R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Nitro On-Road

Reply
 
Thread Tools Search this Thread
Old 08-20-2004, 06:28 PM   #1
Tech Apprentice
 
Join Date: Jun 2004
Posts: 88
Default Need help wierd problem

Here's my problem. I have a MRX 3 w/ a Picco G1 XP engine. I start the car and have it on top of my starter box to do the tuning. After I tune it to where I like it, i get it on the track. I gun it really good and the car responds very well for the first 5 seconds. Then after that it starts to pulse on and off. The power just keeps coming in pulses. If I completely let go of the throttle and let the car come to a stop it's nearly impossible for me to get the car moving again even though the engines still running. At this point I'll pull the throttle all the way down, but the engine just doesn't respond well, it seems to be able to get only to 20% throttle and the clutch won't engage so the car just sits there with a high idle when I'm pulling the throttle. What's really wierd is when I have the car on the start box doing the tunning I don't get this problem. Can someone tell me what's going on?
Illusion-Lighti is offline   Reply With Quote
Old 08-20-2004, 06:34 PM   #2
Tech Adept
 
Join Date: Jul 2004
Posts: 133
Default Re: Need help wierd problem

think outside the box. So, have you checked your throttle servo?

Quote:
Originally posted by Illusion-Lighti
Here's my problem. I have a MRX 3 w/ a Picco G1 XP engine. I start the car and have it on top of my starter box to do the tuning. After I tune it to where I like it, i get it on the track. I gun it really good and the car responds very well for the first 5 seconds. Then after that it starts to pulse on and off. The power just keeps coming in pulses. If I completely let go of the throttle and let the car come to a stop it's nearly impossible for me to get the car moving again even though the engines still running. At this point I'll pull the throttle all the way down, but the engine just doesn't respond well, it seems to be able to get only to 20% throttle and the clutch won't engage so the car just sits there with a high idle when I'm pulling the throttle. What's really wierd is when I have the car on the start box doing the tunning I don't get this problem. Can someone tell me what's going on?
RC Dumb is offline   Reply With Quote
Old 08-20-2004, 06:40 PM   #3
Tech Apprentice
 
Join Date: Jun 2004
Posts: 88
Default

Yea, the throttle servo works fine. It just seems to have the problem when the wheels have a load and only after like 5 seconds. if I let the car sit long enough, I'll be able to get good response again for another 5 seconds.

Would there be any chance that the clutch needs to be replaced? Heck, can the clutch even go bad with enough use?
Illusion-Lighti is offline   Reply With Quote
Old 08-20-2004, 09:32 PM   #4
Tech Elite
 
GrandeGixxer's Avatar
 
Join Date: Jun 2004
Location: Waldorf, MD
Posts: 2,924
Trader Rating: 15 (100%+)
Default

it the engine pulsing? if it is the engine, it could be an air leak.
__________________
Joe Cude
Mugen MBX-7R Mugen MTX-6R Mugen MTC-1 Mugen MRX-6 Mugen MST-1 Tamiya Euro Truck
GrandeGixxer is offline   Reply With Quote
Old 08-20-2004, 09:42 PM   #5
Tech Apprentice
 
Join Date: Jun 2004
Posts: 88
Default

If there was an air leak, wouldn't it also perform inconsistent when the car was on the start box while i was tuning it?
Illusion-Lighti is offline   Reply With Quote
Old 08-20-2004, 09:51 PM   #6
Tech Regular
 
SlobbaTech's Avatar
 
Join Date: Jun 2003
Posts: 423
Default

Might be too lean and cutting out but not enough to stall the engine. There's been few times where I "thought" my engine was rich so I leaned it out then put it on the track and it was on lean side, so engine would have been tuned fine if dind't lean it out while sitting on the box.
SlobbaTech is offline   Reply With Quote
Old 08-20-2004, 10:40 PM   #7
Tech Master
 
whynot's Avatar
 
Join Date: May 2003
Posts: 1,481
Trader Rating: 18 (100%+)
Default

I would make sure that the clutch is set properly .Than I would back out the bottom end needle about 1 turn,Than see what happens. And if that doesnt help back out the top needle until it is noticably running rich and then slowly turn it in until it engauges the clutch and then put it on the track ad adjust to your liking.Hope this may help
mike
whynot is offline   Reply With Quote
Old 08-20-2004, 10:47 PM   #8
Tech Fanatic
 
kidDynomite's Avatar
 
Join Date: Jul 2004
Location: Chicago
Posts: 928
Default Re: Need help wierd problem

Quote:
Originally posted by Illusion-Lighti
...it seems to be able to get only to 20% throttle and the clutch won't engage so the car just sits there with a high idle when I'm pulling the throttle. What's really wierd is when I have the car on the start box doing the tunning I don't get this problem. Can someone tell me what's going on?
I had this same problem recently. I swapped in a new motor for break-in, idled a couple tanks, put it on the track for low run-in, it went for a little bit then just sat ... stop n go etc ... I thought my tuning was off.

The problem was that I didn't add any shims on the SG shaft before putting the Tapered Collet. And therefore it wasn't really locked onto the flywheel.

So you may want to check your clutch assembly.

Good luck!
kidDynomite is offline   Reply With Quote
Old 08-20-2004, 10:53 PM   #9
Tech Apprentice
 
Join Date: Jun 2004
Posts: 88
Default Re: Re: Need help wierd problem

Quote:
Originally posted by kidDynomite
I had this same problem recently. I swapped in a new motor for break-in, idled a couple tanks, put it on the track for low run-in, it went for a little bit then just sat ... stop n go etc ... I thought my tuning was off.

The problem was that I didn't add any shims on the SG shaft before putting the Tapered Collet. And therefore it wasn't really locked onto the flywheel.

So you may want to check your clutch assembly.

Good luck!
Yea I thought about it being my clutch too, but I've been running this car w/o adjusting any of that stuff for weeks now and it just recently started. The clutch wouldn't change its settings on its own would it?
Illusion-Lighti is offline   Reply With Quote
Old 08-20-2004, 11:08 PM   #10
Tech Fanatic
 
kidDynomite's Avatar
 
Join Date: Jul 2004
Location: Chicago
Posts: 928
Default Re: Re: Re: Need help wierd problem

Quote:
Originally posted by Illusion-Lighti
Yea I thought about it being my clutch too, but I've been running this car w/o adjusting any of that stuff for weeks now and it just recently started. The clutch wouldn't change its settings on its own would it?
I-L, Anything can happen. Try spinning the flywheel with your fingers while the engine is cold. Let the piston stick with the compression. If it's really hard to move, your flywheel is probably on there pretty good. If it spins, it's not locked to the collet.
kidDynomite is offline   Reply With Quote
Old 08-20-2004, 11:11 PM   #11
Tech Apprentice
 
Join Date: Jun 2004
Posts: 88
Default Re: Re: Re: Re: Need help wierd problem

Quote:
Originally posted by kidDynomite
I-L, Anything can happen. Try spinning the flywheel with your fingers while the engine is cold. Let the piston stick with the compression. If it's really hard to move, your flywheel is probably on there pretty good. If it spins, it's not locked to the collet.
it's definitely locked pretty good. when i spin it, it'll stop when the piston hits the top. I need to apply a pretty good amount of force to get it to turn over.
Illusion-Lighti is offline   Reply With Quote
Old 08-20-2004, 11:26 PM   #12
Tech Regular
 
gonzoY5's Avatar
 
Join Date: Mar 2004
Location: Miami, FL
Posts: 392
Default

Try a different pipe and header. I had a guy here with a similar sounding problem. Motor would rev up then slowly start losing power. Once he let it sit for a bit, it would have power once again for abot 10 sec. He was using some old header/pipe witha wierd shape that wasn't letting the exhast flow out enough. Once he changed the header there was no problem. Good luck.
gonzoY5 is offline   Reply With Quote
Old 08-20-2004, 11:29 PM   #13
Tech Apprentice
 
Join Date: Jun 2004
Posts: 88
Default

What I can't figure out is why this problem all of a sudden just happened. The car use to run perfectly and then just today. I spent 2 hrs tuning and finally just got tired of it.
Illusion-Lighti is offline   Reply With Quote
Old 08-21-2004, 01:02 AM   #14
Tech Fanatic
 
HELLION's Avatar
 
Join Date: Aug 2003
Location: Colorado
Posts: 802
Default hmmmmmmmmm

your clutch sounds like the problem to me ! check the thrust bearing and end play. Also sometimes servos can act up and will do strange things. Try putting your finger on the servo linkage (slightly loading it) as you give it some throttle (with the engine off) feel for any glitches. I helped a guy once that his car was pulsing. As I looked at it I noticed that he grabed the bellhousing with something that bent it while changing gears but you did say you havent messed with the clutch and thats why I think it's the thrust bearing . They don't last to long if they aren't greased often
HELLION is offline   Reply With Quote
Old 08-21-2004, 09:51 AM   #15
Tech Master
 
whynot's Avatar
 
Join Date: May 2003
Posts: 1,481
Trader Rating: 18 (100%+)
Default

When it is on the starter box and you are reving it up can you feel if it is shifting into 2nd gear and does your motor sound tuned nice and crisp? If it does than it is your clutch when the weight of the car is against the clutch it is making it slip so when you are at a low rpm it is prob. grabing a little but when the motor really starts to sing a high rpm it isnt grabing the clutch bell enough.You need to add some shims so that your end play is just a little bit not real sloppy prob. about .3-.4 mm of end play and when you get that set you need to make sure that your clutch nut isnt to loose also if it isnt tight enough it can bog the motor down. so you prob. want the clutch to kick it atabout 1/4 of throttle but that is a personal preferance. Hope this helps.
mike
whynot is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Wierd glitch problem Perry Electric Off-Road 8 06-29-2007 04:50 AM
wierd engine problem, cannot start uniquexme Onroad Nitro Engine Zone 0 11-19-2006 08:48 PM
Hi all please can ya help wierd problem! karlmaddock Nitro On-Road 4 07-18-2006 07:43 AM
Need help! Car being wierd Revox Rookie Zone 11 06-22-2006 01:36 AM
wierd problem need help. boy_racer2k Nitro On-Road 2 04-02-2005 03:15 AM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 09:51 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net