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CRF50 / PW50 carb cleaning

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Well this will sorta be an intro and a multi part question on two bikes. I bought a 2012 Honda CRF50F for my son and helped get a 2005 Yamaha PW50 for my nephew. Both in really good shape just some minor quirks in both of them that really should be fine after a carb cleaning and the minor fixes I'm doing. My experience with dirt bikes has been from 15-18 years ago. Most of my experience in past 10 years has been fuel injected Harley Davidson Evolution and Twin Cam engines on the various lines including the 09 FLHTCU I have now.

 

The Honda runs/idles good once warmed up, a little hard to start at first and could use a carb cleaning. Did oil change to overkill Amsoil, magnetic drain plug, clutch adjustment, new spark plug, new air filter, cleaned exhaust/spark arrester, lubed and adjusted chain, lubed cables and adjusted brakes. Planning to do valve adjustment to finish off having a good baseline of maintenance. Compression was good on bike. The quirk this one has is it seems the throttle cable is about 1/2-3/4" too short to turn full lock right. With the throttle limited for my son, it is fine full lock left, straight on, or partially turned right, but at full lock right the cable pulls and the throttle opens to between 3/4 and WOT. Stock cable, bars, etc and I've played with the adjustments of the cable with no resolution. Ended up just giving up and ordering a 2" longer cable from Fast50s.com since I found a couple of cracks in the throttle cable jacket that I didn't feel like trying to keep corrosion out. Still curious about the throttle cable being that tight so I was wondering if anyone knows why that might have happened? I just assumed variations in cable lengths that wasn't caught by QC.

 

I was planning to yank the carb and give it a thorough cleaning and reinstall the carb while putting the longer throttle cable on. Anyone have any recommendations on what to watch out for or to double check? I know the pilot isn't removable technically, so hopefully nothing is in too bad of shape in there. I have a 5.56mm casing that I crushed the D shape into the neck for the air screw of the carb, but what was the factory setting on this adjustment? 2 turns out from bottomed out? My links are broken for the references I had saved.....

 

Now the PW50, it has a few issues and I can't seem to find any good resources for service manual info. The carb definitely needs to be cleaned on this one as it has trouble running anywhere but WOT and is extremely hard to keep idling once started, so I'm pretty certain the pilot is clogged on this one. Is the pilot removable/replaceable on the pw50 carbs? I've done about the same maintenance to the PW50 as I have the CRF50. The only difference is the air filter in the PW50 was crumbling in my hand when I tried to change it. Even the new in package (new old stock) air filter that the yamaha dealer had was crumbling and looked like black oily dirt in the package. I ended up cleaning the carb throat and what I could reach with Amsoil power foam and throttle open. It seemed to help a little and I was able to hot restart the pw50 for the first time. For pulling this carb off and cleaning, like the crf50, Is there anything to look out for on the PW50 carb being that it is still using the oil pump system? Will I need to purge the oil pump system or lines once I reinstall the carb? It has never ran out of oil and judging by how oily and smokey the exhaust was when I cleaned it this last time, it seems to be oiling well. I wasn't sure if I needed to run it on pre-mix for a short time and purge the oil lines somehow. Every 2 stroke I've ever ran was always a pre-mix or ran on pre-mix with the oil injection removed.

 

Also, is there any way to adjust to clutch on the PW50? I saw someone's post about this but didn't see an answer? Hopefully cleaning the carb fixes it, but right now it seems like the clutch doesn't engage until the engine is fairly high RPM like 1/2-3/4+ throttle and then it flies. Need to slow my nephew down as the strap tied to the back hoop in frame is wearing down my brother in law lol

 

If anyone has any resource links, etc it would be greatly appreciated. I've searched through this forum a bit and didn't seem to find much or what I did find was broken links. Any help is appreciated as I get very little support from my local Honda/Yamaha dealer.

Edited by slackwolf

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my sons pw was running just as you described when i got it.

I believe the crumbling air filter  in his to be the prev owner using starting fluid all the time like when he started it while showing it. I got a new filter and cleaned the carb which had all kinds of deposits in the bowl. Turns out the pilot jet was completely clogged thats all. Now it runs great!

I left the injection as it was. im not a fan of removing it. I get it, i just like stock...

Edited by MrR0b

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Don't think the guy used much for starting fluid on these bikes and the filter did crumble just like the new old stock filter at the yamaha dealer. They said it's not the first time it's happened on those particular thin foam filters. I know the Honda's filter was the original and never really been cleaned when I got it, so it was easier to just pitch and put a new one in than try to save.

 

How bad was removing the PW50's carb and getting it apart? I've never had much issues with pulling them down and back together, but I know there are some out there that just have their quirks in dis-assembly/re-assembly and wanted to be prepared. If the jets are all removable I was going to drop them in the ultra sonic cleaner and finish off with guitar string.

 

Did you have any issues with the oil injection with removing carb and putting back on? That was a big question mark for me if I needed to prime or purge anything. I know the carb is on the pressurized side of the pump, but you never know if with such a low flow something needed to be done to prevent loss of oiling. I have no issues pre-mixing the gas for a small tank to get the oil system purged, but I'd rather not if I didn't need to since would have to mix something separate than what I have already mixed. Most of my pre-mix is all Amsoil Sabre pro 50:1 or 80:1 with 75% 91 non-ethanol and 25% sunoco 110 for what I tuned my 2 smoke saws to run well on.

 

Wasn't planning to remove the oil system all together, but just wondering about the process of getting it back up and running after the pressurized side is disconnected, if any process at all. 

Edited by slackwolf

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I literally just posted this about pw50 clutch engagement in the other thread, but it never hurts to ensure its seen.

1 is softer clutch springs which is the obvious solution

2 is more unusual and I haven't tried it myself, but apparently cutting the clutch shoes in half to reduce the surface area will make it engage faster. If you try this, I suggest having a spare set of shoes but a few people claim it is just as durable as the full shoes.

3 is to change the shaft drive gears to the gears from a Yamaha qt50 moped, but changing gears will have a give and take affect

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