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Doing and oil change for a friend on his Sportsman 850 just to find out the last guy completely messed up the threads going into the crank case. Any suggestions on how to fix? Thinking helicoil or a self tapping plug. Half the threads are also somehow missing !
 

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The drain was made with half the threads missing (thin castings) it's a cheap way of adding depth to the hole without increasing the thickness of the casting. Tap it to a tapered pipe thread and install a brass allen socket pipe plug
 

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There is a better than not chance a self tapping drain plug will crack the casting due to the side force the "odd" drain plug hole casting will be putting on the self threading plug. A pipe tap can be held straight while cutting so it is not pushed over and "side loading" the hole being tapped. A pipe plug is the best repair until the case gets replaced during a subsequent future repair.
 

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I have used heli-coils for spark stripped spark plugs and other stripped stud holes with great success. If you pack a little grease in the helicoil tap, it will catch all the metal chips and avoid any chips in the crank case.

Wash the threads really well with solvent and blow dry with compressed air. Use RED locktite and install stainless steel helicoil.

The best part of the helicoil is that it hardlly removes any new material from the stripped hole. Just enough to cut the threads.

You can retain the original drain plug and never will know it has been repaired.

The stainless helicoil thread are better than the original cast aluminium. The repair will be better than the original.

D
 

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There is a better than not chance a self tapping drain plug will crack the casting due to the side force the "odd" drain plug hole casting will be putting on the self threading plug. A pipe tap can be held straight while cutting so it is not pushed over and "side loading" the hole being tapped. A pipe plug is the best repair until the case gets replaced during a subsequent future repair.
I agree with not using a self taping drain plug. It will either strip the thread again after one or two oil changes or split the case. I work in a machine shop and had to repair an automotive oil pan that a guy had screwed a self tapping drain plug in and it split the hardened threads on the oil pan insert and the pan had to be removed and new insert for the pan fabricated and welded in.
 

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I agree with deucer that helicoils are stronger than the original thread and retain the original drain plug, but the coils will obstruct the draining oil (at the recess where the threads were missing) and it will take longer to completely drain the crankcase. If time draining the oil is not a factor - use a helicoil, drain the oil hot and allow extra time for a complete draindown.
 

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This happen to me just a week or so a go while I was repairing an older Ranger 6x6. When I started unthreading the drain bolt I was saying some very bad words. Anyhow I found a repair kit on Amazon for like $25 it came with taps sizes M13,15,17&19 with 4 bolts an several washer as well. Kit worked very well an so far so good. I made the customer let me keep his unit for few days just be sure the unit didn't leak. I'll put the link to the kit below, it's well worth the $25-30 imo. Have a good one.

https://www.amazon.com/gp/aw/d/B07874BRL3/ref=sxts_1?ie=UTF8&qid=1532486198&sr=1&pi=AC_SX236_SY340_FMwebp_QL65




Sent from my XT1650 using Tapatalk
 

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I stripped mine out somehow a couple of years ago. After I collected my thoughts, I ended up retapping the hole to accept a 1/2-20 automotive drain plug. The stripped out metric hole ends up being the proper hole size for a 1/2-20 tap.

Mark
 
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