here is a rundown of what I have done to try and get it to start:
I have fresh traxxas 20% nitro
I set the truck out in the sun at 70 degrees or so before trying to start it
I was able to prime the fuel up the the carb (stopped just after it hit the end of the tubing)
I set the carb to a few mm open and also tried opening it up more through the trim on the radio
I set the HSN to about three turns out
I have not touched the LSN, it is turned out away from flush
It has a roto-start or similar backplate with a drill that the previous owner used to start with
It had a #6 plug in it with one shim, I have not changed that
The glow plug glows red/orange when outside the engine in the glow plug heater

Any ideas or pointers for getting this thing to turn over? It doesn't seem to want to catch at all.

 

[olds97_lss]

Is the plug the original that came with it that sat for 6-8 months? That could be problematic.

Does it even fire or try to start? Is the plug wet after you tried getting it running?

 

[Fourthbean]

It is the one that came with it that had been sitting. The plug and top of the cylinder are wet after trying to start but I don't get any gas in the exhaust pipe after trying to start.

Replacing the glow plug is one of those things I should have replaced but have forgotten about. However I did make sure it had some sort of glow to it to make sure it wasn't completely dead. I will hunt down what plug to get for this engine and grab one at the hobby store when I can.

Thanks for the help so far, any suggestions on plug type would be appreciated but I can always do some googling or even *gasp* ask the guys at the hobby shop.

 

[olds97_lss]

A OS #8 typically works in most... unless it's a turbo head. You said the plug had a brass washer right? The tip of the plug isn't tapered is it?

The manual doesn't say: STS 21-30 manual (pdf)

But it does note that using a hotter plug for break-in is suggested due to the richness setting of the needles. This would suggest it doesn't use a HOT plug for normal running.

The only two plugs they sell here, are both long plugs, one medium, one hot. Considering they only sell STS engines, you would probably be safe.

The OS #8 is a medium-hot long plug. I'd suggest steering clear of HOT plugs. Most LHS's carry those as traxxas engines run them, so they typically stock up... I've had timing issues running hot plugs in big blocks.

 

[Fourthbean]

Thanks for the tips, hopefully I can run down to the hobby store later today and then get this thing started.

EDIT: Yes it is a brass washer and the plug is flat on the end.

 

[bentover]

My STS has no compression with out the GP either, but it still pulls hard when it's running way over the 300F range, you'll really fall in love with it.

If the carb gives you headaches, switch over to a Novarossi or Axial carb, the needles are tighter and not as picky.

 

[olds97_lss]

switch over to a Novarossi or Axial carb, the needles are tighter and not as picky.

Wow! I can't believe Axial's carb is a suggestion! I wouldn't give you a plug nickel for Axial anything at this point. I still have a dead Axial 28 that has less than a gallon through it... It's internals are all still shiny new and the pinch is still aggressive.

I keep it to remind me that cheap is typically cheap for a reason.

 

[bentover]

Any carb that has an opening of 9mm will do, STS's carb is 8 or 8.5mm from what I remember, I switched to an Axial carb as soon as I got mine back from my modder and I rarely need to fiddle with the needles, except on drastic outside temps.

 

[frickenjoey]

You just hate Axial so bad don't you Olds....damn man....lol Heck I will give you TWO plug nickels for it! You and Axial's.....me and Picco. Just don't get along.

 

[olds97_lss]

Yeah... I tried to hold my tongue about it... After sending it in to axial and them saying there is nothing wrong with it and that it runs fine, the internals look imaculate, the break-in appeared to be done really well, then sending it back as it still runs like poo... doesn't bode well. But, that's for another time in another thread.

 

[Fourthbean]

I grabbed a #8 glow plug and tried it with one and two copper shims on the glowplug to no avail. I tried leaning out the HSN to the point of it being flush and that didn't help either. The plug is wet if I take it out.

I did notice one thing, when priming by holding my finger over the exhaust it primes fine but there is a good lag before the gas starts shooting up. Like if I stick the drill in there and pump it a few times then it will take 3 seconds for the gas to reach the carb. I don't remember that much of a lag in my OFNA buggy. Could the exhaust pipe be clogged? Does that happen?

Could it be the carb is simply clogged with junk and I need to clean it out?

I honestly wonder if this 18Volt drill has enough speed to get the engine going fast enough to start, but it is what the Previous Owner used to start it.

Any other pointers would be great.

Thanks.

 

[olds97_lss]

Your sure your heater is good?

My engines when tuned well, I can slowly pull the pull start to the point that the engine just rolls over TDC and they will start. A fast starter shouldn't matter. If it's turning the engine over with any speed at all, it should work.

Your getting fuel into the engine... even if the carb was clogged, enough fuel is getting in to wet the plug. One shim/washer on the plug should suffice. Two shims would make it be recessed in the head dome inside the combustion chamber, you don't want that.

What fuel are you using? How old is it?

 

[Fourthbean]

The glow plug heater is showing about half charge and still makes the GP glow, I will put it on the charger before trying again tomorrow to make sure it is doing all it can.

The fuel is traxxas 20% that is 2 weeks old. I just picked up another brand of 20% (sidewinder) that I can try tomorrow (the LHS said it was "the best fuel"). It was much less expensive at 17 a gallon compared to 10 bucks a quart!

I didn't realize how easy nitro engines should be able to start when tuned correctly. I guess that means my buggy is no where near tuned correctly.

Will the low speed needle affect starting? I haven't messed with it because I was thinking it was not in the equation at the moment.

 

[olds97_lss]

Yes. Until your at about 1/3 open throttle, the LSN is doing most of the fuel control.

The HSN (high speed needle) has two functions:
1) Over all fuel flow
2) High speed tune (from 1/3-WOT)

The LSN only affects the engine from idle to about 1/3 open throttle.

Considering the HSN controls fuel flow overall, it will affect the LSN adjustment.

Say for instance, you screw the HSN all the way in. Regardless how you set the LSN, fuel will not flow into the engine, because the HSN is shutting off the entire fuel flow.

But, say you have the HSN set too rich for high speed use, you could still have your LSN set properly for idle and it will get blubbery rich as you open the throttle as the HSN takes over.

I'd just make sure the LSN is set flush with the LSN housing, the HSN set 3-4 turns out from bottom, then start from there. It should be rich, but run.

On a side note, here's a tuning guide that I've found in the past and I really like how things are explained. It's helped me become a more proficient tuner: http://www.nitroreview.com/hintstips/ParisRacingEngineTuningTechTips.pdf

It's a lot of reading, but it contains a lot of good info for people who already "know" how to tune and people who are new to the hobby or never got good at tuning.

As for the fuel your using, I couldn't say. A lot of traxxas owners swear by it. I've never used it, but I've run traxxas engines. I now use byrons 25% nitro/11% oil fuel. Burns good, starts easy, solid power and runs pretty cool. I ran trinity MHP 20% for years until this past year. The manual for my new LRP28 in my aftershock suggested 25% nitro was as low as I should go. So, now I run it in my XTM24.7 powered buggy, my 18TM jato (or trx2.5 when it's installed) and my LRP28 aftershock. Runs good in all three engines. Although, I have an OS21RG in my aftershock now that it's winter (didn't want to shorten the life of the LRP I bought this spring), and it seems to run easily on the fuel as well. But, it's an OS, they can run on mud if you know how to tune

 

[Bando711]

You mentioned the drill............had the same problem with my STS .28

The rotostart is what should be used, it has a one way bearing in it. The drill my not be fast enough or it won't disengage to let the motor start up. If you can get your hands on a rotostart see if that helps. Good luck. STS motors are nice for the money, I run the .21 5 port in my Buggy and Revo. Good luck:bow:

 

[olds97_lss]

Oh really? The OWB is in the driver not the engine?

Looking at the parts explosion, it appears the OWB is in the engine, so a drill or roto start driver should work.

 

[Fourthbean]

Here's what I am going to do today according to your very helpful suggesstions when I try the truck again (this is so I don't forget and can come here to see what my steps are).

Move HSN 3-4 turns out from bottom (should be about where I have it right now)
Remember that further in is leaner (will start easier)
Move LSN in to flush (it is currently out from flush which should be richer, I was thinking this was leaner. Maybe that is my problem with it not wanting to start!)
GP battery is fully charged

 

[hvymetalalchmst]

if those steps dont work, id take the whole engine and carb apart, clean it, inspect it for rust or gumming, and then try to put it back together again. i find it hard to believe that your tune pipe is blocked, or else you would easily hydrolock your engine, although you do say that there is no exhaust coming out - as in no air movement, or non-fluid air flow? if theres no air movement, you should take your tune pipe and flush it out with denatured alcohol to clean it.