Been a while since I last posted, but I have a Honda HHB25 4-stroke petrol blower Model UBAJ-1015484 fitted with a Honda GX25 OHV engine Model GCAAM-1242717 that has got me stumped at this point. Said to have worked last year, but won't start this year. Appears to have reasonable compression, using a simple finger in the spark plug hole method, but refuses to start. Even spraying "Start Ya Bastard" (Ether spray) into the engine through the spark plug hole or directly through the carburetor will not get it to kick over, which is unusual. Pulled the spark plug out and gave it a clean. It throws a good spark, so doesn't seem to be the issue. Pulled the muffler off and cleaned the spark arrestor gauze to ensure there were no blockages. Whilst the muffler was off, gave the motor a few pulls on the starter rope and it throws exhaust compression out the muffler port. Pulled the rocker cover off and checked the valves were moving, but not gap checked at this stage. No issues noticed with them. New good quality fuel put in the tank. Replaced the fuel primer bulb as it was split. Replaced the fuel lines as one was rock hard and the other had gone soft. Checked and cleaned the fuel filter. Carburetor needs a diaphragm kit installed, but that doesn't explain why it won't fire. Can't work it out and has got me stumped. Daryl
Thank you NormK. That did the trick. Just put a new spark plug into the machine with a dose of "Start Ya Bastard", and it fired. That was my first thought that the spark plug may be failing under load. Next option was to consider the coil failing under load. Mower shop only had the slightly cooler NGK CMR6H spark plug instead of the normal NGK CMR5H. To complete the information I detailed above for the machine, the carburetor is a Walbro WYB-17 and takes a K10-WYB repair kit. Now just have to wait for new carby kit so it runs on petrol and not ether. Appreciate your advice. Regards Daryl :-)
It is to note that these 10mm CMR plugs are known failures of all kinds here. I had them to fail completely, fail to fire under compression load, and even had one to cause a two Stihl Hedger to diesel at full throttle.
I also had a couple to short out through the ceramic insulator. I actually disassembly the plug and verified that this had happen.
I also had one several years ago to bring in a backpack blower swearing it had a rod knocking but it turned out to be a missing CMR plug. He was piss that I charged for the plug and labor.
