Octane Spark plug pics...

[F-Type]

Hi

My Octance has run 9 tanks since I swapped the piston, sleeve and ring, after the first set just wouldn't run.

Here's what the spark plug looks like after having been used for about 3 tanks, tank 7-9.

 

[francis Labarbara]

Are you using bacon grease for your 2 stroke oil?
Here is my plug. It has run 1 gallon and never been cleaned.

 

[F-Type]

Nope, I am using a well known synthetic brand oil and high quality alkylate petrol.
The particles are magnetic...

I guess I need to take the ¤#"%"/¤¤/&%¤" shitty crap apart again, to see what happened this time.

 

[F-Type]

Well, this if f....ing annoying. I wonder where those metal particles comes from.

 

[francis Labarbara]

Whats ferrous in the engine? The ring is cast iron, bearings and the pin retaining clips. Not sure about the rest.

 

[Jam Racing 1]

looks like something is scraping the cylinder wall there at the top of your pic

 

[griff7373]

looks like something is scraping the cylinder wall there at the top of your pic

Also looks like your sleeve is slightly turned in the block, judging by notch in the sleeve and the pin in the block. The sleeve looks slightly turned to the left could just be trick of the lens though.

 

[F-Type]

looks like something is scraping the cylinder wall there at the top of your pic

You think so...
Well, I can assure you, something is. Check the spark plug pics earlier.
Question is where does it come from?

 

[F-Type]

I think the sleeve is OK, probably just the perspective given the height difference of the sleeve vs the pin.

 

[francis Labarbara]

After taking my plug out for the pic I put a new one in. Now it runs 30 feet and dies.

 

[F-Type]

Perhaps then if i put mine back in it will just run fine from now on

 

[F-Type]

Well, honing-brush on order. I will try to hone the sleeve of the first set first, the one that I never got running properly and now have replaced with the set of piston/sleeve you see above. Which has been running fairly well for the last 3 tanks, even 1 or 2 wheelies actually. Though still far from excellent running and 3rd gear. No wonder, of course, with these issues.

I have also measured the piston-sleeve play, and it is 0,2-0,3 mm. From what I understand having googled a bit, normal play should be around 0,05 mm on a 2 stroke engine like this. Doesn't feel like HPI has any quality in this engine, perhaps a reason so many people have so much trouble breaking these engines in.

 

[F-Type]

So, I've done some more research, and measuring on my sets of sleeve, piston and ring. What I have found out is that HPI's stuff are way off on what seems to be considered normal measurements on piston play, piston ring gap etc.

I also noticed heavy scratching in my first sleeve, mainly located directly above the exhaust ports, see photo below. Unfortunately i didn't check for burrs before I honed. But I have now checked the second sleeve, and it does have burring on the inside edge of the exhaust port.

I also took a picture showing the piston ring gap. Or perhaps I should say the piston ring barn door opening... Normal gap for a cylinder like this is 0,1mm, I measured mine to 0,35.

These issues could be the result of a sleeve with a too large inner diameter, it will give to much piston play and to big piston ring gap. Burring on the ports is another issue with the sleeve. Clearly, HPI are having quality issues here. In my opinion they now owe me two sets of piston, sleeve and ring. But they just turn me their back. Which is why the two new cars I bought the other day were not HPI-made.

In any case, I honed the original, first, sleeve, with which the car basically won't start at all any longer, at best ignite once or twice, with basically no compression at all. Having honed it so all scratches have disappeared or at least cannot be felt/get stuck in with your nail. One big can still be remotely felt but not get you stuck. It widened the inner diameter some 0,05-0,1mm, unfotunately also increasing the piston ring gap somewhat. Which made me realise that it may not run at all, just because of that.

In any case, in it went, the honed sleeve with the old piston and ring. Choke on, ignition on, a couple of pulls and it ignites once. Choke off and more pulls. Nothing, nothing, nothing. Out with the spark plug. All wet. in with another one, dry, with quite a big gap. Second pull and the car starts and runs for 5 seconds. WHAT? That's a BREAKTHROUGH! A few more pulls and the car starts again, manually increase the throttle a bit to keep it running, and it keeps running. after 30 seconds or so I release the throttle to idle, and then it dies within a second or so. Conclusion: the honing has made a tremendous difference, despite the larger piston ring gap. The engine needs to be broken in "again", and then we will see if I can get some decent power out of it this time. Unfortunately I am not too hopeful. A new piston ring with a tighter gap would be a good thing. But I guess HPI doesn't sell piston rings to be manually tuned to the optimal gap?
Of course the piston ring has some damages to, as a result of the burrs. But I didn't see any way to fix those, other than to make sure there were no protruding burrs or similar.

 

[francis Labarbara]

I can send you a new unused sleeve and piston, no ring. Let me know. Look at OS GT15Hz rings on ebay. I am pretty sure is uses the same guts as the HPI GT15c. Same bore and stroke. Same failures. Both are hobbico.

 

[F-Type]

Ok, great, thanx for the info! I'll give the two sets I have right now some more effort. The first set should work ok now when it has been honed, with the exception of the piston ring gap. But bying a new stock piston ring will probably not solve that, as I need a ring that will have the correct gap in my honed cylinder. The second cylinder doesn't have. by far, the same amount of scratching. Basically just one scratch, so with a bit of luck, that set will eventually work fine, given some more breaking in.
I'll keep working on this, and keep you posted

How come you have a new piston and sleeve without ring?

 

[francis Labarbara]

It came from dollar hobbyz and I broke te ring trying to insert the piston in the sleeve.

 

[F-Type]

Ah ok, bad luck.

I got the car started today and it ran for one full tank without stopping. I hade fixed the throttle a bit above idle in order for the car to run without stopping, as I am sure it would have frequently if I tried running it at idle rpm. It didn't run very clean, but it kept running for a full tank at least. At some points it did a real "gurgle", a real near death experience, before it caught up again. I used a spark plug with about 0,45mm gap and it looked very good afterwards. Now tonight I tried starting it again and it started without problem and ran for a short while, even at idle speed.

Even though the car is far from running really good, it seems to be running better than ever before the honing. Still just one tank through it so far, so we'll see where this goes. If it will be possible to break it in and get it running with full power in the end.

 

[F-Type]

In the last couple of days I haven't had the time to run the car. But I have started it shortly a number of times. Always ignites with the choke on in about 4 pulls. Then always starts and runs within another 4 pulls. Kind'a impressive, considering...

Tonight however I had the opportunity to run a tank. And the car runs relatively fine, considering it is only the second tank after engine renovation, running the honed sleeve. Idle set a bit high to avoid sudden death. The car jumped to second gear straight away as I drove off the first time. Didn't go above half throttle today though. Will go easy to see if it will be possible to get "full power" out of this set with honed sleeve. It did look promosing to today though.

However, the clutch bell was bad as I at a previos time mistakenly ran the car with the engine not properly fastened. So it wore out completely. New bell on order from Towerhobbies, so it'll take a week or so to get here.

 

[francis Labarbara]

The steering servo arm stripped out and then the radio went glitchy which seems to have to do with the spark plug cap.
The Octane is a lot of work for very little fun.

 

[F-Type]

Poor grounding?

 

[francis Labarbara]

Poor design

 

[F-Type]

I've seen some steering servo twitching videos. I assume it is due to poor ground connection of the spark plug/engine to the CDI/Battery, that together with the CDI mounted 0 mm away from the receiver...

So I guess that is the main reason for HPI moving the CDI away from the receiver on the V2.

 

[francis Labarbara]

The cap is made of cheap shiny crap. It is turning black (oxidizing) inside. The 2 halves are held by a wire loop and are now loose.

I have another CDI and I think it is going to be reengineered and filled with dielectric grease.

 

[L0r3x]

Speaking of twitching, I wrap my CDI with aluminum tape for air ducts. I also put an aluminum plate between the CDI and receiver. After that simple fix, no more twitching for me.

 

[francis Labarbara]

I am getting link loss on the radio that goes away if you twist the spark plug cap.

 

[F-Type]

At one point i made a ground cable that attached between the spark plug and the engine using an eye terminal, the other end attached directly to the spark plug wire using a cable tie. I think that is the best way to overcome the grounding problem. Or to fasten it to the engine with a bolt, making a threaded hole in one of the heat sink flanges.