400cc xatv blows rearend

Posts: 64

Hello all. Well I have had my first major issue with the 400cc xtav. My rear has been toasted, sorta speak. After I put a FMF pipe, 145 jet, and a new uni filter, it seems I have too much power now. I noticed a major increase in the midrange and tope end speed. It appears I have more tourqe as well. All the bolts holding down the ring gear have broken causing my buggy to be inoperable for the time being. I have started the parts ordering process already and hope to have this fixed in a week or two.

BTW: Dave from Awesomebuggy.com got a message I called today and called me back like an hour later from China. Now that’s service. I hope he is up there getting his new buggy ready for production.

Posts: 6245

Wow, that is some sweet service. Lets see how fast it takes to get you the parts now.

Posts: 3422

Ouch! Looks like you sheared all the bolts--what grade marking is on them? What are the thin wires in the pictures--were the bolt heads safety-wired together? If so, one might just conclude they've had issues in the gearbox during product testing and came up with a band-aid fix.

Posts: 1087

if you dont want it to happen again i would go with an american bolt ya no what i mean Very Happy

Posts: 64

I am asking the guys at QS who are working with the new yamabuggy if their diff will fit into my old yamabuggy. If so I might go that route. Apparently they mentioned a bad design with my diff on buggy talk radio the other week. If that will not work then I will get another like I had and replace with American bolts if I can.

The only problem I am seeing here is the wire that goes through the bolts. Are these to hold them from working out? How do I get the good grade American bolts to stay in? Drilling every head and running a wire through it does not sound real fun.

What grade of bolts should I use on this, 8? Will this flex enough? Should it flex at all.

I will also add that I have driven this around on pavement a bit and made some sharp corners, maneuverings. With this being a true posi and having zero slip I am sure the wrath of god was all over this diff at these times. I think I will keep it in the dirt from now on.

On another note it looks like the 145 main jet with the needle moved up a notch is a pretty good combo with the FMF pipe and Unifilter I put on it. Still not getting the color I want in the plug but it runs great. If I go to a 150 jet it starts cutting out big time under throttle and backfires a lot when coming off the throttle. Not sure why plug would not show any color here. I have replaced the plug with brand new ones gaped at 35 and ran for 30 minutes at a time. Pulled plug and zero color. I have done this three times while engine is warm and nothing. Any ideas out there? I am also 2.5 turns out on the idle air screw.

Posts: 1087

you could use locktite but you should figure out exatly what the wire does before throwing it grade 8 bolt dont break well shouldn't break

Posts: 64

Worked on the buggy over the weekend. I have two striped threads in the ring gear and I am unable to find bolts that will clear the case when using lock washers and I am not able to find bolts that have holes in them for the wire. My guess is the wire is used to make up for the no lock washers. I think a new rear diff maybe in play here. I guess I will spend the $250.00 clams and get a new one.

Posts: 9

Hi

@yamaboy !

I use a 150er Main jet , but i dont Use an Uni Airfilter , i only demount the Choke sheet from the orginal Filer , but i mean it works not fine , its to Lean , and the Consumption is more than the Buggy goes faster !

witch jet was in your Buggy in orginal Condition ?

Sorry for my bad english !

Thats my X-Atv

her are some threads oft the X-Atv is called in german Taurus !

http://www.buggy125.de/forum/forumdisplay.php?f=169

but is in German !

Posts: 931

You havnt had this thing very long, isnt the rear diff covered under warranty? Van

Posts: 64

On the first question of the jet, mine came with a 128.

On the second question of the warranty, yes it is under warranty. I paid the 250.00 to get this asap. It is in PHX now and I should have this delivered to my home today or tomorrow.
After I send back the original rear diff they will inspect and either warranty this or tell me it is abuse and go pound sand.