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Old 09-16-2008, 09:02 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


(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, 11:53 AM   #2
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I'm no expert, but it sounds like you might have an air leak.

Double checking the obvious, have you changed glow plugs?
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Old 09-16-2008, 12:16 PM   #3
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If it dies when you go full throtle it means you're rich, lean (screw in) the high speed nedlle 1 hour at at time until you can stab the throtle without it dying.
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Old 09-16-2008, 01:07 PM   #4
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When i ran the IGT'S after 10-or-12 Tanks the O-Rings in the top end needel
and the idle needle got very loose.
When i gave it gas to move the vibration moved the needel settings drove me crazy until i changed the o-rings.
There is a kit that offers all the o-rings and some extras.
Check that and see if it's your problem.
you can do a quick check if the needels move very easily with a screw driver then this might be your problem.
Hope it helps
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Old 09-16-2008, 01:41 PM   #5
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I'll double check all the O-rings tomorrow. I know it's not running lean, cuz I've tried virtually every setting the carb has to offer, and the result is almost always the same
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Old 09-16-2008, 03:58 PM   #6
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have you tried leaning out the low end needle, sounds like it's to fat on the bottom end.
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Old 09-16-2008, 04:11 PM   #7
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Here is the easy solution. Take it to the local Hobby shop you bought it from and I'm sure they will be more then happy to lend you hand.
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Old 09-16-2008, 05:52 PM   #8
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Both needles have been leaned and richened, leaned and richened and then leaned and richened again, more times than I care to recall. The problem is, the truggy wasn't bought froma hobby shop, but a retailer on ebay.
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Old 10-22-2008, 11:17 PM   #9
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Lawson I feel your pain..... I had the same problem when I first got my Kyosho GX21 engined buggy a few years ago... now since the GXR28 uses the same carb I can tell you exactly what the problem is as I spent weeks pulling my hair out trying to tune it!!
Someone else hit the problem dead on... it is the inner o ring on the low speed needle leaking fuel past it into the engine!! what happens is you have 2 o rings on the low speed needle, a small one on the inside and a larger one on the outside... the small o ring stops fuel poring into the engine and forces it to go through the needle as it should, when it leaks no matter how much you adjust the settings it will just keep pouring too much fuel into the engine hence it will never tune and run way too rich all the time, I worked this out by sitting down one night after weeks of trying to tune it and figured out this must be the problem! DO NOT USE THE STANDARD KYOSHO O RINGS!! they are too small and that is why you have problems with them.. my advice is (as I did) find a good o ring shop and take the original ones down with you or the needles and carb so they can measure them and replace them with better quality o rings... since doing that I have never had anymore problems tunning the buggy, hope this helps you with your problem
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Old 10-22-2008, 11:59 PM   #10
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Yes aussie you are absoutly right and also change the O-rings in the high speed needle also, the problem there is, the High speed needle will just screw itself out also,due to the O-rings not handling the heat and wearing away and becaming a loose fit, to the eye it will look perfect. get metric size O-rings they work great, dont panic when you have replaced the Rings and when you go to screw the needle in and you see the ring a little on the larger side just crew the needle in slowly maybe use a little after run to lubricate the rings so they dont tear or pinch when screwing the needles back in, this what is needed for the GXR28 Motor, the standard rings are crap, rubbish etc. in the end you find the Needles will be a little harder to turn, but they wont unscrew with all the vibration from the motor, then you will fun againand enjoy the inferno,great car to bash around.
hope this helps.
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Old 10-23-2008, 02:59 AM   #11
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I had the same problem with one of my motors, can't remember which one. But I did notice the needle was very easy to turn. I mean, you could turn it with your fingertips no problem. But it didn't dawn on me until one day while trying to tune, I noticed the high speed needle had gone flush and I knew I didn't set it there. So that was when I ordered a bunch of o'rings from ashford hobby and he helped me get the right ones. After replacing them, the problem was gone. And, you needed a good grip on the screwdriver to turn the needles.

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Old 10-23-2008, 07:05 PM   #12
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My method (right or wrong) is to 1st get her running and try to make high speed runs rich at first, it will spit and spudder with lots of smoke, it will usually die and need to be restarted several times. I gradually lean out the high speed till is starts picking up, and some of the heavy smoke disappears. You can hear the differance from a low sputtering growl, to a more high pitched whine.
Then I tackle the low speed needle, I'll tell you what the late Ron Paris told me, when you have a nitro engine running at idle, if it dips in RPM's and keeps dying, its too rich. it should be a consistant RPM, not drop off. You may have to adjust the carb stop to make sure its idling high enough also. The way to tell if the stop is set correctly is if you hit the brakes and it dies right away, the slide is closing too much making the carb barrell opening too small. Get this set right then listen to it idle, it should be a nice smooth tone without dropping RPM or ingaging the clutch. In all its a careful balancing act to get the needles set right, a temp gun helps to further set the needles for optimum performance.

Last edited by hobbipro; 10-25-2008 at 06:17 AM.
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Old 11-11-2008, 05:59 AM   #13
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Hello Lawson, Im curently having the same exact problem. I check the low needle oring looks find to me, but when i look into the carb i see its spiiting lots of fuel in it. can get it to run right and when i lean it. the idle increase instanly HIGH never go down and die. carb stop setting is almost close! then i found that the high speed needle oring is thorn. Im going to change both high and low needle orings and keep you posted if it fix it. im curious on what the status on your delema.. by the way i just bought this car too i never had fun with it due to this problem i have the kyosho Inferno audi GT2 GXR28SG engine paid $499 and not happy so far im new in this hobby.
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Old 11-21-2008, 01:02 AM   #14
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Hello ,
I have the same problem, so that i want to change the o-rings but here there isn't any shop that sells o-rings so that i must buy it from web , but i don't know the dimension of the o-rings that i need. Can you tell me where can i buy the o-rings and what must be the dimensions that will fit for the lsn & hsn.
Thanks .
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Old 11-21-2008, 02:56 AM   #15
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Sometimes at the races when getting these kinds of problems I cut of a small piece of a fuelhose to use as an O-ring
Speed is only fiction but a 130+km/h MRS4 is for real.
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