Hobbyist Forums banner
1 - 6 of 6 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 · (Edited)
I bat a new gas side shaft 6.5 hp ohv vortex engine this engine does not start. I added oil and gas and pulled on the rope. The engine sends fire out the carb as though the timing is off. I tried putting a small amount of gas down the carb. And Iv Pulled the spark plug and replaced the spark plug with a new one, I tried pulling the plug and poling the starter rope to are out the cylinder thinking I mite have flooded the engine. I checked the compression at first it was 48 psi so I lapt the valves to seet them that brot the compression up to 125 psi. But the engine keeps spiting fire out the carb. It seems like a timing problem. I’ve check the flywheel no problem their. I've tried disconnecting the yellow wire and nothing. I have vary hot spark and I am now its getting gas. I'm thinking it might be a leaky intake valve. I do not now how to do a leak down test. The valves are set at .006 exhausts and .007 int. That seems a bit close?
 

·
Registered
Joined
·
85 Posts
I'm guessing the intake valve has to be open when the plug sparks for fire to come out the carb. Have you opened up the crankcase to make sure the timing is right, what about the flywheel, has it twisted on the crankshaft, might want to check it out. I'm still learning small engine repair, so don't take my word for it, just spouting out what seems obvious to me. There are alot of people on this forum with a wealth of knowledge, someone on here will most likely be able to help.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
Yes your rite the valve timing at the Crankshaft can cause that. But it wood probubly been the valve and yes I did check it. The flywheel is the moast likely cause, I've seen it and I check for a sheered flywheel key. I think your rite the valve must be leaking but it still has compression. I’m stumpt.

Thank You!
 

·
Model Murdering
Joined
·
7,331 Posts
Compression vs leak

A Compression Test is merely an indicater of overall integrity. The correct test would be a Leak Down test. Motors with 12 or 15% leakdown can still reflect a fairly good compression reading and still have valve issues. Most small engines will limp along inspite of poor compression or bad leakdown. So your probably looking at ignition timing if you've verified that the valves are opening and closing correctly. There is however an outside chance that this motor was asembled on a friday and the cam gear was assembled a notch or two off! Verify that your on TDC and both valves are closed. Seen it before.
 

·
Model Murdering
Joined
·
7,331 Posts
Compression vs leak

A Compression Test is merely an indicator. The correct test would be a Leak Down test. Motors with 12 or 15% leakdown can still reflect a fairly good compression reading and still have valve and or other issues. Most small engines will limp along inspite of poor compression or bad leakdown. A leak down tester can be had at any decent auto parts house and requires an air compressor to work. Kinda spendy but a good investment if your gonna play with motors. The fancy name is "cylinder pressure differencial" . In other words If you put a 100 psi in and the guage reads 90 psi you've got 10% leakdown. It's the difference between how much you put in and how much leaks off. Then you gotta find it: listen for the hiss of air in the intake or exhaust for valves, listen at the oil filler for rings or piston/cylinder damage, and finally listen around the headgasket. Some motors leak in more than one place! The test must be made @TDC compression stroke. Myself I woudnt go to that extreme yet. Your time and money would be better spent rechecking the obvious. More than likely your probably looking at ignition timing if you've verified that the valves are opening and closing correctly. There is however a good chance that this motor was assembled on a friday and the cam gear was assembled a tooth off! Seen it before. Still makes OK compression. A buck twenty five seems a little low for a new one lunger! Any one agree?
 
1 - 6 of 6 Posts
Top