Hi all, I've been having a strange problem with my SR125 motorcycle... I recently adjusted the intake valve clearance as the engine was very clattery and the bike hard to start. When I opened up the cover the valve clearance was way bigger than it's supposed to be, so I set it at the recommended clearance. This helped a lot for about 50-100 miles, but then the bike started displaying the same symptoms, so I reset the clearance again, which worked again for a while but now the valve clearance is back too open again... Wondered whether there is likely to be an underlying problem elsewhere on the bike? I'm a bit of a novice on this stuff, but really keen to learn. Any help much appreciated!
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Re: Intake valve clearance keeps increasing
When this kind of problem popped up on my Honda CB 360, I discovered (about the same time Honda did) the 'floating' cam was floating right up into the head ... a bad design. I doubt this is your problem but it is worth a look-see ... how are the cam bearings? review your work ... make sure you are doing exactly what you are suppose to be doing.
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Perfecto, .006 mm intake,.008 mm exhaust.
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make the engine runs for about 30minutes before adjusting the valves, valve clearances: intake valve = 0.20mm(0.008 in) exhaust valve = 0.25mm(0.010 in) for reference only when the engine is cold, valve clearances: intake valve = 0.25mm(0.010 in) exhaust valve = 0.30mm(0.012 in) engine specs: mitsubishi 4g13 1.3L (if you have same engine)
Hi bbg713, I hope I can help you out. The valve lash (tappet clearance) on engines of approx this size should be 0.005-0.007 inches (0.13-0.18 mm) for intake valve and 0.007-0.009 inch 0.18-0.23 mm for exhaust valve (cold engine). Adjust tappet clearance by grinding end of valve stem to increase clearance or grind valve seat deeper to decrease clearance. I hope I have helped you a bit. Any more questions are welcome. Regards and good luck. Denis.
make sure engine is warmed up. Put cylinder one at top dead center,remove the valve cover,loosen all adjustment lock nuts,adust intake and exhaust valves on cyl #1 and intake valve on #2 and exhaust valve on #3. now rotate crankshaft 360 degrees clockwise, now adjust intake valves on cyl#3 and cyl #4 and exhaust valves on cyl #2 and cyl #4.now tighten lock nuts and install valve cover. specs are intake valves 25mm clearance and exhaust 28mm clearance, use a feeler gauge,heres a picture to show you where to check clearance.
You need to remove the valve cover and rotate the crank shaft to TDC then with a feeler gauge you check the clearance between the cam lobe and lifter bucket. There are 3 on intake cam and 2 on the exhaust. The clearance will most likely tighten as the valve seats and valve wear in. If the valve clearance gets too tight they will hang open and not seal for proper combustion. Valve clearance for my 2002 YZ426 are intake=0.10-0.15 mm (0.0039-0.0059 in) exhaust=0.20-0.25 mm (0.0079-0.0098 in) the 450 should be the same or very close
with the cylinder set at top dead center compression. using a feeler gauge between the tappets and the valves there should be .002-.003in clearance on the intake valves, and .006-.007in. clearance on the exhaust valves. thank you.