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2014 TRX420FA2 - Revs before clutch engage


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New member here,

I have searched here and other places and have not found an answer to my problem.   As the title says I have a 2014 420 Rancher that recently started having an issue were the revs before the clutch engages.  

  1. I have checked the oil level (per the service manual) and replace the Valvoline ATV 10w40(less than 5 hours) with 10W30 GN4 for good measure.
  2. I have used the "pin" method to pull a DTC.  I shows a 8-1 which is a TPS error.  This makes some sense, as if the computer doesn't read throttle position correctly, it could have this symptom.
    1. I have checked the source voltage, and tested the TPS off the quad with a Fluke and a power supply at 5v.  It is smooth and does not seem to be a bad sensor.
    2. I am confused by the DTC, because the PS light blinks the code, not the check engine light.  However, there are no PS codes of that value.  
  3. This condition appeared after a couple days of driving in the cold (~32°) and driving though some water/bogs. 


A couple questions.  First has anyone seen this issue, and do you have any suggestions? I have followed the troubleshoot right up to the point of replacing the ECU, which I don't seem to have one on the shelf :)

Second, anyone used a OBDII reader with an a 4pin adapter to pull codes?  If so, what system do you use?

Beyond the rev issue, the quad runs and starts perfectly and when it decides, the clutch grabs tight (no slipping)



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It's always a good idea to check sensors like that from the ecu end of the wiring..  There might be a break in a wire.. Unplug the ecu and use the ohm gauge from there to the throttle and back. I'd imagine there are three wires ? 5volts, earth and variable ? Some modern ecu don't feed exactly five volts, or have an exact earth, both wires have a very small resistor feeding the opposite into the wire, so the 5volt has a resistor feeding a tiny amount of earth so it read 4.5volts, and the earth wire has a  resistor keeping it at about .5 volts.. It's to allow better failsafe operation.. It's something to watch for though when you are checking voltages etc.

I've connected laptops to cars and a suzuki road bike but not a honda. Connecting is pretty simple, you can use a car obd2 reader hot-wired to the bikes plug if you have a wiring diagram showing what wires to connect to. You will have to either read up and discover which protocol the bike uses, or try the different protocol pins on the obd2 plug until you find the ones that communicate.. then the fun starts.. Unless you know which addresses in the ecu to query it's all a lot of trial and error.. but not impossible. The easy way is to take a dump of the entire ram, then take another dump of the entire ram with the throttle wide open(in this case). Then by comparing the two you will see which is the throttle address.. we hope.  Then you need to figure out what sort of calculation needs to be done to that figure you get from the correct address to make it relevant as a percentage or angle..  There are some fairly common practices though, like dividing by 256 then multiplying by 100.. 

It's probably not worth your time and trouble unless you do a lot of work on a specific vehicle..

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Thanks for the response. 

I will check the sensor numbers at the ECU.  I did go back and check the TP sensor resistance, which I missed, the sensor resistance is within spec.  The interesting thing is that I turned on ignition before re-connecting the TP sensor and the error code showed up on the check engine lite in addition to PS light.  I am close to clearing the TP sensor as the problem

I want to go through the troubleshooting on the transmission, which seems to lead me to check oil pressure.  Readings with wheels elevated and engine at 5k rpm sounds interesting.   

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Clear the fault codes and see if they come back.. they may be old codes..

I'll get a manual and have a read. This is one with the electric shift I presume..  I've had bad dashes on those before causing shift problems.. Long time ago now though and I can't remember what the problem was.. not clutch though,,

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Appreciate the input.  This is my first quad and I didn't think I purchased a project, but here I am.  

I have cleared the code, I still have the issue.  It's weird that the code displays on the Power Steering light.  The transmission is a DCT.

I think my next course of action is to check oil pressures.  That should help in the diagnosis.  Taking reading of oil pressure at 5k rpm with the wheels free is an interesting test....



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The atmospheric conditions here have been sh** and I haven't managed to get a manual. I'll give it another go but it sounds like you are following the process so you should get there.

The manuals tell you everything you need to know, but sometimes we need to read between the lines to get the hidden bits..  Like it'll say A causes B, B causes C unless D,  but we have to deduce that there will be no C without the A, and that we need to eliminate the chance of/event D..   Sometimes the mention of A, is pages away from the mention of C too..  If we read the whole section in the manual, twice (haha), then we get it.

If it's a wiring problem, it's most likely that a wire's either broken right where it goes into the terminal in a plug on the end of a wire, and sometimes wriggling each wire carefully will reveal it by it's easy bending compared to the rest of the wires, or it'll be chafing of the loom which we just look for..

If it is a crook dash or ecu, you'll get it if you read carefully..  And follow the process as spelt out.. tedious though it is. They often say test every friggin thing, then if it's none of them, it's an ecu or dash. It's a process of elimination. Very tedious but it does get the right component in the end, rather than taking expensive guesses. If you have a buddy though that would let you borrow his dash or ecu, or bike, to plug your components into, that makes it easier, and it's what dealers do all the time, borrow a part off a customers vehicle to try.


I think that if I was running it in gear at revs like that up on blocks, I'd take the wheels off..

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I was able to fabri-cobble an adapter to test the oil pressure.  I hate the fact that metric bolts have to have 15 different thread pitches.  The access ports for the oil pressure testing are M8x1.5.  Not a stand size for the gauge sets.  I ended up taking a caliper nipple, turning it on my lathe, and soldering it to a separate fitting.  My first attempt with JB Weld was not as successful.  

The results are not what I expected.  The oil pressures for the 1st clutch is within specification.  

The second clutch oil pressure was 0 in first gear and only read 50 psi in second gear.  There is a list of probable causes, and I will need to RTFM, but any suggestions as what might be the most likely issue?



"Free is worth saving up for"

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Morning.. Well I haven't been able to find a manual for that model. The manuals in this site keep getting within a  few seconds of completing and then fail.. repeatedly.

I've been having a read in other manuals though and looking at the parts lists. If one of the clutches is worn out I'd expect it to slip in more than one gear.. if you could get it to load up enough without changing itself down that is. In cars a way to detect slip in a clutch is to pull it down manually at high revs/speed and see if it's slow/slippy feeling or doesn't brake the vehicle sharply.

From my reading, if it's changing gears ok, and the only symptom is the over revving at start, then I'd be suspecting a worn clutch. If it was electrical or valve body problems then I think it would have other problems, not just a slow take off.

As you are suspecting though, it seems logical the throttle position sensor, or the rev detection calculation could cause it..  But I'd suspect then some of the other changes would be at the wrong speeds.

I think if it was me I'd be pulling the clutches out and inspecting them.. It's not something I'd like to do without a definite diagnosis normally, but in this case I think it's the pragmatic thing to do. I see there's also a centrifugal clutch, which will be for taking off.. It would be best to check that first though..



Edited by Mech
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Ok.. Perseverance always wins. Giving up never does.

I finally found the right book.

And, looking through the diagnostic section I see there are five things that can cause low pressure to the number two clutch.

Shift valve.

1st orifice control valve.

2nd shift clutch.

Feed pipe A.

Oil guide pin.

Of those five though, only three can cause a problem with the oil pressure to number two clutch, but not number one clutch. Since number one clutch pressure is right we can conclude that it has to be one of those three.. or the centrifugal clutch is worn which would be the first thing to check as you are pulling it apart.

The three possible faults that only effect number two clutch pressure are..

1st orifice control valve.

2nd shift clutch.

Feed pipe A

I think I'd check the control valve first if that's easy to get at, then start pulling the front cover off.. I'm not sure where the feed pipe is but I presume it's in there. I'd check the pipe and the centrifugal clutch and the number two clutch for wear, or defective seal rings that feed the hydraulic pressure to the no 2 clutch. 



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So I went back and tested the shift solenoid and it's inconsistent.  Sometimes it engages with 12v and sometimes it doesn't.  I have fired up the proverbial parts cannon and ordered a new one.   Its scheduled to be delivered on Thursday, so I have my fingers crossed.

Thanks for your help.  



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I did some more reading and the 1st orifice control valve, which I thought was a solenoid, was actually a shuttle valve in the valve body, and so that's unlikely to give low pressure, it will either move or not, and I think it must be moving for there to be some pressure to the clutch.. I think we can ignore that one.

That leaves the pipe or the clutch pack.. or the centrifugal clutch.

If that solenoid doesn't do the trick(and I'm dubious), then I think the first thing to check is the centrifugal clutch, then the shift clutch and then the pipe..

I'll keep an eye out for the progress.  Good luck.

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As suspected, the solenoid did not fix the issue, although it wasn't working consistently, so it's not a complete miss from the cannon.

From the service manual chart, if 1st clutch pressure is good (which it is), then it's either the second clutch or the shift valve assembly.  Can there be any insight to the results of the second clutch pressure when there is no pressure in 1st gear and only partial pressure in second gear?

I would find it difficult to believe that the other causes, feed pipe/guide pin would be the cause.  If that was the case, then there may be other issues (chunks are bad)

If it end up being the clutch.  I don't know if I have the time or interest to replace.  Do you have an estimate of the hours a shop would charge to replace?

Thanks again for you input. It is appreciated 


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That solenoid might be running on/at a duty cycle, so it's voltage is being constantly switched on and off. Digital gauges aren't very good at detecting that. That might be why you were getting varying voltages at it.

The chart near the beginning of the diagnosis section shows the causes of one, two or both clutches having low hydraulic pressure. I'm not sure what sort of insights you are after about that but if you are a bit more specific about any theories you may have I will try to figure out if they are possibilities.

The 1st orifice control  valve they mention as a possibility for low pressure to the second clutch is a shuttle valve in the hydraulic valve body. Shuttle valves have to be worn right out, or rather the aluminum housing they slide in has to be worn right out, before they cause low pressure.. Normally they don't move because they are jammed by crap, or they break a spring and move one way and stay there.. 

In your case it's most likely that a sealing ring either in the piston that applies the clutch, or on the shaft that supplies/feeds the pressure, will be worn or broken, or, the clutch is so worn that it's piston is moving to far and allowing it's seal to get almost out of it's bore, or, the pipe has a split in it which could allow a loss of pressure down to a certain level.

There is a centrifugal clutch for taking off, and if that was worn it would cause the high revs take off. The two actual clutches are used for shifting gears and since it seems to work right, with no slip once the bikes going, it would seem they do grip well enough despite the low pressure to No2 clutch. When it goes into a gear at idle and stopped, one of the shift clutches lock up to engage a gear and then doesn't get slipped again till it's time to change gears. If one of the two clutches was so worn, or had such low pressure to allow slipping, I'd expect that slipping to be at gear change and under power.

I haven't had one of those apart but I've had the older models with a centrifugal and manual shift clutch apart and they are easy to work on. The only complication with this one is that it has some hydraulic hoses going onto the cover. The cover's easy to get at though so it should be an easy job. I'd definitly be pulling that front cover off and inspecting the centrifugal clutch as the main suspect, but I'd check the pipe and the other two clutches at the time.. and their sealing rings.

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