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Old 05-26-2002, 07:29 AM   #1
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Exclamation XXX-S : Drivetrain problem HELP!!!!

I spent a better part of last night trying to fix the problem to no avail and decided its time to run it by some of the folks here in a clear manner:

When assembling my kit I noticed that my belt would tend to drift depending on the direction I would rotate the wheels (ie- forward or reverse driving). When doing forward rotation, the belt would head away from the spur gear and towards the metal tensioner assembly and rub. When doing a reverse rotation, it would head towards the spur gear.

I also noticed that the pulley would every so slightly rub the spur every so often during a complete revolution. This would give off a scraping sound. I have taken out the complete assembly and worked it to see if anything is loose and the pulley has a slight wobble to it. This wobble also seemed to be prevalent in my spur gear as well.

I also went to work on my diffs to see if it was something there. I noticed that on what I am using as my rear diff one of the bearings that goes over the drive cup and holds the diff slides very easy on and off. While the other once it gets to a point snaps on and is hard to remove. The bearing that goes on easy also seems to allow its drive cup to wobble more as if it is not a snug fit.

the pulley that makes up the rear diff seems to have a wobble in it as well when I went and tested its rotation. This was also detected when I tested my 41T pulley gear to see if my problems were being caused by a bad pulley gear. This wobble was extremely apparent.

Overall, I received a scraping sound whenever I completed rotate the drivetrain and the belt drifts. I however didn't see a wobble in the actual drive cups and I didn't see any effect on my CVDS.

As for my CVDs, one of the CVD axle was an extremely tight fit for the part that holds the set screw and now has become stuck in there as if the part wasn't formed properly. I am not sure how to get it out.


I think this about somes up the problems I am having and the help I need. I have never had an issue like this before with a kit during assembly and I am a pretty big Losi fan so to say the least this is very dissappointing. I am hoping it is something I did wrong so I can take it to someone to correct but clearly it seems as if the parts were not formed right in some way.

If you can offer any help please feel free. Even with these issues, I have seen the car perform and its a shame for the one I have to be sideline as I am still determined to race it.
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Old 05-26-2002, 08:45 AM   #2
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I think you spur gear may be bent as for the pulley loosen the spur gear screws and make sure it is up or in the right postion no pinched or anything, Your diff bearing does not sound like the right size, as for the cvd I have no Idea what could be wrong I don't use the set screws and put a thin band of electrical tape around it followed by a drop a tireglue. This is the last resort if the set screw will not go in right. I say you talk to the hobby shop where you bought it and ask them to help you out, the part may be bad, but I have never recived any problems with losi, except for I was uiulding my XXX and the front hinge pins where way to short I have no Idea whats up. If any body has a Idea on y little problma.


Thanks Hope this helps.
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Old 05-26-2002, 09:31 AM   #3
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Thanks for the info.

I think the spur gear may be bent as well. I do however think the diff pulley gears are not perfectly true as I can see them wobble ever so slightly (the rear one the front looks pretty good) but that could be because of the bearing.

The drive cup the bearing goes over the one that the bearing comes off easily doesn't have that initial ridge on it that the other does.

This really sucks
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Old 05-26-2002, 10:01 AM   #4
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Cain, the belt is gonna slide on its pulley some but it shouldn't slide all the way to where it hits the belt tensioner. I noticed that after a few runs the belt didn't slide as much as it did before I even ran it. Now as for the spurs, I have 4 differant Losi spurs and the all wobble also(not to an extreme where it creates a problem) but they all wobble. As for the spur hittin the belt tensioner pulley, 1) something is assembled wrong or you have a really defective spur cause mine has a clearance of about 1-1.5mm. You might want to shave down the head of that button head screw that holdds on the pulley and make sure you have your washers on the right side. For your bearing issue, my bearings don't snap onto their outdrives either. Make sure your diffs are assembled correctly also(you don't want them too loose). For your CVD issue, I had the same problem with a yokomo cvd one time but I fixed the problem with a dremel. Take the CVD back apart, clean it, put it back together without grease and see if it still binds. If it does, look and see where it's binding. It's most likely you can fix it with a little help from a dremel and use that set screw. A little, little dot of red or blue thread lock is all you need on it. One thing you didn't mention is your belt tension, run the belt in it's loosest position for stock motors unless your over or underdriving the car then your gonna have to find the sweet spot. For mods run the belt a little tighter. Don't worry about the bearings on the outdrives-that's not a problem. I've been racing my XXXS since it hit the shelves and it's been awesome ever since-heck, I placed 3rd in the Amain last week and we have sponsored drivers at our track. Be patient and walk your steps back.
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Old 05-26-2002, 01:47 PM   #5
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Quote:
Originally posted by proudwinner

I placed 3rd in the Amain last week and we have sponsored drivers at our track. Be patient and walk your steps back.
Who is sponsored at our track Ralph?
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Old 05-26-2002, 04:09 PM   #6
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cain,

I've never seen a diff pulley that didn't wobble to some degree. When the diff is together, there has to be some clearance between the rings and the pulley so that the rings will only touch the balls. That little bit of clearance is why they can wobble.

As far as why your belt moves to one side or the other, you might want to stick an old stock motor in the chassis and run it on 3 or 4 volts for a few minutes to break in the drive train. You can also run in the diffs while you're at it. Once that's been done you'll probably see the belt movement mostly gone. One of my XXX-S's did that, but it stopped when I ran it in.

The CVD problem sounds like something I saw on one MIP CVD, the little hole through the barrel where the pin goes was not aligned just right, and once I'd snug the setscrew the CVD would bind instead of flex. I replaced the barrel (you can get the barrel in the MIP CVD rebuild kit) and then it worked fine.

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Old 05-26-2002, 05:10 PM   #7
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Quote:
Originally posted by Mike F


Who is sponsored at our track Ralph?
Davis, world class batteries
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Old 05-26-2002, 05:57 PM   #8
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Interesting, I didn't know that. Thanks PW
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Old 05-26-2002, 08:54 PM   #9
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thanks for the info, the tensioner pulley wasn't assembled properly (loose bearing) and I removed burs from the CVD
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