Troy-Bilt TB4HB EC 4-cycle Blower no start

[ttimtucker]

I'm working on a Troy-Bilt TB4HB EC 4-cycle Blower for a friend. The full model number is 41BS4ESG766. I'm unable to get it to fire. Here is what I've done so far:
-adjusted intake and exhaust valve lash to .004" as per manual (manual says .003 to .006)
-installed new Champion RDZ4H plug gapped to .025".
-Ran leakdown test which shows about 15%; this is in the green on my gauge
-SPC-7200 Spark Check'r indicates a healthy spark (flashing green). In-line spark checker lamp also shows presence of spark. Have not run any tests to see the spark directly.
-Removed magneto and verified that it is properly aligned with the key in the shaft, so I don't have any smoking gun regarding timing.
-I've sprayed starter fluid through the carb, sprayed directly in the cylinder, squirted some gas in the cylinder (3 separate experiments) and can't get it to pop off. For each of these tests the choke and throttle are wide open.
-Compression is 50 PSI; I understand this unit has compression release, so not sure how useful this value is. It does feel rather easy to pull the rope. I did squirt some oil in the cylinder which raised compression to 65 PSI. Not sure what to do with that data.

I don't have tools (like a borescope) to see cylinder walls. I'm not going to bother looking at the carb until I can get the unit to fire.

Any idea where to go from here? Thanks in advance for any advice.

 

[ttimtucker]

Hmm, my next project is a Troy-Bilt TB525 EC trimmer with a very similar engine. Compression is 90 PSI (and this one fires with starting fluid). Based on that, I suspect the TB4HB mentioned in my first post has a compression issue.

 

[slomo]

Sounds like it lacks enough compression to fire. What does YOUR engine manual state for minimum compression on THAT engine?

 

[StarTech]

leak down test would be more useful But these AC engines can have the following compression readings per the AC4 Service manual.

 

[Mark H_NO]

I'm not familiar with your spark tester. I would check for spark directly. Pull the plug, hook it up, ground it, and crank the motor. Do this in the shade, and see how it sparks. I would test starting with throttle at idle also. Choke on, prime, pull several times, then choke 1/2 pull more. It would help to know what the owner's normal start routine is. I seem to get my best results with throttle just a bit over idle.

 

[StarTech]

Better yet have your best friend hold the plug wire end and ground their selves, then give the rope a good pull. If their eyes light up then you know you got spark.


Just kidding.....

 

[Tiger Small Engine]

I'm working on a Troy-Bilt TB4HB EC 4-cycle Blower for a friend. The full model number is 41BS4ESG766. I'm unable to get it to fire. Here is what I've done so far:
-adjusted intake and exhaust valve lash to .004" as per manual (manual says .003 to .006)
-installed new Champion RDZ4H plug gapped to .025".
-Ran leakdown test which shows about 15%; this is in the green on my gauge
-SPC-7200 Spark Check'r indicates a healthy spark (flashing green). In-line spark checker lamp also shows presence of spark. Have not run any tests to see the spark directly.
-Removed magneto and verified that it is properly aligned with the key in the shaft, so I don't have any smoking gun regarding timing.
-I've sprayed starter fluid through the carb, sprayed directly in the cylinder, squirted some gas in the cylinder (3 separate experiments) and can't get it to pop off. For each of these tests the choke and throttle are wide open.
-Compression is 50 PSI; I understand this unit has compression release, so not sure how useful this value is. It does feel rather easy to pull the rope. I did squirt some oil in the cylinder which raised compression to 65 PSI. Not sure what to do with that data.

I don't have tools (like a borescope) to see cylinder walls. I'm not going to bother looking at the carb until I can get the unit to fire.

Any idea where to go from here? Thanks in advance for any advice.

Adding oil to cylinder and raising the compression psi reading 15 psi or 30% indicates worn or stuck rings. You have done a leak down test which indicated only a 15% loss, which is low.

The bottom line is that this is a turd of a blower to begin with. You have done your due diligence. I wouldn’t spend more time on it. So glad I quit working on off brand handheld equipment years ago. Nothing but a pain, and not worth it to the customer.

 

[ttimtucker]

I ended up tearing the engine apart and found extensive scoring on the piston and cylinder. If I were to attempt to repair (which I will not) it would require replacing the engine (that seems to be how it is sold) for about $120, which is a significant percentage of a new replacement blower. Having a borescope would have been a much quicker way to diagnose the problem. At any rate, a good learning experience, and got to have fun taking it apart.