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XR 430 Compression Woes

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I have a 2002 XR 400 that I turned into a 430. Love the power and have been an XR fanatic for many years but ever since I bored it out, the compression is almost too much to handle when it comes to kickstarting. Without a question, it's harder to kick over than my buddy's XR650 and on some efforts I can't get it to kick through at all. When the bike is cold, I can choke it and the Mikuni pumper carb helps it start on the 2nd or 3rd kick almost every time. However, If I accidentally let the bike stall after 10 or 20 seconds, it will usually start again pretty easily but if it stalls out 2-3 times before it gets warm, my troubles start and I can't get the bike started again so I just let it sit for 5 - 10 minutes. Once the bike is warm, it idles fine and does not stall. However, after I've been riding for a while and the bike is hot and I want to come to a stop, I kill the engine at my own risk because it can be a major chore getting it to restart. Again, I may have to wait for 5 -10 minutes or just hope I'm on a hill so I can bumpstart it. Any advice for getting this thing to start a little easier or making the compression more manageable? Sometimes I'll just pull the decompression lever in and it will start with the lever squeezed in. Thanks for your input.

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Did you leave the decompression mechanism on the cam when you rebuilt it...

🙂 dumb question since you pull the lever!!! 🙂

I had the same problem when I put the 426 12:1 compression kit in my XR I could stand and bounce on the kick lever and it would not budge!!! I realized that my valves were way out of spec I would start there

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Try NOT kicking it from TDC. Try kicking it from the piston at the bottom of the stroke just before TDC. You get the mass moving and it's more apt to kick over.

I know this sounds counter to what you would think the norm is but, I have had good luck starting an engine that doesn't want to start when it's hot by holding the decomp lever and kill button and kicking the engine over several times, then release the decomp lever and kill button, put the choke on and kick it over, starting with no throttle. If it doesn't light by the 2nd kick, open throttle to about 1/2 and try again. If it starts, immediately take the choke off. This has worked for me with the stock carb.

For your pumper, since every time you twist the throttle it shoots gas in there, try twisting to 1/2 throttle and "hold it there" while you pull decomp lever and hold kill button and kick it over several times. Release lever and button and while still holding 1/2 throttle(you haven't let go of it all this time), kick the engine over starting with the piston at the bottom of the stroke below TDC. I didn't suggest using choke because with your initial twist to 1/2 throttle you squirted fuel in the there, already creating a rich condition. Doing the decomp lever/kill button/kick routine gets air moving thru the carb to help vaporize that raw fuel and get it moving thru the carb and into the cylinder.

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OK try this, this will get my XR lit first kick cold.

Turn on fuel and choke if its the first start in a while (3 hours+). Kick it over slowly to compression. Leave your weight lightly on the kick start and just tap the decomp lever. It should roll past compression about an inch. Only enough to get past compression. Make sure your decomp lever is out and give it a solid boot without touching the throttle. If you think you may grab the throttle a little bit, grab the bars instead. Repeat this procedure till it starts, then once it starts rev it a little bit and turn off the choke quickly but be careful it doesn't stall. This also works well for hot starts, my XR400 normally takes 1 kick hot as long as I get my piston just past compression.

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