Chain pop off issue, please help solve mystery.

[meatwad]

I have the same chain on my kit and its trying to eat the inside case of my engine just like yours. My conclusion is that the chinese dont care. Boxes of sprocket boxes and piles of chains, whatever... this ain't no burger king.. You're going to get what youre gonna get and youre gonna like it

After fixing and having to tweak every single part of my kit (no exaggeration) and seeing the damage the chain was doing to my engine case I just said to myself La La La I don't care don't care! Hopefully it won't cut through the case and send the piston up into my man jewels.

This is all with having perfect alignment.

I think the chain was called a heavy duty version and it could be that other chain plates or pins aren't as wide and might not rub . Kind of think that they still would.

When the engine is pulling the chain, the problem of the chain riding up the teeth of the front sprocket doesn't seem too happen, it's only when it is riden as a bicycle does the bunching occur. I think its a matter of slack distance between the rollers of the chain and how they mesh with the teeth of the front sprocket. Personally I'm just going to ride it and see if it doesn't wear into shape.

As for the masterlink I don't know. Could be popping off the c clip when it hits the cover . Mine doesn't do that. I'd buy another.

 

[dmfelicia]

Yes I plan on optimizing everything in order to narrow things down. I know now why the clip pops off.
1) The chain does not properly go around the smaller sprocket, it doesn't seat properly (I don't know why yet)
2) This causes the chain to be pulled very tight
3) The weakest link i.e. the master link is pulled outward at each end (see pictures)
4) This outward pulling of each master link pin in opposite directions allows actually causes the pin to pop off.

One solution short of a new chain could be a chain tensioner with a spring set up. I saw a post on this with pics and it looks very doable. I generally would not like to introduce more moving parts into the drive train but this will provide an appropriate amount of tension while allowing slack when the chain runs into troubles traversing over the smaller cog. Of course this is more or less a bandaid fix since the true fix (for me) would be figuring out why the chain does not traverse the small cog and addressing that issue.

 

[dmfelicia]

LOL meatwad that response cracks me up. I feel the same way. I wonder if there are any american companies that make a kit which incorporates pride for craftsmanship. I am sure it would cost more but I am willing to pay for quality especially when my life is on the line.

I do think you are on to something with the source of the problem however, a mismatch between the chain and the front sprocket. This sub-optimal fitting seems like it could be a source of issues.

One question for everyone which may shed light on this mystery. How easy is it to turn the small cog when the clutch is disengaged. Mine is still somewhat tough to turn. I am thinking that if there is a lot of resistance this could cause problems when the bike is in pedal mode rather than engine mode. Reasoning is this. In engine mode the small cog is pulling the chain so it is unlikely that a misalignment of chain and cog will happen. When in bike mode the chain is pushing the small cog and this seems to me to be a much less optimal situation if that cog is resisting a lot I imagine chain bunching and so forth.

Any thoughts.

 

[meatwad]

<< In engine mode the small cog is pulling the chain so it is unlikely that a misalignment of chain and cog will happen. When in bike mode the chain is pushing the small cog and this seems to me to be a much less optimal situation if that cog is resisting a lot I imagine chain bunching and so forth.>>

Pretty much yeah.

In bike mode the chain is just being layed onto the sprocket and therefore it wants to crawl. I's still getting pulled but from the bottom and not the top.

Engine running the slack is where the chain it is coming off the sprocket. Not a problem.

Bike mode the slack is where the chain is going onto the sprocket. problem.

Personally i was going to file the teeth down a bit and take some of the square edges off but my kit didn't come with a puller.

 

[Stan4d]

I have nothing to add, but wanted to say that this disscussion is helping me. I would hear a slight poping sound ocassionally, and this disscussion has caused me to look into it. Guess what? Same problem though not as severe as dmfelica'a. If I find a diff fix I will let you know....in the mean time I gotta try what is listed. THANKS!

 

[Turtle Tedd]

Cabinfever says go buy a 410 bmx chain...THAT WILL DO IT........ 415 chains look like they fit but they will stack ..wind the chain all the way around the sprocket as far as you can to check fit...the smaller the sprocket the worse this is...The KMC KOOL chain (bmx) is one of the best..according to many on this forum..I got one after having similar probs....415 fits only some and is overkill anyway I think

 

[Motorbike Wanabe]

My Grubee kit came with a 415 chain and it had several tight spots. I went to Walmart and purchased two packs of Bell chain. That smoothed out my bike considerably. I would suggest trying that first. My chain popped off occasionally also.

 

[Stan4d]

OK...after looking at how the chain rode along the sprockets, I noticed that my rear sprocket was off center. The poping noise occured at different points in the chain. So That eliminated tight links and the master link. My sprocket was also not true. After centering the sprocket and truing it to the best of my ability the popping noise dissapeared. It may not work for your problem but it solved mine......now to go make up to my wife for spending too muck time with the motored lady.

 

[Hajuu]

Which kits are you guys using? My chain fits very nicely and apart from a small issue with getting master link clips to go on, I haven't had any issues so far.

Sounds dumb but I assume that the clip *is* going on with a nice kind of *snap* as it comes to rest in the front and rear grooves of the master link pins? Cause I lost a master link by having a clip look exactly like it was on, but it wasn't quite on propperly, which will cause it to come off very easilly, especially when going around the small sprocket obviously as thats when the angles are most intense.

 

[dmfelicia]

This has been great. I think collectively we have identified most possible solutions to this problem. I think this problem could be caused by different sources but regardless of the source I think we have identified a fix. Here is a summary of the fixes:
1) Check for tight spots in your chain.
2) Consider replacing the 415 chain with a 410 chain. The thicker 415 chain could cause multiple problems.
3) Check the alignment of your sprockets
4) Check the thickness and beveling of the sprockets, test to see if the chain can ride on and off of the teeth smoothly without sticking. Consider grinding problem spots (on the sprockets)
5) Make sure your chain is well lubricated.
6) Ensure that your sprockets (both of them) are true.
I think I may get the 410 chain to see how it goes. But last night I was investigating and eliminated all tight spots on my chain and also found that the chain went on and off the sprockets well. The alignment between the cogs looks fine as well. But what I did find is very similar to what Stan has found, that is I think my sprockets may be untrue. I suspect this because the chain periodically becomes slack and tight as I spin the wheel. It always gets tight at the same portion of the rear sprocket (for about a third of the sprocket the tension is increased). Before I must have been setting the tension at a "slack" portion of the sprocket and when it went through its high tension point it was over the top tight causing all sorts of problems.

Stan I imagine you trued the rear sprocket by tightening the bolts at the points where it bowed out. How did you determine the true of the smaller sprocket and how did you fix it?

Cheers,
David