2002 yamaha big bear won't start

Reply

  #1  
Old 11-12-02, 10:44 AM
J
jayhuf
Visiting Guest
Posts: n/a
2002 yamaha big bear won't start

Does anybody know how to troubleshoot this ATV. Engine cranks, plug gets spark and gas but will not start. Only has 200 miles on it.
 
Sponsored Links
  #2  
Old 11-12-02, 09:31 PM
S
STIMPY21
Visiting Guest
Posts: n/a
Compression, ignition and fuel, these are what make the internal combustion engine run. At 200 miles surely there is compression, Remove spark plug, put finger over spark plug hole, crank engine a few times. Feel air trying to escape? then you have compression, if not you are probably in for some expensive repairs. Ignition, you say there is a spark, how hot is it, just barely sparking and you could have a damaged spark plug or bad ignition coil or even the electronic igntion components them selves. You must have a good white spark and that spark must be timed correctly, in that it will happen just before the piston reaches top dead center. Fuel, pull of the fuel hose to the carb and run off some gas into a clear glass container and make sure that there is not any water or trash in the fuel. Also there is the possibility that you may have flooded the combustion chamber with many attempts to start it. Look closely at the spark plug after you have attempted to start it several times. is it wet/oily looking? if so I have found that leaving the plug out over night will allow the gas to evaporate, and enable you to get her started.Check these things and post back your findings.We can help.
STIMPY21
 
  #3  
Old 11-17-02, 08:09 PM
C
CobbConstructin
Visiting Guest
Posts: n/a
Dont give it any gas when trying to start it, just turn on the choke and start it.Check out your plug first like he said.
 
  #4  
Old 11-18-02, 04:10 AM
fewalt's Avatar
Member
Join Date: Feb 2001
Location: sw VA
Posts: 3,100
Received 0 Votes on 0 Posts
If you haven't already done so - replace the plug. I have had numerous Japanese plugs arc across the base and not start my Kawa 300. I also had the same problem with my old Honda.
New plug - starts right up!

fred
 
  #5  
Old 11-21-02, 07:53 AM
J
jayhuf
Visiting Guest
Posts: n/a
I replaced the plug and it started right away. After looking at the spark in the dark i could tell it was weak and intermittent.

Thanks to all.
 
  #6  
Old 09-02-11, 05:48 PM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
Mine too

Mine cranks, but will start only if I haul on the pull cord at the same time.

Any ideas?

Carl
 
  #7  
Old 09-02-11, 08:58 PM
M
Member
Join Date: May 2006
Location: Iowa!!!!!
Posts: 4,029
Received 5 Votes on 5 Posts
I'd say weak battery Carl.
 
  #8  
Old 09-04-11, 09:09 AM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
Thanks marbobj,

Boosted it with a fully charged car battery.

Going to try 18 volts. Just a short shot, don't think it will cook anything.

Carl
 
  #9  
Old 09-12-11, 09:18 AM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
I wonder if there is something interrupting the spark when cranking and it makes when the pull start is pulled?

Carl
 
  #10  
Old 09-24-11, 02:44 PM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
I think it's going to turn out to be a weak coil.

Carl
 
  #11  
Old 09-25-11, 06:38 AM
M
Member
Join Date: May 2006
Location: Iowa!!!!!
Posts: 4,029
Received 5 Votes on 5 Posts
It could be anywhere in the cdi layout as well as the stator, actually. If the battery is fully charged the stator shouldn't make a difference unless it's grounded. If you can pull start it without a charged battery the stator should be OK and the CDI and coil good.
 
  #12  
Old 09-25-11, 02:58 PM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
The stator runs the lights fine with the battery disconnected, the spark is weak, could be some shorted turns in the coil.
Hope it's not a power pack but just the coil, BTW does it have a power pack?
It's a bear to pull by hand NPI (no pun intended)

Carl
 
  #13  
Old 09-25-11, 06:39 PM
M
Member
Join Date: May 2006
Location: Iowa!!!!!
Posts: 4,029
Received 5 Votes on 5 Posts
"Bear" to pull by hand - that's pretty good. No power pack, just the CDI unit, the coil, then all the battery and charging stuff. The CDI is battery/stator fed. Normally the stator/rectifier feed the battery then current goes to the CDI, which is the capacitor discharge which saturates and fires the coil when it cuts. If the battery is dead, the stator/rectifier feeds the CDI which does the same thing with the coil as with a feed from the battery. Then you have the ignition switch tossed in there to kill everything. But with all that said it's back to what I mentioned before. It's probably either the CDI or the coil, though - speaking in terms of likelyhoods.
 
  #14  
Old 09-25-11, 07:37 PM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
Thanks Marbobj,

Have you ever heard of anyone replicating a CDI?
Never had much luck reverse engineering one.
Need some yet unknown (to me) chemical, to dissolve the encapsulation.

Carl
 
  #15  
Old 09-25-11, 08:18 PM
M
Member
Join Date: May 2006
Location: Iowa!!!!!
Posts: 4,029
Received 5 Votes on 5 Posts
You're out of my league one that one. A CDI is a capacitor with a resistor in it to control back flow. It essentially replaces the old points design. The points close to saturate the coil and break open to trigger the spark firing - a condenser pulls off excess to control point burning. The back flow is an issue to allow the capacitor to build up again.

To answer your question, I have never known someone to jury rig one or even tried. Most replace the box. To make it worse there doesn't seem to be a good way to check them even in light of their cost, which is pretty ripe.
 
  #16  
Old 09-26-11, 06:44 AM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
I'll look into it.
I'll keep you posted.

Carl
 
  #17  
Old 09-27-11, 01:38 PM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
Yep.....a roll your own CDI is doable.

My Bear is an older one with a gear box.

Any idea what the stator windings should be putting out?

Carl
 
  #18  
Old 10-07-11, 05:44 AM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
Do CDI coils light up at a higher amperage than others?

This one takes near 4 amps on the Merc-o-Tronic.
Most standard coils kick at 1 to 2 amps.
BTW.......4 amps is all the Merc will put out

Carl
 
  #19  
Old 10-08-11, 10:41 AM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
BTW.......if anyone is interested in links to DIY CDI sites, let me know.

Carl
 
  #20  
Old 10-09-11, 05:34 AM
M
Member
Join Date: May 2006
Location: Iowa!!!!!
Posts: 4,029
Received 5 Votes on 5 Posts
In terms of the coil amperage, I can't say I paid a lot of attention to testing output with a meter. I do have a meter for that type of thing. I have used it in testing automotive spark. In small engines I just go by color and intensity. Most commonly it's going to be a bright blue spark on a good coil output or a yellow spark on a compromised one. The CDI vs standard point control for the coil could present a difference, though. If the same coil independently was used in both systems, the output should be about the same since the points vs CDI is more of a control for the release of the spark from the saturated coil. The CDI system is modern, though, where the point condenser is antiquated so the coil may be upgraded on that alone.

The other good possibility is the CDI setup allows for a different coil internally that can produce a higher level spark. I suspect the latter is true. The high energy ignition systems in automotive showed up just before the CDI modules in small engines. High energy setups in Chevy (first of the new coil type that I noticed) were around 1978 and the modules around 1986. The automotive were a little more involved, but the idea was about the same.

What you're doing is interesting. When you get that put together could you post it back with a description of what you did, parts you used, how well it works and some pictures if you could. I think everyone here would benefit from it.
 
  #21  
Old 10-09-11, 12:33 PM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
Marbobj, you are the most faithful responder, thank you.

BTW...the Merc-o-Tronic people advise that the coil only be subjected to a short shot of 4 amp juice, to avoid damage.( the DC voltage applied by the tester is 7v )(similar to a ballasted automotive coil)

Here are some links to home brew CDI sites.

Ignition Solutions for Small Engines and Garden Pulling Tractors

Rick’s Site » How to Convert an ATV to Ford Ignition

CDI Electronic Ignition Unit for the Spartamet

Repairing the KDX CDI

Roll Your Own CDI - Page 31 - Motorized Bicycle: Engine Kit Forum
 
  #22  
Old 10-10-11, 06:04 PM
H
Member
Join Date: Sep 2011
Location: Canada
Posts: 13
Received 0 Votes on 0 Posts
Many thanks to the guys that have done this work on HOME GROWN CDI's
 
Reply

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 Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question