I bought this engine 2 months ago. I've already fixed the carb with a rebuild kit and cleaned it real good too but I still have a problem in slow/idle speed. It acts like running a bit lean but the idle mixture screw is out about 1,5 turns and the carbs passage ways are super clean. Running a little bit on above idle won't work. It surges and sputters. I have checked the fuel system completely, new gas RON 98 (only 5% ethanol max), 1:50 mix with pennzoil, no water in gas, new connectors in both ends (motor and tank) and no internal leaks between fuel pump and the carb.
It has a real good dark blue spark in both cylinders and Champion QL77JC4 plugs gapped at .030".
A very weird thing is that the cam roller is on half way of the timing plate on IDLE. If I move the whole assembly to the left so that the two marks on the plate would line up with the roller it cuts out.. Could it be the flywheel key or what? It was so rainy today that I couldn't check timing with my light..
if flywheel key is broke so flywheel will only spin, no crank(crank will stay in place).
cam roler should have a screav to adjust.
i recomend you to rad some good articles, down at page look for ignition.its about 15hp models, but all omc motors shere the same construcion of carb, ignition http://www.sschapterpsa.com/rambling...n%209.9_15.htm
Thaks, that was a real good link. I think that the 521cc 20-35 hp models don't have any kind of screw in the timing plate like the 9.9/15 hp do. I am pretty sure that the problem is in ignition system (timing)..
Adjust the roller on carb so it hits the mark on the cam when aligned with the marg.
Give full throttle (in gear not running) - adjust the link stopper from carb to vertical shaft at the back. Set the stopper so carb is fully open. (99% is better than 101%).
Back to neutral. Start engine and give a test run.
Check max timing with a timing light at full throttle. There are two sets of marks at the flywheel. One intended for manual start with the alignment at the manual starter housing, one for electric start with the alignment on the electric starter housing.
No one likes the E 10 gas, but is mainly what you get. May be a bit hard on gaskets and membranes as time goes on. Before the E10 was introduced some people used to store the boats/tanks full of fuel, not recommended with E10 even if stabilizer is used. Use a quality 2-stroke TCW 3 oil and it should be no major problems.
I've heard too that the E10 goes stale faster than non-alcohol fuels. In this summer I've used 98 grade that contains max. 5% ethanol. Costs more but you can store it longer time.
Back to the timing issue, I tried to run the motor despite the carb linkage is out of range. Throttle plate starts to open when the cam roller is about in center of the timing plate. The throttle plate is fully closed at idle. when i try to move the throttle lever so that the roller would line up with the two marks, engine cuts out immediately. Now on sunday I'll get the timing light so I can check timing..
Problem solved!! Low spark voltage... Engine runs pretty good when on 22-30 degrees advance (tested with timing light). Less than 18 degrees engine starts to miss and then cuts out suddenly. It smokes like hell, light blue very thick smoke and when it cuts out both plugs are totally wet, especially the gap. Also the sea is full off unburnt oil...
By the way, how engine works with leaking or burnt head gasket?