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Old 04-13-2003, 10:16 PM   #1
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Default Strange problem

While i was racing today i noticed that my car, even though i had it on full throttle, was barely moving. So i checked it out and it looked like the fuel tank was the problem because i noticed something inside where the primper pump goes down, plus it had a hairline crack underneath the tank. So i got a new tank (not the same type as the original, but it was from hpi and it fit the car). Right away i noticed that it primed better and only took a few pumps to get fuel to the engine whereas in the old tank even though i primed it it could get fuel through the line to the tank. That seemed to fix the problem, but while racing and then when i took it home and tried it out it did slow down even though i had it at full throttle. not nearly as often as it did before the new tank. Besides not getting fuel to the engine (which as far as i can tell the new tank is working fine), what would cause the car not to move even if i have the throttle all the way down? all in all the car ran great today except for this annying issue. I didnt get to finish the 2nd heat because of it.
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Old 04-13-2003, 10:22 PM   #2
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This might not solve it, but do you have it too rich?
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Old 04-13-2003, 10:25 PM   #3
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I guess you can check the belts. If your running on 2wd when your suppose to be running 4wd it will be a noticible difference.
Check the teeth on the belts. Also you could be running too lean and the engine would be cutting back at full throttle. Or you could be running too rich. Has the temp changed since the last time you ran? Make sure the throttle servo is opening up the carb. at full throttle. Also see if something is pinching the fuel lines! Or it could be time for a new Motor!
Hope this helps!
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Old 04-13-2003, 10:25 PM   #4
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if I may make a suggestion...

If you have a starter box...ditch the primer pump on the tank. Remove the primer pump thingy and put a screw in it's place. You can bump start the motor breifly without the glow starter in the engine to prime the carb.

I can only answer your question with the knowledge I DO know about real cars. You may want to clean your air filter. If it gets too dirty or clogged it will restrict the airflow into your motor. Essentially strangling your motor of the air it needs to mix with the fuel.

The other possibility I can think of is maybe your motor was getting bogged down for some reason.

Sorry if I'm not more help.
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Old 04-13-2003, 11:51 PM   #5
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Check you motor mounts.. make sure they are NOT lose.. if so. the motor may have pulled away from you spur and hence not going anywhere.. also you spur might be stripped out.
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Old 04-14-2003, 06:51 AM   #6
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Also, check to make sure that your brake is not engaging at WOT. This can happen on the HPI cars, unlike other makes, so this is something to watch out for. Obviously, don't have the engine running to test this.

It happens.
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Old 04-14-2003, 10:21 AM   #7
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Default Strange problem

Best thing to do is get rid of the Primer. Buy one of the primerless tanks next time. Put your finger over the Pipe Stinger and give the Pull Starer a few tugs to primer the engine (works on a Starter Box too).

If you have a 2spd Transmission, the One-way bearing may be slipping. Generally this is from lack of maintenance. If this is the case, replace the bearing and apply a small dab of grease inside it from time to time. (every few HOURS of running)
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Old 04-14-2003, 03:48 PM   #8
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Thanx for the advice. I am in the process of getting a primer less tank, it is on order from my lhs. I have a 4wd without belts. I maybe running it to rich, but then again, i may need a new engine. since i am new to this, there is no telling how much damage i've done to the engine. I was running it with a new filter in it when this started happening. i havent noticed much of a temp change. its running about 240 i believe. when i have it running at full throttle for a couple runs, i noticed it go up to 262.

what is WOT?

the brake doesnt seem to be engaging, although during the main event, my car went bezerk before the race and i couldnt race in the main event. i started it up and when i tapped the throttle to make sure it was working, it went to full speed and it wouldn't respond to any input of the radio. i thought maybe something may have happened to the reciver or transmitter, but when i brought it back home i ran it with no problem. so the only thing i can think of is that someone else had thier radio on and inteferred with mine.

speaking of maintenance, what is the proper maintenenace for a nitro engine? So far i know to put after run oil in it after every day of racing, clean the filters and make sure the screws are tightened. am i missing anything?

edit 7:00pm est 4-14-03:

I ran it out in my street and here is what i found. i tried to run it like i was on a track, making alot of turns, going full throttle for a few seconds, making hard turns, burning rubber, etc.

First, it could just be me, but i noticed that it cools down very quickly. i will run it hard by going full throttle for a few seconds, pausing for a second then doing it again. i did this a few times and the temp didnt go much over 240-250. if i just ran it going 1/4 to 1/2 throttle it would reach maybe 220-230. thats the first thing.

i noticed the more i turned and the harder i turned thats when it would slow down and not move, even though i had the throttle down. so what i did was try to see if the flywheel was moving when the throttle was on and i found that it wasnt. i was able to look at it when the problem happened. i had the throttle down almost all the way when it was slowing down and i looked at the flywheel and it was slowing down and then it stopped, so it wasnt moving the spur gear, but the engine was still revved up. it didnt slow down. then about half a second later, with my finger still on the throttle the flywheel started to move again thus moving the spur gear. so i guess now my questions is, what would cause the flywheel to stop moving even though the throttle is down? like i said, strange problem.

Last edited by alucard13; 04-14-2003 at 04:54 PM.
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Old 04-14-2003, 05:59 PM   #9
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Quote:
Originally posted by alucard13

my car went bezerk before the race and i couldnt race in the main event. i started it up and when i tapped the throttle to make sure it was working, it went to full speed and it wouldn't respond to any input of the radio. i thought maybe something may have happened to the reciver or transmitter, but when i brought it back home i ran it with no problem. so the only thing i can think of is that someone else had thier radio on and inteferred with mine.
I would recommend purchasing a fail safe unit for your car. It will save your car in instanced such as that one. You won't have to chase it down or risk it running directly into the wall. When it senses a disturbance in the frequency signal it will swing the throttle closed to idle and your car will just sit there safe until it's picked up.
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Old 04-14-2003, 08:17 PM   #10
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where can i get one? and how does it hook up?
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Old 04-14-2003, 09:12 PM   #11
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You can buy them from your LHS or online. If you have an M8 radio you will need to purchase one made by Dynamite.

If you own any other type of radio you can purchase any of the ones made. I personally have a KO Propo one, but I think any of them will do fine.
They're actually a very simple little thing. You connect your throttle servo to the fail safe unit and then connect the fail safe into the throttle spot on your receiver. There isn't much setup involved but you should read the instructions on setting it up.

Depending on how large your receiver is, you might be able to fit it all inside your box on your radio tray. That's how I do it, so all the stuff is protected from random fills on my fuel tank.
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Old 04-15-2003, 06:57 AM   #12
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i was looking at an r/c mag and i saw what one looks like. they are tiny. i was looking at some brochures and i saw a radio that was crystal free. how does that work without a crystal and does that mean you wont have any inteference from anyone?
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Old 04-15-2003, 07:44 AM   #13
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The radio being crystal free works like this. I believe, the receiver transmits with the radio a digital signal. It doesn't mean you won't get interference but does save the hassle of swapping crystals or wondering which ones to use when you sign up for a race.

It is a really cool idea and I would get one if I didn't already have a radio.
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Old 04-15-2003, 04:28 PM   #14
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now upon further investigation it seems as though the engine is slowing down, but only after i run it for a bit and use full throttle for several seconds repeatedly. i dont think i broke the engine in right, because at one time i had it running to hot so i think i fried this engine. but on the up side it teaches me a lesson on what not to do. also, i tested the compression and its only at 20psi.
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Old 04-15-2003, 04:47 PM   #15
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Default Clutch

Have you checked your clutch out at all during this.....it might be worn or glazed badly and thats why it doesnt engauge or drive the car after its been running for a while......it might be getting hot and slipping or melting and bogging down your motor. Check it out and or replace it....if its the stock HPI clutch its very inexpensive to replace......Check it out. I hope this is your problem b/c then you dont need a new motor.
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