Atc 350x problems

[Fixer_Upper]

I am 13 years old and have partaken in fixing my fathers old 350x. I have discovered what I believe is an oil leak in the left side case where all the charging instruments are. My grandfather believes the crank seal has blown out and that is why there is oil in the electrical area of the case. It should also be noted that the electrical part was also oil soaked. Is this how it is supposed to be? Also, this motor has a bent valve. What could’ve caused this to happen? It has been noted however that this engine has had valve issues in the past. I will tear into the engine tomorrow so we’ll see what other things I find out about this engine.

[Aulbaugh]

The stator side should have no oil in it.

[tapper190]

I believe your grandfather is correct, there is an oil seal on the crank to keep the oil out. There are a couple of reasons a valve would bend, jumped time, keepers fell off the valve stem, foreign object in the cylinder to name some

[Fixer_Upper]

Thanks for the info! My only question is will I have to split the case to change the seal or not?

[Fixer_Upper]

Update: I broke a valve and bent one. One intake and one exhaust I believe. Does anyone know where I could get new ones?

[Troyg25]

https://www.partzilla.com/catalog/honda/atv/1986/atc350x-a/camshaft-valve

Click on 8 and 9. This will show you what other models parts will fit your machine. It’s a handy site to reference part numbers.

[Shawn Powell]

Also shindy makes new aftermarket ones , an eBay search will pull them up.


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[Fixer_Upper]

Thanks everyone! I finally decided I’m just going to do a complete top end rebuild. I’m going to just replace the worn out rings and all other wearable parts, to ensure that my motor doesn’t collapse on me. Plus, before the motor blew up it only had 80 pounds of compression. It needs a rebuild. Also, I’ve heard of 400ex carb swaps. Is it worth swapping the carb?

[350for350]

I thought it was. It seemed to make a little bit more power or else it just revs up quicker, making it feel like it has more power. Mine's completely stock otherwise.

[wonderboy]

The carb swap is popular, but if I were you, I'd take it one step at a time. I don't want to discount your mechanical abilities, but at 13, just focus on fundamentals and do a nice solid job on your rebuild. Take your time, do a nice clean job, and read up the process in the official service manual. There is a lot of good info to do your top-end job correctly.

Download it here:
https://img1.wsimg.com/blobby/go/4624d5ac-072c-4bbc-83d0-b617c2b8f666/downloads/1cbb7ahoa_938805.pdf


Chapter 6 is all about the top end. One of the critical areas that is highlighted in the manual is where to use hondabond sealant when you put the cylinder cover back on. There are areas around the cam journals where you need to be real precise with sealant application to avoid it getting in the cam journals and ruining the cam. The sealant is required at this particular joint since by design there is no gasket. Take a look at the picture on the bottom of page 6-17.

...and use a torque wrench as much as possible. The most common problem I see on these old machines is overtightened bolts that pull out (strip) the aluminum threads.

[atctim]

^^^As noted above, please buy the correct bonding agent - Hondabond - you can buy it on amazon or from your local Honda dealer. Do not, I repeat, DO NOT use RTV or any other silicon type sealers. Hondabond only.

[BOB MARLIN]

Be careful on the sealant. Don't use silicone, oil makes it useless. Use just enough to do the job. If you use too much it will squish out into the inside of the engine and drop into the oil passages where it might cause problems. I've taken more than a couple apart to find the oil screens plugged with pieces of silicon.

[Fixer_Upper]

Thanks for all the helpful information! I’m glad you notified me of the sealant because I didn’t know that. It also appears that this is not the first time that a engine failure has occurred. Someone else had already gotten into it and rebuilt it in the early 90s (I think it was the 90s) because the head is already stripped out when someone else was in there. They also used silicon. I will be sure to keep you all posted!

[ps2fixer]

For the valve cover, you don't want to see the red or blue RTV, but the company makes a Gray RTV that is correct for that application. It's benefit is a slower cure time. My dad builds chainsaws up and tried a couple different gasket makers for the base cylinder gasket (base gasket delete to increase compression) and he found the Gray RTV is the easiest to work with and it always seals. Big trick is to not over apply it. The other gasket makers that are like Hondabond, Yamabond, etc set up too quick for him and he couldn't get the engine to pass a leak down test. On a 2 stroke an air leak is very bad and can make the engine burn up.


https://www.amazon.com/Permatex-82194-High-Torque-Silicone-Gasket/dp/B000HBGI8K/ref=asc_df_B000HBGI8K/?tag=hyprod-20&linkCode=df0&hvadid=312097317052&hvpos=&hvnetw=g&hvrand=15689934576372320777&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9017107&hvtargid=pla-437600037492&psc=1&tag=&ref=&adgrpid=57631863970&hvpone=&hvptwo=&hvadid=312097317052&hvpos=&hvnetw=g&hvrand=15689934576372320777&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9017107&hvtargid=pla-437600037492

Here's a couple vids.

Not a valve cover, but it's how I've always applied RTV. Thing I have to say is, if there was originally a gasket, buy the gasket. The valve cover on the 350x is the only place I can think of where a sealant should go.

https://www.youtube.com/watch?v=UXN4FqQH-xM


Here's a video showing the results of someone doing it wrong and based on the guy's description, applied 10x or more too much sealant and didn't use it where gaskets should be. Gaskets have a thickness and Honda engines are designed with that gap in mind. Nothing is idiot proof, so any good thing can be screwed up by someone.

https://www.youtube.com/watch?v=2WzELjtjslo