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Discussion Starter · #1 ·
95 bayou 300 2wheel. This is my first four wheeler. The guy I bought it from showed me slight drip on his floor from a drain plug he recently retapped. I figured I could handle a small leak from a second hand machine. Well after a few times of riding it the bayou seems to be running low on oil. Now maybe this is normal operations as well so I refilled the oil. But the next day I notice my drip on the floor was slightly larger. I wanted to see this drain plug for myself so I took off the skid plate and found a pretty rough looking installed drain plug. It does have a small drop but also seemed to have an excessive gasket and maybe some grey looking “jb-weld” ish material around it. So that’s scary but I figure surely that’s not the only source since my floor spot Grew a bit. I went on to find recent moist around the head gasket for the top end. I’ve never seen it drip but it drips on the new starter the guy installed so it seems the head gasket leaks too. He did say he replaced that gasket when I inquired about the darken stains around that area of the motor. He said he replaced that gasket during. Ring replacement when the bayou was smoking. It no longer smokes by the way. So I continue on thinking well maybe I can do another top end gasket myself some day but still the oil on the floor suggests a more visible leak. I mean it’s not a lot but it grew as I mentioned. Then I find my what seems to be an awful thing. The pull cord and starter was replaced by the preavious owner and it appears there’s a busted area on the crankcase where the left side cover mounts to the L-case.I have not seen oil from there but that looks scary to me. Does this area hold oil? I wondered if it doenst maybe I’ll leave it be but if it does it’s probably the reason I lost some oil. I also found tonight oil on the rubber boot cover I think is for the drive shaft or something. Idk my first ride so I’m unsure of how to proceed. Especially with the case cracked like that. I don’t know how the engine works but if there is indeed oil there in the operation of things it seems like I must do a major engine over haul….. any insight would be so very helpful. I bought this for my daughter but I may have been bitten by going with such an older model. Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Automotive exterior Vehicle Rim Gas Automotive tire Product Motor vehicle Automotive lighting Bumper Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Automotive exterior Vehicle Rim Gas Automotive tire Product Motor vehicle Automotive lighting Bumper Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Automotive exterior Vehicle Rim Gas Automotive tire Product Motor vehicle Automotive lighting Bumper Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Water Wood Automotive wheel system Font Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Automotive exterior Vehicle Rim Gas Automotive tire Product Motor vehicle Automotive lighting Bumper Automotive tire Wood Bumper Automotive exterior Automotive wheel system Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Automotive exterior Vehicle Rim Gas Automotive tire Bumper Gas Auto part Cylinder Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Automotive exterior Vehicle Rim Gas Automotive tire Product Motor vehicle Automotive lighting Bumper Automotive tire Wood Bumper Automotive exterior Automotive wheel system Land vehicle Vehicle Hood Motor vehicle Car Automotive tire Bumper Automotive exterior Rim Gas Helmet Hood Automotive tire Automotive lighting Automotive design Tire Automotive tire Tread Hood Vehicle brake Automotive tire Bumper Gas Auto part Cylinder Automotive tire Motor vehicle Bumper Rim Automotive exterior Automotive tire Water Wood Automotive wheel system Font Automotive tire Automotive exterior Vehicle Rim Gas Automotive tire Product Motor vehicle Automotive lighting Bumper
 

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Did we have a little trouble uploading photos? Lots of duplicates.

I'm not an expert on 4-wheelers but hopefully some of our regulars will give you some advice. From looking at the photos, my biggest concern would be the drain plug. You can well imagine would would happen if that falls out while riding.
What did the PO tell you he did to fix it? Helicoil? Keensert? Did it not go in square?

I would not be too concerned about the broken case where you can see the case screw. It does not appear to be leaking.

The rubber boot in photo 31 needs work. There must be an oil seal inside that needs replacement and a new boot while you are at it.
 

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Discussion Starter · #3 ·
Did we have a little trouble uploading photos? Lots of duplicates.

I'm not an expert on 4-wheelers but hopefully some of our regulars will give you some advice. From looking at the photos, my biggest concern would be the drain plug. You can well imagine would would happen if that falls out while riding.
What did the PO tell you he did to fix it? Helicoil? Keensert? Did it not go in square?

I would not be too concerned about the broken case where you can see the case screw. It does not appear to be leaking.

The rubber boot in photo 31 needs work. There must be an oil seal inside that needs replacement and a new boot while you are at it.
Thanks for the reply and sorry I did have some photo trouble lol. I’ll work on that. The case break is good news. I thought the same given it was so clean there. I also thought the same on the drain plug regarding how crooked it seems. But I thought we’ll maybe it’s supposed to be at an angle. The PO said he used a tapping set for drain plugs from auto parts store. That’s about all I know. If the plug is indeed really jacked up, think I could tap again myself?
 

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No worries, there is always a learning curve.

If he went oversize to put in a bigger diameter plug, there is only so much metal to work with. Once a hole is crooked other drills will try to follow the same crooked path. Assuming you have enough metal to work with, you would need to make up a drill guide that will hold the drill at 90 degrees. Most, but not all drain plugs are straight. If you can find another Bayou you could compare. Also when you do your first old change you can probably tell if it was accidentally drilled crooked.
 

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Well that really sucks. He should have told you about that before he sold it to you. Just saying he re-tapped it is hardly full disclosure. Have you priced a new engine case?

I don't know if the alloy is weldable and if it is, I don't know if anyone could weld it without tearing the engine apart.
I've never seen one this bad before. Maybe others have, and can share what they did to fix it.

Where the crack runs the full length, I don't think JBWeld is gonna do the trick. Looks like a new boss needs to be welded in place after the old one is removed.
 

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Discussion Starter · #7 ·
Yea this blows a bit. Right side of case cracked for drain plug. Left side cracked at the side cover mount. I guess I need a whole new case. Any idea should I be able to find one what other parts should be replaced while im
In there ?
 

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Hard to say exactly what other parts you will need other than oil seals and gaskets. If you don't have one, I would invest in a factory service manual that will give you wear limits that you can check, along with torque specs and disassembly-reassembly procedures.
 

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If you are looking for a used crankcase set, here are the models that use the same crankcase as yours. Hopefully this helps you find one. A brand new set is close to $700.

43389
43390
 

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Let me offer this perspective. Since you have no emotional attachment to this particular ATV, and you're not trying to restore one like you've had your youth, do you really want to invest your time and $$ in something that has obviously lead a hard life, and has had an unknown number of hamfisted repairs and suspect maintenance? If you want to fix it right, the engine will need to be torn down, cases replaced, out-of-spec parts replaced, possible machine shop work, new gaskets (which can be expensive or hard to find), reassembly, etc.? I'm sure it all can be done, but unless you or a really good buddy are ready and able to take it on as a project, perhaps you should cut your losses and look for something in better shape, with a known history.

Personally, I love to see machinery restored to it's original condition, or at least, kept in useable condition, no matter what it may be. But many times, that takes donor parts from like vehicles. Perhaps what you bought would be best sold as a donor for parts. At least you could recoup some of your expenses.

As an example, I'm currently working on a used Polaris ATV. But I bought it in a non-running condition, from a friend, who's brother bought it new. I know both of them, it wasn't thrashed to death, it has an electrical issue keeping it from running. My friend offered it to me instead of selling it for parts. I bought it cheaply enough to take the chance that I could fix it and use it on my property. But I also know that I have to keep in mind not to throw money at it, past the point of what I could buy a comparable one, or it's value for parts. This perspective is given from someone who can do most of the above mentioned work. Someone who can't do it, or doesn't want to learn as they go, is going to have to pay someone else to do it. That gets expensive really quickly.

BUT: If you decide to fix it anyway, please post pics of your progress! 😁
 

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Yes, it is always wise to consider all of the above before getting in too deep.

Sell it as a parts donor? Buy a parts donor and make one good ATV out of two? Or look on Ebay where there appears to be a good selection of inexpensive engine cases? Either way, as XY points out, its a lot of work. But if you enjoy this kind of work, and you have the time and the skills then why not?

I do this kind of thing for fun and enjoyment. It is a lot cheaper than what many of my friends do for fun like sailing or travel.

One final thought. Have you considered returning it to the seller for a refund? He mislead you about the reason for the leak from the oil plug.
 

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We aim to please.

As a Kawasaki community, everyone chips in with advice when and where they can.
Collectively, with 118,000 members and over 2 million posts we probably have more expertise than any dealer.
This is not intended as a slight to dealers but there is no substitute for the real world experience of that many members.

Whether it is carb tuning, engine repairs or mods, you folks have come up with the tips, shortcuts and knowledge that allows others to gain from your experience.
 

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A general word of caution to everyone. Though I do not think it was the cause of your failure as I see no sealer trapped in the bolt hole, be very careful when applying sealer. If one gets sealer in the female bolt hole and then installs and tightens the bolt, the tremendous hydraulic pressure created can blow out the casting almost exactly as your picture depicts. Don't even ask me how I know.
 

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I don't doubt that your casting failed but I cannot see how any sealer like RTV could do that. Pipe dope paste is used all the time without any such failures. If too much is applied, it just squishes out of the way. Try it on a nut and bolt. Apply as much as you want but the nut will spin on with your hands.

Of course if by "sealer" you mean something like JB weld then that's a different story. Fully cured JB weld that is stuck inside the thread grooves can certainly cause a failure when the drain plug is forced into the hole.
 

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Nope, black RTV and a 6mm bolt. Muffled pop followed by a tink. Pop was aluminum failing, tink was piece hitting floor.
 

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............the tremendous hydraulic pressure created can blow out the casting almost exactly as your picture depicts. Don't even ask me how I know.
This can happen in a blind hole, where the sealant has no path to escape. In that scenario, a thin-walled aluminum casting could definitely be damaged from the hydraulic forces.
 

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Ahhh, now I see what you mean. You mean a blind hole, one that is not drilled all the way through. Yes of course that will create tremendous pressure capable of breaking the casting.

You threw me for a loop because this thread is about a crankcase drain bolt and I thought you were referring to drain bolts. No possible way to have a pressure build up with a drain bolt.
 

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Discussion Starter · #20 ·
Before I tear this thing down id like to ride it some more. I think the drain plug with at least not fall out and the leak there is minor. Of I could ask your opinion on two things.
One - the split in the left side crankcase on the bolt. Does that area hold oil? The split area seems very clean to me. Should I lose oil there? Other than water and mud getting inside should I be worried about riding it like that for now ?
Second question- seems to be a small leak at the propeller shaft rubber boot. The one where it connects to the engine. If I have to pull the engine I might as well wait on this one till then, does that seem ok? Seems like a small leak.
 
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