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Zip ties instead of O-ring

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04 WR 250F

Main 175

Pilot 42

Starter 72

PAJ 70

Leak 40

Needle OBDU S - 4th from the top

Boyesen AP cover

Aftermarket exhaust and air filter

Gray wire mod

Think thats about it.

Ok, so I just couldn't leave well enough alone. I bought this bike used a couple years ago and it has been great. I have a big riding trip coming up, and been trying to get all my toys ready to go. This WR has seemd to run fine, other than not wanting to start up cold quite as well as I would like. I decide to pull the carb and give it a good cleaning. Noticed few things worth mentioning.

1. Zip ties over the timing adjustment screw, like the O-ring mod.

2. Inside the AP it was full of chalky buildup. Not sure why, pretty much like the buildup you get from having hard water in you house.

3. No small screen at the bottom of the valve seat.

4. The float height seemed to be be out of adjustment, it was to high, so I reduced it to 8mm.

I was tempted to play with the jetting, but then decided to remove the zip ties and clean up the AP, and see where I ended up first. I didn't mess with the AP screw, so not sure it is correct. Now that I think about it, I also kind of messed up, and didn't bother counting the turns of the fuel mixture screw. When I put it back together, I set it too 1 1/2, and honestly didn't think to play with it when I was trying it out earlier.

When I gave it a try I was able to get it to start, but had to give it a little throttle. I gave it a little time to warm up with the choke, but it didn't want to stay running. It also back fired, which it hasn't really done in the past. I just got back from Home Depot, where I picked up some O-rings for the AP screw. Its to late now for me to be out playing with the bike, but was hoping to get some advice.

Why was the AP full of deposits? Is this because of the zip ties? I thought the mod was supposed to hold it tight, but still allow it to move. I didn't change the jetting, so I am wondering which of the things I corrected above backfired (no pun intented) on me? :lol: I will probably be able to get it going again when I can play with it again tomorrow, but some pointers would be appreciated.

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You need to re-build the apump system with a new diaphragm and spring. There are three tiny orings that often get missed, on the apump cover. You need to clean it out in there, and be sure the nozzle is not clogged. 50 leak jet is preferred. The Oring is used because you don't want it tied together, as it will bind. Preferably, you should replace the linkage spring with the correct spring, from merge racing or R&D. Makes a big difference.

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the chalky stuff is most likely from water leaking into the ap,from the plunger cause your gasket that covers the throttle cables was leaking.and that 40 leak jet sounds a little big.maybe try a 50 or 60.and a new gasket on the r.h. cover should stop the water from getting in.

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Thanks for the help guys. Now that you mention it, the water thing makes sense. I remember running through the woods a while back and coming up on what looked like a doable mud hole. My friends couldn't stop laughing as I found out it was more like a small lake. Swallowed most of the bike. Was pretty amazed we were able to get it going again. Thats probably were the water came from. I don't have a larger leak jet, but maybe Yamaha will have some. Amazes me I live in DFW, but seem to have to order everything.

I'm not sure about the 3rd O-ring Krannie mentioned. I only remember two, and I'm not seeing a third in the service manual. I think the diaphram was still ok after I cleaned it up, but I do have another from a spare carb I could try. I did do the O-ring mod. I also have another stock AP cover, I think I read a post where William was saying the Boyeson cover was worthless and to use stock if you still have it.

I did play with the throttle screw and was able to get it to run and idle again. I ran it around for a while and tried adjusting the throttle screw. I think it seemed best about 3 turns out, so I may need to adjust the pilot a bit. Although I was able to get it going, it didn't seem to want to idle correctly. It will stay going with a pretty high idle, but it doesn't seem to stay stable when I try to lower it. It didn't want to start without the choke on, even after really being warmed up. Seemed like it wasn't getting enough fuel, and it was poping and backfiring a bit. Actually saw it shoot a flame out the back. Wondering if messing with the float height could be causing some problems. It seemed out of spec, but was doing fine before I messed with it. :lol:

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Thanks for the help guys. Now that you mention it, the water thing makes sense. I remember running through the woods a while back and coming up on what looked like a doable mud hole. My friends couldn't stop laughing as I found out it was more like a small lake. Swallowed most of the bike. Was pretty amazed we were able to get it going again. Thats probably were the water came from. I don't have a larger leak jet, but maybe Yamaha will have some. Amazes me I live in DFW, but seem to have to order everything.

I'm not sure about the 3rd O-ring Krannie mentioned. I only remember two, and I'm not seeing a third in the service manual. I think the diaphram was still ok after I cleaned it up, but I do have another from a spare carb I could try. I did do the O-ring mod. I also have another stock AP cover, I think I read a post where William was saying the Boyeson cover was worthless and to use stock if you still have it.

I did play with the throttle screw and was able to get it to run and idle again. I ran it around for a while and tried adjusting the throttle screw. I think it seemed best about 3 turns out, so I may need to adjust the pilot a bit. Although I was able to get it going, it didn't seem to want to idle correctly. It will stay going with a pretty high idle, but it doesn't seem to stay stable when I try to lower it. It didn't want to start without the choke on, even after really being warmed up. Seemed like it wasn't getting enough fuel, and it was poping and backfiring a bit. Actually saw it shoot a flame out the back. Wondering if messing with the float height could be causing some problems. It seemed out of spec, but was doing fine before I messed with it. :lol:

Your right, it's only two.

fcr-carb-accelerator-pump-rebuild-kit-1.jpg

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a larger number leak jet actually delivers a smaller amount of fuel squirt,its assbackwards when it comes to the leak jet,kinda sounds like you might have a needle,and/or pj issue.peace and wheelies

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So I figured out the problem. Didn't think you could put the slide plate on upside down. I was wrong. :lol:

Its acting better than before now.

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