Done it a thousand times,but the old brains fuzzy this morning ? Think its a 3/4" or 7/8" but don't hold me to it. OPT

 

the hub nut is 1-1/4" maybe 1-3/16" unless the cv shaft was replaced with an aftermarket one. then it will be smaller. the smaller one will have a cotter key instead of a lock nut.

The rear chain for that model should be looser than that as well. That is what we call a non-concentric model, chain gets tighter as suspension is compressed. 1/4" of slack with suspension fully compressed. I find that three fingers mid point between front and rear sprocket with no-rider gets you pretty close.

There is no front gear case, so a grease nipple(left side) instead of oil.
I have never had to hold the bolt to tighten front eccentric clamp. There is an arm on the bolt that will hit the frame so you don't have to.

To get a stripped 1/8" NPT plug out of the hub. try pounding a 5mm allen key in, it's .010" bigger than 3/16". failing that try a non-tamper proof torx socket often works. hammer it in.
I think a t30 may be the right size.

there are 12 grease nipples.
a-arm to frame mount 2
lower ball joints 2
U-joints 2
front eccentric 1
middle eccentric 1
tranny output shaft support 1
rear swing arm pivots 2
rear axle carrier 1

Better change the counterbalance oil, hopefully it's not milky.
center of engine between the starter and the engine mount( on the flat surface)
ten mm hex
fill at dipstick under carb (75ml 10 wt. oil)

 

Right on all counts with the info except 1997 was the year the concentric drive was introduced on the Scrambler 400 and 500 and the sprocket was in line with the swing arm allowing tighter chain tolerances. Good info! PS: That is IF he has a 97 model! First started out being a 98 that was the first year of the front gear case. Hopefully he will find out what model it is! OPT

 

I thought it was a 98 that's what the guy told me. It's ether a 96 or 97 I assume now. So tightened all the chains and still have a grinding noise when I punch the gas if I ease into it don hear a thing a thinor when I'm just riding at a decencent pace. Most likely the silent chain? Sprockets all look fine and I know the chain is old as well

 

Sounds like the chain has stretched. It's a pain to have to split a tranny because of this,but actually the hardest part is removing all the stuff around it and getting the transmission out of the frame! After that just take the manual step by step when you get one. Another thing that most manuals don't list in taking out the tranny is the stop bolt underneath on the drivers side that braces the transmission against the frame. You have to loosen the lock nut and screw the 9/16" bolt back in towards the transmission so you can be able to turn and twist the tranny out of the frame. Keep us updated. PS: Have had internal chains so loose that some atvs would just sit and grind and not move at all. At least if you baby it without any loads you can ride it until you decide to tackle the job! OPT

 

So out on the trails and things are going good. About 2 hours in I put it in reverse and it dies? I have to use the home to start it and It. Felt like it needed gas but was by getting power. I get back add some gas and coolant because it.seemed to be running hot. I start it again using the choke and release.choke and it idles so high it might blow. So I can get it in gear when I play with choke and ride it but I let.go of the gas and stop it will die. It will even backfire now? So this sucks but had a blast.till it acted up. Any ideas I'm a novice.

 

If it died when you put it in reverse could be the reverse limiter module(under the front panel) shorting out. Common problem,just pull the black wire from the limiter. When you say it was running hot,did the hot light come on,was the fan working? Idling high could be a crank seal(usually the one behind the front clutch) Or a leaking,damage intake manifold. Plus try changing the spark plug(BR8ES) first. Backfiring could be carb related,crank seal or electrical breakdown (check if you have good spark) Plus check if you have too much throttle cable slack on the thumb lever,if too loose then could be cause of backfiring. Should have no more than 1/8" slack or the etc switch contacts inside the throttle housing could touch causing it to back fire. OPT

 

Ok I.will try to look into that stuff. And yes the fan did kick on. The light temp light would go off and on so I figured its not working correctly. Might have to just take it to a mechanic which sucks

 

So got a new spark plug and got it to turn over. Still idle is way to high so I undue the carb and see a penny size hole in the jug the bottom part I believe its called the crankcase. So I'm pretty much screwed. No idea how a hole was blown in it. But I guess I'm going to try and sell the thing this seems to be like I'm getting into a money pit. Any ideas

 

If the case or cylinder is cracked or broken it's usually because part of the piston skirt has shattered and got caught up in the crank shaft and will beak cases.Not much room around the crank case cavity, so either the front or rear section of the case takes the brunt of the metal.Never had too much luck repairing cases(depends on how big and where it's located) You might try Ebay for some used cases if you are planning to repair.Yes they can become a money pit when this happens. OPT