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Discussion Starter · #1 ·
Just rebuilt motor crank was fried. Sled has no power just bogs. Idles just fine but when you lauch it takes of great for 10 feet then it boggs and will not go any faster. Need some ideas on what to do. Not sure if it is in the carbs or electrical system
 

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clean out the carbs. check your fuel pump too/hoses. sounds like its just not getting enough gas at higher RPMs. I believe there is another thread almost identical around here somewhere. ill try to find it for ya
 

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Check your fuel pump and all your hoses. you probably have a small crack in a hose and are losing pressure. Read through this thread and try some of the things smallengine suggested in it. He will probably speak up any minute and add to this thread also though.

http://www.snowmobileforum.com/showthread.php?s=&threadid=3424
 

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Thanks, Maverick. When it bogs, give it a little choke. If it picks up, then start tracing the fuel system. Like Mav' said it's either the fuel pump or the high speed jets/needles in the carb.
 

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Discussion Starter · #6 ·
Today I went back through the carbs and checked fuel delivery and everything is ok on that end. Then I ran it on the stand and it seemed to rev out and run decent. So then I took it out in the grass and it took off ok not great the first time but let off throttle and gave it the gas again and back to bogg no power. I am going to go back through the carbs again and check the float height, but after that I am about to let it stump me and let someone else fix it. I hate the thought of letting this thing beat me.
 

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Discussion Starter · #9 ·
The plugs are not wet that look to be burning proper color after it has been ran. The float level is in check and everything else seems to be working properly
 

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probably a stupid question...but do you have the brake locked on by any chance? off the ground it would have enough torque to spin the track but with your weight on it it would seem like it was bogging.
 

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How are these 2 strokers timed? I don't know much about them, but if we were talking about these symptoms in a car engine I'd be thinking timing, especially since you said you replaced the crank. Is there any type of vacuum advance?

Steve
 

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Discussion Starter · #13 ·
The track spinns free can turn track by hand. When I got the sled it was not running right. The guy I bought it from said he believed the cdi was bad. He had put new stator and coil in the sled. Ended up crank had bad rod bearing and end bearing. Put it back together and it runs better but still has original bog. I got a cdi and all the guys old parts, put them on and still same issue. Only thing electrical left would be timming sensor.
 

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Discussion Starter · #15 ·
The crank seals were brand new along with all the other gaskets. Both cylinders check at a little over 120 psi.

I checked with my local cat dealer and they told be how to check the timming position sensor. They said at 2000 rpm should reed 2.5 volts and at 4000, 4.6volts at 3000rpm, and 4.8 at 4000. My sensor is not corelating with there specs. At 2000 rpm I am only reading roughly 1.5, and after that does not matter what the rpm is I never read over 3 volts. I am thinking this might be the problem. Not sure if any thing else would cause this.
 

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This is totally in a different direction but after my friend somehow ripped out his motor mounts on his ZR700 and we got it all welded back in (the frame was ripped out too) the problem ended up being his secondary pulley. It ran great when the track was off the ground but when you tried to take off on grass or snow it just bogged and ran like it was fouling out plugs. After ripping apart carbs, checking float level, replacing fuel pumps, etc etc it ended up being the secondary pulley was toast. Just figured I'd throw another wrench in the works so you don't spend tons of money troubleshooting engine stuff in case its not.......
 
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