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No matter what I try, I can't get the carb dialed in. This is on my 96 300. I've gone through ever orifice several times and have dipped it overnight. Tried all sizes of jets and a couple of needles and slides. Best I can get is a crisp bottom and decent mid, but falls on it's face once into the powerband. I looked on eBay for a replacement carb and have seen brand new units selling for $60, so I'm assuming it's a knockoff. Also considering a Lectron, but those cost more than I paid for the bike. Thoughts?

 

I should note that I do plan to burn out the pipe and repack the stock hockey stick. My boys crf250x has more hit and speed than this bike. Tired of wrenching on it and spending $$$. Would rather ride!

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sounds like you know your way around a carb so lets look at some other causes of a bike to not hit power band...

 

-Silencer packing full of splooge

-PV sticking or not assembled correctly  (does a 96 have a PV?)

 

 

 

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Did you verify float height? 96 is a long time in carb years... try a rebuild first. 

 

Those are crappy, knockoff carbs.

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Have you tried a smaller main? 

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Sorry, not a good connection right now. I put an adjustable PV on it with a red spring, and lowered the float. It acts like it was to hit the band, but loads up. I'm going to take the exhaust off and burn out the pipe then repack the muffler. Had a chance to ride a 2015 300 w/green spring today. Night and day difference, so I know something isn't right with my bike.

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Sounds like a power valve issue . Check the push rod and the retaining screws as I've seen them fall out. 

Run the bike and pull the choke up. See if it runs better

As said lean the jetting off and see if it helps. It's all clues to pointing it in the right direction. 

Check the crank seals or other air leaks. Does it tick over nicely? 

 

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Just got back from a weekend ride. 1st time I took it out, it acted like it was loading up real bad and at every RPM range.  Took it back to camp and continued riding on my boys bike (took both bikes for a solo campout).  When I came back to camp for lunch, I decided to tear into the bike again.  I've never been able to keep the stock float setting without puking fuel everywhere and running bad, so I set it way low.  When I do this, it has a pretty good bottom/mid but doesn't run for crap once it hits the band.  I initially thought that maybe it wasn't flowing enough fuel and was starving itself.  A plug chop would show that and it isn't the case.  My petcock is gutted and flow is not an issue.  Talking with some other 300 riders this weekend, one person suggested the Slavens head while everyone else seemed to be leaning towards a plugged pipe or PV.  

When I remove the pipe to burn it out, I'll uncap both sides of the PV covers on the cylinder and take a look at things.  Not sure what I'm looking at, but if its all gummed up or has broken/missing pieces, I'll know I'm working in the right direction.  The spring and adjuster down by the water pump looked clean and functioning. I took that apart first expecting to find a broken spring.  It had a yellow spring under a non-adjustable cap.  I bought an adjustable cap and the PV spring pack from Slavens.  It currently has the red spring installed with the adjuster set flush.

One fella that pulled in next me had a 2017 and couldn't get the Mikuni dialed in.  He swapped to a Lectron and was trying it out for the first time.  Out of the box, he said it was already better the the Mikuni ever was, so now he was just getting finicky with it.  He admitted to being a real anal-retentive type.  I've thought about going this route too, but am hesitant spending that kind of money on a bike this old and knowing that I'll be getting a 2018 FI model next year.  I'm so sick of carb problems.  I just want to ride and plug-and-play is sounding better and better these days.

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At the risk of a lot of negative feedback from my vintage 300 brethren....First of all a PWK 38 is quite different than the PWK 36 (But you know that) the jetting jetting requirements between the 2 are different. I went from a dialed in Lectron on my 13 Beta 300, took 2 rides to get my PWK dialed in. Am curious as to why a 38 vs a 36 is on your bike - just asking as I don't know what the stock carb came on 96 300s, the later years came with 36's. 

My first 300 was an 01 300 EXC, ran like a raped ape, but could never get it to run right down low without blubbering, tried for a few years to make it right, and after reading a 30 page thread on KTMtalk where someone tried everything at major expense (I mean EVERYTHING), I sold her and moved to a more modern 300 and my jetting problems were nil compared to the 01.  Having never owned a 96 I might be talking out of my butt, but juz zayin.

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My manual states that the PWK 38 was stock for 96/97, but not sure about other years.  I know that somewhere in the early 2000's a switch was made to the 36.  For the record, I have no idea what the differences are between the two.  I've read that the earlier SEM ignitions made it difficult to jet the 38s, but I've also read that the newer ignitions on the 38s were hard to jet, as well.  Seems everyone struggles (which is why I cannot wait for a FI model!). I hesitate to get newer carb'd model for fear I'm going to have similar issues.  I also fear selling what I have because any 300 is wicked hard to locate in my area for a good price.  People want mint for their 10yo bikes, so I'm better off keeping what I have until the FI models are here.  Just trying to make it last a little longer......

 

As for the other questions:  If the clutch was slipping, it would rev to the moon.  That is not the case.  Its acting like its constantly loading up when on the throttle.  If clutched, it revs to the moon.  I tried a 2-stage reed to replace what was in it when I bought the bike 3-4yrs ago, but it didn't make a difference.  Can't remember if I still have those in it or if I went back to the single stage.  Either way, the reeds and block were in good shape.  I don't believe any seals are leaking because I have ZERO fluid loss, either in the trans or radiators.  I built my own fan assembly for under $20 that works extremely well!  Don't even remember the last time it boiled or steamed.  Also, just this weekend I tried riding with the choke on for a bit just to see if I was indeed running lean.  Nope......ran even worse and blew lots of snot.  Lastly, it starts up really easily hot or cold.  Never wants to hold much of an idle, tho. Sometimes it does, sometimes not.  If riding a downhill trail, it will stall almost every time if I don't keep blipping the throttle while the clutch is pulled.  Hope this info helps everyone.  Really do appreciate the comments.  She's an old turd, but still fun to ride!

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Maybe its the stator breaking down under load. Those old stator's fail whenever they feel like it.

If the power valve is right and the jetting is at least somewhere near correct it's time to start looking elsewhere for an explanation. 

Check to see if the timing is correct first , or the flywheel nut hasn't come loose.

Also check the woodruff key hasn't snapped either.

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Also have you tried removing the left side power valve cover and whilst in neutral rev the bike. You should see the powervalve gears moving . 

If it moves freely you can eliminate that as the issue.

 your old 300 is very similar to the mid 2000's engine still so should have loads of poke still.

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As I understand it, when a woodruff key breaks, there is no electrical signal generated at all and won't fire.  That is not my situation.  I can believe the SEM getting weak under high rpm, tho.  When I have time this week, my intent is to pull the PV cover and look for condition and movement.  If that looks good, then I'm going to burn the pipe.  If that doesn't help, I might look into a replacement carb before I get into replacing or upgrading the ignition.  I've followed others doing this upgrade on KTMtalk.com and it doesn't look fun, nor cheap.

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No, if the flywheel has only slipped a few degrees it might still start but run rough.

It certainly worth checking  as it's free and quick to check

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On 5/9/2017 at 5:47 AM, notinthedirtagain said:

 I've read that the earlier SEM ignitions made it difficult to jet the 38s, but I've also read that the newer ignitions on the 38s were hard to jet, as well.  Seems everyone struggles (which is why I cannot wait for a FI model!). I hesitate to get newer carb'd model for fear I'm going to have similar issues.  I also fear selling what I have because any 300 is wicked hard to locate in my area for a good price.  People want mint for their 10yo bikes, so I'm better off keeping what I have until the FI models are here.  Just trying to make it last a little longer......

 

 

the 38s aren't hard to jet at all on the ktm

what makes it hard is the crap needles and jetting chart ktm supply , ditch these two things and the job becomes easier

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Tried to heat up and melt down any goo inside the pipe and it didn't do much. Started melting the end of the gun. My torch is buried deep in a room I can't get to just yet. Muffler packing was pretty black, but not as bad as I predicted. However, I think I discovered the problem. Took the left PV cover cover off and a screw immediately dropped out. Another was loose. Cleaned and reinstalled and it definitely has more hit. Still not like the 2015 I rode, but much better. For a 21yo bike, it'll do. Hoping it cleans out with more use. New screws, locktite, high temp rtv and packing material ordered.

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i never burn pipes out , i degrease them a couple of times and then i use a piece of balustrade wire in a cordless drill with the end frayed out so it "scratches" the inside of the pipe and just work it in and out for about 5 minutes

 

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