Did my timing chain come off?

[Gwbarm]

Inspect your gears really closely for damage, I generally like to put on a new cam gear when I replace the chain. Im a little concerned as to why it came off, they can be noisy for a while and not come off, just inspect everything down there really closely when you get it apart

[p5200]

A youtube video, showed a guy who had 2 atvs just like mine that had the chain off the bottom gear. He was replacing the chain on one and pointed at the other one and said it had the same problem. He never said if he had anything broken but, it must be a common problem for these particular atvs.

[Gwbarm]

May be a common problem with the 300 engine

[Mech]

Check the ratcheting mechanism on the tensioner really carefully..  If a motor backfires or bounces backwards as it's coming to a stop, the tension comes on the wrong side of the chain and can subject the tensioner to pressures it wasn't designed to take..  A defective ratchet can fail under those conditions..

[Gwbarm]

I was also thinking faulty tensioner, plus the rubber piece wears and causes it to not be as effective.

[Mech]

Yeah, we can inspect the chain for wear, and the slippers, and be pretty certain whether they are ok or not. The tensioner is the tricky bit. And that backfiring throwing the chain or timing belt is well known. Some motors they warn you against rotating backwards because the belt can jump.

[p5200]

Things were going pretty good untill I screwed up. The main drive gear shaft had left hand threads but, I had to try taking it off with my impact the wrong direction. I know, the nut is ruined I don't know for sure about the drive shaft threads but, I probably, ruined it too. 😞 There are some plastic pieces also. I'll post a couple photos.   Photo of shaft threads may be ruined, and photo of some of the black plastic pieces.

[p5200]

Anyone know what size nut/thread type besides being being left hand threads?

[Gwbarm]

I’m thinking it’s 21 but I’m going from memory from the looks of it fine thread pitch probably .75 you can measure it with a ruler and come close if you have a tap and die set they have thread pitch guide with them for measuring the pitch

[p5200]

I've got a set of calipers I use for reloading ammo if that would work. No tap and die set but, could probably get one. I wonder what a machine shop would charge if I get a new lock nut for them to go by? first, I have to find another nut.

[Gwbarm]

I had crank threads buggered up on a Yamaha DT 400 I was building, I measured with mm ruler, of course your tap and die set never has the one you need, but was handy measuring the thread pitch. I then ordered the one I needed to straighten the threads up, it worked, of course machine shop would be better but I didn't want to haul the bike there to get it done. If you have calipers you could definitely measure it with that, I did that also, but mine were not really expensive ones so I double checked with mm ruler. Will your nut start back on there at all. You might get away with just buying a new nut, get two, get it started and let it straighten out the threads.

[Mech]

I'd get a thread file first and try cleaning that thread up. The thread file will tell you what the pitch is, Hopefully the threads will come right and a new genuine nut will do. if you need to find a nut,you will have to make an educated guess what size it is by measuring the diameter. It will be a metric diameter and although most metric threads are whole mm steps you can get special threads in half mill, so measure carefully.

You won't get a left hand thread in any common tap and die set, but they can be bought quite easily individually if you really need one. If the tread file won't clean up the threads though then neither will a die nut.

And yeah, zap guns are hard on threads always and shouldn't be used for routine undoing stuff. They spin too fast and promote galling even in good threads.

[p5200]

The nut that came off doesn't hardly have any threads left I wondered if trying a new nut on there would straighten things up. If I can figure out what nut I need, I'll order a couple and give it a try. If I can find my wire brush I can clean the threads a little better where I can see them better. This Diabetes and Glaucoma has really done a number on my eyes.

[Mech]

Oh ok, sorry to hear about the eyes. Mine aren't what they used to be either.. 

Get a thread file for metric threads, they are cheap and come with eight different pitches on each one. You hold them near the thread and look(squint) to figure which one fits best..haha. Then you just gently rub them up and down over the old threads at the right angle for left hand threads.. turning the shaft or rocking the file as you go..

Edited February 26, 2023 by Mech

[Mech]

And seriously, those rattle guns are not good for working on things..  Nuts and bolts need to be turned slowly, especially while they are still tight, but even after they are loosened off, if you try to wind a nut down long threads too fast, even by hand, they will get tight.. 

[p5200]

I'll try and find a thread file and give it a try. Thanks 

[p5200]

this here, tells about the thread. I don't know if that's the pitch or just the spacing of the threads. It's the primary drive gear lock nut.    

[Gwbarm]

Looks like 20mm nut 51 ft ads torque, with a note probably saying left hand threads.

[p5200]

Is 20mm the size of the threaded section or, the size of the bolt head?

[Gwbarm]

Yes the threaded section not the wrench size.

[p5200]

ok Thanks!

[Mech]

Yup, it's the theoretical diameter of the outside of the threads. Once you get the file you will be able to figure the pitch, which is the mm distance between threads. That will be about 1.25mm probably.

Good manuals eh ?

[p5200]

I think this will be the nut I need but gosh, that's a lot to have to spend just for the nut but, if I knew for sure I could thread it back on I wouldn't think twice about buying it.   1996 Honda TRX300EX TRX 300EX crank shaft primary / oil pump drive gears & nut | eBay

[p5200]

Found same thing for less than half the price so, I jumped on it. I guess if it won't thread on after cleaning up the threads, at least I'll have the nut for someone to go by to re -thread the primary gear shaft.   USED OEM 87-08 HONDA TRX 250X 300EX 300X CRANK OIL PUMP & PRIMARY GEAR W NUT | eBay

[Gwbarm]

That seems too much look on motorsports.com hem parts.

[p5200]

Too late, I already bought it lol! I'll check the place you recommended because I guess I should get the chain guide and the plastic tensioner which, I think is what the broken pieces of black plastic are from.

[Gwbarm]

Just checked OEM part $9.36 

 

part # 90235-HAO-680 Nut, Lock,(20mm)

 

 

 

 

 

 

 

 

 

 

 

 

 

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[p5200]

Oh boy, another brain fart for me! If I don't get my head straight, I'll never get this thing running. 😞  Thanks!

[Gwbarm]

The second one is a good price.

You did good , because they would get for shipping on top of the part price.You got free shipping plus the gear if you need it. 

[p5200]

I hope, I'll be able to get the nut to thread on. I'm thinking since the nut is so smooth on the inside that a lot of what I'm seeing on the shaft is fill in from the nut threads. I guess I should look for a black plastic tensioner piece at least, since I'm pretty sure that's what broke. It's the one that's bolted in I wonder, if I took the bolt out if I could pull it out and get a better look at it? Thanks