Doodlebug chain popping off

Zlash

Zlash

New Member
#1
#1
Recently I switched my stock DB30 (new style) to the Predator 6.5 HP and all went surprisingly well for a first time swap, started first pull, and ran no issues. I got to put some hours on it, probably anywhere from 6-8. But now I'm having this problem where the chain just wont stay on. I threw it going up a hill in a neighborhood and its been messed up ever since. I try re-aligning the chain by moving the motor all over, changing the tension all the way from super tight to where it was when it threw it, but it doesnt help. Its even more straight now then when I was originally riding around on it yet it still throws the chain within seconds of movement on any sort of power or speed.

I looked at the sprocket and posted the picture so everyone else can be the judge. But being the fact that it threw the chain when the motor alignment never even moved, I'm feeling the sprocket has to be worn out and just want confirmation that its the sprocket or possibly the chain. 14455722_1415478611801240_1064475324_o.jpg
 
Sixpac440

Sixpac440

#2
#2
If its lined up ... the front and rear sprocket are tight and the back wheel is tight I would suspect the chain ...

Do the links feel sloppy?

Another thing to look for is a cracked, broken frame or motor mount ....
 
mrpat

mrpat

#5
#5
I just had the same problemo. Everything all lined up but chain keeps wanting to fall off. My chain is old and just worn out.when I took the chain off and put it in a straight line on the floor, it has a slight bend to it. Also there are a few links that are extremely tight.

Spend the extra couple of bucks and buy the good chain, you will thank yourself later.

Sent from my SAMSUNG-SGH-I337 using Tapatalk
 
Zlash

Zlash

New Member
#6
#6
Thanks Six. Been browsing here and a few other sites for a few weeks just never had a reason for an account until now. :laugh:

As for the frame being broken or cracked, the only thing I can tell is, when I put the Predator in I did cut the rear fender bracket off at the top and partially on one side to make room. I ended up mulling it over for a while and had a "meeting of the minds" with a few others to come to a conclusion wether or not the bracket was structurally integral to the frame, which it didnt seem. I dont feel like thats the issue either considering I put many hours and miles onto it before I had a problem after I cut the bracket off.

If the sprocket doesnt appear to be too worn I'd suspect the chain. Because when I bought it (used) the chain had no oil on it, dry as a bone. A number of the links feel pretty "seized", like a link locks into one position and its difficult to get back straight by normal hand force. As for sloppy, no. Just feels very stiff and unforgiving. Its the stock chain if that helps identify its definately the chain.
 
creia

creia

#7
#7
Zlash said:
A number of the links feel pretty "seized", like a link locks into one position and its difficult to get back straight by normal hand force. As for sloppy, no. Just feels very stiff and unforgiving.
Click to expand...
There is your problem right there. Get a new chain and lubricate it properly.
Michael
 
Zlash

Zlash

New Member
#10
#10
Awesome. I knew it had to be one or the other. That's the exact chain I was looking at too.

Now just 2 more questions. First is, should I spring for the one you linked, or the 120 link version? Will that be long enough? If I remember correctly the stock chain is 140, and I did take some links out. I have the OldMiniBikes plate so moving the engine back ain't a problem. Second question is, I know most people bend their bracket out and reweld but I don't have access to a welder. Does cutting it off actually affect frame integrity or no?
 
Raskin

Raskin

#12
#12
Zlash said:
Awesome. I knew it had to be one or the other. That's the exact chain I was looking at too.

Now just 2 more questions. First is, should I spring for the one you linked, or the 120 link version? Will that be long enough? If I remember correctly the stock chain is 140, and I did take some links out. I have the OldMiniBikes plate so moving the engine back ain't a problem. Second question is, I know most people bend their bracket out and reweld but I don't have access to a welder. Does cutting it off actually affect frame integrity or no?
Click to expand...
IMG_20160922_153754.jpg is this the bracket you mean..most I've seen just bend it back some if clearance for motor if thats what you mean..I would not remove it
 
Zlash

Zlash

New Member
#13
#13
Unfortunately is was the only way I was able to do it. I moved recently and had to leave all sorts of equipment behind because I just can't move it right now. I tried heating it and hitting it with a hammer (only tools I had at the time) but it didn't budge one bit. So I went to harbor freight, bought a $21 grinder and had the bracket off in less than 2 minutes.
 
Outlaw Ace

Outlaw Ace

#14
#14
I haven't heard anything but good advice so far. A bound or rusted chain will jump off, so will a stretched or loose bouncing chain. The chain tensioner on the DBs is ok but if you make an arm off the mount and add a spring even the most worn loose chain will stay on, my old blue monster's chain could be lifted off the sprocket it was so loose and worn but it never derailed. Somethin to consider when you replace your old locked up chain.
 
Zlash

Zlash

New Member
#16
#16
I heard a lot of people saying the stock tensioner isn't very good, so I may look into building something up if a new chain doesn't help.

A few days ago I ordered the 120 link RLV chain and when that comes in I'll give an update of wether or not that fixed it. Should be here Monday.
 
Zlash

Zlash

New Member
#17
#17
So another update for today. Quite a lot was found out so, here we go.

Chain came in today, but was too short even with the motor pushed all the way back. As a last ditch effort to use the stock chain I took it off and cleaned it for a good few hours, making sure to unsieze any links completely or as best as possible. Once I was done it was pretty loose and willing to move again. I took it for a ride and sure enough, it popped off again.

Ended up driving it back very carefully and finally decided to dig in deeper as to what could be wrong. I took the entire rear axle, sprocket, and wheel off. After doing that, I found the sprocket-side bearing utterly destroyed. Twisted metal and rubber all inside and a number of balls missing. The brake side bearing wasnt nearly as destroyed, but it feels pretty seized and not willing to spin.

On top of all that, I think the sprocket has a very, very tiny, maybe even 1mm bend in the center. If I lay it on a flat surface and push down on all areas of it, it doesnt wobble or make any sort of noise. Its only visible if you look directly at the center hole.

So since the bearings are shot, I'm going to order new ones off of ebay. (I know OldMiniBikes sells them but their shipping is just kinda ridiculous to me, ebay has 2 of the same bearings, shipped for free, for under $10.) I will most likely order the 6201-2RS ones since they seem to be the strongest unless I'm missing something. I'd hazard a guess that thats what keeps throwing the chain, also because my brakes have been acting up a lot lately ever since it threw it the first time. As for the very slighty bent sprocket, I dont know if I can chalk that up to an issue given its incredibly small defect.

Let me know what you guys think.
 
danford1

danford1

#18
#18
The sprocket most likely is OK. The bad bearings will definitely throw a chain. Your rear wheel can't stay in alignment with bad bearings.
You mentioned the new chain was to short. Did you order more new chain with another master link?

Danford1
 
Zlash

Zlash

New Member
#19
#19
As of yet, no. I'm kinda holding off for now because I cant be totally sure the stock one is done. Sad part is, the new chain only misses by I'd say like, 3 inches. I cant bring myself to spend another $25 ($50 total for both chains) on 3 inches of chain without technically needing it.
 
Zlash

Zlash

New Member
#20
#20
Got an update, all good news.

New bearings came in a few days ago, slapped them in, and all went well. Chain doesn't pop, bike rolls way smoother, brakes work way better, and got a few more MPH.

Think my next endeavor will be a smaller sprocket for more speed.

Thanks everyone.
 
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