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212 cc Power Loss Need Help Troubleshooting

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I have an old style 212 cc predator modded with header, performance air filter, 1.3:1 ratio rockers, 22 lb springs, stock carb jetted .020 low/.035 high, stock cam and governor removed. It was putting out decent power and revving up around 5000 RPMs. It ran great for about 2 months but suddenly it began starting harder and lost a lot of low end power. It also does not rev out as high as it did before (revs about 4000 rpm now). Does anyone have any idea what could be causing this? I checked the plug and it was fouled so I installed a clean plug and it runs the same. Could this be bad gas? Has anyone else experienced anything like this before? Any comments, advice and recommendations will be greatly appreciated.
 
If your gonna be using ratio rockers you need to be in the 6000+ rpm range other wise you are not gettin the full potential of the engine. Your jetting seems low also, try a .024 low and .038 main and see if that doesn't wake it up a good bit also. As far as your issue, you could be coil binding the springs with those ratio rockers and that will limit your rpm. Valve lash also could have loosened up and Is making it hard to start as well. Check to make sure the flywheel didn't slip and shear the key also. I would be concerned that you can only turn 5000 rpm with 22lb springs....you can turn 5000 in these engines strait out of the box with only removing the governor and adjusting jets a little so you have done something wrong with the parts your using...my guess is ditch the ratio rockers if you plan to keep those springs or If you aren't gonna turn more than 5000rpm
 
If it was running good, and now it's running bad, and you haven't done anything to the engine, then something must be wrong inside. 1st thing I would look at is the timing, and the 2nd thing would be the valve lash. Easy things to check.

Could be a leaking head gasket. Could be the carb. Could be the Rod. Could be the compression pressure, but nobody checks that. lol. The valves might be leaking or the rings have gone bad.
 
Gentlemen, thank you for your responses and advice. You were right about the timing. I sheared the timing key. This actually worked out for the better. I replaced the 8 degree key with a 4 degree key that I had laying around and the engine loved it! It starts easier and idles better. I had to turn the idle screw down to stop the clutch from engaging... It also makes a lot more power in the bottem end and revs out better! I am tempted to try the stock timing key just to see if it will idle better and prouduce more low end and mid range torque. What are your thoughts on using the stock key? Also why do you think the engine sheared the 8 degree timing key?
 
Kart43 said:
Do you have a tach or are you estimating your RPM?
Click to expand...

I was estimating my RPM. However, I just got a tach today and ran some test on the gokart see what RPM the engine idles, driver clutch engages, driven clutch shifts and max RPM. It revs just over 6000 RPMs.
 
As I suspected, if you are using RPM as a diagnostic, or tuning tool you must have a Tach, your ear and butt is not calibrated.
 
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