[Goober]

I revealed my 86 TRX350 to my riding friends this weekend and put almost 70 miles of rough trail riding on her. Yeah she got muddy but never failed to complete a trail segment.
The spark plug kept getting fouled musta cleaned it twice a day. Reduced the idle jet setting by a quarter. I am going to clean the NOS OEM air filter and reoil it--after 25 years in the bag it might need it.
The carb has a new starter jet BUT it might have some 31 year old dirt in it still.
Any other suggestions?

BTW I got rave reviews even by strangers I met on the trails!! Pumped!!! Thanks
New plug?

 

[retro]

Yep, it looks great with dirt & mud on it!

You didn't mention the elevation you ride it the most at, so I assume its generally under 1500-2000 feet range? With bone stock jetting the spark plug will begin to show a rich running condition above 1000 feet elevation. Above 2000 feet the plug is likely to foul often, unless the motor is being pushed a bit. 2500 feet & up ya gotta retune for... or else.

Assuming elevation isn't an issue I'd go back to looking at the basics. Beginning with the Ign. coil... & then check the spark plug wire, the float level in the carb, vent hoses clear, etc.

You have an 86 which means it gets power for the CDI & Ign coil from the alternator only, so operating at low RPMs under load (slow, low RPMs riding/climbing grades/heavy payloads etc.) leaves the ignition a bit under its optimum. If you suspect that this may be a contributing factor you can test for it by riding in the same/similar conditions, but use lower gear selections in order to raise & keep the RPMs up a bit more... see if it quits fouling the plug.

 

[Goober]

Good comments Retro I usually ride at 3200-5500 ft and the peak you see in the BG is 6800ft. I never thought about our elevation much that 5000 number was for mountain folks--ooops I guess that's me now.
I will take a look at my jet numbers pretty sure they're stock

 

[retro]

Yer onto it...! I think the FSM lists jet sizes/specs for high elevations, so I'd start with those and fine tune that recommended setup if its still not ideal, by taking plug readings. Betcha its gonna put you real close though.

 

[shadetree]

Yep, it looks great with dirt & mud on it!

You didn't mention the elevation you ride it the most at, so I assume its generally under 1500-2000 feet range? With bone stock jetting the spark plug will begin to show a rich running condition above 1000 feet elevation. Above 2000 feet the plug is likely to foul often, unless the motor is being pushed a bit. 2500 feet & up ya gotta retune for... or else.

Assuming elevation isn't an issue I'd go back to looking at the basics. Beginning with the Ign. coil... & then check the spark plug wire, the float level in the carb, vent hoses clear, etc.

You have an 86 which means it gets power for the CDI & Ign coil from the alternator only, so operating at low RPMs under load (slow, low RPMs riding/climbing grades/heavy payloads etc.) leaves the ignition a bit under its optimum. If you suspect that this may be a contributing factor you can test for it by riding in the same/similar conditions, but use lower gear selections in order to raise & keep the RPMs up a bit more... see if it quits fouling the plug.

you better re-read that service manual bro !...the 1986 does NOT get it's fire from the stator !..it gets it's fire from the battery .

 

[SamUK]

There's always one brainbox isn't there ^^^ haha :laugh:

 

[retro]

you better re-read that service manual bro !...the 1986 does NOT get it's fire from the stator !..it gets it's fire from the battery .

The 1986 TRX350 Foutrax is an AC-CDI system. It was used for 1986 models (brought over from the 85-86 ATC350X motor) only. It is powered from stator windings of the rotating motor. It it not dependent on the starting battery for anything. None of its major components interchange (CDI, Stator, Kill switch, Ignition switch etc,) with the DC-CDI systems used in subsequent years.

In 1987 the TRX350s got their own (all new design) DC-CDI ignition system powered by the starting battery. In 1988 the new DC-CDI system was upgraded with what Honda termed a "Revolution Research Line" DC-CDI that continued to be used on all 88 & later (thru 92 in Canada) models.

The RRL equipped DC-CDI incorporated the regulator/rectifier into its schematic which allowed monitoring of motor rotational speed (or lack of it) to provide a more robust safety shutdown/fuel pump control system, in event of any catastrophic crash & burn scenarios.

Its pretty easy to get each of those CDI schemes mixed up (don't ask me how I know ) so when I'm troubleshooting an '86 I immediately think of the ATC350X AC-CDI carryover... works for me so far.

 

[shadetree]

all I know is, and was told from my guy at Honda, the 1986 does not fire the plug from the stator, it fires, draws juice from the battery. where is on later models, the firing process was incorporated into the stators to fire the spark plug. don't have my service manual in front of me right now ?, but I will scan through it, and see where I seen this .

 

[Goober]

Thanks for the comments and compliments I need to go check out my bros at the local Honda shop--see if they have a jet kit, get a fresh plug and ping them for local tuning tips.

 

[retro]

The guy at Honda who told you that was dead wrong. I posted the FSM info above that proves it. No battery is required to provide ignition to an 86 TRX350, its not even in any part of the ignition circuitry. The 86 is an AC-CDI and all later years are DC-CDI requiring a battery. I got into trouble with those differences when I gave some wrong troubleshooting advice in a thread a while back, and I ate my crow.... but ain't doing it again! LOL

Honda techs are humans too... we all make those kinda mistakes, no biggie...

 

[retro]

Thanks for the comments and compliments I need to go check out my bros at the local Honda shop--see if they have a jet kit, get a fresh plug and ping them for local tuning tips.

Great idea!!!

 

[misterclean59]

On an old machine like this the needle jet and needle are probably worn causing it to run slightly rich. I had a friend ask me about poor fuel economy on his high mileage Gold Wing. He was at his wits end trying to fix it. I suggested this all all four carbs. He came back and that was it. It didn't run any better, just more efficiently.

 

[hodge5]

Beautiful quad, Goober. Man, do I want a 350D, real bad.

 

[_Wilson_]

I might be able to help you out hodge, i might be selling my 86 350d friend of mine got a deferent machine and I'm going to try and purchase his 300, maybe a while before i know anything .... So keep me in mind.

 

[Goober]

Thanks Hodge I love this thing.
When we got to the top of the trail there was a bunch of UTVrs waving me up like I was the Rally leader! My daughter told me the group waited for us to leave the peak so they could watch me descend. So cool.

Guys at the Honda shop hooked me up with a 132.5 main jet and a couple plugs for less than $10.
I have a spare carb bought for $40. Needed a rebuild & starter valve; main jet baffle was missing. The float looked rough; ordered a new float cuz guys didn't have a float gauge to check it. So I have like $160 in this second carb!

 

[retro]

I'm buying spare parts for mine when I find them cheap too... You got a real nice bike. Shes worth it IMHO...

Great trail riding story too!

 

[hodge5]

I might be able to help you out hodge, i might be selling my 86 350d friend of mine got a deferent machine and I'm going to try and purchase his 300, maybe a while before i know anything .... So keep me in mind.

I will- thanks.

 

[Goober]

Found the problem
The fan wire wasn’t connected properly to the Fan Control Unit. The sputtering was the engine overheating. Reconnected and runs fine now