Topic: question on chain conversion

[Powderman]

I think what I am reading here verifies what I said. Lets say your 630 sprockets are 50/25 (2/1), if you want a 530 chain and change to a 50/25 (2/1) 530 chain you will have both sprockets smaller in diameter. With this set up your speeds and RPM will remain the same. So all you would be looking for is a chain/ sprocket package in 530 with the same ratio you had with the 630. Doesn't matter if it's a 50/25, 48/24, 38/19,etc. Am I wrong?

It has everything to do with gear diameter and nothing to do with tooth count.  Pick the 530 sprocket that is the same diameter as the 630 you are replacing to maintain the same ratio, and forget about tooth count.

Sorry Andrew diameter and gear count is related.

Using a 2/1 ratio it wouldn't matter what size chain is used if the gear tooth size are the same on the front and rear it is going to be a 2/1 ratio no matter how many teeth are on the sprocket.

[Dave Voss]

There are two common methods used to calculate a chain ratio, by sprocket tooth count, and by sprocket diameter.  Each method works mathematically, but only the diameter method takes into account the physical size that may be important for the application.  For instance, the diameter of the front sprocket on a motorcycle cannot be too small or too large, otherwise clearance for the chain will not be present.

When using the sprocket diameter method to calculate chain ratios, it is important to determine the diameter correctly, as it is not the overall diameter at the tips of the teeth, but rather the diameter at the center of the chain link rollers as they engage the sprocket.  This diameter can be approximated (close enough for ratio calculations) using this equation:  Sprocket Diameter = (pitch x teeth)/'pi'.

So, the diameter of a 14-tooth 630 sprocket is (0.75" x 14) / 3.1416 = 3.34".  To change the 630 sprocket to a 530 sprocket, with the intention of retaining the same diameter, perform a reverse calculation starting with a diameter of 3.34", divide by 'pi', then divide by the pitch (0.625" for 530 sprocket) to get a result of 16.8 teeth.  This shows that a 530 sprocket with 17 teeth is the closet equivalent to a 630 sprocket with 14 teeth.

This method can also be useful when the chain clearance necessary to accommodate a smaller or larger sprocket needs to be know in advance.  For instance, if a 16-tooth 530 front sprocket is currently installed, and there is 0.25" of space between the top of the chain and the engine case, how much larger can the sprocket be?  Using the formula above, the 16-tooth sprocket diameter is 3.18", a 17-tooth sprocket would be 3.38", a 18-tooth sprocket would be 3.58", and a 19-tooth would be 3.78".

The difference between the 16-tooth and the 17-tooth sprocket diameters is 0.20", half of which will be on top, so 0.10" is needed, and that will fit without issue.  The difference between the 16-tooth and the 18-tooth sprocket diameters is 0.40", half of which is 0.20", so that will also fit, but not by much.  The difference between the 16-tooth and the 19-tooth sprocket diameters is 0.60", half of which is 0.30", so that will not fit at all.

So, when the pitch of the chain and sprockets is the same, calculating and comparing ratios by counting sprocket teeth can be easier to do, but when converting from one pitch to another, the diameter method is best to ensure that the replacement sprockets position the chain in the same relative location as before to prevent fitment issues.

[andrewk]

I think what I am reading here verifies what I said. Lets say your 630 sprockets are 50/25 (2/1), if you want a 530 chain and change to a 50/25 (2/1) 530 chain you will have both sprockets smaller in diameter. With this set up your speeds and RPM will remain the same. So all you would be looking for is a chain/ sprocket package in 530 with the same ratio you had with the 630. Doesn't matter if it's a 50/25, 48/24, 38/19,etc. Am I wrong?

It has everything to do with gear diameter and nothing to do with tooth count.  Pick the 530 sprocket that is the same diameter as the 630 you are replacing to maintain the same ratio, and forget about tooth count.

Sorry Andrew diameter and gear count is related.

Sure they are related but when comparing chains of different sizes,  tooth count is not apples to apples.  You guys are hung up on the number of teeth and forgetting that the chain links are different lengths, so it takes a different amount of teeth to achieve the same ratio.  The diameter of the gear is what determines the ratio, not the teeth.

[andrewk]

Good explanation dave voss.  +1

[turkey4me]

Could use a little input on chain conversions...

Converted the chain on a 78 750F from 630 to 530.  A lot of what I researched came from this thread

Stock sprocket set up for 630 chain is 14/43 with a 3.07 gear ratio
530 O ring chain should have the same width as 630 chain just different pitch  5/8 vs 6/8. 
As long as I don't go too big on the front sprocket this should work...  I ended up using a 530 O ring with a 15/46 sprocket combo and GR of 3.06.

I question if my is clearance is correct.  There is a fair bit of noise coming the front sprocket.  When I turn the wheel by hand there is a series of noisy clicks coming from the front sprocket.  Can't imagine how loud this would be at 5000 rpm.  Visually it looks like the chain pins are hitting the engine case.  I can insert 0.060" feeler gauge between the chain pins and engine case but that's about it.  Does this seem acceptable or have I just invented an aluminum cheese grader?

[MCRider]

IMO a 15 on the front of a 530 set up is way too small unless you're dragracing. You should run a 17 or 18 on the front with corresponding rears to get you ratio./48 same as the early Ks.

The small diameter 15 may be why its hitting the case. ITs putting the pins on a path that the 17 would avoid. Many people have done this conversion and I've never read of case interference.

I haven't done this myself, so OCICBW.

[turkey4me]

Thanks MCRider for your input.  530 15T sprocket does look pretty small. 
3.0" diameter compared to a 530 17T which is 3.4" 
I have one of each and the clearance is much better on the 17T sprocket.  When I changed it out I could see a slight amount of rubbing on the case and that's just from turning by hand....  Looks like I need a 52T rear and a 17T front.

[CB_Jeff]

Folks, some feedback on the 630 to 530 chain conversion on the '77 and '78 750's.
I recently did a 530 conversion on my K7 with a 17T gear up front and a 48T in the back.  The verdict, great in town and way too revvy on the highway.  At 55 mph in 5th gear I am running at 4k rpm and running at 65 or so has me north of 5k RPM.  While I like the in town characteristics, the highway RPM issue is a deal breaker.  That being said I am going to switch the 17 out for an 18T in the front and see how that goes.
Also, just for the record I did confirm that I am running all 5 gears and nothing is slipping.  The best way to describe the 17 / 48 combo is that it feels like I am running two - 4th gears.

[flybox1]

Folks, some feedback on the 630 to 530 chain conversion on the '77 and '78 750's.
I recently did a 530 conversion on my K7 with a 17T gear up front and a 48T in the back.  The verdict, great in town and way too revvy on the highway.  At 55 mph in 5th gear I am running at 4k rpm and running at 65 or so has me north of 5k RPM.  While I like the in town characteristics, the highway RPM issue is a deal breaker.  That being said I am going to switch the 17 out for an 18T in the front and see how that goes.
Also, just for the record I did confirm that I am running all 5 gears and nothing is slipping.  The best way to describe the 17 / 48 combo is that it feels like I am running two - 4th gears.

I'm running 17/48 530 as well, and dont see an issue with my 5000rpm 60-65mph.  Its right in the wheelhouse as far as RPM's go 

[CB_Jeff]

For comparison I recently rode another K7 that had the 530 conversion with 18T up front and 48T in the rear and was pretty effortlessly north of 75 mph in the same RPM range.  I will also be the first to admit that these speedo's are less than spot on in terms of accuracy.

[flybox1]

I will also be the first to admit that these speedo's are less than spot on in terms of accuracy.

It is well known they read 8-10% high.

[CB_Jeff]

Just ordered the 18T front, I will check back in once I have road tested it.
I put 500 miles on the 17 / 48 combo over the last three weeks and definetly like the pull on the low end, but ran into a couple of scenarios (like passing at highway speeds) where it felt a little shaky as the engine was already wound-out a bit.   
More on this later.

[flybox1]

Cool,
Also, (if you have PD carbs) be sure your accel pump is in working order, and use it (from 0 throttle position) when you need to pass 

[Airborne 82nd]

I'm running 17/48 530 as well, and dont see an issue with my 5000rpm 60-65mph.  Its right in the wheelhouse as far as RPM's go.
Fly could you say where you got the chain & sprockets also how long was the chain.
Thanks in advance

[madmtnmotors]

My recently completed "Evolution" build is sporting a 530 chain with 17/48 sprockets. The speedo is on the high side of 70mph, on its way to 75 before the tach hits 5000rpm in 5th gear. That's with a 17" 130/90 rear and 110/90-19 front. The new clutch plates must like the Bel-Ray 4T EXL! Running the 20w-50 summer blend since we will be seeing daily highs in the 90's for the next 4-1/2 months... 


Edit: 104 links seemed to be the sweet spot for my K8 with the 530 and 17/48 sprockets. 102 was too short and 106 ran out of adjustment (too long). 106 might work with 18/48 sprockets. With 19/48 sprockets I would at least start with 106 links and cut down if necessary.

[flybox1]

can't remember where I purchased them, but I know the sprockets and chain came from different vendors.
I got a 110 link EK heavy duty chain (non O/X ring)
I set my rear axle holder hash mark near the front third of the swingarm indicator marks, tightened my axle down, put on my chain, and cut it to fit where the axle was mounted. Maybe 4 links or so needed to be removed.

Strange, madmtnmotors, as I have the same sprockets, and rear wheel size, and hit 60-65@5000rpm.
My front is 100/90-19
No worries tho.  I'm happy w how it performs.  Love the 20w50 BelRay 4t EXL!!!

[tlbranth]

IMO a 15 on the front of a 530 set up is way too small unless you're dragracing. You should run a 17 or 18 on the front with corresponding rears to get you ratio./48 same as the early Ks.

The small diameter 15 may be why its hitting the case. ITs putting the pins on a path that the 17 would avoid. Many people have done this conversion and I've never read of case interference.

I haven't done this myself, so OCICBW.

I was hoping someone would bring this up. If you go below a certain number of front sprocket teeth, the chain's whipping motion will cause problems. I read about this back in the 70's so my numbers might be off but I'm pretty sure you need to be 17 teeth and up to not annoy the chain.

[CB_Jeff]

Time for my report back.  I swapped out my 17T 530 front sprocket for a 18T 530 sproket and am happy with the result... and I feel like that gearing is much closer to the stock K7 gearing than with the 17t front sprocket.  As with all things there is trade-off and that trade-off is low-end pull... with the 17t sprocket the stop light to stop light acceleration was better, but with the 18t front sproket is is like I have a true 5th gear overdrive that will pull pretty hard at 60+ mph.  I will confirm the highway speed rpms on my next ride and get back to this post with some more details.