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Discussion Starter · #1 · (Edited)
This is the 23 HP Vanguard that hesitates a second or two before spinning over and starting. There was some discussion on it possibly being a valve and/or decompression issue.

The engine started running crappy while mowing yesterday and quickly got worse. Had to use my 400 to finish mowing. Btw.. jumping off my 420 onto my beater 400 felt like getting in a 6 ton grain truck after driving a shortbox F150. The 400 feels heavier and bulkier and rougher riding. Noisier too. Got at least one spindle going bad on it. Growls and is loud. It's the no grease type <insert applicable profane language here>. I did the spindle bearings around 2007 so no complaints. Just don't need any extra work right now. The 23 HP Vanguard on it runs super nice though.

I've been running the 420 VG with the choke part way out. I think the intake gasket(s) might be bad. I had the intake off last winter and put it back on with the existing gaskets. They looked fine but I still should have waited to get new ones.
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When I got off to see what was going on before I quit mowing with it I saw some black smoke belch out in front of the carb, which was kinda odd to see because it appeared to originate from the bottom of the carb not the top. So maybe the gasket is bad. I didn't take the carb off the intake when I had it off the engine though. Anyway, I shut it down immediately to avoid the 420 going out in a blaze of glory.

That VG has never idled very well. Hunts and hunts.

I can see and hear the governor compensating constantly for the rough running so I'm pretty sure it's fine. I always assume a governor is good unless all other possible causes have been eliminated.

I bought an offshore carb for the VG a while ago. Was only a few bucks more than a carb kit and I've had good luck with them so I figured why not? Turned out the throttle lever is on the wrong side and after further review of eBay offerings all the clone carbs appear to be like that. I have chinese carbs on a K532, a 14 HP Kohler, a 12 HP Kohler and 8 HP Honda. Also a little 6.5 HP clone. I put one on a Ferguson 30 several years ago too. They all work good. I have one on the shelf for my Ford 800 too. Some guys have had a different outcome so I've been lucky (definitely not typical for me).

I googled the problem to see what the interweb thought might be the problem. Some of the posts I saw were pretty amusing. One guy said his VG was backfiring and causing the deck to seize up. Another speculated that his muffler was going bad because it was making louder noises sometimes and making the engine run crappy. I've come up with a few outlandish theories myself over the years so it's nice when somebody makes me feel like an amateur in that respect.

So after I do some more mowing today with the 400 and lots and lots of weed whacking, I'm gonna dig into the 420 VG and hopefully find out it's just a gasket issue.
 

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Army - the rough running at idle and having to run with choke at high idle does sound like the engine is getting too much air from somewhere other than through the carburetor and that could be a gasket issue, but in my opinion, the "hard to crank over" symptom sounds like a completely different issue so you might have 2 problems. Like you mention in the first paragraph, I'd check the valve lash and the compression release mechanism while you have the engine apart.
 

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Discussion Starter · #3 ·
Army - the rough running at idle and having to run with choke at high idle does sound like the engine is getting too much air from somewhere other than through the carburetor and that could be a gasket issue, but in my opinion, the "hard to crank over" symptom sounds like a completely different issue so you might have 2 problems. Like you mention in the first paragraph, I'd check the valve lash and the compression release mechanism while you have the engine apart.
Yeah I think you're right about separate problems Mike. My dog will verify it's possible to have ticks and fleas at the same time.

The rough running turned out to be a break in the right spark plug porcelain. I'm generally an optimist and usually don't think worst case scenarios right off the bat. But because of the other issues I've had with the 420 I immediately had visions of whatever it was being a major problem. I was annoyed and pretty discouraged on Sunday afternoon. When I was going to sleep last night I was even imagining it being a bad lobe on the cam. But.. then I removed the plugs Mon morning as a starting point and the right one came out in 2 pieces. It looked ok when I put the socket on it so it must have broken off completely when I removed it. I was just intending to have a look at them as a starting point to see if one or both were fouled. They actually were sooty black which was probably because I was running with the choke closed a bit. It still runs better that way so I'm pretty sure I still have a gasket issue on the intake ports. Hopefully I can get it through the mowing season and replace the gaskets after that. Don't wanna do that right now if I don't have to.

So now I'm baffled about the puff of black smoke that belched out frontwards from where the carb bolts to the intake. I only saw it once but I'm positive it happened. There's no black sooty stains anywhere around the carb base or the intake ports though. So WTH was it? I hate it when I can't figure out something like that.
 

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Great news on the broken spark plug. That’ll make you sleep better!
Some guys recommend pointing an unlit propane torch at the intake where leaks are suspected. If the engine speeds up, it’s sucking in propane and igniting it. I’m not suggesting it because it’s never worked for me and it can be dangerous if not done correctly.
 

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Discussion Starter · #5 ·
I mowed for an hour yesterday with it and it purred the whole time. Made my day. Not gonna bother testing. I'm just gonna assume the gaskets need to be replaced. The cheapie carb came with those gaskets too, plus the gasket to bolt the carb to the intake. I'm gonna use them as the pattern to make extra gaskets before I use them. Got lots of gasket material and a wife who is a whiz with an exacto knife. She can cut out perfect circles without a pattern to follow. Kinda freaky to see her do it. She spent 3 years in college to get her diploma and is an accomplished graphic artist. Her speciality back then was 'mechanical artwork', as they called it. She also used to do what was referred to as 'paste up' art before digital tech came along. She'd cut out images and shapes by hand and use a fancy camera to put it all together.
 

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Don't you just love it when its just something simple like a spark plug? Too bad that's not the cause every time.
Do you still need to run part choke?
 
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