Twin Cam Six Speed Touring Primary Chain Drive

[Ohio HD]

I know this might be a long shot, but I'll ask anyway. Does anyone know what the center to center dimension is from the crank shaft to the transmission input shaft on a 2007 up Twin Cam touring bike? I would have to pop a primary cover and remove parts to get a measurement. So I'm hoping someone may have the info.

I'm trying to figure something out as far as the number of chain links needed.

Stock these bikes use an 86 link primary chain with a 34 tooth motor sprocket, and a 46 tooth clutch basket sprocket. What I'm trying to figure out is if I use a 32 tooth motor sprocket with a 49 tooth clutch sprocket, can I use the 86 link chain. My calculations based on no slack in the chain says yes. There's a little more than 1/2 link more difference, measures as .6 link difference. I think the tensioner might take that up. The change from 32 to 34 motor sprocket with the 46 tooth clutch requires about a -1 link less chain, measures at -0.943. And a thick shoe is used to adjust the chain.

As I mentioned all of this is based on theory without the tensioner travel and shaft centerlines in the equation.

So if anyone might know that center to center measurement, I'd appreciate it.

Also if anyone happens to know the number of chain links the chain supplied with the 49 tooth baskets for 2007 up Touring bikes that Evo Industries sells, I'd like to know that as well. I don't know why I've never counted mine when I had it apart.



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[Ohio HD]

I did something scientific. I used my calipers to measure the compensator nut in a service manual drawn view. Scaled that and then measured the CL/CL in the drawing, I get about 9.375". I need to measure one though so I can make an accurate model.


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[rigidthumper]

I have an 07 case and trans sitting on the shelf- i can bolt them together and take a measurement if you want?

[Ohio HD]

If you have time, that would be great. Don't feel you need to rush and do it. Just when you get a minute or two.   

[rigidthumper]

Will do

[rigidthumper]

11 1/4" from output shaft to input shaft. 

[Ohio HD]

Thank you sir!

That'll help me do some calculating to see if I can use the 32 x 49 combo with the 86 link chain.

Much appreciated Mister!!     

[Ohio HD]

I need to look a little bit more into things. I think at worse case I need to shave a small amount from the chain tensioner block. But I'm betting the 86 link chain will slide in there with the 32 x 49 combination.

[Ohio HD]

I think there's enough in this adjuster to take care of using an 86 link chain where a calculated 86.6 ~ 87 link is needed. The body of the adjuster where the fastener goes thru looks like I can machine 0.125" out of there if needed, If it breaks, make one out of steel.

[PoorUB]

Maybe I am missing something, but if the calculations say 86.5 - 87 links, how will an 86 link fit? Seems like you need an 88 link.

[Ohio HD]

Yes, you're missing that I said I was estimating the CL distance. Now that I know what it is, it's as I suggested, the chain adjuster needs to be at the bottom of it's travel.

OEM chain calculation (without a tensioner in the equation) 85.16 minus 86 actual links = chain 0.84 too long, adjuster will take that up.

32&49 chain calculation (without a tensioner in the equation) 85.83 minus 86 actual links = chain 0.17 too long, adjuster will have to be at the lowest position to take that up.



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[kd]

I think if your calcs are correct it will go together.  Even if it takes a little trimming on the adjuster.  Not too much I hope as I fear this new engine will give it a workout on occasion.     As I see it, the test will be when it is up to temp and the sprockets grow.  If it's an easy (as in loose) fit cold you're probably going to be OK hot.

[Ohio HD]

The way I look at it is the primary chain is a 428 chain. That means 0.50" pitch. So adding three teeth as in the Evo Industries basket, you add 1.50" to the chains needs. So an 88 link chain is needed. Then take two teeth away from the motor sprocket, you recover 1.00". So you loose 0.50" from the stock setup. When you drop the chain adjuster on a stock inner primary, the chain drops to the inner primary case. So I think it'll all work.

Keep in mind that these are calculations based on supposed standards. I think it'll fit. Will only cost me $400 to find out.   

[Ohio HD]

FYI I don't have time to research the calculations to make an Excel sheet. So I used commercial calculators on line to get some numbers together. What you see is the results from those.

[PoorUB]

Yes, you're missing that I said I was estimating the CL distance. Now that I know what it is, it's as I suggested, the chain adjuster needs to be at the bottom of it's travel.

Ah, ok, I thought your were using the new center distance info. I didn't go back and reread your original post.

I come up with just under 86 links. it will be tight, but should work. The only issue I see is fitting in the adjuster. There might not be enough slack to get it in there.

[kd]

Tie wrap it down snug and it should be possible to jigger it together.

[Ohio HD]

I'll be using the tensioner that comes with the sprocket from Vulcan works.