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Splitting Cases... Literally!

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Well the time is finally upon me... this week will be the time to start the operation....

 

Last year my side case on the 300 developed an oil leak. It took me some time to find it, but it was determined to be a hair line crack behind the motor mount bolt on the right side by the kick start. I did the ole JB Weld patch job to get me thru the tail end of camping season/hunting season. Mac was kind enough to send me a set of good used cases that I could use. I was going to upgrade my 355bbk for a 380bbk but after talking with some of you, & research, I have decided to keep the 355. I've got 2 sets of gaskets just in case I mess 1 set up. I haven't bought a new set of rings as the bbk isn't that old & really has low hours on it. What are your thoughts?? Should I pick a set up just incase?? I'm open to ANY & ALL tips & tricks for this process. I've rebuilt top ends, installed clutches etc but NEVER pulled a 300 motor let alone split the entire thing apart to change a side case... I've read that you need to be careful not to have the transmission gears fall out ect...I do have a Service Manual, knowledge, skill, power & air tools, & most of all... common sense !! 

 

Thanks for any input, advice & help anyone can provide! 

 

Cheers!

 

(pic just for reference of the beast incase it dies on the operating table...)

 

 

IMG_7016.JPG

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In the past, I've had a chain reaction of events that caused a crack in the rear case including other things (everything). Mine happened when I had a mudrun the very next day so it was a late night in the shop and a long drive on a few hours of sleep (I did get first in the 400-500 class). I never reuse rings anymore, I hone and use new rings. I've done a few with zero issues but also had some that came back because the rings never reseated. For me the little money for rings isn't worth another tear down so I only go new now.  A couple photos to make you feel better.

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I agree 100% with @toodeep. New rings. They are cheap. Fresh rings and a quick hone and your sure your rings will seat and not give you fits down the road. As for spliting cases. Be very careful and deliberate with every move. When your splitting make sure you are tapping all the shafts with a rubber mallet. I had to do this over and over again to make sure the whole transmission could stay in the one side. You want to remove the shift fork guide rods then the shift forks and take the whole trans out as one solid unit in both hands. Like your removing a heart or atleast from seeing it on tv. Never done that lol. Then check all the shafts for thrust washers. Have your manual handy to see which ones need them. They can sometimes fall off so make 100% sure you find all of them. They can stick to the bearing sometimes and blend in there also. Now is a good time to finger check all the bearings. Any noise or grind at all CHANGE IT! LoL

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I should have added, output shaft side down when taking it apart to keep all the gears in place (last pic). ^^^^^^^ (what slammed said) A clean environment is your friend for that one washer that sticks because of oil residue and then falls.

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I'd hone and re-ring it too. Ring seal never fully recovers when they are reused in a bore that was fully broken in.

 

I'd replace all of the seals in the cases as well if the cases have never been split before, or recently. Disassemble and inspect all bearings, oil pump, clutches, cam chain etc. & replace worn parts as needed.

 

You'll be spending as much time on cleanup of parts as ya will assembling them... don't forget to insure that all case threaded bolt holes are clear all of the way to the bottom of each bolt hole. Running a tap down each one by hand while flushing them with solvent and air can sometimes save ya a lot of grief later on. Routine preparations = routine work.

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Your not joking on the clean up. Scrapping gaskets can take the longest. I use gasket stripper (now called paint stripper) that comes in an aerosol can to help soften/loosen the gaskets. Spray it on and go clean other parts, come back spray again and go clean other parts and so on until they loosen up. Yours looks to be a mid 90s so it should have the green gaskets that will stick to both sides in pieces that really bond. 

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Another way to loosen stuck gaskets on cases and covers is to lay them down in a cookie sheet and simmer them in water on your kitchen stove. After 15 minutes or 20 minutes in simmering water they'll peel right off with a scraper, sometimes in one piece. Be aware that most of the ball bearings will fall out onto the cookie sheet as the case gets hot though. If you're replacing them anyway you'll be happy that they fall out. If not ya gotta clean them up, oil them and reinstall.

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I didn't see anyone mention it , you can nail some 2x4s together to make a box for the case to sit in , keeps it steady while working on it ---- I tink the dimensions of that cradle  is in the manual ----- all but like 2 of the case bolts come out on the same side , then when you flip it over on to that cradle and those two bolts will be up and the last two you take out and the first two you put back in 

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@toodeep wow man Carnage what'd you do lol I gotta hear this story. @retro I agree with you while @Wheeler has it split I'm assuming, he would be wise to put a top end on it. G&H Discount ATV Supply makes one I know of. 

 

http://www.ghdiscountatvsupply.com/honda-atv-trx-300-fourtrax-engine-motor-top-rebuild-kit-machining-service/

 

Edited by F250 guy

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@F250 guy that happened when it was a 350cc machine. 3rd gear, WOT going through a mud hole when the U joint let go. It took a while for things to come to a stop and broke about everything from the front to the rear of the machine. Just a few seconds after a bang costs a lot of dollars.

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16 minutes ago, toodeep said:

@F250 guy that happened when it was a 350cc machine. 3rd gear, WOT going through a mud hole when the U joint let go. It took a while for things to come to a stop and broke about everything from the front to the rear of the machine. Just a few seconds after a bang costs a lot of dollars.

Hope ya got it fixed. 

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Thanks for the tips guys. I had been leaning towards getting new rings but wasn't sure. You have all confirmed what I was thinking! 

 

On Monday I'll call HighLifter & see if they can hook my up or send me to the vendor like they did with the gaskets. HL doesn't sell the 355BBK anymore so it's a pain to get the parts when you need them.

 

I'll be sure to take my time, & clean everything up nice. I was planning on getting new bearings, seals ect... 

 

Plan is to start the removal this Thursday... 

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16 minutes ago, Wheeler said:

Thanks for the tips guys. I had been leaning towards getting new rings but wasn't sure. You have all confirmed what I was thinking! 

 

On Monday I'll call HighLifter & see if they can hook my up or send me to the vendor like they did with the gaskets. HL doesn't sell the 355BBK anymore so it's a pain to get the parts when you need them.

 

I'll be sure to take my time, & clean everything up nice. I was planning on getting new bearings, seals ect... 

 

Plan is to start the removal this Thursday... 

Just a guess on my part butt. Couldn't you if you get your parts next time measure everything and write it down what part measurements ect for each part names PN so you know ring size brand ECT ECT, you maybe able to cross reference next time you need parts after this vendor visit.

 

What I'm saying get all the info you can on all specs of parts and you should be able to cross reference anything. 

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I'll be watching this one.  PLEASE take lots of pics!

 

I've done a lot of front to back motors, but thus far haven't split cases on a sideways motor without dropping everying out and all over the place.

 

I have SEVERAL 300 motors, and the plan is to split cases on all of them to clean them out and know what I have putting them back together, so I'd love to see lots of pics to refer to when I tear into mine.

 

I have a 350 Rancher (needs crank) and a 500 Foreman to do first, but after that I get into the 300's.

 

Took the day off tomorrow and had planned on getting the Rancher motor knocked out, and now my kids have a basketball tournament 3.5 hours away, so I'll be in the car or the bleachers all day tomorrow instead.🤬

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49 minutes ago, jeepwm69 said:

I'll be watching this one.  PLEASE take lots of pics!

 

I've done a lot of front to back motors, but thus far haven't split cases on a sideways motor without dropping everying out and all over the place.

 

I have SEVERAL 300 motors, and the plan is to split cases on all of them to clean them out and know what I have putting them back together, so I'd love to see lots of pics to refer to when I tear into mine.

 

I have a 350 Rancher (needs crank) and a 500 Foreman to do first, but after that I get into the 300's.

 

Took the day off tomorrow and had planned on getting the Rancher motor knocked out, and now my kids have a basketball tournament 3.5 hours away, so I'll be in the car or the bleachers all day tomorrow instead.🤬

He'll keep you updated, them kids of yours are what's most important 😁 hey if ya want to after the tournament take them and show them how to do it with you watching. You'll get it done twice as quick, and get on to other projects. 

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Ha, two teenage girls who used to like getting muddy on the farm with me, and now I can't get them to hang out with me at all. 

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2 hours ago, jeepwm69 said:

Ha, two teenage girls who used to like getting muddy on the farm with me, and now I can't get them to hang out with me at all. 

Was worth a try to suggest to ya. 

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haha, i've split many trx300 engines, they are fairly easy once you do a couple of them. i use a milk crate to rest my engines on. the main thing when doing engine splits ?..MAKE SURE YOU HAVE THE CASES FACING THE CORRECT WAY WHEN YOU OPEN THEM UP !!. always have the output shaft facing down when the time comes to split the main cases !!!, if you don't ?, your gonna have tranny gears flying everywhere !..lol.

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21 hours ago, shadetree said:

haha, i've split many trx300 engines, they are fairly easy once you do a couple of them. i use a milk crate to rest my engines on. the main thing when doing engine splits ?..MAKE SURE YOU HAVE THE CASES FACING THE CORRECT WAY WHEN YOU OPEN THEM UP !!. always have the output shaft facing down when the time comes to split the main cases !!!, if you don't ?, your gonna have tranny gears flying everywhere !..lol.

Yeah I split a 350 Foreman case and it was like dumping out a bag of gears.

 

On the front to back motors with the flywheel down the transmission stays in place.

 

With the older motors I wasn't sure and guessed, and guessed wrong!

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Or don't rest the cases on cardboard boxes like some idiot did and had tranny parts all over the garage floor....lol

 

I like putting puzzles together but this was a whole different ballgame....

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Thanks for the tips! Today will be the day I start to pull it from the quad. I've got a few things to do this am before I start. Then clean up the garage, &  start to remove what I have too, to get the motor out. 

 

I'll be sure to take lots of pictures which will hopefully make it easier for others in the future....

 

 

Edited by Wheeler
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I have a half dozen partially disassembled 300 motors in the shop.  Local kid keeps buying them, taking them apart, and not being able to put them back together, so I've been picking them up cheap.

 

I figure I'll disassemble one of the few complete motors I have, carefully laying everything out on giant sheet of cardboard on the shop floor, then dig through the pile of motor parts, matching up what goes where, and then cleaning and reassembling them one at a time using the spread as a guide. 

 

I can look at the schematics, but it requires jumping around to multiple pages so figured the "match game" will work just as well.

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5 hours ago, jeepwm69 said:

I have a half dozen partially disassembled 300 motors in the shop.  Local kid keeps buying them, taking them apart, and not being able to put them back together, so I've been picking them up cheap.

 

I figure I'll disassemble one of the few complete motors I have, carefully laying everything out on giant sheet of cardboard on the shop floor, then dig through the pile of motor parts, matching up what goes where, and then cleaning and reassembling them one at a time using the spread as a guide. 

 

I can look at the schematics, but it requires jumping around to multiple pages so figured the "match game" will work just as well.

fich pages on partzilla kinda gives ya a rough idea, but does not get into full detail !. this is where hands on comes into play, you must take a few apart, put them back together, this is the only true way you will ever learn how they go together, and of course, come apart !..lol. worse comes to worse ?, TAKE PLENTY OF PIC'S AS YOUR TEARING IT DOWN !.

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17 minutes ago, shadetree said:

fich pages on partzilla kinda gives ya a rough idea, but does not get into full detail !. this is where hands on comes into play, you must take a few apart, put them back together, this is the only true way you will ever learn how they go together, and of course, come apart !..lol. worse comes to worse ?, TAKE PLENTY OF PIC'S AS YOUR TEARING IT DOWN !.

Yeah I've learned the hard way it's hard to figure out which particular shim goes in which particular spot, and the schematics don't help much other that telling you A shim goes in there.  If you have a pile of parts like I do you don't necessarily know WHICH shim goes where.

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42 minutes ago, jeepwm69 said:

Yeah I've learned the hard way it's hard to figure out which particular shim goes in which particular spot, and the schematics don't help much other that telling you A shim goes in there.  If you have a pile of parts like I do you don't necessarily know WHICH shim goes where.

yep, unless you take a few apart ?, you will not know where those thrust washers, shims go ?!..lol.

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