Problems with full throttle - Pocket Bike Forum - Mini Bikes
Reply
 
LinkBack Thread Tools
post #1 of 22 (permalink) Old 05-31-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Problems with full throttle

I have a rather old GP-MX3 from MPB. I finally got it started today after having to replace the sparkplug and getting a new airfilter. After running it for about 45 minutes off and on. I put it in my garage for a couple of hours. I came back out to ride it again, and whenever I put to much throttle on it, the engine bogs out and dies. I havent the slightest idea what it is. I do know a little about pocketbikes but not that much. Any ideas?
Burl25 is offline  
Sponsored Links
Advertisement
 
post #2 of 22 (permalink) Old 05-31-2010
Hooligan
 
SpyGuy's Avatar
 
Join Date: May 2008
Posts: 8,578
Images: 23
Re: Problems with full throttle

Welcome to the forums.

Sounds like either a gas problem of a reed problem. Gas problem, you change out the fuel lines for larger lines, modify the petcock, and put in an inline fuel shutoff valve. For the reeds, you need to do a little more.

If it's doing this at WOT (Wide Open Throttle), it could be your reeds. This is a phenomenon known as "top end reed flutter." As simply as possible, the reeds are like a one-way valve, opening to introduce the fuel/air mix into the cylinder, then snapping shut to seal the cylinder for the compression stroke. At WOT, your reeds are flapping back and forth so fast that they aren't sealing on the cylinder well, resulting in a loss of compression and thus loss of power. Solution here is to get and install new reeds on your machine, lilike a triple stage set (Black Widows are fairly popular), or do the cheap triple stage reed mod that davation came up with, done by layering two single reeds on top of each other. (Look in the air-cooled mods at the top of the air-cooled section for complete details on the mod.)

"I'm going off the rails on a crazy train." - Ozzy Osbourne

Dear haters: Please be patient. I have so much more for you to be annoyed about.
SpyGuy is offline  
post #3 of 22 (permalink) Old 06-01-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Ok, is there a quick fix? Because i am not motorcyle literate enough to really understand that
Burl25 is offline  
Sponsored Links
Advertisement
 
post #4 of 22 (permalink) Old 06-01-2010
Hooligan
 
SpyGuy's Avatar
 
Join Date: May 2008
Posts: 8,578
Images: 23
Re: Problems with full throttle

Quickest fix, try this first. Put some new fuel lines on the bike, 1/4" INNER diameter - you can pick them up at your local hardware store. This is normally one of the first mods people do to the bikes, anyway, for better fuel flow ... If this doesn't work, come back, and I'll tell you what you need to do to change your reeds. Trust me, if you plan on keeping the bike and riding it, you WILL learn how to work on them ... they're really not all that hard.

Air cleaner--> carburetor--> intake manifold--> reed block--> reeds (inside engine)--> reed stop (inside engine)--> engine case

"I'm going off the rails on a crazy train." - Ozzy Osbourne

Dear haters: Please be patient. I have so much more for you to be annoyed about.
SpyGuy is offline  
post #5 of 22 (permalink) Old 06-01-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Quote:
Originally Posted by SpyGuy View Post
Quickest fix, try this first. Put some new fuel lines on the bike, 1/4" INNER diameter - you can pick them up at your local hardware store. This is normally one of the first mods people do to the bikes, anyway, for better fuel flow ... If this doesn't work, come back, and I'll tell you what you need to do to change your reeds. Trust me, if you plan on keeping the bike and riding it, you WILL learn how to work on them ... they're really not all that hard.

Air cleaner--> carburetor--> intake manifold--> reed block--> reeds (inside engine)--> reed stop (inside engine)--> engine case
Would a new gas filter be better to? Mind you this bike is 4 years old and has never had anything done to it besides a new spark plug...
Burl25 is offline  
post #6 of 22 (permalink) Old 06-01-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Also, its cuting out at no more than even half throttle. The engine bogs then dies. But if i let the bike slowly accelerate i can get the throttle going to full after about a minute of accelerating
Burl25 is offline  
post #7 of 22 (permalink) Old 06-02-2010
Hooligan
 
SpyGuy's Avatar
 
Join Date: May 2008
Posts: 8,578
Images: 23
Re: Problems with full throttle

Yes, a new filter would help.

Have you cleaned the carburetor? A dirty carb is like 90% of the problems with these bikes.
http://www.pocketbikeplanet.com/f167...ial-41644.html

"I'm going off the rails on a crazy train." - Ozzy Osbourne

Dear haters: Please be patient. I have so much more for you to be annoyed about.
SpyGuy is offline  
post #8 of 22 (permalink) Old 06-02-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

OK i will clean it out today
Burl25 is offline  
post #9 of 22 (permalink) Old 06-02-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

-wrong thread-

Last edited by Burl25; 06-02-2010 at 03:48 PM.
Burl25 is offline  
Hooligan
 
SpyGuy's Avatar
 
Join Date: May 2008
Posts: 8,578
Images: 23
Re: Problems with full throttle

Did you clean the carb out yet?

"I'm going off the rails on a crazy train." - Ozzy Osbourne

Dear haters: Please be patient. I have so much more for you to be annoyed about.
SpyGuy is offline  
post #11 of 22 (permalink) Old 06-02-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Cleaned the Carb, changed fuel lines, new fuel filter... Set my idle speed way low. This helped a little, it still cant handle more than 30% throttle until i get to about 15 MPH then I can slowly get the throttle to maybe 50% and get to maybe 25 MPH... Its still bogging out
Burl25 is offline  
post #12 of 22 (permalink) Old 06-02-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Also, my exaust pipe is just terrible, it leaks and the silencer seems to make it louder... Can you recommend me a good exhaust pipe?
Burl25 is offline  
Hooligan
 
SpyGuy's Avatar
 
Join Date: May 2008
Posts: 8,578
Images: 23
Re: Problems with full throttle

Well, you can either get the stock exhaust pipe, which runs about $20-$30, or you can save a littl more money and throw a performance pipe on there. JetPros are pretty popular, and help give the engine a little more power.

I'm thinking reeds, amigo. The stock reeds on these things are terrible, and unfortunately create the same symptoms you're describing. The carb is usually most of the problem .... the reeds are usually next. (And if you've already had the carb off the bike, you're over halfway to the reeds already.)

"I'm going off the rails on a crazy train." - Ozzy Osbourne

Dear haters: Please be patient. I have so much more for you to be annoyed about.
SpyGuy is offline  
post #14 of 22 (permalink) Old 06-03-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Yeah, i found out how to change the reeds, and ill check out a jetpro. and is it normal for stock pipes to be terrible?
Burl25 is offline  
post #15 of 22 (permalink) Old 06-03-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Also should i pay the extra for a carbon fiber reed?
Burl25 is offline  
Hooligan
 
SpyGuy's Avatar
 
Join Date: May 2008
Posts: 8,578
Images: 23
Re: Problems with full throttle

Stock pipes are okay, not great. Once you get a JetPro on it, you'll feel the difference in the powerband. And yes, the CF reeds are the way to go.

If you want to do a little DIY modding, there's a mod you can do with the old tin reed that will help performance. Read this thread:
http://www.pocketbikeplanet.com/f47/...cag-39770.html
Use the CF reed on the bottom, and cut up the stock tin reed to do the mod.

"I'm going off the rails on a crazy train." - Ozzy Osbourne

Dear haters: Please be patient. I have so much more for you to be annoyed about.
SpyGuy is offline  
post #17 of 22 (permalink) Old 06-04-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Ok, are the reeds supposed to be off set in their length? And the jetpro pips that i find are near 200$, i would be a new bike before i spent something that rivals the price of the original bike.

I want a pipe that bends out the side of the bike like on real motorcylces, but i cant seem to find one.
Burl25 is offline  
post #18 of 22 (permalink) Old 06-04-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

And alot of people in that tutorial topic say that you have to rejet, i havent the slightest clue what that is.
Burl25 is offline  
Hooligan
 
SpyGuy's Avatar
 
Join Date: May 2008
Posts: 8,578
Images: 23
Re: Problems with full throttle

Rejetting is taking out the main jet in the carburetor, and putting in a new one, usually a larger one.

For the pipe, try looking at a motocross/dirtbike pipe. I've heard they'll fit, but not having personally tried putting one on a bike, I couldn't tell you for certain.

"I'm going off the rails on a crazy train." - Ozzy Osbourne

Dear haters: Please be patient. I have so much more for you to be annoyed about.
SpyGuy is offline  
post #20 of 22 (permalink) Old 06-07-2010 Thread Starter
verified
 
Join Date: May 2010
Posts: 32
Re: Problems with full throttle

Well, The problem was the fuel mix, it was old gas. Ran the fuel out, and used richer fuel. Now she runs better than before. I picked up a performance exhast. Today im repainting the frame red then the body black.

Im also having problems with the overflow pipe leaking all of my gas out unless i turn the gas off on the carb. So im going to clean the carb again really good.
Burl25 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pocket Bike Forum - Mini Bikes forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may 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 On

 
For the best viewing experience please update your browser to Google Chrome