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1995 Jetting help - too rich - I'm stumped.

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Recently picked up a really clean '95 KX125, owner said top end was done within 25-30 hours ago. Runs nice and strong but very rich. Getting a lot of spooge out of the pipe and governor cover plus some smoke after fully warmed up. Not a ton but some more than normal.

So I drained the gas, cleaned out the carb, changed plug, checked the float level, replaced air filter, replaced silencer packing, cleaned out some of the power valve and replaced a worn o-ring causing the spooge leak from the governor valve cover.

Rode the bike and still getting the spooge out the pipe, maybe a little less smoke.

I took the carb back apart to check out the jets and needle position are stock (162 main, 42 pilot, 2nd clip from top needle and 1.5 turns out on air screw) and it has an FMF pipe, silencer and Vforce Reed & cage. So I changed the main jet to FMF's suggested 158 main, left the pilot the same because didn't make sense to go larger to their recommended 52. Not really any difference.

Lastly, I followed Spanky's jetting guide online and ended up changing the pilot down to a 40, not much of a change. Then changed the needle position to the top position to make bike more Lean. Took it out for an hour, had ton of spooge on rear fender and dripping down pipe. Powerband was hitting a little weird as well since I changed the needle position.

So I'm totally stumped! Any suggestions??

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Just a shot in the dark but I wonder if your right side crank seal is bad and you are burning your trans oil.

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I would do a leak down test and see what you can determine from that.  If the bike isn't responding to changes in the jetting you may have another issue.  Hypothetically changing to smaller jets with a leaky RS crank seal would richen the oil/gas ratio which could cause more spooge.

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the pipe is saturated with oil. when you hear it up, it will blow it out.

repack, then rejet.

if your transmission level hasn't dropped, this is true. if it had dropped, you'll need case seals.

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I would do a leak down test and see what you can determine from that.  If the bike isn't responding to changes in the jetting you may have another issue.  Hypothetically changing to smaller jets with a leaky RS crank seal would richen the oil/gas ratio which could cause more spooge.

I did not know that about jets and the RS seal. I started to research how to perform a leak down test, doesn't look difficult. I have a mightyVac, just need to find the adapter for the spark plug. Or make one. Are there any good write ups on here that your aware of?

 

the pipe is saturated with oil. when you hear it up, it will blow it out.

repack, then rejet.

if your transmission level hasn't dropped, this is true. if it had dropped, you'll need case seals.

I repacked it once and have only ridden for about 3 hours since. But, depending on how much I'm blowing out, I guess it could need another repack already....

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Jet block o-ring? Has the carb been dipped? This is a common problem on the KDX's after someone tries to clean the carb.

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Jet block o-ring? Has the carb been dipped? This is a common problem on the KDX's after someone tries to clean the carb.

Cleaned the jets, which o-ring are you referring to? Also, not sure what you mean about dipping the carb?

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I did a pressure/vacuum test on the engine and glad to say that everything checked out good, held the pressure and vacuum. I also did a compression test and it came out to 120 psi. According to my manual, it's ok. They say anything below 109 is a problem.

 

Anyway, I now have it narrowed down to:

  • Reeds - have VForce Deltal reeds that may be original but in good shape. But they may be letting some gas through, hard to tell. 
  • Piston and rings. Sounds like may need to do this in the future.
  • Carb jetting. Already played around with this, not seeing much of improvement. 

Could reeds and piston/rings cause a rich oil spooge out the silencer?

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I did a pressure/vacuum test on the engine and glad to say that everything checked out good, held the pressure and vacuum. I also did a compression test and it came out to 120 psi. According to my manual, it's ok. They say anything below 109 is a problem.

Anyway, I now have it narrowed down to:

  • Reeds - have VForce Deltal reeds that may be original but in good shape. But they may be letting some gas through, hard to tell.
  • Piston and rings. Sounds like may need to do this in the future.
  • Carb jetting. Already played around with this, not seeing much of improvement.
Could reeds and piston/rings cause a rich oil spooge out the silencer?

pop the pipe of and look inside. probably just some wear, and needs a rejet

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If your reeds were letting in more gas/oil then can be combusted I would think you might get some more spooge.  Could explain why your bike is running rich as well.

Edited by DylDog

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What does the plug look like after you re jetted it? Maybe you just have a punch of left over spooge in the expansion chamber that is just clearing out now.

 

Also 120PSI is kinda low on the compression, I'd do a top end, with that number your bike had more on the top end then the PO said, which is normally the case. It's not wise to re jet on a worn top end either as you'll need to chage that again when you do, do one.

  Now a days every bike on Craigslist "Has fresh top end 20 hours ago"  Best advice is to always plan a top end rebuild for a new to you used bike as it's better to be safe then sorry.  The OEM and some aftermarket cast pistons only last for so long before you have the skirt shatter and end up taking the motor out.

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Cleaned the jets, which o-ring are you referring to? Also, not sure what you mean about dipping the carb?

The o-ring/rubber gasket between the jet block and the carb body. (assuming this is a Keihin PWK carb) The jet block is the grey metal piece under the main jet/tneedle jet assembly. It is scured by two T20 security type Torx screws. You can get the part here  https://jetsrus.com/carburetor/a_carburetor_parts_selection.html

 

 Dipping the carb is the process of submerging the assembly in a chemical solution. We used to do this to automotive carburetors all the time. The chemicals damage the o-ring material causing it to swell and leak. This creates the mysterious rich condition.

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pop the pipe of and look inside. probably just some wear, and needs a rejet

I did this and noticed some wear on the piston, it appears to have scuffing (for a lack of better words) on the piston. Would this be considered normal wear? I'm hoping I don't need to replate but I'll find out once I pop off the cylinder.

 

If your reeds were letting in more gas/oil then can be combusted I would think you might get some more spooge.  Could explain why your bike is running rich as well.

Yes, I think your right so I ordered replacement petals. I did notice some gas on the back of the carb towards the air filter boot.

 

What does the plug look like after you re jetted it? Maybe you just have a punch of left over spooge in the expansion chamber that is just clearing out now.

 

Also 120PSI is kinda low on the compression, I'd do a top end, with that number your bike had more on the top end then the PO said, which is normally the case. It's not wise to re jet on a worn top end either as you'll need to chage that again when you do, do one.

  Now a days every bike on Craigslist "Has fresh top end 20 hours ago"  Best advice is to always plan a top end rebuild for a new to you used bike as it's better to be safe then sorry.  The OEM and some aftermarket cast pistons only last for so long before you have the skirt shatter and end up taking the motor out.

I have a feeling it's still running rich but I will say that after looking at my plug, it's looking lean. Here is a pic:

IMG_20151106_193837441_zpsdixfvqog.jpg

IMG_20151106_193946687_zpsrlgbhwv2.jpg

 

I fouled a plug right before I made the last changes and that plug was completeley black with oil. This plug is the opposite but I'd say I was getting just as much spooge, if not more. And when I dropped the needle the lowest, it wasn't hitting as crisply.

 

Lol, your right. Of course the guy said the top end was done 20 hours ago, not that I believed it. I am about to order a new top end kit, was going to just go with the wiseco prolite, I'm sure they're decent. I also noticed the exhaust manifol area had a lot of carbon built up. Is it safe to use a dremel to get that out?

 

The o-ring/rubber gasket between the jet block and the carb body. (assuming this is a Keihin PWK carb) The jet block is the grey metal piece under the main jet/tneedle jet assembly. It is scured by two T20 security type Torx screws. You can get the part here  https://jetsrus.com/carburetor/a_carburetor_parts_selection.html

 

 Dipping the carb is the process of submerging the assembly in a chemical solution. We used to do this to automotive carburetors all the time. The chemicals damage the o-ring material causing it to swell and leak. This creates the mysterious rich condition.

Gotcha, I know what your talking about. Yup, it is the PWK35. I don't know if they have done any sort of dip before I got it but I guess it can't hurt to throw a new o-ring in.

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Also, I was thinking after I put the new reeds in, new top end kit and carb rebuild kit what jetting should I go to? I was thinking either going to FMF's recomendations which is 158 main and 52 pilot (which seems awfully rich) or going back to OEM which is 162 main and 42 pilot. Any suggestions?

Revert to OEM and then make adjustments from there.

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