Front sprocket or chain stuck?

S

scearus

New Member
Hello all, I'm very new to this, just got my first motor kit 2 days ago, and have been working on it since. Everything is now put together, but... When I disengage the clutch, so that the bike should be freewheeling, it clanks around. I've read many a thread, my chain is tight, and spent a lot of time aligning it. It would seem like the sprocket where you attach the chain to on the motor is getting stuck, or something of the sort. Please help?
 
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Re: Front sprocket for chain stuck?

Welcome to the forum. We're here to help. And I know exactly where Cooper City is :) I'm an old Florida transplant.

Two things come to mind. Either your clutch cable is too loose or the chain alignment is off.
Where the clutch cable attaches to the engine (clutch actuator arm) there should be little to no slack in that cable. It must be able to pull the arm in about an inch to fully disengage the clutch. This is a very common problem and tightening the cable usually fixes it.

If the chain alignment is off or if the chain is too loose or too tight it might be derailing at the front sprocket. There is very little room inside where the drive (engine) sprocket is and the chain can bind if one of the two problems exist.
If the engine is not mounted exactly square with the rear wheel (driven) sprocket that can also cause a problem. Make sure the chain runs in an absolutely straight line between the two sprockets as viewed from the rear looking forward. It can not run at an angle.

As for tension, you'll want 1/2 to 3/4" slack in the chain. Measure this by leaving the clutch engaged (handlebar lever out) and roll the bike forward gently until the piston comes into the compression stroke. The top chain run will then go slack. That's where you want the 1/2 to 3/4" of slack.

Good luck. Let us know what you find.

Tom
 
Re: Front sprocket for chain stuck?

Not a lot of people know where my little town is lol... Glad to know you do!

Anyway, chain problem is all fixed up, but starting the bike is very difficult. It takes quite a lot of pedaling to get started, choke needs to be full open, and it's... How should I say this, jumpy? It takes gas and goes, but like, tires out and goes again. Like a barely working junker. If I pedal through that, I can get it to go for like... 2 minutes or so, before giving out, and trying to start it again.

Any suggestions?
 
Re: Front sprocket for chain stuck?

Confirm that you have good fuel flow from the fuel tank to the carburetor. Remove the fuel line from the carb, open the petcock and observe the flow. It should be steady. It doesn't need to be a fire hose, just a steady stream.

Some have encountered a problem with the fuel tank cap not venting. These are gravity flow fuel systems and rely on atmospheric pressure to allow fuel to flow from the tank. If the cap doesn't vent it's like holding your thumb over a straw. The fuel will not flow from the tank due to a vacuum effect. Try loosening the fuel tank cap and se if your engine runs longer.

The other issue is dirt and rust in the tank clogging the fuel filter that is attached to the petcock. We always recommend that new tanks be cleaned before installation and an in-line fuel filter be installed.

These little engines all have their own personality and require some testing to see what is needed to get them started. Some require a lot of choke, some don't need any. Some like a little throttle, some like a lot. You'll need to experiment to see what your engine likes.
Let us know how you're doing.

Tom
 
Appreciate this thread. I just put mag wheels on after destroying a rim from a sprocket adapter slippage. Chain is seeming really jumpy to the point that I lack confidence in its complete safety. I placed a exhaust port on at the same time... seems like the engine idles deeper and lower... Wonder if I should increase on the carburetor perhaps? The old sprocket was 36 tooth, the one that comes with the mags is 44... Just wondering what is making this jumpy.
 
Good question, I personally feel it is too loose. I am using the engine mounted one as pictured. Can lift the chain about 1 3/4 inches on both the top and the bottom. Wondered if I should be investing in a second tensioner?
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What do you like to use for chain tensioner? I just went with a recommend when I ordered first parts for first build. Hmmm, I've been hearing people talk about removing a link or half link. I pulled the chain as far as it would go around the rear sprocket and just bridged the link with the master link. On the side, a guy at work moved my bike in park, can you damage anything by not pulling the clutch in first doing so? Obviously, it was hard to move, I am guessing the cylinder just moved as he moved it...
 
Bike seems to not pick up as well at low speeds as it did with the 36 tooth sprocket, is that because I went with the 44 tooth? It is the one that comes with the mag wheels...
 
BTW, I only have the mag on the rear simply because I finally got it running again and is in test phase. Will probably switch the front when time permits. Bought them at bike berry, had a burr on it that I had to snap off and sand down... Ruined a new tube as the next day found that it sliced it. Personally I think the quality was better with the original spoke build rims, but had wrecked that back rim when the adapter slip happened. Spacing is tricky with the mag hub, brakes make different sounds, etc... Really need to address this chain tension issue...
 
Hoofbeats64 said:
What do you like to use for chain tensioner? I just went with a recommend when I ordered first parts for first build. Hmmm, I've been hearing people talk about removing a link or half link. I pulled the chain as far as it would go around the rear sprocket and just bridged the link with the master link. On the side, a guy at work moved my bike in park, can you damage anything by not pulling the clutch in first doing so? Obviously, it was hard to move, I am guessing the cylinder just moved as he moved it...
Click to expand...

The arch tensioner (http://custommotoredbicycles.com/parts) that crassius mentioned is in my opinion the best design. But you can just add your stock kit tensioner to your bike and it should work fine if it gets a solid grip on the chainstay. Ideally you should run without a tensioner if you can get the chain to the right length with a half link but I don't know how many miles you have on your bike so it may have some stretching left in it.

As far as your chain alignment goes, maybe it changed with the mag wheel and new sprocket. Check to see if it is still in a straight line.

No damage was done by moving the bike "in gear".
 
Chaz said:
The arch tensioner (http://custommotoredbicycles.com/parts) that crassius mentioned is in my opinion the best design. But you can just add your stock kit tensioner to your bike and it should work fine if it gets a solid grip on the chainstay. Ideally you should run without a tensioner if you can get the chain to the right length with a half link but I don't know how many miles you have on your bike so it may have some stretching left in it.

As far as your chain alignment goes, maybe it changed with the mag wheel and new sprocket. Check to see if it is still in a straight line.

No damage was done by moving the bike "in gear".
Click to expand...
Good to hear, I was worried that moving the bike in gear could wreck the clutch and related harmony. Need top hang the bike again and start wrenching... I noticed the engine pulled ever so slightly to the left. As you say, alignment is key. With these mags they don't tell you, be prepared to science the heck out of buying spacers of many sizes to make this work... The chain was loose enough apparently on my ride home came off the rear sprocket.
 
When I first put on the chain, I pulled it around the rear sprocket and the length fit just right for the link at the back side of the sprocket. Yes, tension is now the issue... makes me think to re-examine that chosen link and if I could remove just one and pull it tighter.
 
I just want to pause and give thanks to you guys for the forum and help... I see you as my fellow scientists and engineers. I think literally to take on these kind of projects you need true grit and determination. The science of this gives us permission to fail and to try again.
 
Hoofbeats64 said:
I just want to pause and give thanks to you guys for the forum and help... I see you as my fellow scientists and engineers. I think literally to take on these kind of projects you need true grit and determination. The science of this gives us permission to fail and to try again.
Click to expand...

You are very welcome. You can tell that I'm a scientist from my avatar. There are many helpful folks here on the forum who generously share their knowledge and I am always glad to learn from them.
 
Looking back I probably would have scrapped the advice of shimming with an inner tube and just cold welded the sprocket adapter to my hub. The shimming fail and ruined a brand new wheel. Expensive mistake. Only problem being that if spoke work is ever to be done, that would have been a challenge too.
 
Currently with this chain tension issue. I am guessing the half link works by removing a full link and placing the half in its place. I trust this works on a standard 415 chain versus buying a half link chain?
 
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