Bike Won't Start!

Last week, I had my 00 426 torn down changing the oil and checking valve clearance. I reassembled the bike, gave 'er a test kick, and it fired right up no problems. It was popping a bit though, so I decided to remove the carb and clean it out. I pulled the carb, removed all the jets, the slider, the needle, etc., blew out all the carb passages with compressed air, reinstalled everything, and reinstalled the carb. I also installed a fuel filter after finding some grungy buildup in the top housing you remove to take out the slider and needle.

After reinstalling the carb and installing the fuel filter, my bike will not start. When I first turned the fuel on, a little ran out the float bowl overflow hose then stopped. The thing only ran for a few seconds, and only with the throttle half open. Once I let off the throttle, it died. I tried a variety of things to get it to start, including opening up the throttle. It started with the hot start pulled open.

Also, it would temporarily lose compression. I was able to kick it through 3-4 times without full compression. There was still some compression, but it was constant, and not enough to stop the piston at TDC, and there was no need for the compression release. Flicking the comp release lever a few times seemed to fix this problem, but it would come back. There was no regular pattern to the compression loss.

I am at a complete loss and need some help! If its any help at all, I've got a 162S main (S for stock???), 42 pilot, and all other jets are stock. I started out with the fuel screw at 2-3/4 turns out, then backed it down to 1-1/2 turns. The bike has fresh Mobil 1 15-50 (red cap) in it- it has only been run about 2-3 minutes since an oil/filter change.

Please help! I have no idea what is happening, and its starting to worry me.

Do you happen to remember reinstalling the throttle valve(slide) correctly? What I am referring to is the two-piece slide. The slide has the separate plate that is simply held in place by the carb throat. You can actually install this plate upside down and the cutaway will be on top instead at the bottom. Air drawn across the venturi is severely upset.

After re-reading the post, I would also add that it appears that the pilot circuit might be restricted. Sometimes, the pilot air jet gets slightly clogged with air filter oil. This is not to discount the possibility that the throttle plate was installed upside down.

Also, don't discount the possibility that one of the valves might be too tight. With a 5-valve head, valve lash adjustment can be critical.

[ April 23, 2002: Message edited by: Boit ]

I'm guessing that you're flooding it somehow. I'm guessing that the compression is coming and going due to flooding (just a guess because I have no idea what makes this happen but when it happened on my bike it was because it was flooded with carb cleaner). I would say take the carb back out and sit down with the manual and be sure that everything is in properly. I'm guessing that something got put in wrong or misaligned on accident.

I think you do NOT have a carb problem. Check your throttle cables to be sure they got back on right but you have the sudden loss of compression syndrom. Use the search button. There is a current one in this forum now under 'stuck valve?'. I have had it twice and this recent time tore the head apart. You can read about that under 'valve problems' on the 250F forum. The bottom line is, its frustrating, and may take a couple of hourse, but stick with it. It will disappear and run fine.

Happy kicking,


Howdy pardner, Please take "boit's" advice!!!! I had the same problem with my bike. It's a very easy thing to do. After cleaning my carb out I installed the slide plate upside down. It looks just the opposite how it's suppose to go but trust me and Boit that you should look at the plate to make sure that it's on right side up. I took my carb apart at lest 12 times to try to find the problem and that was it. And man the bike has never ran so good.

Good luck,

DL :)

Thanks a million guys. Sure enough, the plate in the slider was in upside down. I turned it around, and the blue beast was back to life with one kick! Thanks again, I appreciate the help.

I'm not exactly batting .400 here.


I feel like crying!!!!!!!!!!!!

You see, ThumperTalk rocks!!!!!!!!!!!!!!

Hey, you guys gave excellent advice on things to check. The root cause could have been any of the suggestions. Being helpful is all that counts.

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