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WR250F 07 WR250F odd compression issue after dead battery & difficult to kick start

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The bike is a 2007 WR250f that I bought used two years ago. Its my first bike and realizing its age I expect certain things to go wrong with it and others will need refreshing. It has run very well since I bought it, never giving me any issues other than things you expect to replace like tubes, chain, etc. I had just completed replacing my fork seals/bushings and linkage bearings so I can turn a wrench but I don't know all the intricacies of starter clutches, decompression cams etc so forgive my ignorance.

Two weeks ago, my buddy and I were out riding and wrapping up the day of riding. We were on our way back to the truck and started down a trail with some tight downhill corners. I was coming down while engine braking and stalled due to going too slow in too high of gear and not pulling the clutch in time. When I went to restart my bike my e-start wasn't working. It just gave me a low whine. Not a big deal, I can just kickstart my bike. I never really had an issue with it starting before, either by button or kick. I grab the hot start lever and give it a kick. Nothing. Give it another kick. Nothing. I check my fuel valve and make sure it has gas. Both fine. After several minutes of kicks and not a single turnover, I realized it was pretty easy to kick the lever, easier than it had been in the past. It was still operating as normal, just not giving me the same resistance as usual. I never got the bike started so I coasted downhill and bump started it thankfully, getting out of the trail vs having to push it out. I got the bike home and pulled my starter out, cleaned it etc while I was charging my battery (which never got above 10v). I replaced it with a Yuasa battery and picked up a new pair of plugs just in case (also had to buy the yamaha spark plug tool because I couldn't get my plug wrenches into the head. 

In cleaning the starter, it really wasn't that dirty or worn down. The brushes still had a ton of life in them and the carbon deposits weren't bad at all. I hooked it up to the battery and ensured it spun freely when connected straight to the battery. Starter is fine. Used my multimeter to test my switches, relay etc and all of that was fine as well. I remove the spark plug and its clear its been there a while. Its rusty. The threads are wet and black and looking it up it sounds like I fouled the plug via oil meaning I was likely running a very rich mixture or my piston rings are worn and allowing too much oil in the combustion chamber. I don't actually know myself. After replacing the plug and battery, I turn it on and it starts right up. The bike runs and starts right up on the e-start. The kick start is still giving me issues and feels soft compared to before which is why despite the battery and plug clearly needing to be changed, I think something else might be causing the compression issue. We went out riding the following weekend to see how it rode and it rode fine. I adjusted my mix to be leaner given the condition of the plug.

My guess is that the piston rings are getting worn and allowing more oil which caused the plug to foul and it just happened to coincide with my battery crapping out. If it was just my air fuel mix being way too rich, I don't understand the lack of compression. Thats my guess but its not too educated. I'm not sure if this could be a starter clutch issue or if the plug fouling and compression could be completely separate issues altogether. Due to the age, I'm guessing I'll have to replace a top end fairly soon. I've only put 50-60 hours on it since I've owned it (I know, I don't get out to ride as often as I want), and its clear someone did the top end at some point before me but no idea how many hours since it was done.

Any ideas? All are appreciated and thanks in advance.

 

IMG_20200516_005445.thumb.jpg.09aec365eddf4e7ec7c12c0de4b81fb0.jpg

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8 hours ago, verman84 said:

We went out riding the following weekend to see how it rode and it rode fine.

Then there is nothing wrong with it.  Stop looking for problems to solve, that don't need solving.

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11 hours ago, verman84 said:

The bike is a 2007 WR250f that I bought used two years ago. Its my first bike and realizing its age I expect certain things to go wrong with it and others will need refreshing. It has run very well since I bought it, never giving me any issues other than things you expect to replace like tubes, chain, etc. I had just completed replacing my fork seals/bushings and linkage bearings so I can turn a wrench but I don't know all the intricacies of starter clutches, decompression cams etc so forgive my ignorance.

Two weeks ago, my buddy and I were out riding and wrapping up the day of riding. We were on our way back to the truck and started down a trail with some tight downhill corners. I was coming down while engine braking and stalled due to going too slow in too high of gear and not pulling the clutch in time. When I went to restart my bike my e-start wasn't working. It just gave me a low whine. Not a big deal, I can just kickstart my bike. I never really had an issue with it starting before, either by button or kick. I grab the hot start lever and give it a kick. Nothing. Give it another kick. Nothing. I check my fuel valve and make sure it has gas. Both fine. After several minutes of kicks and not a single turnover, I realized it was pretty easy to kick the lever, easier than it had been in the past. It was still operating as normal, just not giving me the same resistance as usual. I never got the bike started so I coasted downhill and bump started it thankfully, getting out of the trail vs having to push it out. I got the bike home and pulled my starter out, cleaned it etc while I was charging my battery (which never got above 10v). I replaced it with a Yuasa battery and picked up a new pair of plugs just in case (also had to buy the yamaha spark plug tool because I couldn't get my plug wrenches into the head. 

In cleaning the starter, it really wasn't that dirty or worn down. The brushes still had a ton of life in them and the carbon deposits weren't bad at all. I hooked it up to the battery and ensured it spun freely when connected straight to the battery. Starter is fine. Used my multimeter to test my switches, relay etc and all of that was fine as well. I remove the spark plug and its clear its been there a while. Its rusty. The threads are wet and black and looking it up it sounds like I fouled the plug via oil meaning I was likely running a very rich mixture or my piston rings are worn and allowing too much oil in the combustion chamber. I don't actually know myself. After replacing the plug and battery, I turn it on and it starts right up. The bike runs and starts right up on the e-start. The kick start is still giving me issues and feels soft compared to before which is why despite the battery and plug clearly needing to be changed, I think something else might be causing the compression issue. We went out riding the following weekend to see how it rode and it rode fine. I adjusted my mix to be leaner given the condition of the plug.

My guess is that the piston rings are getting worn and allowing more oil which caused the plug to foul and it just happened to coincide with my battery crapping out. If it was just my air fuel mix being way too rich, I don't understand the lack of compression. Thats my guess but its not too educated. I'm not sure if this could be a starter clutch issue or if the plug fouling and compression could be completely separate issues altogether. Due to the age, I'm guessing I'll have to replace a top end fairly soon. I've only put 50-60 hours on it since I've owned it (I know, I don't get out to ride as often as I want), and its clear someone did the top end at some point before me but no idea how many hours since it was done.

Any ideas? All are appreciated and thanks in advance.

 

 

The valves sound like there tight if it only starts with estart and it's lost compression they would be going tight. If it was a worn piston loosing compression it wouldn't cause starting issues. Check your valve clearences.

On 7/9/2009 at 11:50 AM, BINXS said:

I have the Powercore 4 and running the stock jetting. The low-end and midrange is where I noticed the gain. Seriously, I just finished riding about an hour ago and can't believe the difference. The instructions advised that depending on what bike you "may" have to move the kickstart back one notch but I didnt need to, it fit perfect. We're at 2,000' altitude and I'm thinking I can get more out of the top-end by jetting down my main jet. I'm open to any suggestions and plan to play with jetting next week

 

Edited by Daniel meyer
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