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Old 09-16-2008, 09:01 AM   #1
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Default Kyosho GXR28 - Tuning Problems :(

I'm having an absolute nightmare of a time trying to tune this engine, It's fully run in (10 tanks or so through it) and I was hoping to be able to have some fun with it. The thing is constantly stalling, occasionally at idle, but usually as soon as I try to give it some revs. Depending on the carb settings, I can sometimes drive it around at low speed for a while, but it keeps spewing a load of fuel out of the exhaust, then gives up and stalls on me again. Full throttle is unthinkable! Instant stall.

I've read through 2 or 3 tuning guides on here, and been as accurate as I can with the carb settings (if it says to adjust by 1/8th at a time, I've been doing 1/16th just to be sure I don't miss a sweet spot) I've literally spent hours per day for the last few days just adjusting and trying again. I've had it from very rich, to very lean, and back again. And still the problem persists!

This is only my second nitro care, and the first required almost no tuning. So my experience and knowledge is limited, to say the least. It's with this in mind that I ask, is there something I might be overlooking? Or possibly something that I'm likely to be doing wrong?

I'm so sick of this damn car stalling and dying on me that I'm about ready to give up, I really am desperate!

Please help!

Many thanks in advance

James



(ps. I've placed this thread in both the off-road and on-road section as the gxr28 engine is used in a selection of off and on road cars, and I was hoping to get maximum help, if this is a problem, please accept my apologies, and could the mods delete/merge the thread/s as applicable. Thanks again)
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Old 09-16-2008, 09:34 AM   #2
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The very first thing you should do is check for air leaks. If you have one, the engine will not run well no matter what you do with the needles.
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Old 09-16-2008, 09:45 AM   #3
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Ok, check for air leaks, no problemo. I'll do that right now.

Erm, how do I do that?
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Old 09-16-2008, 09:52 AM   #4
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Read

http://www.rchobbies.org/engine-tuning.htm
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Old 09-16-2008, 10:21 AM   #5
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Ok, just finished checking, i submerged my engine to make sure I didn't miss anything, hopefully this wasn't a stupid idea and won't have donw any damage. There are 2 spots where air appears to be leaking, but I'm not sure how important they are, I'm going to upload a picture now, should take 2 or 3 minutes
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Old 09-16-2008, 10:31 AM   #6
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Ok so here's the engine



As you can see, it's leaking from behind the silver wheely thing (quite possibly not the technical name for it) well, between the silver wheely thing and then engine.

Also bubbles were coming from the throttle pully thing. that attaches to the servo rod. It looks like it was coming from the end, but it had that black squashy thing on, so it's hard to be sure.

I also checked the fuel system, which had no leaks whatsoever.

Are these leaks on the engines problems, or are they normal? And if they are problems, how can i fix them, they both seem to be kinda in awkward places

Thanks again
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Old 09-16-2008, 10:53 AM   #7
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Front bearing is leaking. Gotta replace it. By the way, the "wheely thing" is the flywheel.

The other leaks are coming from your low speed needle. Possibly the o-ring is torn. Unscrew the needle and pull it all the way out and check the o-ring(s) for damage.

You just broke it in? How much did you pay for the motor? Just curious, I'm not familliar with it.
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Old 09-16-2008, 10:56 AM   #8
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Replace it? Damn, spending money already, it's brand new! It came as part of the kyosho st us rtr package. I've only had it 5 or 6 days
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Old 09-16-2008, 11:17 AM   #9
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On second thought if it's that new, return it to Kyosho. I'm sure they would fix it free of charge for you, being that new..

One thing to keep in mind is that RTR vehicles generally come with low-quality engines, so this isn't out of the ordinary for this to happen.
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Old 09-16-2008, 11:58 AM   #10
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Hmm, it was bought from ebay, hopefully this wouldn't matter. Perhaps I'll give kyosho a call tomorrow, I hope they have some kind of representation in the UK
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Old 09-16-2008, 12:57 PM   #11
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These engines are great as long as you treat them right.

You say you have had a gas car before but do you know how to tune one?
It is a bit of a black art and only comes with practice.As this is a troublsome engine it seems a good chance to learn.

The air leak test is great idea but there is always a little leakage on any engine so unless it is severe dont worry too much. as you are not racing at world champs you wont notice any difference.

Things to do before you do anything else.

1. Make sure you are running good quality fuel with 30% Nitro content.Model techinics or Byrone are best IMHO
2. Make sure the plug glows bright red and is correct one for the engine.
3. If fuel is coming out of pipe it shows the engine is rich (much better than being too lean) but beware most people have top end rich and bottom end lean so consider to richen the bottom end when you lean the top.
4. If in doubt go back to basic settings with the needles and check they are tight and the o-rings are ok, when you constantly mess with the needles the o-rings can get damaged. I think for that engine the main needle should be just below the needle housing and the bottom the sameish.
5.Go to a model shop, As you got this on e-bay they will charge you but they can check your engine out and repair if required.

If you have trouble with a car you go to a garage. dont be afraid to use your local hobby shop.
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Old 09-16-2008, 01:16 PM   #12
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Yeah I've mostly heard good things about the engine, but apparently they're a pig to tune. I've removed both needles and the O-rings all look fine. I'm gonna give it another try tomorrow, hopefully I'll have better results.

The fuel I'm using is Byrons 20%, and I swapped the glow plug out for a better one, as I thought maybe it was that causing the problems. I'll try it again with the original plug.
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Old 09-16-2008, 03:44 PM   #13
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Your engine will run best on 30% as per the manual!!
It will be cooler faster and live longer, In fact as far as i know most engines are designed for 30%

Good luck tommorow
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