Pulley chain tensioner blew off - good replacment?

FrizzleFried

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My brother has locked up his engine 3x in the last 6 months. One time ended with him on the ground with chunks of flesh missing from his leg and arm. He'd been riding motorized bikes for 2 years prior... always with the stock tensioner... then I bought him a spring tensioner.

Yup... all 3x he locked up he was using the spring tensioner.

No thank you.
 

Chainlube

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I personally don't really understand the use of the rigid "arch" tensioners. The spring loaded ones vary tension with load, and assuming the appropriate rate spring is used and load set accordingly, it will almost eliminate the low end "lurching" that the rigid "tensioners" cause to be transmitted to the wheel.

I could see using the arch if it also had the idler on a spring loaded moment.

The grubee style (I prefer the nylon wheel one however. quieter) is the best option.

The arch's, while they work for alignment issues, are pretty horrible at what they are intended to do...... maintain a consistent chain tension.
I have a user built arch tensioner, but I use it to take out the slack, not put any tension on the chain.
 

TheWizzerd

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My brother has locked up his engine 3x in the last 6 months. One time ended with him on the ground with chunks of flesh missing from his leg and arm. He'd been riding motorized bikes for 2 years prior... always with the stock tensioner... then I bought him a spring tensioner.

Yup... all 3x he locked up he was using the spring tensioner.

No thank you.
I did say... assuming the proper spring is used and set up properly.

Are you referring to the chain skipping a tooth on the drive sprocket on the engine and jamming in the case there? If so, there was likely way too much slack on the chain, and the spring idler couldn't do its job maintaining pressure and essentially wasnt working. If the spring tensioner is set up properly with proper spring tension (hence why most have multiple spring positions), it will not move much while under load. Maybe the width of the chain worth of movement. If its swinging more than that, your chain is too long and/or spring pressure too low. You cant just slap them on there and expect them to work properly. They require adjustment.

There is some variance in the springs that come with those tensioner kits. Maybe you got a wimpy one that was causing the troubles.


As chainlube suggested with his unit, it is indeed mostly about taking up the slack rather than applying a specific tension, a spring tensioner does that dynamically according to load.

Another benefit of the spring tensioners is they automatically take up the chain stretch and dont require periodic adjustment if you are using a crummy stock/kit chain. Which is another subject entirely.....

I have never had a chain jump with a spring tensioner, but I have with a rigid tensioner. I have personally had better luck running no tensioner over a rigid idler. But that requires careful alignment.
 
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I have both of these types of tensioner. Both on different bikes. I really liked the case mount tensioner, it works well. Then I bought the second type, the arc tensioner for my Seattle and man I love it! I think I'll be using the arc on all my builds going forward. They cost a little more but are def worth it
 

weefek

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My brother has locked up his engine 3x in the last 6 months. One time ended with him on the ground with chunks of flesh missing from his leg and arm. He'd been riding motorized bikes for 2 years prior... always with the stock tensioner... then I bought him a spring tensioner.

Yup... all 3x he locked up he was using the spring tensioner.

No thank you.
Sounds like he has too much play in the chain. That will happen real easily if there's too much play and you don't have the little bracket thing they make to stop chain binding around the main drive sprocket.

I've got 500 miles on mine since the middle of May and only that the lockup issues during the first week when I didn't know what I was doing.

Using the grubee chain tensioner, case mounted, of course.

It's easy to take up the slack with the stock tensioner and not have issues. With the spring tensioner it needs to be as tight as possible. It picks up the slack from uneven gears tbh.
 

ImpulseRocket89

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It's easy to take up the slack with the stock tensioner and not have issues. With the spring tensioner it needs to be as tight as possible. It picks up the slack from uneven gears tbh.
Even if the gears were perfectly machined and super high quality there would still be uneven tension in the chain drive. The issue is the chains themselves. Even the most high quality chain on the market will have uneven tensions from link to link - usually in sections - that cause variances in chain tension. This is why you set the chain tension on a motorcycle with the tightest section of chain.

This same principle is why I am personally a fan of the fixed style tensioners and why they have fewer issues with the chain popping off. The biggest issue with spring based tensioners is that they have to be able to match the amplitude and frequency of the changes in chain tension and if they fail to do either of those things the chain can become slack enough to come off.
 

TheWizzerd

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Even if the gears were perfectly machined and super high quality there would still be uneven tension in the chain drive. The issue is the chains themselves. Even the most high quality chain on the market will have uneven tensions from link to link - usually in sections - that cause variances in chain tension. This is why you set the chain tension on a motorcycle with the tightest section of chain.

This same principle is why I am personally a fan of the fixed style tensioners and why they have fewer issues with the chain popping off. The biggest issue with spring based tensioners is that they have to be able to match the amplitude and frequency of the changes in chain tension and if they fail to do either of those things the chain can become slack enough to come off.
This is why I prefer the sprung tensioners..... they compensate for that.... however, you do have to use the right spring and have them set properly. Many of them out of the box will not provide the proper load. You still have to get the chain close to fully tensioned/no slack before using them. If not, they will still jump. You cant just put an untouched chain on and them work as you can with a rigid idler. Especially the case mounted ones as you have no lateral adjustment to move it toward the rear sprocket to take up some slack.

I have never had a chain jump and jam in the case with either, or have one jump the driven sprocket for reasons associated with the tensioner. Only time I had a chain jump the driven sprocket was when a link on a stock chain gave way partially. I seen it was backing out before the ride, and "fixed" it by peening the pin back over, but its was too far gone to hold.

The stock chains are junk. The MMG 415H hold up well , but yes, they all stretch....they are designed to. Too hard and not stretchy would result in
far more breakages.

But.... they both work. To each their own.
 

ImpulseRocket89

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Too hard and not stretchy would result in
far more breakages.
Which takes everything back to setting proper tension with a fixed roller being the more ideal method (in my opinion). You set the slack at the tightest spot in the chain over the greatest free span of said chain and it will never get any tighter than that. Thankfully for most of these bikes there is no rear suspension and pivot point to alter chain tension with movement of the rear wheel so the tension can be set a bit tighter.

Either method has its merits at the end of the day. The real secret is just knowing how to do the setup properly.

As far as chains go... If you want to go full "Rolls Royce" in terms of 415 chains I give you this

I run DID X ring chains on two of my motorcycles. One of them is pushing 9000 miles and has had regular cleanings every 1k miles and only a dry lubricant and wax were used. Worth every single penny but they definitely hurt the wallet.

Not quite sure if I want to go that far with my motorized bike though lol.
 

TheWizzerd

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Either method has its merits at the end of the day. The real secret is just knowing how to do the setup properly.
True...

I agree with D.I.D. chains.... but they are as much as the engine kit, and sometimes the bike and kit together.

A ProTaper oring chain is about as far as I would go on a mo-bike. A good mid range chain like the MMG's (similar to pro taper) will do absolutely fine if set up properly. I would rather the extra money go into a good set of wheels.
 
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