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Discussion Starter #1
So a little backstory, the first fourwheeler I ever rode was a TRX350D. The mountain I worked at when I was a kid had a small fleet of Honda's and this was the oldest so it was the usual go to for cutting and marking mtn bike trails and race courses. The body was hammered but mechanically it was such a reliable machine it always seemed to survive another year. Keep in mind they were used just about every day year round in central NH.

A buddy found this thing on one of the local FB groups and knew I had been looking for a manual shift Honda 4x4. Outside of that, I didn't really care what year it was from. It was listed as needing a fuel pump and was picked up cheap. I couldn't pass up saving this thing.




I've already got it in the garage and began tearing it down today to assess some stuff and get it cleaned up. It needs a serious bath of Simple Green and a visit with the pressure washer when its not 30* outside. For now, the rear plastics and racks are off so I can access everything fairly easy and get it all cleaned up.

What is wrong:
1) No Spark
2) Dead Fuel Pump
3) Front Wheel Bearings are a little worn
4) Steering stem bushing is toast so the handlebars kind of rock around on the steering shaft
5) Rear Brake Pedal cable snapped
6) Rear Brake Handbrake cable seized

I already have a slew of parts on the way. (Pump, Ignition Coil, CDI, Stator, Pickup Coil, Fuel Pump Relay, Ignition Solenoid, Both rear brake cables, Acerbis Handguards, ODI Rogue Lock On Grips) I figure whatever doesn't fix it will be saved as a spare since parts are getting harder to find. Bringing my meter home tomorrow to start ohm'ing out various parts so I have a direction once the parts all get here.

Today I grabbed a new battery and put it on the tender so it would be fully charged. When the ignition is turned on the oil light and neutral light come on as expected. Push the start button and the solenoid and pump click lightly but nothing else. I can jump the poles on the solenoid and the starter spins freely and will turn the motor over. Pulled the plug to check for spark, jumped the poles on the solenoid and tried kicking it and have nothing there so it looks like a combination of issues.
 

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Looks like a great start to the project. You already have the "hard" part done, which is it looks good. More often that not these things look they have been through hell. Getting them running is the easy part.

Rob
 
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Discussion Starter #3
Looks like a great start to the project. You already have the "hard" part done, which is it looks good. More often that not these things look they have been through hell. Getting them running is the easy part.

Rob
Thanks! The plastics definitely all in one piece but the shine from the rain has ya fooled :laugh: They are in pretty good shape with no real cracks. Just lots of spiderwebbing on the cockpit side of the fenders. Once its running I'm going to move on to the cosmetics.
 

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Good job. Gots lights.
Stick with OEM Parts that will keep you straight and true. I started with cleaning the scale out of the fuel tank, petcock. Overhauled carb. Check your valves to make sure they’re operating.
 

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Discussion Starter #5 (Edited)
NC shuts down whenever it snows so I got some extended garage time today.

Downloaded the Service Manual off here and went to town with the multimeter trying to diagnose this no spark thing.

1) Igniton Coil Primary coil resistance 0.3-0.4 where it calls for 0.1-0.2. Both Secondary checks were within spec. When checked from the CDI end of the harness, its .2-.4.
2) Pulse Generator - Ok
3) Alternator Exciter Coil - manual says there is a Bl/R wire (Black/Red Stripe) but there is not one in that bunch of connectors at the chassis end on my bike. I have Yellow, Blue/Yellow and Green/White which matches up with the 88+ Wiring diagram. Everything here seems to check out in spec.
4) RR Line - Ok
5) Charging Coil - Ok
6) Regulator - Ok
7) Ignition solenoid - Ok
8) Ignition switch throws 12v to everything it should once its pressed

Going to start with the Ignition coil and solenoid. Solenoid checks out on the meter, but I can get it to turn the starter when the poles are jumped, not when the button is pressed. Battery is fully charged and verified by both the tender and the meter when connected at various points of the harness. The Coil's primary resistance is at the limit or over depending on how its tested. Those two are easy to change.
 

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I'd start with that solenoid too since you mentioned it weakly clicks when the starter button is pushed. Also check and clean the frame ground cable that comes out of the wiring harness under the seat, where it bolts to the top of the frame at the seat bracket.

3) Alternator Exciter Coil - manual says there is a Bl/R wire (Black/Red Stripe) but there is not one in that bunch of connectors at the chassis end on my bike. I have Yellow, Blue/Yellow and Green/White which matches up with the 88+ Wiring diagram. Everything here seems to check out in spec.
You might be looking at the wrong specs column in the manual? The Fourtrax & Foreman have differing systems:



Readings should be taken at the CDI harness plug after unplugging the CDI, so you'd notice if there are any faults... such that a wire is bad or plugs are corroded etc., between the CDI and other components undertest.

You mentioned that the fuel pump runs when the ignition switch is turned on correct?

Also the '88 and up models kill the ignition if the motor overheats... so check the fan control circuits and oil sensor as well.

Finally, if IGN & Kill switches are good, check the regulator/rectifier connections (between each yellow wire and yellow to ground) as the manual shows.

Sounds like you are getting close...!
 

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Discussion Starter #7
I'd start with that solenoid too since you mentioned it weakly clicks when the starter button is pushed. Also check and clean the frame ground cable that comes out of the wiring harness under the seat, where it bolts to the top of the frame at the seat bracket.

3) Alternator Exciter Coil - manual says there is a Bl/R wire (Black/Red Stripe) but there is not one in that bunch of connectors at the chassis end on my bike. I have Yellow, Blue/Yellow and Green/White which matches up with the 88+ Wiring diagram. Everything here seems to check out in spec.
You might be looking at the wrong specs column in the manual? The Fourtrax & Foreman have differing systems:

Readings should be taken at the CDI harness plug after unplugging the CDI, so you'd notice if there are any faults... such that a wire is bad or plugs are corroded etc., between the CDI and other components undertest.

You mentioned that the fuel pump runs when the ignition switch is turned on correct?

Also the '88 and up models kill the ignition if the motor overheats... so check the fan control circuits and oil sensor as well.

Finally, if IGN & Kill switches are good, check the regulator/rectifier connections (between each yellow wire and yellow to ground) as the manual shows.

Sounds like you are getting close...!
Thanks for the extra insight. All of those tests at the CDI plug were good. I will clean that ground though and see if that helps any. The quad was sold with a dead fuel pump being the culprit. However it clicks when the start button is pressed but I don't hear it run or hum like a normal pump. Just a dull click. I've bucket tested it and its dead.

Now here is the kicker, the fan is hard wired to a toggle switch on the handlebars. But, its been like that for a long time. The oil light flickers on when the key comes on then goes right back off. Although it doesn't do it every time I turn the key on and off.

Is there a way to test the fan control circuits and oil sensor? I haven't flipped through the manual to test those yet.
 

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Yeah those tests are in the manual. Your fan control box sounds like it is functional at least though, since the temp light comes on normally for a few seconds then goes off, when you turn the ignition on. The oil temp sensor resistance from the center connector post to ground should measure just over 10k ohms at room temp if I remember right... The spec is in the manual.

You can test the fan control unit by turning the ignition switch on, then unplug the wire (green wire I think?) from the oil temp sensor (it is under the little cover on the extreme lower- right side of the motor, just forward of the foot peg) and ground that wire. The fan should run while that wire is grounded. If not, check whether the previous owner left the fan motor connected to the harness coming from the fan control module, when the fan manual over-ride switch was added on.

You can still buy those OEM fuel pumps. Check around... its been a while since I shopped for them. They are a bit pricey at $121 + shipping on Partzilla, but the cheaper china knockoffs will waste both your time and your money, so... good luck!
 

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I like what ya sayin what ya sayin (ZZ Top).

Thermo sensor will cause light to come on steady when circuit closed (low resistance or lead grounded); too high resistance will leave circuit open.

There are things you can test in the fan control and those you can’t. You can run the fan (to make sure it works) and you can test the oil thermo unit BUT can you test the fan control overheat circuit without running it?

I found my blue wire disconnected after mine overheated on the trail and quit. Connected it and fan works good. I had to drive it in low gear for ten minutes before it got hot enough to verify that it works.
 

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Be very careful with that fuel pump cushion it only goes on one way. It also tears easily especially if your hands are wet with fuel.

OEM fuel pump is the best. Beware OEM “replacement” or similar weasel words.
 

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Discussion Starter #11
Be very careful with that fuel pump cushion it only goes on one way. It also tears easily especially if your hands are wet with fuel.

OEM fuel pump is the best. Beware OEM “replacement” or similar weasel words.
Good deal. I'll give that fan relay test a shot when I get home next week. Most of the parts should also be there by then.
 

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Discussion Starter #12 (Edited)
Alright. Got home from a work trip and got to work.

I have spark now. New coil fixed it. However it still won’t hit. Fuel pump and relay work as they should. New solenoid fixed the starter issue. But it still won’t hit even on starting fluid.

Tried a new cdi, fuel relay and regulator...same situation.

Starting to run out of ideas.

Do these things still generate spark if the Run/off switch is bad?
 

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If you got good spark while cranking it should fire. It sounds like you got everything working now (new NGK spark plug too?) so the next thing to check is the compression. It should reach max between 178-206 PSI with the throttle held open while cranking it with the starter. Let us know how it goes...
 

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Discussion Starter #14
If you got good spark while cranking it should fire. It sounds like you got everything working now (new NGK spark plug too?) so the next thing to check is the compression. It should reach max between 178-206 PSI with the throttle held open while cranking it with the starter. Let us know how it goes...
Yep. There’s the issue. Only rises to the mid 60’s on my gauge.

Damnit.
 

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Ok, next two things to check are the timing chain slack and the valves lash. Valve lash should be .003" on both intake and exhaust valves, COLD motor. Take your pick where to begin... but complete them both before checking compression again. Do you know how to do those or would you rather have some help..?
 

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Discussion Starter #16
Ok, next two things to check are the timing chain slack and the valves lash. Valve lash should be .003" on both intake and exhaust valves, COLD motor. Take your pick where to begin... but complete them both before checking compression again. Do you know how to do those or would you rather have some help..?
Yeah I have the wrenching part down. Just suck at diagnosing. I’m leaning toward a stuck valve or jumped timing. I pulled the plug to do the compression test and it was bone dry. Kind of odd considering how much I’ve been cranking the machine.
 

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I'm thinking along the same lines as you... and you are doing fine with both the wrenching AND the diagnosing! One other thing... make sure the intake or the exhaust hasn't been plugged up by a rodent building a new winter home...
 

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Discussion Starter #18
Watching 24hr of Daytona in the garage so I pulled the valve cover. Cam chain is tight. Can’t find my feeler gauges so I’ll grab some in the morning, reassemble and set the lash.

I did palm the valves to ensure the stem retainers didn’t fly across the garage and all the valves all move freely. So none are stuck.
 

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Discussion Starter #19
Because pictures are cool. Valve cover and rocker assembly off, threw on the new ODI rogue lock on grips and some Acerbis handguards. Also touched up a lot of the metal in between diagnostic attempts today.
 

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Are the rocker heels (where they follow the cam lobes) in good condition? Is the cam timing correct too?

To verify, rotate the motor until both cam lobes are facing down and the "T" mark on the flywheel lines up with the mark in the left side cover. That is TDC on the compression stroke... The two marks on the cam sprocket should be a fairly close match (never perfect due to chain wear) to the top surface of the head. Photo attached... Have fun!
 

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