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How to tell if glow engine is finished?

Started by jdquinn, February 12, 2018, 19:03:22 pm

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jdquinn

As per the title I have a little .18 pull start glow engine in a HPI Bullet buggy.  It's not doing so good. 

I bought the car in well used condition without seeing it run, it did have reasonable compression so took a chance on it.  The only fuel I had at the time was some 5 year old 15% heli stuff so I put that into it.  After a lot of tuning I eventually got it running somewhat reliably and was pleased with it apart from the smog spewing out of it.  I assumed this was due to the extra oil in heli fuel so bought some 25% car fuel from my lhs.

Since then I really struggle to start the car.  When it starts I can't keep it going.  I thought I knew how to tune glow engines with previous heli and plane experience but I just can't get this thing dialled in at all.

I have a .46 aero engine lying around and tried turning it over by hand on the 8mm crank but couldn't get it past tdc.  The car engine is quite easy to turn over by the crank.  I don't know if this is because of the smaller capacity and naturally lower compression to allow for the high revs.  Anyone any ideas?

My inclination is that the engine is just too long new. :-).  I think the extra viscosity of the heli fuel is filling the wear gaps and allowing the engine to run.




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FrankS

Have you checked the plug, the other day my Laser was playing up, plug was showing 2amps but it didn't want to now. I went through all the checking fuel pipes etc etc in the end I pulled the plug out and at 2amps there was no glow, changed the plug and it's running better than ever.

jdquinn

Yes, the plug is good. I tried several plugs as I was thinking the same.


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Martyn Griffin


itsme

Quote from: jdquinn on February 12, 2018, 22:28:26 pm
Yes, the plug is good. I tried several plugs as I was thinking the same.


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First, feel the crankshaft (turning by hand) is there any looseness at tdc? If it feels ok take the head off and check the piston and liner. If it is ABC look to see if the chrome has worn off. If it is a ringed engine look for lines or scratches on the liner. All begins can be repaired, but there are limits as to how worthwhile that is. Check for leaks around the carb and backplate.

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itsme

Quote from: itsme on February 13, 2018, 09:13:45 am
First, feel the crankshaft (turning by hand) is there any looseness at tdc? If it feels ok take the head off and check the piston and liner. If it is ABC look to see if the chrome has worn off. If it is a ringed engine look for lines or scratches on the liner. All begins can be repaired, but there are limits as to how worthwhile that is. Check for leaks around the carb and backplate.

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That's 'engines' not 'begins'

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jdquinn

There is a leak on the carb barrel as it's a slide barrel not rotary but it takes considerable pressure to make it leak.  Backplate is sound.  I'll check the others tonight.


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itsme

Quote from: jdquinn on February 13, 2018, 11:04:10 am
There is a leak on the carb barrel as it's a slide barrel not rotary but it takes considerable pressure to make it leak.  Backplate is sound.  I'll check the others tonight.


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Its more likely to be just worn- ABC with the chrome worn (new piston and liner needed) or ring shagged. (new ring if you can get one) Think I would just put my hand in my pocket and buy new.

jdquinn

A new non oem direct fit replacement is only £37.  It might not have the same theoretical power output but it's more power than I have now.


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itsme

Probably cost you that in bits...

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jdquinn

Ok, I've just pulled the engine apart and if it wasn't already gone it definitely is now!  I just couldn't get the sleeve out to inspect the piston.  The cable tie trick worked eventually but only to raise the sleeve above block.  I sprayed oil and warmed it in the oven but only BF&I did the trick.  Anyway although it's destroyed now there is signs of deterioration on the sleeve and piston but not through the chrome yet.  I'm fairly confident the engine was toast anyway.  New piston and sleeve is almost £70 so I think a replacement new engine is on the cards now.


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itsme

Quote from: jdquinn on February 13, 2018, 23:12:12 pm
Ok, I've just pulled the engine apart and if it wasn't already gone it definitely is now!  I just couldn't get the sleeve out to inspect the piston.  The cable tie trick worked eventually but only to raise the sleeve above block.  I sprayed oil and warmed it in the oven but only BF&I did the trick.  Anyway although it's destroyed now there is signs of deterioration on the sleeve and piston but not through the chrome yet.  I'm fairly confident the engine was toast anyway.  New piston and sleeve is almost £70 so I think a replacement new engine is on the cards now.


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oven for half an hour and it should pop out. But an ABC motor should be tight at TDC and if yours was not then its a new piston and liner. Not worth the hassle, nice shiny new motor!

jdquinn

Definitely not tight so new motor being ordered today.  Thanks for help.


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jdquinn

New motor arrived from HK.  It was supposed to be a EG Sport .18 with a 12mm SG crankshaft.  What arrived was a Vertex .18 with a standard short threaded crankshaft.  Quite annoyed at this as I was looking forward to a fresh motor install.  HK are refunding me plus I get to keep the engine which is some consolidation.  I'm contemplating swapping the crankshafts as my original is in reasonable shape.  I don't have any precision measuring instruments to hand; what's the chances it will swap out?


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PDR

Pretty well none, looking at the photos. Even if the shaft sizes are the same and the crank-disk to front-bearing distances are the same it's unlikely that the shaft ports are going to be similarly sized or positioned. These are front-induction engines, and the size/position of the shaft ports determine the induction timing, which in turn determines whether the engine will even run at all (let alone have power or throttling). You will also need the crankpin sizes to be coincidentally identical, and of course the drive pin on the back of the crank pin to be similar enough to engage with the starter.

Nothing's impossible, but it is very unlikely.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

jdquinn

Just stripped the new engine to compare shafts.  Although the overall length of the block is similar the two cranks are very different.  I now have to look for in gumtree or eBay for 'rc car in good condition, needs engine' :-)


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jdquinn

Well I found a solution, it's possible to buy a full replacement clutch to suit this engine and my car for little more than a tenner.  So I got a full replacement engine and clutch new for £13.00. Not bad! :-)


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