Help with chain alignment

GasX · Nov 29, 2012

I just got my KW machine Works chain tensioner and when I put it on the frame it made obvious my chain alignment issue. The drive sprocket on the transmission and the rear sprocket don't line up that well, but I thought the chain tensioner would sort it out. If you look at the picture, you'll see that the tensioner is not remotely in line with the rear sprocket rendering it useless. However, you can see a spacing nut on the axle in the picture. If I remove it, I think everything will line up, but won't my frame not like the reduced width?

Any thoughts on resolving this issue would be appreciated. Perhaps moving the spacer to the other side might work...

TIA

GearNut · Nov 29, 2012

The chain alignment between the engine sprocket and the rear wheel sprocket must be sorted out first.
Move the sprocket mount left or right on the wheel hub if you can to correct alignment.
If the sprocket mount is moved as far to the left as possible and you still need the sprocket to be further to the left you can use correct sized washers in between the sprocket and sprocket mount. The bolt hole of the washer should not fit too sloppy on the bolt. Be sure that the sprocket bolts will still thread into the sprocket mount at least 3/4 of an inch. Longer bolts may be needed

After those sprockets are aligned, then align the tensioner.

I don't know how the construction of that tensioner is done, but if the tensioner wheel is mounted on a bearing than you can also use washers in between the tensioner mount and tensioner wheel to space the wheel out further from the mount. Once again, be sure that the wheel mounting bolt has plenty of length to thread on securely. A longer bolt may be necessary.

GasX · Nov 29, 2012

I don't think I can move the sprocket adapter as it is right up against the brake arm already. My best bet (I think) is to eliminate the bolt in the picture, I just don't know how important it is...

crassius · Nov 29, 2012

bend your brake arm into an "S" shape to clear the sprocket & if needed enlarge the hole in the center of the sprocket to go out over it a bit (takes an hour or so with a round file)

borntofli · Nov 29, 2012

Get rid of that fancy thing and use the cheap one and shim your motor so a tensioner just has to keep a little slop out.......

2door · Nov 29, 2012

GasX said:
I don't think I can move the sprocket adapter as it is right up against the brake arm already. My best bet (I think) is to eliminate the bolt in the picture, I just don't know how important it is...

Not sure what "bolt" you're talking about. Do you mean, nut? I see a rather large nut on the axle that seems to be thicker than standard size. The other ones I see are apparently axle adjusters to set chain tension.

The problem with any tensioner is that they are usually made straight and mount parallel to the chain stay. That means they will not line up with the chain path due to the taper built into the bike frame. Kit supplied tensioner brackets usually need to be bent/twisted to get the tensioner wheel to line up with things.
As GearNut pointed out the critical alignment is betwen the engine drive sprocket and the rear wheel, driven sprocket. Then the tensioner, whatever type, must be installed/adjusted to meet that alignment.

Due to the fact that you have a way to adjust the chain tension there's a good chance you will not need a chain tensioner. Especially a high dollar thing like you have.
A photo from the side would help us offer more advice.

Tom

skitchfish · Nov 29, 2012

Tie a small loop in a piece of fishing line and hook it on back of tooth of wheel sprocket.
Run the line across sprocket as close to the center as possible. Move line in and out until you are just touching the opposite side of sprocket without bending the line. This will give you a quick, easy, ball park reference of how far your adapter needs to move.

Make sure your wheel is where it supposed to be when doing this alignment also. Check that tensioners are equal length and reveals on dropouts are the same. Dimension from
wheel to chainstay on either side should be fairly close to the same providing your wheel is relatively true. Looks like you have plenty of room to move before you hit that tensioner bolt. An 8th of a inch goes a long way as far as function.

Venice Motor Bikes · Nov 29, 2012

I think Pirate still sells 'bent' brake arms to allow the sprocket to be moved out more... Or you can do what I do & heat it with a torch & bend it in a vice.

GasX · Nov 29, 2012

Venice Motor Bikes said:
I think Pirate still sells 'bent' brake arms to allow the sprocket to be moved out more... Or you can do what I do & heat it with a torch & bend it in a vice.

I think that they only have the star kind or round kind - whatever kind I don't have. I think the vice is my plan of attack...

GearNut · Nov 30, 2012

I think the nut you are referring to is responsible for locking the left side hub bearing cone and brake arm together. If you choose to remove it it must be replaced with another nut.

If you look closely at the tensioner you can see that the manufacturer took into account the differences in chain line and chain stay angles. The tensioner sprocket does not run true to the chain stay but pretty darned close to the chain line. While this must be a "generic" angle chosen by the manufacturer as different frames use different angles on the chain stay, the OP should be ok with using this particular tensioner.
Still though, with the frame having horizontal dropouts I agree that there is a good chance that a tensioner will not be needed.

crassius · Nov 30, 2012

you could saw that nut in half, then put that amount of washers on right side of axle to get better alignment, then use your spoke wrench to re-dish the tire back to center, but that seems a lot to go thru for something that might be a simple fix if looked at in person rather than in a pic taken at a bad angle

GasX · Dec 1, 2012

Anyone ever use one of these?

http://spookytoothcycles.com/compon...age=vmj_ace.tpl&product_id=532&category_id=41

crassius · Dec 1, 2012

looks easy if it isn't TOO fat

only takes me maybe 30sec with just a hammer to make my bends in them tho

biknut · Dec 2, 2012

Your problem is that you need to bend your coaster brake arm, to allow the sprocket adapter to be able to slid out farther on the hub.

It's one of the hardest parts of the process of making a motor bicycle. It helps to have a vise, and big hammer. A oxy acc torch makes it a lot easier. After you get the arm red hot it will bend like butter, but you can tough it out without one if you have to. I just spent all day making one fit my new bike, and I have all those things.

The KW Machine chain tensioner is made to fit wide tire Felt bicycles, with offset mounted engines. It might not ever work on your bike.

biknut · Dec 2, 2012

GasX said:
Anyone ever use one of these?

http://spookytoothcycles.com/compon...age=vmj_ace.tpl&product_id=532&category_id=41

I have one of those and it works real well.

biknut · Dec 2, 2012

crassius said:
looks easy if it isn't TOO fat

only takes me maybe 30sec with just a hammer to make my bends in them tho

Yeah I can bend one up with a hammer in half that time. It won't fit anything though lol.

crassius · Dec 2, 2012

other builders here send me rear wheels when they do a coaster brake bike to get arms bent and center hole hogged out to clear the dust cap and sometimes, tire dished to the right to clear chain so white walls don't get marred

have done maybe 80 or 90 of them and all came out OK

that said, I do not build coaster brake bikes myself since I do not trust those brakes at full speed, and I hate not being able to rotate pedals back to get a good start uphill

biknut · Dec 2, 2012

crassius said:
other builders here send me rear wheels when they do a coaster brake bike to get arms bent and center hole hogged out to clear the dust cap and sometimes, tire dished to the right to clear chain so white walls don't get marred

have done maybe 80 or 90 of them and all came out OK

that said, I do not build coaster brake bikes myself since I do not trust those brakes at full speed, and I hate not being able to rotate pedals back to get a good start uphill

I envy you. I wish I knew a way to cut the center hole bigger. That would sure make things a lot easier. Usually there's plenty of room for a bigger hole, so I don't understand why they're always so small.

CTripps · Dec 2, 2012

biknut said:
I envy you. I wish I knew a way to cut the center hole bigger. That would sure make things a lot easier. Usually there's plenty of room for a bigger hole, so I don't understand why they're always so small.

I just widened a center hole for a project in progress. I used an 80-grit flap wheel on my Dremel tool. I only had to open it up about 1/32" all the way around, but it took about 5 minutes and left no messy filing marks or burrs to clean up.

2door · Dec 2, 2012

Keep in mind guys that the center hole doesn't have to be perfect. It's the outer diameter, the sprocket teeth that must be concentric to the hub. That center hole could be square and still work. There's no need to shoot for precision when enlarging it.

Tom

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