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Airbusboy

2003 Rancher ES valve issue

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Hey guys...newbie here...and I need some ideas.

 

My issue. Original owner. 2003 Rancher ES. 100% factory. No mods. 900 miles on the clock, not 9000, only 900. I decided I would adjust the valves due to some slight clatter and the ATV being 17 years old. I also installed new air filter. Now she has very low power, especially at high rpm. Will run fine at mid-range and down...about 3/4 throttle and up...not so much. Compression checks at about 145psi. Backfiring and sputtering through carb above 3/4 throttle. Tried new proper plug...no change. I've tried a knock-off new Chinese carb, the original Keihin factory carb rebuilt TWICE and finally a brand new factory carb, with all adjustments left from factory build...no change. I tried a NEW CDI box...no change. I've rechecked the valves and both are set right at .006...cold.  I even tried a brand new factory intake manifold...no change. I've tried SLOWLY pulling out the choke knob when she starts sputtering at higher rpm and it only dies, not improves. I have NOT tried pumping the primer knob while it's running badly. I've tried running it with and without the airbox...no change. I also added a clear-bodied fuel filter, which I thought might be impeding the fuel flow at higher rpm so I removed it...no change. I'm out of ideas....anybody got any suggestions?  Thanks in advance for your thoughts!

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Hi, welcome to ATV Honda!

 

5 minutes ago, Airbusboy said:

I decided I would adjust the valves due to some slight clatter and the ATV being 17 years old. I also installed new air filter. Now she has very low power, especially at high rpm. Will run fine at mid-range and down...about 3/4 throttle and up...not so much.

 

So, are you saying that the motor was fine until you adjusted the valves and replaced the air filter? Or was it down on power before you did those things?

 

You have ruled out the slide diaphragm in the carb being the culprit. So the next thing to check is the exhaust which may be restricted. Perhaps mice been nesting in the muffler...? Another (longshot) possibility is the woodruff key on the flywheel may be partially sheared. Check your exhaust for plugging first though.

 

Keep us updated if ya can. I am moving this thread into the utility section now.

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Yes agree with retro, not sure if the problem has occurred before or after the valve adjustment.  If you can please clarify that @Airbusboy.

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Welcome to ATVHonda , from reading your post , I would guess you were not on top dead center of the compression stroke when you adjusted the valves 

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Admittedly, it was running fine before I adjusted the valves. I had decided to adjust the valves purely because of age and a VERY slight valve clatter. I had recently installed a 'Silent Rider' secondary muffler but pulled that off thinking that might be restricting the exhaust...no change. I had been negligent on the air filter for quite some time and when I checked, I noticed some deterioration of the old filter, which is why I replaced it. Before reinstalling the box I inspected the inside of the metal can that the new filter slides over and it appears clear with no clogging. Plus, running the ATV without any filter box/restriction doesn't change the issue of low power so I think it has nothing to do with air intake. With two rebuilds on the original carb (again, age reason not mileage), a Chinese knockoff AND a brand new Honda carb, PLUS removing the fuel filter (possible restriction?), I don't feel like it is a carb/fuel flow issue. Could the original fuel line be restricting due to leaded fuel over the years? I thought about trying to re-adjust the valves SLIGHTLY loose (like .008 instead of .006) but not sure on that. How can I check the exhaust for possible blockage? Oh and thanks for your ideas! Oh and no, I was at BDC on the first valve adjustment but on the second, third and fourth valve adjustment I'd watch for the intake rocker to close THEN go look through the window for the 'T' mark and also physically verify that BOTH rockers were slightly loose so I KNOW I was at TDC. I'm ready to blow it up!  

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     Here's what I thought I'd try next.....1) adjust the valves AGAIN to verify the correct .006 setting. 2) replace the entire fuel line from the tank petcock to the carb inlet.  3) double check compression and 4th, try loosening the fuel tank cap while the issue surfaces IN CASE she isn't venting properly while running. 

     I already drained the tank and put in fresh, premium fuel. I'm running out of ideas. SURELY the valves aren't set properly since it WAS running fine till I decided to do the valves yet I've set them multiple times! I'm reaching for that stick of dynamite!

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24 minutes ago, Airbusboy said:

Oh and no, I was at BDC on the first valve adjustment but on the second, third and fourth valve adjustment I'd watch for the intake rocker to close THEN go look through the window for the 'T' mark and also physically verify that BOTH rockers were slightly loose so I KNOW I was at TDC. I'm ready to blow it up!  

 

I had an 02 rancher for many years and miles and though it was years ago, I think I set them on the wrong stroke or at BDC the first time I set them.  After that I always verified I was TDC compression stroke by watching the valve movement and the piston movement with a wooden dowel throw the spark plug hole.

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It's odd...it acts just like the main jet is clogged and not giving fuel for the 3/4 throttle and up range, yet 3 different carbs don't help! I don't get it. 

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occam's razor: simplest answer is usually correct - simplest answer is that something was done wrong with the valve setting

 

But, how well is the fuel flowing? Could you have dislodged something and clogged your petcock.  IIRC, there's a screen where the fuel enters. Crimped fuel line?

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I thought of that, which is why I'm going to try completely replacing the line from the petcock to the carb. Someone said you can see the filter/sock on the inside of the tank when the fuel level is low...anyone able to verify that?

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If we assume that the valves were adjusted properly, the only other change made was the air filter. Maybe try another filter, ie. this one isn't flowing properly.

What kind of oil was used on the filter? Running without an air box isn't a good test, they require one to function right.

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gonna take a stab at this, for one..PLEASE MAKE SURE YOUR ADJUSTING THE VALVES ON THE COMPRESSION STROKE !. second; make sure your diaphragm on the top of the carb does not have any tears or cracks in it ?, as well as sealing when you put the top back on. third: have a look at the air cut-off valve !. ( black plastic thing on right side of carb, has an air line attached to it ).

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Another thing that comes to mind is the spark plug cap. These are known to fail and give similar issues.

Maybe it just loosened up a bit, being on and off a few times....

Look for corrosion at the end of the wire and cut some off if necessary.

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Now the spark plug cap is something that I hadn't thought of....I'll check that tomorrow. As for the other ideas....3 different carbs...problem still persists so it can't be a slide, diaphragm or air cut off issue. I thought it might be a float level issue, thinking maybe I'd bumped it wrong when changing carbs, but 3 different carbs yield the same problem.  I read on one sight that a crack in the intake boot could cause my symptoms, which is why I replaced THAT too...but no help. 

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Any thoughts on setting both valves slightly loose (about .008) and see what happens? I'll put up with some clatter long enough to test the results.....

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I'd recommend leaving the valves as is for now.

With the exhaust, usually you can tell by the sound of the quad when running if it's blocked - they tend to get quieter.

If you remove it and shake it, sometimes the sound of a loose baffle is obvious.

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28 minutes ago, Airbusboy said:

Now the spark plug cap is something that I hadn't thought of....I'll check that tomorrow. As for the other ideas....3 different carbs...problem still persists so it can't be a slide, diaphragm or air cut off issue. I thought it might be a float level issue, thinking maybe I'd bumped it wrong when changing carbs, but 3 different carbs yield the same problem.  I read on one sight that a crack in the intake boot could cause my symptoms, which is why I replaced THAT too...but no help. 

not enough fuel reaching carb then.

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I guessing since it happened right after you say you adjusted the valves , then you adjusted them on the wrong stroke  or  , it jumped a tooth on the cam chain or the diaphragm in the carb is blown , you mention one of the 3 carbs you tried as being chinese , that china try didn't even count in my book , sometimes you can get a good one , more times then not they are junk , so that left two carbs , did you visually inspect  the diaphragm on either one , and made sure you lined the lip up before tightening the cover down , cause 3/4 to full throttle no power is exactly the symptoms of a leak in the diaphragm 

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Not a carb issue. Two methodical rebuilds on the factory carb plus one brand new Honda carb...same thing. COULD be a fuel flow..maybe? Will see what happens with a new fuel line from petcock to carb inlet installed tomorrow. Got a bud coming over tomorrow to have extra set of eyes on the fifth time of setting the valves...and yes, compression stroke position is verified. TWO CDI units didn't change anything. Vent in cap clogged? 

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nah it wouldn't be the gas cap vent from when you described in the 1st post... 

 

17 hours ago, Airbusboy said:

I've tried SLOWLY pulling out the choke knob when she starts sputtering at higher rpm and it only dies, not improves.

 

sounds to me like it's not a fuel supply issue, but a carb issue or the valve adjustment. fish mentioned timing jump. but this happened right after you adjusted the valves ??? then you started hunting other issues ? i would have checked the adjustment first before heading in other directions

 

17 hours ago, Airbusboy said:

No mods. 900 miles on the clock, not 9000, only 900. I decided I would adjust the valves due to some slight clatter and the ATV being 17 years old. I also installed new air filter. Now she has very low power

.

did this bike sit up for an extended time with ethanol fuel ? and no gas treatment ? 

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Seems you think you have tried many things and have ruled them out , but since it still don't run right , you need to forget what you have already tried , and have an open mind , start over ----- I heard the " it ran great before " thing all the time , but it has to fail sometimes , look at it like this , it just did 

 

Maybe the chatter you heard was from a loose timing chain , do you know how to check the timing chain slack ----  do you have a manual 

 

Maybe the connecting rod is bent , it can happen from flooding out in water , but it can also happen from a carb leaking fuel into the cylinder and then trying to start the engine with gas in the cylinder and a hydro-lock occur 

 

the tank vent being clogged will take a couple of minutes of run time  before any effects will happen 

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I MAY have stumbled onto the problem. I just pulled it down AGAIN to recheck the valves. The intake was reading about .007 and the exhaust a bit more...BUT...I did a compression check again and this time she read right at 200PSI!  WHAT?  I've got a buddy on his way over with HIS tester and we're going to see what his gauge reads. Is it possible that my exhaust muffler is clogged and that is why she's reading that high? If she can't breath at high RPM wouldn't that cause my issue that I'm getting? I just checked and neither Amazon nor Ebay has a seller with OEM mufflers so.....can you pull these apart and clean 'em out? 

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Thanks for the ideas so far. No, she has never been flooded with water and with only 900 miles on it, I doubt the timing chain has become slack but who knows?  She doesn't sit for more than a few weeks at a time and I always run premium, non-ethanol when I can. I DID try that 'Silent Rider' secondary muffler recently though. That thing has a pipe that goes inside the OEM muffler and turns 90 degrees to vent. I took it off already trouble shooting this problem. Reckon pushing that pipe down into the outlet of the OEM muffler could've caused this?

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