Need some help, Scrambler 50 runs for five minutes then bogs down, doesn't stall but loses power, had it to the dealer for major service $300 later and 5 trips an hour each way, still does the same, Had two recent graduates from the motorcycle institute work on it for four hours, clean, vent lines, carb and new fuel filter, still no help, any other suggestions before the 6 year old takes a hammer to it.

Thanks

 

Sounds like you (or your young rider) is going through some emotional times. If you can, please explain more detail about "loss of power". For example, does it gradual'y loose power like its not getting enough gas, an electrical type problem, etc. This may help us....

Here's a few things:
- Replace with fresh gas (probably already done).
- Replace inline gas filter (probably already done).
- Ensure gas tank is full. Sometimes, the R and ON lines are accidentally flipped around.
- Clean Air Filter (problably already done).
- Check float level (hopefully, this was already done).
- Clean Carb (hopefully, this was already done).
- Check Spark Arrester / Muffler for too much carbon (hopefully, already done).
- Change Plug (hopefully, already done).
* If you feel its carbon overlaod (because of low RPMs), install a hotter plug and ensure it has a "P" in its coding.
- Check compression 3 times (cold, warm, hot) and tell us the numbers. Could be rings that leak or reed leafs that leak with a warm / hot engine.


These are the basics. Please advise if they did these things already.


Hopefully, this helps...


BTW: Welcome to this forum....

.

 

Hello, thanks for the suggestions,
In terms of "loss of power" the machine at start up runs great, Runs about 500 feet than it does feel like a fuel problem, it gradually loses it power though still running, sit for about a minute then it will move a few more feet, then eventually go into a very low idle, then shut down. Immediately after machine will start and run great then process starts all over. Then it's time for OLE Grizzly and the tow rope. The items that have not been checked is the compression, The dealer suggested we not keep a full tank of fuel in the machine as we are in Connecticut and in October they changed the additives in the gas at which time they sold us Yamaha fuel stabilizer with conditioner. I will fill it up today and work on the compression numbers. I thank you for your suggestions

 

Based on your description of loss of power, it definately sounds like fuel type problem. RE: runs, idles down, stalls, then re-starts again. Also sounds like a pinched vent, plugged gas filter / gas line or improper set float. Could even be too much crud in the spark arrester / muffler.

.

 

Take the petcock out of the tank. Run a drill bit up inside the tank and clean out the hole. Wash out tank throughly. Take a drill bit and run into the fuel intake of the carburetor. Make sure a clean hole is there to the pin on the float. Replace the fuel lines and you have solved the problem. One of those three will be your culprit. Just do them all and you won't have anymore problem.

 

Hello Onebadamx, I have the exact same quad and the exact same symptoms. I have been looking into this for some time. the problem only started for us since the cold weather set in. We are in Illinois, so about the same climate as you. I have totally disasembled the carb and cleaned it blown out all ports on it and verified that there is more than adequette fuel getting to the carb. I have not yet checked the exhaust system for blockage, however that seems a bit unlikly due to the fact that the things runs like a champ for about 30 seconds and if we let off the throttle for a few seconds it regains its ability to go again. Either way I plan on taking the exhaust off of it and flushing it out to be sure.
Something that I noticed is that the throttle cable splits into two leads one to the carb. and the other goes into the bottom cover on the engine. I have just put the dog up on saw horses in the garage and I am going to take the covers off of the right side and bottom to see where that thing goes and what for.

If you have figured this out I would really appreciate knowing what you found, and Like wise I will post anything that I discover.
Thank You

 

Hello, after many tear downs of the carb, and all other items listed I think we just figured it out yesterday, our machine ran great all morning a ton of doughnuts in the snow today. Put your seat belt on for our fix. It is as simple as duct tape. We took the air intake off the carb and covered the carb three quarters of opening with duct tape ( getting to much air) and then put the air intake back on. Runs great today.

Thanks all for the help, Let me know if this cures your issue.[img]i/expressions/face-icon-small-smile.gif[/img]

 

Wow! I never would have thought of that. I have the side covers off of it right now, I am getting ready to try flushing the Exhaust. That other piece of the throttle cable goes to some kind of device on the engine. A cam of some type The cable is very cheaply mounted, and when I got the cover off it appeared that the cable was pulled partly out of the mount. Still not knowing what the thing is for And I don't know if I pulled it out like that taking the cover off I cannot say if this has to do with the problem. Anyway I am going to flush the exhaust since I have it off already anyway. Then I will see what happens. If it still does the same thing. I will certainly try your fix. Thank You very much for responding!

 

Awesome You got me in the right direction. Thank You! After I finished flushing the Exhaust, ( It was really nasty with oil residue ) I put it all back together and Still had the same result. So I set to the task of implementing your fix. As I was removing the air cleaner I noticed a sticker on the housing that stated that the Carb is factory set for 40 - 80 degrees and 0-3000 feet alltitude, it said to consult owners manual for jetting and adjustments for operation in other ambient conditions. Unfortunatly I do not have the owners manual, but with a bit of trial and error It is running really good now. I set the main fuel metering pin to its highest setting and then adjusted the neaddle valve to 1/2 turn out. It runs great for the kids, the only time I have it bog down now is if I am on it and get it really overloaded. But thats not a problem as i only ride it to troubleshoot the problems. Anyway. If you want implement this, I'd be glad to give you more details. Honestly I think that your fix is far easier, and the way to go if you don't plan on running it to much in the colder weather.

Thanks a ton! You've help me make three little kids much happier!

 

Great to hear. Don't feel unfortunate for not having the owners manual as I have read it and the service publication completely, as the manual only states "CONTACT YOUR DEALER" Which started in September with many trips and $$$ later. No mention of cold temperatures just altitude. Thanks to a young ATV enthusiast the six year old is smiling and sliding again!