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Rwoody

Polaris Magnum 425 - No Top End

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Ok so today was a great spring day here in the east side of PA, So i figured why not work on the old green machine for a bit. I started out trouble shooting the no spark and found that one of the connections was loose. So she has great spark again. Fired her up and ran it for awhile and got it good and hot. Shut it down and waited a minute or two and she would not start. Turned over great but would not start. After about 15 minutes of letting it cool down it fired up. So before I got off to the races and tried to find a problem I pulled the plug again and checked it. Burning like it should be. So i fired it up got it hot and shut it off. No start again until it cooled down. I checked a few things and after it cooled for about 15 minutes it started up. So again I ran it until it was hot. (The engine was just hot enough for the fan to come on) again it would not start with the electric starter. So just for sh#$s and Giggles i decided to us the pull start. She fired on first pull. I ran it to it was warmed up again and the same thing. No electric start but will pull start every time.   

  I have metered and checked the connections to the starter and solenoid and ignition switch all test good. I have no idea why once its hot it will not start by electric but pull starts first try. Any Ideas????

So on to the next thing. I was confident enough to take it out for a ride and immediately it bogged at half throttle so I got a cloth and covered one hole and she ran good. So for the time being I put a small air breather on one side and that seemed to do the trick she idles great and runs up to high throttle with a load on (Me). I had no idea this machine could get up and go like it does. So next is a true test in the hills next weekend. I will post back

Russ when i changed the cam on this one I installed the compression release incorrect and it almost would not turn over. Once I figured that out it turned over fine. I am glad the wrench is going to take care of that for you. Now with this one figured out almost i have 2 425 4x4's to get going. Got them all in a package deal. 1 4X4 runs great the other has issues like the greenie. 

Thanks for all the posts and suggestions. I will post how the run goes 

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Put a meter  on the battery  when  you try to  start it  hot.  I suspect  the  battery  may  not  have   its full capacity  and the extra  load of trying to run the  starter  hot   drops  the  voltage too  low  to  fire the ignition properly.

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I was kind of leaning toward the Battery or the starter. When I picked this machine up it would not turn over and the starter was froze up. I will test that this evening thanks for the information. This particular machine gave me so many headaches I started writing things down so I would not do the same thing twice. In the begging of the notes I put starter frozen and was able to free up but its drawing higher then normal amperage. Note: clean and see if can be freed up more> So that very well can be the issue. Thanks I really appreciate the feedback and the suggestions.

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I  don't  know  about the  starter on your Polaris,  but I  imagine  it  is  very  much like those on the   Honda  and  Suzuki. I  just rebuilt the  one on my  Honda.  There  are reasonably priced rebuild  kits for them  that  have  the  new  brush assembly  and the  bushings  the  rotor  runs in as well  as  all the  seals in the  kit.  There  really should be  no  drag on the  motor unless  possibly one of the  bushings / bearings holding the rotor  is worn  and allowing it to  drag  on the  field. My  Honda  had   permanent  magnet  fields  that  are very  powerful and  insert the rotor  into the  case  unsupported and it  grabs  quite  tightly to them ..  The  starter operates  through a  gear train to  a  one way  bearing (sprag) to  start  the  motor . There  should  be  no  drag  on that  gear train.

If the  starter  was frozen  before, I'd definitely recommend  pulling it  apart and  installing  a  rebuild  kit .

 

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First I want to Thank Everyone that commented on this post. I have finally got these things going. I first had issues with a 4x4 425 Magnum with the top end as I thought 4 years ago. I pretty much left the machine sit for some time and when I got back into figuring it out. The funny part is I ended up with 3 Polaris 425's, 2 4X4's and one 2X4 all with the same issues. After getting them all back together with all parts installed. The 2 I acquired were pulled apart by previous owners trouble shooting. So needless to say I had to acquire some parts. So the over running theme was the same All would start and Idle but would not accelerate. One had bad valves and out of tune carb. One had bad valves and cam and out of tune carb. My original 4X4 had cracked carb (still have no idea how that happened) but new carb and fine tuning and she is running strong again. 

The reoccurring theme here is the Carbs and the air cleaner set up. The jetting on the 425 seems to be real critical for the older machines. At least with these 3 machines it was. The rebuild kits I installed apparently were not the correct ones so I induced a lot of the problems when I rebuilt them. So now with my pocket quite a bit lighter I am now educated a bit on jetting and its importance. It took me a while and lots of questions on this forum and reading others to finally figure it out. So again Thank you to all those who post here and other places about the issues and what you discover.

So now the only issue I have is the starting issue when hot. I have not dug into this yet but I believe its the Starter being corroded. When hot you can actually see the spark trail off with a spark window tool. cold the machine has great spark but after you ride and get it good and hot it will only start with a pull on the rope. The spark fires once then after that is so week you can barely feel it, so something is stealing the spark or shorting it out. Once I get a chance I am going to go over all grounding connections and terminals to ensure I have good grounds and connections. this machine has a lot of rust so I am pretty sure it was out in the elements for some time or used as a salt spreader and plow.

Have a good day and keep em running        

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