Is my engine on its last leg??

Old 04-26-2018, 03:25 AM
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Default Is my engine on its last leg??

My main needles were tuned perfectly, car was running wonderfuly, but one morning few days ago i went to fire it up and noticed the piston was stuck! And it wasnt at tdc, was stuck in middle... Took off the heat sink took off the button and there was gunk not sure if it was dirt or rust but it wasnt clean and had built up a thin layer of gummy substance on piston head. The cylinder was gritty... i tried to heat it up using an smd heatgun/solder and then used a screw driver at the flywheel and the pullstarter cord to free it loose.... i guess i "shoulda" taken.the motor out cleaned it up... but i thought just freeing it and running it would clear it all out

After that the pull cord spring broke and spent another hour or hour and a half fixing that.... went for a spin and it fired up okay and drove okay... for a while.. till it heated up properly then turned off... and was a pain to turn on, by that i mean i needed to open more throttle for it to fire up... in other words it wouldnt idle...

After another day of trouble shooting and taking the motor apart except for the crank/bearings i soaked them with wd40 cleaning them that way... and finaly cleaned everything and the carburator this is after 5 gallons

It still fires up great, runs fine then drowns and dies rich... i retuned it for when its hot/warm/running temp..... leaning bottom end so that it doesnt load up and stall... also the drop in idle speed i readjusted the idle... now it doesnt shut off and runs fine when at operating temp

Now if i fire it up cold it will fire up with high idle and wants to roll, and show signs of runnning lean, pingging as in engine starving for fuel, but runs fine other than high idle..... as engine warms up the idle steadies fine and low...

Basicaly i need to tune it for when its warm and another tune for when its hot, richening and lowering idle for first half tank, leaning and increasing idle for second half.... otherwise it wont idle!

Is that sign of loosing compression???, when i took it apart to clean piston and sleeve it would reach maybe 1/8-1/16 from top of sleeve.... a week earlier it was just 1/4 inch from top.... seems whatever got in there took a toll on my piston... should have been more careful with the air filter and should have cleaned the engine bearings earlier... i can see signs of rust on the topside outside of the inside bearing.... also the crank wasnt rolling with ease before i cleaned it, but that should have caused firing up issues if it wasnt okay...

Last edited by b3master; 04-26-2018 at 07:57 PM.
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Old 04-26-2018, 04:12 AM
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Sorry for long post, basically i need a cold engine tune and hot engine tune to keep idle alive and steady and keep engine from loading up....

In shorter words its loading up...

I tried a diff glowplug, tomorow ill be in a position to try different fuel....
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Old 04-26-2018, 09:21 AM
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What brand engine is this?
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Old 04-26-2018, 09:50 AM
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Originally Posted by sebtarta View Post
What brand engine is this?
sh .21 in a nanda BD8 buggy, same as the Exceed rc Madfire from nitrorcx

Last edited by b3master; 04-26-2018 at 08:05 PM.
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Old 04-27-2018, 05:08 AM
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One of the first symptoms of bad compression is the inability to idle low and steady, especially when hot. Toss it.

edit: I am of course assuming you know how to tune properly. If so, the engine sounds like it's done.
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Old 04-27-2018, 09:06 AM
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I agree the engine is done however is not a racing buggy and even though it cannot idle low it's still got plenty of go plenty of power so I can drive it in wide open areas with the wide open throttle till the tank runs dry roflol, im still able to fire it up even when hot, i just gotta get used to max idle and all is well!! Im gonna empty out another gallon with it like this till the backup arrives...

I already have two engines on order on the way :-D

It will complete 5.5 gallons soon... what a bummer only last week i had tested the p/s and had good pinch at 1/4inch from the top... but latly i wasnt running the tank dry and hence i beleive there is much fuel in the crank that caused a buildup of rust that scratched the p/s, its either that or by mistake dirt got in when removing the glow plug washer with tweesers, but im keen to clearing the glowplug area out with contact spray before removing to make sure no debris gets in when its off.... just one of those freak things i guess.... maybe dirt from cooling head fins got in.. gonna find me a good brush to.use on the cooling fins before removing glowplugs from.now on.... that is IF i ever have to remove the g/p for nonsense reasons....
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Old 04-27-2018, 09:37 AM
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Hose clamp pinch time? Or could it do more harm than good?
Could it go oval?
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Old 04-27-2018, 09:45 AM
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Originally Posted by b3master View Post
Hose clamp pinch time? Or could it do more harm than good?
Could it go oval?
I've found that the point when the piston gets pinched in the sleeve tells little about how it will run. Hose clamp method I did once with a worn out traxxas 2.5. Froze the sleeve, clamped it tight (using a worm clamp lol), put the sleeve upside down directly onto a cast iron frying pan set on medium high, and let it get hot.
It squeezed the sleeve too far, and I had to preheat the engine to about 300 degrees to get it to start. After a few tanks it wore in and ran well. I think I still have that engine somewhere. Make no mistake, I got lucky because the whole process is pretty arbitrary and probably a waste of time.
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Old 04-27-2018, 10:00 AM
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An engine can still have good compression but not idle. The first thing to go when the piston seal goes south is the idle quality. A liner that’s been overheated will often be bellmouthed at the bottom. What happens is it loses piston seal at the bottom of the stroke causing poor transfer of air and fuel into the combustion chamber and thus a weaker mixture strength.. Sometimes this can be band-aided by adding some castor oil to the fuel to thicken it up and add a little more “meat” to the sealing of the piston. In reality, it’s better to replace the piston and liner or replace the engine.
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Old 04-27-2018, 12:35 PM
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Originally Posted by SlowLST2 View Post
.. Sometimes this can be band-aided by adding some castor oil to the fuel to thicken it up and add a little more “meat” to the sealing of the piston.
Can I use 2 stroke engine oil to the nitro fuel? Or full synthetic automotive oil?

The motor gonna be replaced and i will get p/s to prolong this motor's life... or just experimenting... meanwhile what can be used to thicken it up?

I found some hose clamps around the house but they all look seriously uneven, if im hardly gonna slightly tighten and heat not sure it would matter.... meanwhile gonna leave the liner as is better partialy working than a completly ruining it... when it fails to fire up ill clamp the hell out of it
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Old 04-27-2018, 01:26 PM
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I said castor oil for a reason. No, you can’t use petroleum or automotive synthetic oil. It won’t mix with methanol.

Dont bother trying to pinch that liner. It’s not worth it. Get a new engine.
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Old 04-27-2018, 01:54 PM
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Yup, i don think i can get my hands on any, ill try to find some, but highly dought it....

2 motors are on their way gonna take 4-5 weeks

Will chek out if the pison sleeve at second hobby shop are actualy for my motor or not.... first hobby shop want $50 for the p/s.... I rather pinch the hell outta it first hehehhe
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Old 04-27-2018, 03:17 PM
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Buy a Novarossi. Nothing to worry about for 10-12 gallons if you treat it right. SH is nice for a little while, then it’s time to upgrade to the real world. Novarossi has gotten more affordable than it ever has before. I’d not hesitate to run one over the SH junk these days. Forget the Pullstart and get a bump starter or rotostarter.
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Old 04-27-2018, 08:25 PM
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can i ask where your located that you have difficulty finding these things? if we know where you are it might be easier for us to help
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Old 04-28-2018, 12:07 AM
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I really appreciate the want for help, let's just say it's a third world country that doesn't have any of the listed available, and requires 4 weeks for stuff to arrive and a week or two to get customs clearance lol

i rather get a new cheap rtr buggy than a single engine.... drive it till it dies all together, break it in in a more appropriate modern way and be more careful with the details, burning off the fuel in the crank case, making sure piston is at bdc, beware of flooded engine to prolong the life of the owb and pull start. Im sure and positive id get 10 gallons without issues till the whole thing melts and falls apart at once lol, i would have got my money's worth happily
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