QuestionQUESTION: Hi, I have a stump grinder with a 24hp V2 670, producing white smoke. One of the cylinders is staying cold while the other one is at normal temperature. The ignition is fine, it even runs on the bad cylinder only, when the spark cap is pulled of the good cylinder.
I think the head gasket is blown. If you want to take of the cylinderhead, do you need to remove the valves, springs and rods or can you loosen the cylinderhead bolts and remove the head at once ?
Thx for helping out,
Pascal
ANSWER: You can remove the head at once but this sometimes puts stress on the valves. I always loosen the valves to make sure I don't cause any damage.
Valve clearance specs can be found at the link below:
http://www.honda-engines-eu.com/en/images/1000.pdf
I would start by checking the valve clearances before pulling the head. I have had a lot of Honda intake valves stick and cause poor engine performance. Also, I would use a cylinder leakdown test to determine if the head gasket is leaking. You do not need to remove any parts, other than the spark plug, to perform a leakdown test.
Let me know if this helps.
Eric
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QUESTION: Thx for your quick reply. I just did a compression test with a surprising result : the defective cylinder has the highest compression, about 120 psi/sq inch. The good one has about 100 psi. So the problem could be the carburator. I took it to the workshop to put it in the ultrasonic cleaner. I will have it back next thursday.
Going to check the valve clearance now.
Pascal
ANSWER: The cylinder with the high compression may have a valve issue. Check to make sure the valve gap clearance is within specs and see if the intake valve is sticking.
Eric
---------- FOLLOW-UP ----------
QUESTION: Hi Eric,
After a long search, I finally found the defect. The engines has not been used for more than a year and the carb was clogged. Although I had it cleaned ultrasonic, this still was not sufficient. I removed the "blocks" around the pilot screws (which are blocked in Europe for the emission restrictions) and cleaned the holes with carb cleaner.
Additionally, there was a spark problem with the spark plug head. I thightened the fitting with a pair of pliers so it snaps tighter on the spark plug. All of a sudden I got more rpm, the engine kept on running on the bad cylinder only and it was building up heat. So there was no fuel AND no spark, no wonder I could not get it going.
Anyway, the coil might still be defective, I will let it run again tomorrow and check the spark plug colour after a while to see if it is nice coffee brown. If not I might still replace the ignition coil.
I hope to be stump grinding soon, thanks for your help.
If you have additional suggestions plse let me know.
Pascal
Belgium
AnswerGlad to hear you are making progress. I have also had carburetors that I had to clean two or three times before they started working. I am curious about the plug head. Some Honda plug wires have a screw inside the high tension (spark plug wire) lead. Did you have to tighten the spark plug wire or just the piece that screws onto the spark plug end? Some of the NGK plugs have an adapter you can install for mower engines; most motorcycle plugs do not require this adapter.
As for the ignition coil, you can ohm them if you have the specs but I once had a Japan made trimmer, forget the brand, where the coil would test good but if you let the trimmer sit over night it would not start the next day. The trimmer did this 2 or 3 times on me until I finally just replaced the coil. To this day I still don't know for sure why the coil would work when I took the unit apart to test the coil but after letting it sit it would not have spark the next morming. I would do all you can to verify the coil is bad and reading the spark plug, like you mentioned, is the bet way to gauge the health of the coil.
Let me know if you end up replacing the coil.
Eric
