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Discussion Starter · #1 ·
Just got in from a weekend ice fishing trip. - 15 C
Quad just not running right. Will be looking at fuel filter first ,whats next?
Quad runs really good at first for the first 15 mins then it starts running like the choke is on or on one cylinder if it was a two cylinder. louder and no power.
When it starts happing i am normally in 3 gear then after 200 feet i shift to 2nd then about 200 ft again I have to shift to 1st . it starts again and does not goo away.
Almost sounds like floating valves when over speeding the engine.
If I shut the engine off then hit the starter ,if feels like the timing is out and has a hard time to crank for a 1/4 of a revaluation ,then it cranks normal and starts.
When I let the quad cool down ,it runs fine again .
I did shut off the fuel and let it run till it stopped so i could hear the electric fuel and it sounded normal.
Fuel fitter ? Electrical ? Failing spark plug ?
Any one else have this before.
 

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is the fan coming on at all ??. if not ?, it will go into safe mode by shutting down the c.d.i., which the fuel cut-off relay to the fuel pump works off of.
 

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If you think it's fuel choked or starved take a look at the spark plug

Mine did similar. I rode with the choke on and fouled the plug.
I did the same exact same thing. Was trying to operate at 1/2 choke.
After removing choke it started running ok, but not as good as previously, but was not taking throttle at low rpm smooth as it should and would spit every once in awhile and when I went to check the spark plug it was not even tight.

Replaced the plug with proper NGK and runs great.

Heads up when going after the spark plug, I had too use a thin walled socket for clearance instead of a regular spark plug socket. I think someone (previous owner) did not have proper socket is why the spark plug was left loose in the jug.

Watch your exhaust and see if you see any soot as an indicator of running too rich due to carb flooding or choke not fully off and gently move your choke control towards choke and towards off and see how it responds.
 

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Discussion Starter · #5 · (Edited)
is the fan coming on at all ??. if not ?, it will go into safe mode by shutting down the c.d.i., which the fuel cut-off relay to the fuel pump works off of.

Fan did not come on at all ,this might be it . hot oil light did not come on either but might be in line with the fan system.
On the other hand it was very cold out side ,wind chill factor was around -35
Might have to wait till summer to get it hot.But will check for broken wires etc.
Thanks for that unknown in put.
 

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is the fan coming on at all ??. if not ?, it will go into safe mode by shutting down the c.d.i., which the fuel cut-off relay to the fuel pump works off of.

Fan did not come on at all ,this might be it . hot oil light did not come on either but might be in line with the fan system.
On the other hand it was very cold out side ,wind chill factor was around -35
Might have to wait till summer to get it hot.But will check for broken wires etc.
Thanks for that unknown in put.
bad oil temp sensor switch ?, or bad fan control unit :). right hand side, behind metal cover ( if it's there ? ) forward switch, unplug it, turn key on, ground that wire to the engine/frame for a good ground, fan should kick on if fan and control unit is good ?, if not ?, then control unit for fan is bad ?, or fan is bad ?. if fan does come on ?, then the oil temp sensor switch is bad.
 

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Good info about oil cooling fan on 86 Honda.

First chance I get I'm going to try and find the oil temp sensor wire on mine and ground it and see if the fan will run. Appears the oil temp sensor sens a ground signal to the fan control unit (My 86 Honda fan is old and don't look very healthy) The oil temp light does briefly come on when key is first turned on but that may not really indicate the fan will run or the oil temp sensor is ok. The light might just be indicating that their is 12v to the fan control unit. (looking at the wiring diagram)
Not a good thing when they overheat.

Wondering if his 86 Honda oil cooler fan would ever run at minus 35F though?

My Yamaha does not use a fan on the oil cooler, owners manual says to speed up the engine if the RED oil temp light ever comes on and engine has been running at slow speeds on very hot day. Never have seen the Yamaha or the Honda oil temp light come on continuously when operating the engine on hot days though.
 

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Good info about oil cooling fan on 86 Honda.

First chance I get I'm going to try and find the oil temp sensor wire on mine and ground it and see if the fan will run. Appears the oil temp sensor sens a ground signal to the fan control unit (My 86 Honda fan is old and don't look very healthy) The oil temp light does briefly come on when key is first turned on but that may not really indicate the fan will run or the oil temp sensor is ok. The light might just be indicating that their is 12v to the fan control unit. (looking at the wiring diagram)
Not a good thing when they overheat.

Wondering if his 86 Honda oil cooler fan would ever run at minus 35F though?

My Yamaha does not use a fan on the oil cooler, owners manual says to speed up the engine if the RED oil temp light ever comes on and engine has been running at slow speeds on very hot day. Never have seen the Yamaha or the Honda oil temp light come on continuously when operating the engine on hot days though.
heads up !!. these models have to get very...VERY hot before the fan kicks on !. you can't get them to kick on just sitting there ?, you have to ride/work that puppy, then once they get hot ?, then the fan will kick on ( if everything is working ? ), been there, done that !..lol.
 

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Good info about oil cooling fan on 86 Honda.

First chance I get I'm going to try and find the oil temp sensor wire on mine and ground it and see if the fan will run. Appears the oil temp sensor sens a ground signal to the fan control unit (My 86 Honda fan is old and don't look very healthy) The oil temp light does briefly come on when key is first turned on but that may not really indicate the fan will run or the oil temp sensor is ok. The light might just be indicating that their is 12v to the fan control unit. (looking at the wiring diagram)
Not a good thing when they overheat.

Wondering if his 86 Honda oil cooler fan would ever run at minus 35F though?

My Yamaha does not use a fan on the oil cooler, owners manual says to speed up the engine if the RED oil temp light ever comes on and engine has been running at slow speeds on very hot day. Never have seen the Yamaha or the Honda oil temp light come on continuously when operating the engine on hot days though.
heads up !!. these models have to get very...VERY hot before the fan kicks on !. you can't get them to kick on just sitting there ?, you have to ride/work that puppy, then once they get hot ?, then the fan will kick on ( if everything is working ? ), been there, done that !..lol.
I suspected that it would have to get very hot before the fan or light would come on. I've felt the Big Bear Yamaha almost set my britches legs on fire in the summertime idling along thru brush and the oil temp light never ever came on.

I do not see any specs listed for the operating temp of the oil temp sensor but suspect it might be around 300F.
 

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Good info about oil cooling fan on 86 Honda.

First chance I get I'm going to try and find the oil temp sensor wire on mine and ground it and see if the fan will run. Appears the oil temp sensor sens a ground signal to the fan control unit (My 86 Honda fan is old and don't look very healthy) The oil temp light does briefly come on when key is first turned on but that may not really indicate the fan will run or the oil temp sensor is ok. The light might just be indicating that their is 12v to the fan control unit. (looking at the wiring diagram)
Not a good thing when they overheat.

Wondering if his 86 Honda oil cooler fan would ever run at minus 35F though?

My Yamaha does not use a fan on the oil cooler, owners manual says to speed up the engine if the RED oil temp light ever comes on and engine has been running at slow speeds on very hot day. Never have seen the Yamaha or the Honda oil temp light come on continuously when operating the engine on hot days though.
heads up !!. these models have to get very...VERY hot before the fan kicks on !. you can't get them to kick on just sitting there ?, you have to ride/work that puppy, then once they get hot ?, then the fan will kick on ( if everything is working ? ), been there, done that !..lol.
I suspected that it would have to get very hot before the fan or light would come on. I've felt the Big Bear Yamaha almost set my britches legs on fire in the summertime idling along thru brush and the oil temp light never ever came on.

I do not see any specs listed for the operating temp of the oil temp sensor but suspect it might be around 300F.
your pretty damn close on the temp !!..lol. my service manual is out in the shop , but if I remember right ?, it's around 250F something ?. my bud told me all about these models, I was in the same boat on this many moons ago, noticed the fan was not coming on ?, he told me these models have to get very hot to kick the fan on ?. ( he's head mech at my local Honda dealership ), sure enough, I road the crap out of her, and then the fan kicked on !. sitting at idle ?, they won't come on at all.
 

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Discussion Starter · #11 ·
Got into the garage today ,just to unload my gear . Tried to turn the fan by hand it it did not turn because it was frozen in ice. broke it free ,feels good. Have to wait a few weeks till all the ice build up melts away . Hopfully there is an inline fuse for the fan .
Anyone have a wiring diagram. they can post .
Thanks.
 

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Got into the garage today ,just to unload my gear . Tried to turn the fan by hand it it did not turn because it was frozen in ice. broke it free ,feels good. Have to wait a few weeks till all the ice build up melts away . Hopfully there is an inline fuse for the fan .
Anyone have a wiring diagram. they can post .
Thanks.
the fan fuse should be in the fuse box in the trunk :).
 

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Discussion Starter · #13 ·
Got into the garage today ,just to unload my gear . Tried to turn the fan by hand it it did not turn because it was frozen in ice. broke it free ,feels good. Have to wait a few weeks till all the ice build up melts away . Hopfully there is an inline fuse for the fan .
Anyone have a wiring diagram. they can post .
Thanks.
the fan fuse should be in the fuse box in the trunk :).
Thanks ,I will check it . High oil temp light does come on as soon as you turn the key on ,then shuts off as it is suppose to.
Did not come on when out quading ,not sure if it does every time the fan kicks on.
The fan did come on last year when driving in deep snow because I was doubling someone . Did not come on this year riding single.
 

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Got into the garage today ,just to unload my gear . Tried to turn the fan by hand it it did not turn because it was frozen in ice. broke it free ,feels good. Have to wait a few weeks till all the ice build up melts away . Hopfully there is an inline fuse for the fan .
Anyone have a wiring diagram. they can post .
Thanks.
the fan fuse should be in the fuse box in the trunk :).
Thanks ,I will check it . High oil temp light does come on as soon as you turn the key on ,then shuts off as it is suppose to.
Did not come on when out quading ,not sure if it does every time the fan kicks on.
The fan did come on last year when driving in deep snow because I was doubling someone . Did not come on this year riding single.
if the oil temp sensor is working right ?, and the fan control unit is working right ?, and the fan is working ?, the oil temp sensor sends a pulse to the fan control unit, which then kicks the fan on. it's posb you blew the fan fuse if the fan seized up from ice ?. or worse case ?, you burnt out your fan control unit ?. this is on the front left of frame, behind the splash guard, sits in a rubber holder on top of the frame tube.
 

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Discussion Starter · #15 ·
the fan fuse should be in the fuse box in the trunk :).
Thanks ,I will check it . High oil temp light does come on as soon as you turn the key on ,then shuts off as it is suppose to.
Did not come on when out quading ,not sure if it does every time the fan kicks on.
The fan did come on last year when driving in deep snow because I was doubling someone . Did not come on this year riding single.
if the oil temp sensor is working right ?, and the fan control unit is working right ?, and the fan is working ?, the oil temp sensor sends a pulse to the fan control unit, which then kicks the fan on. it's posb you blew the fan fuse if the fan seized up from ice ?. or worse case ?, you burnt out your fan control unit ?. this is on the front left of frame, behind the splash guard, sits in a rubber holder on top of the frame tube.
A lot of good information here. Its going to be a few weeks before I have a look at it. Just moved into a new house and busy fixing up the old house on weekends and after work . Took last weekend off for the first time this year.
Will be posting what I find ...
 

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Got into the garage today ,just to unload my gear . Tried to turn the fan by hand it it did not turn because it was frozen in ice. broke it free ,feels good. Have to wait a few weeks till all the ice build up melts away . Hopfully there is an inline fuse for the fan .
Anyone have a wiring diagram. they can post .
Thanks.

See if you can download a freebie HONDA SERVICE manual from one of these links from this site.
I downloaded the Honda manual awhile back and not sure which one of these links it came from. I had to try twice to get the download to run on windows 10. It covers the 86-89 fourtrax and foreman 350 4x4 and shows wiring diagrams. Lots of good info.
See the note at the bottom of my C/P about the oil temp sensor degrees when the fan and or light comes on and see the note at the bottom of pg 22-3 that indicates that after 87 the fan control unit shut off the motor. (it says motor??I do not know if this is the engine or what, because I do not see the fan control unit connected to the CDI in the wiring diagram, but it may be a sneaky path for such????or on a different wiring addendum wiring diagram somewhere???
Anyway try these links for a service manual and more fan control info.


Not sure which exact one but one of these links is a free download for a Honda 1986 350 Fourtrax Foreman Service Manual. I downloaded one awhile back from one of these links. Try the links one of them will get you the manual if no one else chimes in with a exact link for such.

Hint: Burn yourself a CD disk when you get it downloaded and if your computer crashes in the future you can re-install and also view the CD on other computers.


The link is from this site.
http://www.hondaatvforums.net/forum...lp/7699-need-service-manual-1987-trx350d.html

Free Service Manual download link
1986-1989 Fourtrax-Foreman 350

Link forum post about Honda fan control
http://www.hondaatvforums.net/forums/honda-fourtrax/81250-1988-forman-fourtrax-trx350d.html

I also seen on pg 22-3 of the Honda service manual that the fan should come on and run when the oil sensor reaches 270-306F and the Oil temp light should come on as a warning when the oil temp is over 378-414F.
 

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Thanks ,I will check it . High oil temp light does come on as soon as you turn the key on ,then shuts off as it is suppose to.
Did not come on when out quading ,not sure if it does every time the fan kicks on.
The fan did come on last year when driving in deep snow because I was doubling someone . Did not come on this year riding single.
if the oil temp sensor is working right ?, and the fan control unit is working right ?, and the fan is working ?, the oil temp sensor sends a pulse to the fan control unit, which then kicks the fan on. it's posb you blew the fan fuse if the fan seized up from ice ?. or worse case ?, you burnt out your fan control unit ?. this is on the front left of frame, behind the splash guard, sits in a rubber holder on top of the frame tube.
A lot of good information here. Its going to be a few weeks before I have a look at it. Just moved into a new house and busy fixing up the old house on weekends and after work . Took last weekend off for the first time this year.
Will be posting what I find ...
If it is the fan control unit, you'll have to find a used one. I just replaced one for a friend, and couldn't find any new. I'll include a link for the ebay seller that I got one from- he's got another.

D820 HONDA TRX350 TRX350D TRX 350 D 4X4 FOREMAN 86 - 89 FAN TEMP CONTROL BOX | eBay
 

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Discussion Starter · #18 ·
plug nut

First thing I checked was the spark plug ,found that the rubber boot was not pushed all the way down onto the spark plug . Then I pulled the boot off to find that the spark plug did not have the nut on the end,only the treads and no nut was found in the boot. Can any one confirm that a 86 honda 4 trax should or should not have a nut or tab what ever you want to call it at the end of the plug for the boot to connect to .
 

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Depends if the plug cap has been changed I would think. Look in the cap and see what size the bit that fits on the plug is, some push on the thread and some push on a fitting screwed on the plug
 
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