Troy Built Trimmer Wont Rev Up

[BillCT]

I have a TB20CS trimmer that suddenly just stopped the other day. I discovered there was no spark so I installed a new coil, gaped it with a business card and it started right up but it would not rev up at all. It'll idle perfectly but not high enough to trim. So I've done the following:
1. Installed a new Champion Plug
2. Replaced all the fuel lines including the filter
3. Replaced the carburetor with a new one
4. Drained and replaced the fuel.
5. I removed the intake and inspected the Reed Valve. It appears to be OK, has a slight bow like it's supposed to and appears in like new condition. It's stainless steel.
6. Checked the compression and it's slightly over 120 psi.
7. Removed and checked the spark arrestor
8. Ran without muffler to verify it wasn't plugged
It'll run at WOT but it runs like the mixture is not correct, no power and won't rev up, but if the high mixture needle valve is adjusted it'll stall out. It reacts exactly the same with either carb. Idle is fine.
Any ideas?? (Besides throwing it out!!)

 

[Jeff P51]

Check ignition timing. I recently worked on trimmer with same symptom and found flywheel key sheared off and slipped enough to throw off ignition timing but still run, but wouldn't accelerate.

 

[Hammermechanicman]

OEM or Ebay coil?

 

[BillCT]

Check ignition timing. I recently worked on trimmer with same symptom and found flywheel key sheared off and slipped enough to throw off ignition timing but still run, but wouldn't accelerate.

Ok will do, never thought it could do that. Thanks

 

[BillCT]

OEM or Ebay coil?

First replacement was an EBay and was marked 173 on the bottom, the second was OEM and came in a bag stating it was OEM for several models and makes and was also stamped 173. I’m thinking it came from MTD somehow.

 

[BillCT]

Ok will do, never thought it could do that. Thanks

I pulled the flywheel, key is in the flywheel as it should and has not moved. Doesn’t look like there’s anything to this flywheel that could go bad, magnets seem pretty strong.

 

[Jeff P51]

Wow, that's a real head scratcher..seems like u have replaced almost everything. What does plug look like..black, tan ,white..? Crankcase need to be sealed also or it won't get enough fuel. Have u checked crankcase seals? I fabricated some plates to cover intake and exhaust ports, put piston at bdc and applied pressure with a pressure/ vacuum tool..(available at harbor freight) about 8- 10 psi...it should hold pressure..

 

[BillCT]

Wow, that's a real head scratcher..seems like u have replaced almost everything. What does plug look like..black, tan ,white..? Crankcase need to be sealed also or it won't get enough fuel. Have u checked crankcase seals? I fabricated some plates to cover intake and exhaust ports, put piston at bdc and applied pressure with a pressure/ vacuum tool..(available at harbor freight) about 8- 10 psi...it should hold pressure..

Haven’t checked crankcase seals but I can. Has great compression 120 psi. I could spray carb cleaner around carb and crankcase seals when running I guess to see if there’s any change. I put in a new plug the old one looked normal, grey / sandy color. After running it’s slightly black but not really excessive or wet. I can take a picture later and post it.
thanks for the input.

 

[bertsmobile1]

You have not answere Hammers question
Where did you get the coil from ?
did it have a brand name cast / stamped into it ?
The ratio of faulty to good ones sold through annonomus vendor platforms like Amazon/ ebay is about 3 to 1

 

[Jeff P51]

Remove spark plug , ground it to the head..pull starter look for nice blue spark