chain tension

[pdog]

Hi I'm new. My first build from Bgf has gone ok. so far I need to get some sealant for the gas line, try to bend the exhaust to fit inside the crank arms, I'm running the Heavy Duty 415 chain to I think a 48t rear wheel sprocket with the stock tensioner and my chain keeps slipping inward every time I start the motor. I have tried to slide it everywhere. thinking about getting a spring tensioner and or a new rear sprocket. Other than that the quality of their kit has been ok. Any suggestions on drive chain tension?

 

[mark880088]

you can have yours welded on. I made my own that mounts across the frame so it can't pivot in. Pretty easy to do.

 

[ResetBTTN]

Are you able to slide your rear tire back? What's your cycle? I have an OCC Schwinn Chopper and I had a chain tension issue and it was solved after just loosening the rear tire bolts and sliding the tire back until the chain was as tight as it could be. Locked the tire back down and BAM! No more prob.

 

[pdog]

thank you. I have a magna bike someone gave me with the kit. the rear tire is about all the way back I could try a little harder. i'm also thinking maybe I should buy a half link? I measured it and I think a half link would fit so I could cut an inside link and an outside link and use the half link and masterlink to connect an inside link and an outside link on the chain. but would that half link of slack matter so much or could I make up for that with a tensioner? im thinking of looking for springs and just modifying the stock tensioner too. would letting the clutch out slowly help with the chain whiplash from starting my motor?

 

[pdog]

oh and I don't know how to weld. could I use a propane torch for that? I wouldn't miss my eyebrows!

 

[ResetBTTN]

I've heard that half links will take out that slack. It was an option of mine before I realized I could just slide the tire back. Easy fix. I would try that first and if it works you may not even need the tensioner. I didn't wanna use the pulley that came with my kit. Couldn't and wouldn't fit on my seat stay or chain stay to be used anyway. I use a heavy duty size 41 chain...anything less than that my 80cc has broken the link or snapped the chain in half.
I'm not a welder either so I cant help you there. If you won't miss your eyebrows then weld away lol.

 

[pdog]

thanks for your reply reset button. I appreciate the support and I think it is important for anyone starting to build bikes to have others around to talk to about whatever is going on with the build so the newbie can know what can work and what doesn't really work. As a newbie I sometimes feel like what I am trying to do is hopeless and it won't work but then I talk to people and/or see what they have done and then I have faith that what I am doing in my build can work if I stick to it and get the adjustments right. As far as my build goes I was working past dark last night then looked at it a few minutes today and noticed I somehow ripped a spoke out of the rim probably via the tensioner getting jammed in it either during engine engagement or possibly after when I was pushing the bike. Say a prayer for me that my chain stays on today because I need this for transportation since the bus doesn't run anywhere that I need to go on the weekend. Currently I am lucky to be able to pedal during the week 2.5 miles or 4 miles to a bus stop and then the I can transfer from one bus to another and so on to make it about anywhere in southern New England within 1 day for a very cheap bus fare. But with no bus on the weekend I am doing this bike project to solve that problem because I got sick and very tired of doing a 35 mile round trip pedal powering my way to work in a city on Saturday and Sunday. This motor bicycle project is a lot of fun and it is exciting to me that I will be able to travel on a bicycle for such a cheap rate at a rate of speed that is as fast as most people would ever want to go on a cheap bicycle. As always I would appreciate any other suggestions on chain tension but for now Im going to go with the good suggestions of trying to move the wheel back and adjust the stock tensioner and I might try customizing the stock tensioner simply using a spring or three. God Bless and thank you!

 

[crassius]

the main reason for a tensioner shifting sideways is a slightly off center rear sprocket that has had the chain tension set when it is at it's loosest point rather than at its tightest point (when the chain gets tight, it pushes the tensioner down)

other problems here are a rear fork too small for the tensioner to grip (add a small piece of metal under the tensioner clamp), or sometimes the cheap bolts for the clamp are stretching (get better bolts)

 

[pdog]

thanks crassius...good input! yes my rear sprocket is far from being evenly tightened and perhaps I should od that b4 I ruin the cheap rear wheel entirely. the chain however is as tight as it can go without adding a half link.....unless straightening out the path of the chain by tightening rear sprocket / re-centering engine can get me the extra slack I need in order to cut an inner and outer link. right now I am POSITIVE I can only cut one inner link (as I posted b4 meaning I would need a half link in order to cut off just one inner link and one outer link then use the master link and a half link to connect 2 inner links on my chain. (I think I slightly misspoke on my previous post when I said: "I measured it and I think a half link would fit so I could cut an inside link and an outside link and use the half link and masterlink to connect an inside link and an outside link on the chain." When it should have said that a master link and half link connect 2 inner links on my 415 chain. OOPS! I'm sorry if any newbies like me got confused or made any cutting errors due to my idiocracy.) Ok I guess Ill be back late, hopefully with storie of my chain not falling of this time.. cheers!

 

[2door]

pdog,

Here's a lot of good reading for you. http://motorbicycling.com/showthread.php?t=11815

The Google Custom Search feature can provide you with a lot of information. Questions that have been asked and answered hundreds of times can be found with a simple keyword, such as 'tensioner'.

Good luck. The chain tensioner issue is one of the most common problems encountered by the first time builder. You'll figure it out.
Have fun, ride safe.

Tom

 

[ResetBTTN]

Pdog,
2door hit on exactly what I was going to say. It's a wealth of information and the best part is you don't have to wait for someone to answer your post....hundreds of people already have because hundreds have already had the same issue you're having. Post your questions still but check the archives right after. It's helped me a bunch.
Best of luck to you with getting it up and running.

 

[pdog]

thanks 2Door. Ya I'm aware that just about everything anyone has to say on here about motorized bicycling has been answered except original thoughts on some one of a kind customs. That being said we need people to repeat themselves frequently or this would turn into mostly a reference site for amateurs with a few people that have advanced knowledge talking about new customs. Which is fine if that's what ya all want. Anyways my update is I got the tension job done. So I do say: thank you everyone that have answered my boring questions that repeat questions that have already been answered. It helped me even though I have already read these same questions and answers before because I guess I just wanted reassurance that I was doing the right thing. Also now I'm not getting engine power even thoug it sounds like the engine is about to fire up. I'm getting really strong compression, my spark plug is tight on both ends...I'm thinking carb adjustment. Also wondering: Does it matter if my fuel line is twisted (not kinked)? or does it have to be straight line for gravity feed?

 

[pdog]

chain falling off

ok so I got everything done but now I cant find any reason my chain is falling off. I have it as tight as it possibly can go. then I use the stock tensioner and the bike pedals fine then I can start the engine and ride around the block but it seems if I change speeds to much or go too slow then the chain falls off the rear sprocket usually inward but once outward!! what can I do? has anyone ever tried a rear derailleur on the engine drive side?? please I need help on this one!!

 

[ResetBTTN]

Pdog,
A chain falling off means its definitely not tight enough. When it's being driven by the motor there is going to be some whipping and waving in a loose chain. All those whips and waves in a loose chain one whip or wave will eventually rise above your sprocket and off it goes.

When you push down on your top chain how much play do you get? Take a finger and push down on the top chain. You should get less than or equal to an inch if play. Anything more than that and you got whips and waves when that engine is driving the chain.
Even if you have your tire pulled all the way back you may have to remove a link or two or get half a link. Also what size chain do you have?

 

[2door]

Chain tension and alignment are critical. The engine drive sprocket and the rear wheel driven sprocket MUST be exactly aligned or you will have chain derailment issues.

Also the rear sprocket MUST be precisely centered on the rear hub and have no lateral wobbles. It must spin true as viewed from the side and the top. If the sprocket wobbles in either plane you'll have chain problems.

The tensioner wheel also must align with the chain path. If it isn't it will pull the chain to one side and cause derailment. Almost without exception the tensioner bracket will need to be bent/twisted slightly to achieve wheel to chain alignment.
Chain tension should be 1/2 to 3/4". This is measured by rolling the bike forward, clutch engaged, until the piston comes up against compression. At that time the top chain run will go slack. That's where you measure the tension/slack. 1/2 to 3/4" of slack.

A chain that is too tight will run rough and is just as prone to derailing as one that is too loose especially if the sprocket alignment isn't perfect.

Tom

 

[kevyleven007]

its the golden rule=anything that can go wrong will.Make sure its perfect.You shouldn't need a half link unless you running with no tensioner on either side.thats why you have a tensioner.just keep trying different things until something works.make sure the tensioner lines up with the sprocket PERFECT.and is on TIGHT.GOOD LUCK

 

[buzzie41]

hi, heres what i've used on my bikes.

 

[pdog]

Thanx again guys..Good responses from Resetbutton and 2Door and Kevy. I will go check all my specs again to be sure. Then I will give it a try and see if it runs better today. I also found a spring in my garage that has full hardware to hold it down so I might try the spring in addition to stock even though everyone knocks it. I have tools to make a custom spring setup--maybe off a piece of sheet metal double bolted onto the frame for stability and centering. Or maybe I could drill thru my frame if I still want to after I look at it again. Whatever works. Hah hopefully I won't do that Buzzie! I have one more QUESTION: Will the way I have been improperly stopping always cause even a properly installed chain to come off at least partway? (I have stopped accidently by slowing down too much with my hand off the throttle for a bit until the engine died then the chain popped off.) and to stop should I get off the throttle then squeeze the clutch and lock it in then hit the kill switch? I know this is basic but just going over it cuz I'm a newbie and I know I made mistakes when I tried to stop too quickly thanx!

 

[pdog]

I have a 415 heavy duty--I think it ends up being wider at least outer diameter than the 415?? I wish it was a little skinnier for wheel/frame clearance but I know it clears by the hair on it's chainy - chain- chain (ha- ha ! ) if I get it near perfect straight. Im definitely tightening certain bolts on the rear wheel drive sprocket to try to straighten it but the clearance to the spokes/rubber is already pretty tight so I have to be careful.

 

[pdog]

cut a whole inner and outer by sliding rear wheel FORWARD to the max... works great I just hope the rear wheel doesn't come loose at all when im moving at high speeds or im screwed