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2009 Honda Rancher TRX420FPM
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Discussion Starter #1
Hi, I purchased a 2009 Rancher trx420fpm that was in pretty rough condition. It would slowly crank but would start. Now it cranks over very slowly but when it gets to the top of the compression stroke it stops and will not turn over anymore. I have already replaced the battery and starter. Valves are in spec. If anybody could help that would be greatly appreciated. Thanks!
 

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battery and starter brand new ?. battery fully charged ?. all cables tight and clean to engine and ground on frame ?.
 

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2009 Honda Rancher TRX420FPM
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Discussion Starter #3
Yes it has a new battery (190cca) as well as a new DB Electrical starter. The cables to the battery and starter are tight. Is there a cable that runs from the starter to a ground on the frame?
 

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Yes it has a new battery (190cca) as well as a new DB Electrical starter. The cables to the battery and starter are tight. Is there a cable that runs from the starter to a ground on the frame?
there is a ground cable that runs from engine to frame.
 

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make sure you have all your battery cables and ground cables connected to the correct spot !!!.
 

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2009 Honda Rancher TRX420FPM
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Discussion Starter #6
Okay. Obviously I have one running from the battery to the frame. That's all there is that I could see. Is there another heavy guage ground cable that I might be missing that goes from the engine to the frame?
 

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Okay. Obviously I have one running from the battery to the frame. That's all there is that I could see. Is there another heavy guage ground cable that I might be missing that goes from the engine to the frame?
yep..there should be another ground cable running from engine to frame.
 

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most of these models have a ground cable that splits off the frame, one end goes to the battery, the other goes to the engine near the starter, most are connected to the starter mounting bolt.
 

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2009 Honda Rancher TRX420FPM
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Discussion Starter #10
Okay thanks for the info. I just ordered that ground cable. I'm hoping it solves my issue. I will let you know what happens when I get it. Thanks!
 

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Okay thanks for the info. I just ordered that ground cable. I'm hoping it solves my issue. I will let you know what happens when I get it. Thanks!
i hope it solves your problem ?, but i can not tell you for 100% it will ?, you very well may have starter issues ?, starter solenoid issues ?, i do not know ?, but what i do know is..that model calls for two ground cables !.
 

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2009 Honda Rancher TRX420FPM
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Discussion Starter #12 (Edited)
I didn't feel like waiting for the OEM chassis ground cable to get here so I made one out of some old jumper cable wiring. I connected the ground cable from the starter bolt to the frame. This did not help at all... Below is a list of everything I've tried doing but haven't gotten anywhere.

▪︎Attempted to jump atv off with a known good car battery. Starter still doesn't turn over fast at all and comes to the top of the compression stroke and stops.
▪︎Did a Voltage drop test across the wires in the charging circuit. Only found 0.5 volt dropped from the whole circuit.
▪︎Jumped the starter solenoid. Did not help.
▪︎atv has a new starter and battery.
▪︎Bench tested starter and it works when supplied 12v

I'm starting to think there is something mechanical going on here rather than electrical at this point. The motor gets hard to turn over when it gets to the compression stroke (this is where the starter hangs up). Do you think the auto decompression on the cam could possibly be bad? I appreciate any feedback since everything I've tried at this point has got me no where. Thanks.
 

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I didn't feel like waiting for the OEM chassis ground cable to get here so I made one out of some old jumper cable wiring. I connected the ground cable from the starter bolt to the frame. This did not help at all... Below is a list of everything I've tried doing but haven't gotten anywhere.

▪︎Attempted to jump atv off with a known good car battery. Starter still doesn't turn over fast at all and comes to the top of the compression stroke and stops.
▪︎Did a Voltage drop test across the wires in the charging circuit. Only found 0.5 volt dropped from the whole circuit.
▪︎Jumped the starter solenoid. Did not help.
▪︎atv has a new starter and battery.
▪︎Bench tested starter and it works when supplied 12v

I'm starting to think there is something mechanical going on here rather than electrical at this point. The motor gets hard to turn over when it gets to the compression stroke (this is where the starter hangs up). Do you think the auto decompression on the cam could possibly be bad? I appreciate any feedback since everything I've tried at this point has got me no where. Thanks.
time to slowly year the top end down, and start seeing what the piston maybe hanging on ?. anytime you take on a very well broken in atv ?..THERE IS NOT TELLING WHAT ALL DAMAGE IS DONE TO IT ??!.
 

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Discussion Starter #14
Okay let me tell you exactly what has happened since I got it. I bought it running but it had the slow crank but would fire up. I tore the whole thing apart and replaced lots of parts on the fourwheeler its self. As far as the engine goes the centrifugal clutch was worn out so I bought a used good one as well as a new one way bearing and clutch friction plates. While trying to hold the cam from turning while getting the nut off for the clutch I broke the cam off. Then on top of that my dumb self turned the motor over and bent the exhaust valve. So i took the top end apart and found way too much play in the rod. So the whole motor came apart. When I split the cases the metal oil filter screen was literally slammed with metal. I was able to make out from some of the big pieces that it came from at least the piston. I couldn't find a crank for a 2009 so I found a good used one from a 2013 420. Installed that crank and replaced the exhaust valve. The cylinder and piston are in pretty good shape (the piston didnt have any carbon build up on it and the cylinder did not have any deep grooves or anything like that). Once I put everything back together the fourwheeler started right up. I rode it maybe 3mins and it shut off. Since then it has been hard for the starter to turn over the motor when it gets to the compression stroke. The fourwheeler was definitely beat on and not taken care of. I'm sure it was probaly sunk at one point. Any pointers you can give me as far as what to look into next?
 

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Okay let me tell you exactly what has happened since I got it. I bought it running but it had the slow crank but would fire up. I tore the whole thing apart and replaced lots of parts on the fourwheeler its self. As far as the engine goes the centrifugal clutch was worn out so I bought a used good one as well as a new one way bearing and clutch friction plates. While trying to hold the cam from turning while getting the nut off for the clutch I broke the cam off. Then on top of that my dumb self turned the motor over and bent the exhaust valve. So i took the top end apart and found way too much play in the rod. So the whole motor came apart. When I split the cases the metal oil filter screen was literally slammed with metal. I was able to make out from some of the big pieces that it came from at least the piston. I couldn't find a crank for a 2009 so I found a good used one from a 2013 420. Installed that crank and replaced the exhaust valve. The cylinder and piston are in pretty good shape (the piston didnt have any carbon build up on it and the cylinder did not have any deep grooves or anything like that). Once I put everything back together the fourwheeler started right up. I rode it maybe 3mins and it shut off. Since then it has been hard for the starter to turn over the motor when it gets to the compression stroke. The fourwheeler was definitely beat on and not taken care of. I'm sure it was probaly sunk at one point. Any pointers you can give me as far as what to look into next?
oh man, you will not like my advice ?!. i would tear it all back down, and start over, this time take your time putting it back together with all the correct parts. before you put that crank in..DID YOU CROSS THE PART NUMBERS OVER TO MAKE SURE THEY WERE THE SAME CRANKS ?. ANYTIME A MOTOR IS SUNK ?, YOU MUST SPLIT IT..AND CLEAN IT ALL OUT !..otherwise..your just pizzing time and money away.
 

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Discussion Starter #16
I don't mind having to tear it down again. As far as cross checking the parts I'm not entirely sure how to do that. I had read on one of the forums that the newer cranks work in the older models. I did inspect and compare the 2013 crank to the 2009 and everything matched up and looked to be the same (that Includes the key way as well). While the cases were apart I did clean them out pretty good I thought. Maybe I missed something? As far as it being sunk I'm just speculating that cause it did have a snorkel on it and was in pretty rough shape. Also looked like when the piston blew up they just put a new piston and used top end on there since none of the metal was cleaned out of the bottom end. As far as the rockers go for the top end are they all the same when it comes to the 420 models? I was trying to cross reference part numbers but wasn't sure if they were all the same or not.
 

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I don't mind having to tear it down again. As far as cross checking the parts I'm not entirely sure how to do that. I had read on one of the forums that the newer cranks work in the older models. I did inspect and compare the 2013 crank to the 2009 and everything matched up and looked to be the same (that Includes the key way as well). While the cases were apart I did clean them out pretty good I thought. Maybe I missed something? As far as it being sunk I'm just speculating that cause it did have a snorkel on it and was in pretty rough shape. Also looked like when the piston blew up they just put a new piston and used top end on there since none of the metal was cleaned out of the bottom end. As far as the rockers go for the top end are they all the same when it comes to the 420 models? I was trying to cross reference part numbers but wasn't sure if they were all the same or not.
just go to partzilla.com, look up your model, then find the crank, click on that crank part number, then look down on right side, see if it list this crank to fit a 2013 model ?..if it does ?..then your good.
 

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just go to partzilla.com, look up your model, then find the crank, click on that crank part number, then look down on right side, see if it list this crank to fit a 2013 model ?..if it does ?..then your good.
Cranks are the same. I put a 2012 crank in an 08. No issues. Different part number, same part.
 

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2009 Honda Rancher TRX420FPM
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Discussion Starter #19
Okay yeah I looked it up on Partzilla website and it says they aren't the same part but I feel like the 2013 one should work in the 2009 I have. I Just got finished with tearing down the top end and found that the main bearings are shot. I can hear and feel the noise and grinding while turning the crank by hand without the piston and cylinder on there. I'm gonna split the cases and probaly put all new bearings in.
 
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