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Old 06-04-2003, 03:04 PM   #1
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Default Pixy help

ok i had a big airleak and for the most part have fixed it. i used a little sealant around the carb and boom idles fine...or so i thought. now it idles but i gets these little "bursts" if air leaks that cause it to lean then idle right then lean etc etc

whats going on here, where is the last part of my leak?

also when it leans if i goose the throttle and bring it back down to idle, it idles right...as if burning out an air bubble
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Old 06-04-2003, 09:03 PM   #2
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need more detail to help you, how hot, current needle settings , car type, Pipe type.

you might need to richen the low end slightly.
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Old 06-04-2003, 09:50 PM   #3
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its a tc3 with the run of the mill rear exhaust made by AE

richen it? it was running at 170


friggin pixy, i hate this engine. nearly 6 months of owning it and i cant even get a friggin run out of it.


i got another one for you, i changed to a longer back pressure pipe as someone told me might be my problem, it basically made the car totally lean out everytime it ran and even when i switched back it still did it?

also what gasket do i need? ive been using the mugen 12 gaskets, which is what was leaking today(somehow) and then i use the mugen 15 gasket which still leaks....almost tempted to break down and buy the dynamite pipe even though i hear its garbage
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Old 06-04-2003, 10:05 PM   #4
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You know everyone always wants to blame the engine LOL

Q does your fuel tank look like a margurita blender when you hold the car and rev it up good??????????
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Old 06-04-2003, 11:48 PM   #5
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i have to blame it, ive taken apart all my engines, bought new ones and put them all together. all run fine

this one has never been touched and it sucks for reliability for me



yeah i think it does, i just know it splashes because its hard to see from above when its idling


also, what gasket? im going nuts with the gasket
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Old 06-05-2003, 09:47 AM   #6
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Default Do you shop at hobby city in Vacaville

Are you the andrew from the store in Vacaville?
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Old 06-05-2003, 10:51 AM   #7
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I may doing the wrong thing here, but with the pixy (3-port) i just got on my 705, i add another shim (total of 0.4mm thickness in size on mine now, stock is 0.3mm thickness) and ran a colder plug like MC-9, with a 30% nitro fuel and the new Legal RD Pipe (kinda long on the header). It ran OK, but seem to become lean in the bottom or somewhere after about 4 mins of racing on track (sound like the engine going to die at idle and i gotta keep pressing the trigger to wake the engine) and i lose top speed if i richen the top. If i richen the bottom, its hard for me to start the engine up when cold, it just won't fire or idle. The worst part is, if my engine die after about 5mins of racing on track, to start it again is so darn difficult, it just don't fire up. And my temperature max after 5 mins is between 250~260 range.


Motorman,
Any clue whats going on here or what mistake i made here? Do i have a hydrolock here or do i have a leak somewhere? The engine already have about 9~10 tanks through it preparing for big series race here, if not, i just have to swtich back to my novarossi base engine.

Last edited by nizee; 06-05-2003 at 10:59 AM.
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Old 06-05-2003, 08:42 PM   #8
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nizee, have you tried a hotter plug? It seems this is what we use to solve the Pixy problems. Apparently, you need a hot plug to be able to cope with the fuel mixture.
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Old 06-06-2003, 08:13 PM   #9
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Quote:
Originally posted by InitialD
nizee, have you tried a hotter plug? It seems this is what we use to solve the Pixy problems. Apparently, you need a hot plug to be able to cope with the fuel mixture.
Maybe i try it tomorrow and see how it goes.
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Old 06-08-2003, 11:10 AM   #10
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Heres the problem. THE HEAD CLERANCE IS WAY TO HIGH. All pixi's have this issue, the compression is really low, way to low. Stock the head clearence is like .031 thousanths, suitable for a 21 but way to much for a 12. you need to be around .018 on a pixi. Herein lies the problem. if you put a .004 shim on it you can only reduce it to .029 this is way to high still. I had to alter my head button in a lathe to correct htis problem by cutting the register so it would sit deeper in the cylinder. it needs about .015 taken off it where it sits on the liner and then to be reshimmed to get .018. you could go with the .004 shim and lap .005 to .008 off the top of the liner by lapping the top of the liner with 125 wet or dry paper and some oil.

To much head clearance makes you have to run the engine way to lean to get it to rev properly and consequently it kills plugs and overheats the crank and causes it to vaporlock and die. If its in a TC3 you have double trouble because of that cars fuel delivery issues and propensity to dump exhaust heat down the carb because of the way its organized in the car.

you need to measuer the head clerance as the shims installed mean diddly. everyone assumes that with all of them removed the manufacturer has machined it for zero head clerance without head shims and this is just not so in most cases.

A hotter plug will help as it will advance the timing which usually requires a richening of the engine. however you need to address the root problem.

Dennis
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Old 06-08-2003, 07:55 PM   #11
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Thanks for the advice and tips Dennis. Really appreciate it.

I kinda solve erratic tuning problem only to notice i have leak on the carb. I seal it and now it ran great, well kinda, I have the above setting on my previous post which about 0.4mm shim in total (way too much from what u state) and change to hotter plug. I'm running the Serpent 705 on it.

The problem now i ran for 15mins (plus maybe about 3 mins warm-up time) main last weekend, the engine seem to have ran ok, but towards the last couple of mins, the engine seem to hesitate in the bottom or somewhere (kinda like when i press the trigger, its hesitate for a while slowly reach RPM then blast to top speed). I HAVE my main needle at 5 1/4turn and lower needle at 3 turn now. Any idea what i did wrong here?

I will try your method this weekend. Put only 0.1mm shim in there and sand off about 0.127mm to 0.2032mm from the top sleeve. Hotter Plug?
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Old 06-08-2003, 08:53 PM   #12
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just set it up to .018 to .021 (measure the head to top of liner and the register to the base of the head button and subtract. add appropriate shims or remove appropriate material to get there)and use an odonnel 77 plug if you can get one. it will tune up easy.
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Old 06-08-2003, 10:33 PM   #13
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HI Dennis,

What about Novarossi, what head clearance, 0.016 to 0.018?

I just ran in the MAX, I found it to have similar performance as Rody Tuned but so far the fuel economy seems to be better. I am hoping to get better performance from the MAX (because it cost so much money) by making fine adjustment on the head clearance.

Any help is apprecaited.

tks
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Old 06-09-2003, 06:05 AM   #14
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Quote:
Originally posted by kitracer
HI Dennis,

What about Novarossi, what head clearance, 0.016 to 0.018?

I just ran in the MAX, I found it to have similar performance as Rody Tuned but so far the fuel economy seems to be better. I am hoping to get better performance from the MAX (because it cost so much money) by making fine adjustment on the head clearance.

Any help is apprecaited.

tks
Chris
Hey Chris

How much u pay 4 the MAX in HK???
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Old 06-09-2003, 08:12 PM   #15
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about HK$2200. Every hobby in HK have at least one on display so I think price will come down little bit more( may be). Been raining here fore few days so I can't really give a real performance report , just ran-in, but so far I only think is good as Rody tune.
tks
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