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Zach

Problem while ensembling bottom end on 400ex

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Hi i was wondering if anyone could help me out. I bought a 400ex sportarx for really cheap but engine was done so i started rebuilding it. As soon as i put the 2 crankcase sides together the transmission wont shift or spin freely. Ive triple check everythingto make sure that its all where its supposed to be and still cant find nothing wrong. And i even put the star looking thing(sorry dont know the right term for it) to make sure its not in between gears. 

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Probably have a gear flipped backwards somewhere in the transmission, or an extra shim in there.

 

Most of us here are utility wheeler guys and thus not real familiar with the sport ATVs, but the principle is the same.

 

I've done it more than a few times when reassembling cases.  Everything has to be just right or it will bind up.

 

https://www.partzilla.com/catalog/honda/atv/1999/trx400ex-a-fourtrax-400ex/transmission-99-04

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Sport quad guy clocking in! LoL.

 

Ok so transmissions are very tough. Need to be precise. And one shim thats too thick in the wrong place makes a world of difference. Also the service manual does you no favors. Alot of the gears on the pictures look backwards. It is very hard to tell from there pictures which side the bevel goes on and which side the flat side goes on. You gotta make sure those are all bevel facing the sliding gear. So it would be gear bevel 》sliding gear(the one with big teeth on both sides) 《gear bevel. Pictures make this look confusing.

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@SlammedRanger Everything looks like there on the right side and they shims seem to be right i think. It seems like as soon as i start bolting the case together its squeezes to tight and i realize that on the left side there lil marks from a gear (on the inside of the case where the outside sprocket goes) where the transmission sits so im thinking that maybe that last shim is wrong? But how do i check that? Im new at building quad engines and I know my way around cars but absolutely this is isnt the same and the first for me so i dont have any Knowledge in this department.

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When you bolt it together can you still move the shaft that the sprocket goes on in and out? It should move in and out about a 1/16th inch. Not much but some. If its not moving at all its binding and that would indicate that shaft is the one in question. Honestly would be the easiest option. The other shafts are harder to get to to see if they have no in and out play. All the shafts will have a small amount of deflection. If it has none that is the problem area. Could be any shim being too thick. And we are talking very small tolerances. So you will need a caliper to measure them. The manual will have these thicknesses somewhere hidden. If we need to go down that path i will help you. But hopefully its just the main shaft. That makes life easier.

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Sounds good i will get a caliper tomorrow and check that. And ill ask one of my buddys for his manual and Just to be clear the shims are the washers? Right? 

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Yes the washers are more like shims in this purpose. They keep the gears from hitting anything they shouldnt. But most important is to narrow down which shaft is binding up. That will be the one we need to pay the most attention to.

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@SlammedRanger so i couldn’t find any specs regarding the thickness of the shims in the manual but i did find that theres a direction to put them on and i did not know about that. And it seams like the last gear on the main shaft on the side were the splines for the sprocket is somehow against the case since i see a few marks on the case from it.

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I would bet that is your culprit right there. That gear is probably on backwards. Like i said before. The manual does nothing to help you with gear direction. I have found the diagrams show it wrong and make it look like they go the wrong way.

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Posted (edited)

Wow just read the whole transmission section in the manual step my step ( ignoring the diagram) turns out that all the gears were on the wrong side.. i should of payed way more attention haha. Everything fits nice and good together now and shift properly without any binding. Thank alot for the help. Also i rip my new gasket by accident is it possible to use gasket maker by chance? And if yes is there a specific type i should use?

Edited by Zach
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27 minutes ago, Zach said:

Wow just read the whole transmission section in the manual step my step ( ignoring the diagram) turns out that all the gears were on the wrong side.. i should of payed way more attention haha. Everything fits nice and good together now and shift properly without any binding. Thank alot for the help. Also i rip my new gasket by accident is it possible to use gasket maker by chance? And if yes is there a specific type i should use?

Glad you got it sorted! Always glad to help out! I would suggest against using gasket maker on the center case gasket. If it leaks down road its a long road to fixing it from that point. Also since the 400ex is designed to have a gasket it is required for proper spacing in the transmission gears and shafts. Some quads use gasket maker from the factory and are designed to not have a gasket and in that case it would be 100% ok. But sadly not in this case. I have used hondabond on side covers in a pinch and had no problem. My .02

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i just gotta ask zach, you did not by any chance post a video on youtube about a trx400ex purchased , and has a problem did you ?. i seen a video on the home screen there..but did not watch it, is this you ?..lol. as for gears going back together backwards ?..i'm willing to bet...about 99.99% of us here...at one time or another has installed gears on backwards ?, i know i have !..lol. as for the gasket ?..if i gasket it there to start with ?, THEN BY ALL MEANS...PUT A GASKET BACK ON THERE !..DO NOT USE YAMABOND, RTV SEALANT, OR ANY OTHER GASKET MAKER STUFF WHERE A GASKET IS CALELD FOR !..you will regret this down the road.

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@shadetreeno haha did not post a video about it. And sounds good i will get an other gasket tomorrow then

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