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Discussion Starter #1 (Edited)
With the time I've spend on these forums, I thought I had posted before, but apparently this is my first. So hi, I'm David.


I inherited a worn out hulk of a 1998 Honda TRX 450. The vehicle had sat uncovered outdoors for three or four years. I have been following the basic maintenance outlined here: https://www.hondaatvforums.net/threads/getting-an-atv-running-thats-been-sitting-a-long-time.50803/



Last year I cleaned the carb as best I could (soda blasted too), adjusted the carb, and got the engine running with a new spark plug. However, the machine refused to run with the choke fully off. After very little run time, I inspected the (new) spark plug and it was absolutely solid black. Having cleaned and tuned as much else as I could along the line, I tried adjusting the valves to see if that would improve the performance. However, when I tried to adjust the valves, the intake valve adjustment screw was damaged, and I was unable to complete the adjustment. The vehicle has sat this way since last spring-ish. Here is a picture of the valve adjustment screws, I was unable to remove the nut on the intake adjustment screw due to the visibly damaged threads: https://i.ibb.co/PT8tQp1/IMG-20191026-161941.jpg


What I would like to know is, what would cause this damage to the adjustment screw, and what else should I be looking for to prevent the vehicle from dying with the choke off? Thanks!


Edit: For reference, I did overhaul the carb with a moose kit, however I supposed I shouldn't rule out that it could still be dirty?
 

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Hi David - yeah, it looks like this is your first post here.

Damage to the tappet screw is usually caused by over tightening - as long as the good screw will screw into the rocker arm, simply get a new screw and nut - if the threads in the rocker arm are damaged you need to chase the threads at the least or replace the rocker arm at the worst.

As far as not running without choke, that is a carb problem - regardless of installing a kit or soda blasting, I suspect an internal passage is blocked with fuel residue and it needs a thorough cleaning in a heated sonic cleaner.

Let us know how you progress.
 

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Discussion Starter #3
Pulled the carb last night, not surprisingly, there was quite a bit of gunk in the bowl and several of the jets had clogged passages. I have access to an sonic cleaner at work, so I'll be giving it a proper cleaning.












Going forward, I'll try running the machine with an inline fuel filter to keep crap out of the carb, although I have had trouble with fuel starvation in the past.
 

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Check the fuel filter on the petcock - if it's in good condition an inline filter is not necessary

What kind of solvent do they have in the sonic cleaner? Is it specifically for white metal?
 

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Discussion Starter #5
Unfortunately, back when I was cleaning the gas tank, I attempted to remove the petcock and one of the bolts stripped the plastic it sits in and wouldn't unscrew (it's a terrible design). I was never able to remove the petcock, and a new gas tank/petcock is more than I'm willing to pay for this older machine.


The solvent we have is Alconox Powdered Precision Cleaner (https://alconox.com/alconox/). The company's website states that this solution may be used on soft metals, however it is recommended to rinse the item immediately after cleaning.
 

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OK - well an inline filter should not restrict flow

I use Master Fluid Solutions Master Stages Clean 2020 Master Fluid Solutions

I think the Alconox is a bit more aggressive - the SDS are similar, but Alconox discloses it's ingredients (phosphates) while Master Fluid does not (proprietary) and the Master Fluid has a flash point of 212 degrees F while the Alconox does not have a flash point.

Let me know how it goes
 

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Discussion Starter #7 (Edited)
Success!

Last Friday I ran the carbuerator through the cleaner and on Saturday I carefully cleaned the jets and reassembled everything.


I had not purchased a new tappet screw, but as I was inspecting the "damaged" screw, I realized that the "damage" was a ring of metal wrapped around the threads, and the threads themselves were not damaged. I suspect this may have stripped off the inside of the tappet nut?


I inspected the rocker arm threads, and they appeared good. I adjusted the valve clearances and the tappets tightened down fine. I believe that ring of stripped metal was preventing the nut from tightening before, causing the tappet to come loose and lose spec.


I reinstalled the carb and gas tank with an inline fuel filter. Well, it must have been the dirty carb because after warming up it idled beautifully at 1400rpm with the choke FULLY OFF! I had no issues with the inline filter, again it must have been the dirty carb restricting fuel.


I'll inspect the valve clearances after a few hours and ensure that they are still in spec.


On a test drive, the bike felt only slightly less powerful than I remember it with regards to acceleration and top speed. Any thoughts on what to check or clean next?


EDIT: The bike is indeed loosing power, but the issue has gotten worse. Yesterday it idled fine, but when I added any throttle at all it sputters, backfires and dies. It idles great with the choke back on, and can take some throttle with the choke on. Another thread mentioned the vacuum piston, which makes sense as it sounds like it's choking on gas, but I'm not sure. I'm going to re-check the needle valve, needle seat, and related parts tonight and will update.
 
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