I recently purchased a 250 D and am having problems with my chain and keeping tension and the sprocket seems to be out of alignment,and also i would like to purchase some skid plates for my undercarriage,any help would be great!!  

check the rear motor mount, these like to break loose.

if you are still having trouble with the mount check the front mount and make sure they are both tight.
check your swing arm bushings and your axle bushings.

check online you'll find skid plates, check ebay they have a ton of different products.  

My 1985 3 wheeler had the same problem. In my case it was caused by worn out swing arm bearings and worn out axle breaings. Since your vehicle is so much newer it might not have the same problem but you never know. Bad bearings would allow the angle of the front and rear sprockets to not match up and would allow the chain to come off. If you axle wobbles within the bearing carrier then the bearings are bad.  

I had same problem with my 250 D. I loosened up the chain tensioner and realigned the sprockets and lock tighted the bolts. Most 250 D's I have seen everyone lock tights all the bolts since they have a tendency to back off. I had the chain come off riding trails and had to limp it back to the parking area to fix it and a guy told me to lock tight it. Has worked so far with no problems other than ball joint looseness issues which I drilled them and put grease fittings in and cured that problem too. Next I am changing sprockets for lower end pull and doing an exhaust swap for more power since these are only 233cc engines.  

Great thread.. I could have written it myself.. same damn problem.. just got my 250 taotao 3 weeks ago and the chain keeps poppin off.. especially up hills.. fortunatly, it's easy to put back on, but it is a nuesance.  Anyway, I will try locktight on my bolts this weekend.. also where can we purchase different size sprokets.  I was also told the china chain sucks.. will this help to replace the chain?  It's been a blast so far.. a little unstable compared to my friends rides.  I like the idea of adding zerks.. you just drilled them out and put them on?  Any websites that have good parts.. accessories, upgrades?

Thanks guys.. great thread.. need all the help I can get.  

When I purchased my atv the owners manuel was wrong and i would like to know what type of plug should i use ,factory plug had no #s?  

When I purchased my atv the owners manuel was wrong and i would like to know what type of plug should i use ,factory plug had no #s? Is a 250d 233 cc  

you can get buy i think with the ngk b8es
just make sure the thread and element are not longer than the factory plug.

the b8es is standard on honda fourtrax 250cc engines.  

Our neighbor just bought one of these.. it's brand new and won't start.. we've checked the oil, fuel is on, brake peddle is depressed and battery is good..  what else are we missing?   It's was started and loaded in the truck and once we unloaded it at home.. nothing.. will not run.. Also, the owner's manual is a joke.. all it talks about is safety.. nothing what so ever about the mechanial aspects of this bike.  

Try to hold the kill switch in while starting,I had same problem coulpe of times till I figured it out  

try getting a chain alignment tool and a new chain.  you also may wont to loctite the the bolts that hold the rear sprocket to the axle on. about 3/4 in is the right for the chain.  good luck..... any one seen an engine rebuild kit for them yet... think i have a blown head gasket on mine.  

I finally got a plug that fits and I would like to know the plug gap?Your help is appreciated..  

Was wondering about your exhaust swap, i would like to change mine for a little more go. I am swaping sprockets as we speak and will know more bout it soon..  

I also have the 250D and it was a nightmare to keep the chain on.  I put a chain tensioner on it and it very rarely falls off now.  It fell off once this past saturday after about 6 hours of riding. The only problem is the chain tension uses skate board bearings on the roller so they only last a few months of riding in sand or water.   The main problem with these atv's is the rear swing arm bushings.  They cause it to flex to much left or right which tosses the chain.  

i have read on here that you can use washers to shim the swing-arm so that it wont pitch the chain the chain off.

you might want to look into that.