Losi 3.4 killing plugs without prejudice

[Johnny nitro]

Long story short my losi 810 small block 3.4 is killing plugs regardless of brand, fuel, colour or religious beliefs ...I've tries everything from tuning slightly rich to slightly lean...I've even got a priest to bless my car:lol:......and nothing.

Here's a close up pic.

[badger906]

well there isnt any hint of burnt fuel on that, so it means its very lean!

even if the needles are set to factory you could have a massive airleak causing it to run lean

[Johnny nitro]

Would a air leak cause the coil to be distorted like mine is at the 1 o'clock and 5 o'clock positions in my picture (look carefully)

[Feisty84]

Block up the carb air inlet and exhaust with your fingers and connect some spare fuel tubing to the fuel nozzle on the carb. Blow air down the fuel tube and use some soapy water on a brush to find if air is escaping from somewhere... Common points to check would be the carb o-rings, pinchbolt area, backplate, and front drive bearing.

[Feisty84]

Yeh an airleak could cause that if it was severe enough and I would have thought that you'd get a certain amount of running-on when you ease off the throttle. Also forgot to mention the air leak test will need the piston at top dead centre to work.

[badger906]

thats basically been cooked

a healthy glow plug that just gone through age, should be brown or black at the bottom, where fuel has burnt onto it, yours is clean, which means the fuel is basically vaporizing

[Johnny nitro]

Only issue I've had with it is that It doesn't return to idle straight away after a high speed run....it doesn't move on it's own it just has a high rev sound for about 3 seconds then it settles into idle again.,.is this running-on?

Edited May 3, 2011 by Johnny nitro

[dja1000]

I consider this to be the HSN being too lean, where after the high speed run the engine continues to run lean until the carb shuts restricting the air/fuel?

If it was me i would richen both by 1/4 a turn and see how it goes from there, leaning only when the engine is hot ie. after a full power blast at idle the temp goes down.

Edited May 3, 2011 by dja1000

[Dazmania]

I am too suffering from plugs blowing for fun, which I can tell you isn't fun at all and becoming very expensive now with the ratio being 1 plug per tank!

I have tried a variety of plugs now and still find my plugs are blown when I stop the engine. When I remove the plug, they are as clean as a whistle and from what I have read above, I may have an asir leak!

I am now contemplating buying a new engine just so I can start again but only had my Hyper 4 months, where am I going so wrong?

[dja1000]

if in doubt richen both needles 1/4 of a turn, watch the temp get some water and drop it on a drop at a time if you have not gun.

Watch the way it idles.

In my experience an air leak is most evident at idle? someone will tell me i am wrong but when my GO engine leaked it gave a poor idle that would speed up and down.

A good idle is fast initially then slowing after 10-15 sec to a gurggle, but not too much it chokes and cuts out. I can idle for a couple of mins before it loads up and dies.

Edited May 4, 2011 by dja1000

[Feisty84]

I knew my GO engine had an air leak when the piston melted.... :rofl:

[dja1000]

I knew my GO engine had an air leak when the piston melted.... :rofl:

I had a Go.25 in my Caster RTR and the engine was shocking, in fairness the exact same engine is fitted to my Dads Ishima and he used to abuse it, and it was as fast as any engine i have seen since and they are supposed to be the same!

Would not have one again, did not like the poor support or the way you tune them. Other people like them though

[Johnny nitro]

Just had a spare few hours so I did the air leak test, turns out the carb slider bellow has a split in it and I'm also getting a MASSIVE air leak from the front bearing....I've ordered a new bellow but I'm at a loss as how to fix the leak from the bearing

[ADW]

I have a Go 25 and it runs very hot, could this be as a result of an air leak. (i,m running it rich) How do you check an engine for air leaks?

[Feisty84]

You can leave the engine in the car to check for a leak, although its easier to remove it. All you have to do is block up the exhaust and carb ports and use some spare fuel tube to blow air into the fuel nipple. At this time you should use a brush with soapy (washin up liquid) water and brush over areas like the front bearing, carb pinchbolt and slider, and the backplate. (just to name a few common area's)

If the area is leaking then bubbles will appear in the soap mixture. I think its quite common for engines to leak a bit from the front bearing although the only fix is to buy a new bearing.

My GO .25 only had 5 litres of fuel through it before it blew and it was a sod to tune. running spluttingly rich and smokey one minute, then with the vary smallest of adjustments it'd all of a sudden be running stupidly hot and it also used to carry on running by itself when it was up to speed. Used to have to use the brake to slow it down so it would shut off. Oh well, guess you live and learn. lol

[ADW]

Hi Feist84,

Thanks for response

I have had 2 GO .25 engines (came with RTR) and have had similar problems, Running rich then turn needle less than 1/8th of a turn and the engine runs lean and starts cooking. They seem impossible to tune correctly. They also tend to go through a lot of glow plugs. How is the Caster ZX1.5 going for you?

Rgs,

Alan

[Feisty84]

Yeah as far as the buggy is concerned its all going great. Got another high torque metal gear servo for the steering, and moved the stock metal gear servo to the throttle. I bought the front sway bar kit, a high downforce wing, and some Nanda racing tyres (the chunky looking ones) Also bought an Argus A52 .21 competition engine (great value at

[Feisty84]

Forgot to say, a bit more regarding the engine engine...

If you are planning to try and resolve the problems with your GO engine then i'd firstly advise the check for an air leak. The more experience I have gained about it makes me think that the way it behaved in my buggy must have been to do with an air leak.

My engine used to leak air at the front bearing and it may be that you require some better quality bearings to deal with this. It also leaked a small amount from the carb slider (not so sure how to deal with that)

Also run the engine rich enough to keep the temps down to around 240F. I managed this with the stock pipe and it ran well enough. The HSN was a tad in from flush and the same with the LSN. Richen both needles right up until it begins to splutter, so the pull away is a bit hesitant and it still runs at reduced performance at full throttle. Lean off the HSN just enough so the engine is able to clear the rich idle and get up to a decent speed but with a healthy level of smoke. Then lean off the LSN just enough so you can get a clean pull away after idling for 10 seconds. You should also be able to see a detectable level of smoke while running at low speeds. With these engines I think you need to do the adjustments in very small increments to get it right. Double check the temps after a high speed run and be prepared to richen it slightly if the temps have crept up again.

When my engine blew it also happened to coincide with a new JP3 exhaust pipe (I did set the needles back to factory to retune) and the fitting of a new blank backplate to remove the pull start backplate. Due to that it was difficult to diagnose exactly what made it go pop. lol

In my case I was struggling to get a tune and keep the temperatures down with the new exhaust. This resulted in the piston starting to melt around the gudgeon pin... which then caused the conrod to pull the piston down at a dodgy angle... which then made the piston collide with the exhaust port (ouch )

When I removed the glow plug to see what was going on, the coil was replaced by beads of alloy lol. It then turned out that these little beads of alloy were all over the inside of the engine too..

The conrod had been chaffing against the backplate too although it moved freely enough when I installed it. Must have been the gudgeon pin issue.

I'm aware that chucking more money at it isnt ideal.. especially when its over

[ADW]

Hi Feist84,

Thanks for update.

I have 2 of the Caster ZX1.5R RTR and i'm very happy with the buggies. I bought the second as a back up but apart from using the engine the second one is almost new. I've decidied to convert this to electric so going to order the conversion kit. The drive train and diffs take alot of abuse and the wear rate is low. The Caster servos are not the best and gave me problems so I replaced them with savox (252's). Savos servos are excellent quality and have never given problems. I had the piston and liner repalced in the Go engine but still impossible to keep temp low. Will have to check it for leaks in paticular the front bearing. I have also replaced the pull start with the back plate. If this fails will have to look at replacement engine. Probably would get combo (engine and exhaust). Have heard good reports about the Alpha combohttp://www.apexmodels.com/gbu0-prodshow/21-BT5PA-Z852AP.html

Rgs,

Alan

[Feisty84]

Also give this some careful consideration:

http://www.m-k-racing.com/product_info.php?products_id=8237

They are based on the Alpha design and have recieved nothing but praise from all the RC forums i've been reading.

If you can get a combo with the Alpha pipe (or Argus's own version of the Alpha pipe then you can get excellent run times.

Cheers, F

[Johnny nitro]

In a effort to check my front bearing I stripped my engine right down to the mill..and I can quite clearly see light through my bearing....is this normal?

[Feisty84]

Looks bad to me.

[Johnny nitro]

After a long wait for parts (2 months was ridiculous) I rebuilt my engine with new front bearing and bellow, checked for airleaks and all was good..put in a brand new os8 plug and one tank later POP bye bye plug, this happened for all my remaining os8 plugs 4 in total and I was less than happy.

While this is happening another guy comes onto the field wielding a hyper9 and upon hearing my "displeasure" with my losi come over with a osr5 plug saying "this won't blow mate, thank me later" my first thought is "smug ******* I'll show him" and for the first time I fired up the 810 actually hoping the plug would blow so I could show this flash git he knows nothing lol.

Turns out he did know something and some months later it's still going strong on the same plug!, last night I even put in a os8 just to see if it would still blow..which it did after one tank.

Weird huh?

[jony nitro]

Ah peace at last for you

Edited October 8, 2011 by jony nitro

[kingscott]

My Gxr managed to loosen it's own head over time!! I had the same problem. nipped it up and its now fine.

I had all sorts of issues regarding tune, temps and eating plus. I only noticed what the problem was finally when the car lost control at full pelt a twice when out!! when I started to strip the engine the head was not tight, the air must have been getting in the "head gasket".

How it ever ran is beyond me, but its ok now.