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Backfiring in reverse...

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  #1  
Old 09-13-2018, 11:37 AM
Paxman Merv's Avatar
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Default Backfiring in reverse...

Here's one i have never come across before...Hopefully someone here has!
Got an old (mid nineties i guess) 2 stroke Sportsman 4x4 in the shop with a real odd issue.
Story goes that a couple of months ago the starter packed up so the guy has been using the pull starter & carried on. All was well going forwards but go to reverse & all hell breaks loose. Goes backwards for a few yards then starts popping, banging & backfiring with clouds of exhaust smoke from pretty much everywhere. Had to try it & sure enough, just as he said.
Did a few basic checks, nothing to amiss at first glance then did a volt test while it was running. All starts well at about 13V at idle but managed to get well over 30V at the battery with about half throttle.. Obviously an issue there, screwed regulator i guess, but would that cause the odd behavior in Reverse.
Many thanks in advance!
 
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  #2  
Old 09-13-2018, 12:23 PM
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There should be a reverse over ride switch on the left handle bar. Push that in when backing up and it should run fine.
 
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Old 09-13-2018, 12:25 PM
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Should look something like this.



 
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  #4  
Old 09-13-2018, 06:01 PM
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A lot of people don't know about the reverse override button. You should be able to go maybe 5 mph without pushing it. If you push the button and it still won't run good in reverse, the rev limiter module is probably shorted out. You can just unplug it and have full power in reverse without pushing the button. It's a safety feature but as long as the person riding knows it's been defeated it's okay. Then you can back up 40 mph.
 
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  #5  
Old 09-15-2018, 07:58 AM
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Thanks for that Gents!
Will get the voltage regulator sorted first i reckon then try to find the reverse limiter.
Still cant see why it pops & bangs in reverse but runs great forwards...engine still turns the same way so this will take some finding.
Keep the ideas rolling in people!
 
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  #6  
Old 09-15-2018, 06:20 PM
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They quit making 2-stroke Sportsmans a long time ago unless they sneaked past when I wasn't looking. Seriously though, my younger brother had one of those old Sportsman 400s (378cc I believe) and it would be at least 22 years old now because he had it before I bought my '97 Sportsman 500. I've never seen under the hood of one, but on some other models the reverse limiter module is under the hood to the side of the steering column. If it shorts out it can cause problems like limiting in forward gears too. But once you get the voltage regulator taken care of, it may be okay. I think I can go 10 mph in reverse, but not 15 before the limiter kicks in. It's one of those things I never paid any attention to. I just go slow and/or push the yellow button, usually both. Good luck.
 
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Old 09-16-2018, 06:27 AM
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Thats great Frank,
Getting onto the Dealer in the morning. Parts can be a bit tricky to source here in the UK especially with the older models.
Get the voltages right then see what happens i guess.
Will see if i can but a pic up of the rats nest that's masquerading as a wiring loom & hopefully, when everyone stops laughing, someone could point me in the right direction of the reverse limiter!
Many thanks all thus far.
 
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Old 09-16-2018, 01:51 PM
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You're very welcome, Merv. If you can find the VIN you can figure out what model year it is. If it doesn't still have the sticker on it, my best guess on the location of the VIN would be either on the right side of the frame by the floorboard, or the left side of the frame where it comes down behind the front tire. The VIN should a 17 digit number, but they also used shorter numbers a long time ago. The 10th digit is the year code. Then you can look up part numbers to see if the parts you need were used in different years or on other models.

ATV Vin Number : Check and Decode Your VIN

http://parts.polarisind.com/browse/Browse.asp

You can find a picture like this one for a 1995 Sportsman 4x4, where number 41 is the rev limiter. If you scroll to the right of the part number it says #4060112 was substituted by #4060203. Farther right, if you click Usage it tells you what other ATVs used the same part. In this case a 1997 Xplorer 400L and several other ATVs from 1994-1997.


 
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  #9  
Old 09-17-2018, 04:44 AM
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Fantastic!
So i guess the box circled in Yellow is the limiter & have included the vin.

X2297078X
 
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  #10  
Old 09-17-2018, 03:39 PM
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That sure looks like a limiter to me. The bad news is, that isn't the VIN. It may be below that on the side of the bottom frame rail. I'm still not sure on the location. It should be a 17 digit number or 13 digits, depending on the age. The good news is, the 94 in the model number means it's a 1994 Sportsman 400L and some parts are still available.
 
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