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Can anybody help with setting up my old Kyosho GT-12 glow engine?

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Hi! I finally figured out how to log into the forum! How's it going everyone?

I have a question about an old Kyosho GT-12 glow engine. I've recently started running nitro buggies (you may have seen my Mardave Marauder) and I'm having trouble with setting my engine up.
After a lot of tinkering I've reached a point where I'm not sure what to investigate next. The engine fired and ran fine but after shutting a wide throttle opening the engine would die. I've tried different fuels and glow plugs but it's now at a point where it only runs with the starter on the plug. I fitted an OS no.6, (a hot plug), and have tried Byron Race 20 and Model Technics Qwikfire 16 fuels. Mixture screw is 2.5 - 2.75 turns out. Compression is decent.
My understanding is that the plug is still too cool, but I'm surprised as the OS is labelled as hot. Do I need to go even hotter? Any thoughts or ideas would be greatly appreciated.
Cheers, Chris

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It's been a while since I last messed with Nitro stuff, but I'll give it a shot. (sorry if I'm being too basic)

1. Is the tank pressurised slightly when running, there should be some tubing between the exhaust manifold and the tank, the exhaust pulses pressurise the tank and it makes fuel flow to the carb.

2. Are you pull starting it or running it from an engine starter (IE is the engine turning in the correct direction, 2 strokes can run either way)

3. Is the carb and needle assembly meant for the GX12 or is it off something else.

To help diagnose the problem, remove the fuel line and keep trying it, if it runs better after a short while and then sudenly dies you're running it too rich, if it gets worse you're running it too lean, adjust the carb to suit.

A fairly worn out engine should still start and run, but a very worn motor will be a pain to keep going.

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Hi derv_scaler, thanks for your reply. Any input is helpful!

"A fairly worn out engine should still start and run, but a very worn motor will be a pain to keep going." I think this sums it up nicely, this engine must be 20 years old.

A little more background: I bought this engine and fitted it to a Kyosho Rampage, a late 80s buggy based on the same chassis as the Ford RS200. I went for it because they are reputed as good reliable engines - I wanted something that was keeping in the period, wouldn't be too fussy, and a little quicker than the OS 10 that the Rampage originally came with. Oh, and it was also cheap!

I had it running a little better today with the glow plug (unidentified) it originally came with, but it isn't keen on idling, on any needle setting. I have used silicone around the carb joint to seal against air leaks, and I can't see any blowing around the cylinder head, but there is a small weep of oil from the output shaft - between the bearing and flywheel.

In answer to your questions,

1. The tank is pressuried

2. I am pull starting it, it is turning anti-clockwise

3. Carb looks original, but unsure on it's history. I'll do the richness test tomorrow

I've bought a couple of plugs to try - an Enya #3 and a Taylor, with an idle bar, as an experiment.

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How old is the fuel??

Does the fuel work ok in other motors???

If its a tired motor, then up the % nitro and see how you go.

I love the smell of nitro from rc cars………………………………………………...

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Hi Cowboy,

Yeah I'm enjoying the smell, the noise, the fumes, the oil over my clothes...! I'm a big fan of the internal combustion engine, and it's really satisfying to work on these little two-strokes.

The Byron fuel is brand new, the Model Technics 4 months or so. Both run in my Irvine 20, in the Marauder.

Does upping the nitro increase the fuel's combustability? Does it increase it's running temp? Maybe I should get a thermometer...

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That's the basics out the way then :)

Funnily enough I was basing my experience of Nitro motors on a Kyosho RS200 I had years ago with an OS10 in it.

The output shaft seal leaking points to a worn or perished crankshaft seal, if oil is getting out then you can guarantee that air is getting in, this leads to a lean mixture and you can only compensate for this with the mixture screw so far as the cases themselves will expand and contract with heat at a different rate to the steel bearings, in addition to a weak mixture you'll also suffer from what's known as 'secondary compression' which is the engines ability to breath in fuel/air mixture from the carb into the crankcases.

Full size 2 strokes as used in motorcycles suffer the same.

My advise would be to get a new crank bearing/seal and an o ring for the carb body (if it uses one, I can't remember as it was over 20 years ago I had the RS200)

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Upping the % nitromethane does several things. It increases the calorific value of the fuel. ie the fuel air mixture when ignited will produce more heat and so will produce greater expanding power within the confines of the combustion chamber. ( same reason they use nitromethane in drag racing cars, more horsepower = faster 1 / 4 miles ) However, increasing the % nitromethane ( all other things being equal ) can lead to the fuel air mixture igniting earlier than it did with the lower nitro fuel. This is where your hot / cold plugs enter the equation. It takes time for the fuel and air mixture to burn. Ideally you want the greatest rate of expansive force occurring as the piston starts its downward journey. Hotter plugs help start the combustion process earlier than cold plugs. Its a bit counter intuitive, but you normally get better top end ( high RPM + HP ) with higher % nitro and a cold plug. Back to the issue at hand, how old is this motor??? I've got an old burns with GS21, and compared to its older Vanning brother with an ancient OS21, I"ll take the start-run-refuel-run-run-clean challenge with the older OS any day of the week.

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Thanks for the info guys. I've got a few old motorcycles and the first rule when restoring an old stroker is 'change the crankcase seals'. I'm going to get a set of two bearings and change both, once I've managed to get those tiny siezed screws undone... The engine is, I estimate, 20-25 years old, these were fitted to the Sandmaster in the early 90s and I guess my example was pulled from one. It's going to take a while to source some seals and get those screws out - watch this space.

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Okay, so I've cheated a bit and bought another engine - an OS Max CZ12 SE with some nice hopups, and on the test bench it ran like a watch.

A really loud, smoky watch, mind you...

I'm still determined to get the GT12 running though! I'll update as and when, cheers guys.

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Progress is progress :)

Whenever I need bearings and seals for something I measure the existing ones and see If I can match them up elsewhere, the majority of the time a standard size is used so while the bits might be hard to get hold of from OS you may find them elsewhere.

Got any pics of the car in question?

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Is your glow plug battery fully charge? It seems you have fresh fuel, new plugs, compression is ok and for the carb needle setting, use you ears to hear how the engine is doing, maybe is doesn't need the 2.5 or 2.75 turns or may needs more. The final solution, without installing a new engine is to bring it in to a LHS or your local nitro track where the guys there should be able to help.

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I haven't yet been able to undo *any* of the screws holding this little engine together, they are tiny button crossheads and I just can't get the leverage with my little screw set. It needs a soak in WD40 or nitro fuel and some screwdrivers with bigger handles I guess... If I ever get them undone, I'm definitely replacing them with hex heads.

Here's a question: If the outer bearing also acts as a crankcase seal, would a universal metal-shielded bearing be sufficient, or are purpose-made OS ones airtight/oiltight?

I really just need to get it apart to diagnose the issue I think.

Tamiya 1/10, I have tried the carb needle on many settings, at the last run it would idle for about 3 seconds then slow down and need a blip of throttle. I noticed it would bog down easily under load as well. I haven't dismantled the carb yet - that could be the issue.

Derv_scaler, I haven't yet looked into how to upload pics - I'll get on it.

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Re your bearings:- unable to recommend placing shielded bearings in place. The balls are spinning pretty fast, they probably need all the caster / synthetic lube thats misting around for a reason. Its not too difficult to remove the shield, its normally just held in place with a thin wire clip. I've had some luck removing the clip with the sharp edge of a box cutter, once its pried away from the inner lip of the outer section, grab it with some pliers and your done!!!

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Here's a tip for getting stubborn screws to undo, boil a kettle full of water and pour it slowly over the part (in this case the engine) - this will get heat into both the part and screws, plus any thread lock that may have been used, the heat causes the metal parts to expand (and thread lock to soften) and as different metals expand at different rates it will help loosen the screws off.

I agree with OZ on the bearings, you need to use rubber sheilded bearings for an air tight seal, you can usually pick 1 of the seals out to allow lubrication to the inner bearing race whilst keeping the outer seal intact and air tight.

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This is all good information. Heat is the answer here - of course. I understand now what you mean Oz, to remove *one* of the shields, not both! Rubber was what I thought would be more suitable for an airtight seal...

I do need a decent small screwdriver set first - I've been getting by with a cheap watchmakers set for a long time...

Um, not really suitable.

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I picked up a set of cheapy screwdrivers from Maplins (of all places) and have found them to be very good with decent handles so you get a nice amount of torque and the tips are tough enough to withstand a good bit of torque.

http://www.maplin.co.uk/p/rolson-15-part-precision-screwdriver-set-n25cx

Just noticed they're on special offer, I paid £9.99 :ouch: - only of use if you're in the UK though....

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Here's a few pics. OS CZ currently fitted, the last pic is the rather sad-looking GT. I intend on getting a new body shell soon too.

post-38902-0-21399400-1416433465_thumb.j

post-38902-0-21063500-1416433533_thumb.j

post-38902-0-74187500-1416433679_thumb.j

post-38902-0-47430700-1416433698_thumb.j

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