Piston hit intake valve on ETQ generator. Need new head?

Michael_Gee

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  • / Piston hit intake valve on ETQ generator. Need new head?
Hey all,

Well, my ETQ TG52T42 generator, with only 52 hours ?on it, seems to have suffered from the piston slamming into the intake valve. Since the piston seems to not have any issues, I can only assume there must have been a valve guide failure, causing the valve to fall into the head. In any case, the valve is bent so I'll need a new one of those, and probably a retainer, but I'm wondering if the damage done to the head is significant enough to require a replacement. I've attached some photos of the damage to everything and would like some "professional" opinions.
Since this engine appears to be Chinese and the company who imported it (Eastern Tools & Equipment Inc) is no more, I've found that coming by parts for this is challenging, but not impossible. I suspect I'll just get this one up and running and sell it to get something more reliable and that I can easily get parts for.
 

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Born2Mow

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  • / Piston hit intake valve on ETQ generator. Need new head?
I've done this type repair a lot. I do not think you need a new head, especially since it's a constant speed engine and not a racing engine.

Heat the head on a hot plate until your saliva will dance. That's about 200°F. (Or a large pot of boiling water.) Then the broken guide will easily drift out. Make a new guide from brass, iron, or a 3rd party guide. The guide's OD should be 0.001" larger than the head. Lube the new guide and it can be pressed back into the re-heated head. Don't finish the ID until the guide is installed.

You'll need to kiss the valve seat with a cutting stone. The more care used in seating the new guide, then the less material will need to be cut from the seat.

You'll want a new valve, collar and 2 keepers. The piston is usually not badly hurt.

Root Cause: There are only 2 reasons this happened: Keeper failure or Valve timing. Either the 2 valve keepers slipped off the valve, or the valve stem notch gave way in a mechanical failure. But also, the exhaust valve should come slightly closer to the piston crown than the intake valve. Could be an initial setup failure to with poor valve timing.

Hope this helps.
 

Michael_Gee

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  • / Piston hit intake valve on ETQ generator. Need new head?
Thanks. Lots to take in there so I've got some follow up questions if you have the time to answer them.
First off, his it the manual with parts list (https://images.homedepot-static.com/catalog/pdfImages/cd/cd041a72-f464-449d-8177-d232aac1c386.pdf). This might make it easier for use to ensure we're talking about the same parts (mostly for my edification).

The guide actually came out (See image) when it failed but your method of heating it up and putting a new one back in sounds like a plan BUT I suspect you are much better equipped to make parts than I am and this thing looks like it requires a lathe BUT if I think I might be able to get a replacement.

As far as the value seat, I don't have a cutting stone but I do have a lapping tool and compound which I assume will work.

As far as the collar, I'm looking at page 24 of the manual and I assume you mean the "RETAINER,EXH VALVE DOWN SPRING" (Part 7). If so, that looks like it's only for the exhaust. The intake just has the valve stem seal, which I can only find pieces of the current one. See other images for better idea where it broke.
 

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Born2Mow

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  • / Piston hit intake valve on ETQ generator. Need new head?
No, sir. Part #7 is a static seat that simply protects the alum head from the twisting steel valve spring. Without that, the spring would soon dig a well !!

You need parts #5, #10 and #11.

As far as the guide.... you'll need to measure the hole in the head very carefully. Sometimes the guide will spin and loosen up the hole. Don't try to clean up the hole because the fit is very close. There is no spare metal there, and even polishing the hole can get you into trouble.

The guide needs to be lubed and installed quickly, but without a hammer. I have made adapters, cut at 45°, to sit atop the valve seat. Then pushed the guides in using a bench vise as a press. Some sort of press (either a vise, arbor press, or a hydraulic press) applies a much smoother action and allows the guide to seat in the same spot as the old one... which is REALLY important when you can't cut valve seats.

Practice the guide installation several times with a COLD head. Remember the head is going to be Hot and you'll be wearing clumsy oven mitts. Where ever you work, put a soft landing under the press. Dropping the cyl head onto a concrete floor might dampen your day. ?

Hope this helps.
 

Michael_Gee

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  • / Piston hit intake valve on ETQ generator. Need new head?
No, sir. Part #7 is a static seat that simply protects the alum head from the twisting steel valve spring. Without that, the spring would soon dig a well !!

You need parts #5, #10 and #11.

As far as the guide.... you'll need to measure the hole in the head very carefully. Sometimes the guide will spin and loosen up the hole. Don't try to clean up the hole because the fit is very close. There is no spare metal there, and even polishing the hole can get you into trouble.

The guide needs to be lubed and installed quickly, but without a hammer. I have made adapters, cut at 45°, to sit atop the valve seat. Then pushed the guides in using a bench vise as a press. Some sort of press (either a vise, arbor press, or a hydraulic press) applies a much smoother action and allows the guide to seat in the same spot as the old one... which is REALLY important when you can't cut valve seats.

Practice the guide installation several times with a COLD head. Remember the head is going to be Hot and you'll be wearing clumsy oven mitts. Where ever you work, put a soft landing under the press. Dropping the cyl head onto a concrete floor might dampen your day. ?

Hope this helps.
Thanks for your suggestions.
I got a new head, valve, and retainer. I lapped the valves and will be putting it all back together this weekend. I'm still very surprised that only the exhaust has the retainer SO....dumb question time. Why is this only on the exhaust? I haven't put that together yet because of this.
I really want to thank you for your assistance with this.
 
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Michael_Gee

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  • / Piston hit intake valve on ETQ generator. Need new head?
So, I also noticed the intake also doesn't have a "ROTATOR,VALVE" (or that little cap that is in between the end of the valve stem and the valve rocker) on the intake. I did some searching and found that while Briggs & Stratton did have that for both intake and exhaust, the Generac did not. Maybe it's a cost-cutting decision. The funny thing is the guy who I watched teardown the broken Generac also thought it should have been there and didn't realize it wasn't supplied until he tore it down. This thing only had 20 hours on it. He also did another video where he had 2 Generac's, one with only 7 operating hours while the other had 200. Maybe it's just a coincidence but Generac doesn't seem to be a reliable product. ?
 
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