Yet another gearing question

[1980mcneil]

Want to make the K5 into a real crawler. We have some very tight single track here in Washington and I'm trying to avoid lots of clutch work. If I could knock first gear down a third or half that would be perfect for crawling. And I could do most of my trail work in second or third. I pretty much never use fifth.  Especially at the speed it's meant for.  So I won't be loosing top end for what I do.
Without modifications. What's the smallest front, and largest rear sprocket I can run? ( That would give the desired effect 1/3-1/2 of stock speed)

BTW. Already have the heaviest powerdynamo fly.  PSP2 pipe and Reed spacer.

[Foxx4Beaver]

14-52 would probably work well. What are currently running?.

[1980mcneil]

It's stock.
I looked on a chart and looks like 14-52 would go from 3.38 to 3.71.
Seems like a 10% difference.  I think I'm trying for closer to 33%
Do you know the lowest front I can run without mods or rubbing?  Largest rear?
Of course I don't really know what I'm talking about.  Just using this chart

https://www.google.com/search?q=sprocket+ratio&oq=sprocket+ratio&aqs=chrome..69i57.10067j0j4&client=ms-android-att-us&sourceid=chrome-mobile&ie=UTF-8#imgrc=FSeyeJMaB88yiM:

Looks like a 4.58 would give me the desired result.
So a 12-55 or 13-59. If that's even possible or I'm using the chart correctly

[Foxx4Beaver]

You could go to 13 on the front...but watch your case!!...there's several controversial threads on here about running 13T fronts allowing the chain to tear up the engine case. My bike will never see a 13. There's a member on here that says he modifies the case a bit so there's no issue...but again, that's entirely up to you.

[1980mcneil]

Looks like I would need a 63-64 on the rear to get the results I'm looking for.  Is that doable? 

[Foxx4Beaver]

oh man...you'd probably have to do away with the rear chain guide, or modify it for such a bigger sprocket. That's if you can even get a rear that big for the K5...anything's possible.

[1980mcneil]

Yeah.  I don't want to modify :/  don't want to rub on the front either.
So it sounds like the answer will be the 14 on front, and whatever the largest rear I can run.  I'm also going to an 18" rim.  Maybe I could run a slightly lower sidewall to get closer to my objective.
I'll do some more research on a 13 up front

[Foxx4Beaver]

there's a few members you can PM for suggestions...zz3gmc, alward25, GREENKAW24.

[KXDINO]

the old wheelie king doug domokos use to use a huge back sprocket on a early 80s kx , so check that out , i would get a custom one made , i had one done for a different model that they didnt make one for ,they done it in alloy.

[1980mcneil]

Don't think I'll go custom.
I've done some more research.  Hoping I can run a 13 up front, 52 or larger in back.  18" wheel possibly smaller overall diameter.

Couple other things I've come across in my searching
1. 14oz stealthy fly weight.  Will it work with the MZB/powerdynamo?

2.  Heard of using up to 4 exhaust copper crush gaskets to help smooth power?

[alward25]

If you use the Power D ignition you don't need a flywheel weight.  The Steahly will not work anyway.  Use a reed spacer to smooth out the power.  I ran 14/50 in the woods with a Power D 38oz flywheel and a 140/80/18 IRC M5B.  I did not run the spacer but I am a little crazier in the woods than some.  Bike was a tractor in the Oregon Coast range.

[zz3gmc]

Ive tried 49,50 and 51t rear sprockets and finally settled on a 14/51 combo. I race enduros and trail ride my 500. I had a 14oz Steahly which worked well but during its current rebuild Im installing a PD ignition. The 50 worked well but the 51 let me pull taller gears and smoothed the power delivery.

[wierdo]

hava look at the what the short trackers are using. I don't know what you mob in the usa call them,  aussies call them solos ( 500 cc single speed). I done some pit work for a friend who rode solos those guys have some gear setups, boxes full of cogs sprockets and chains.   

[1980mcneil]

Couple things alward25.
The powerdynamo website says my flywheel is 35oz or 2.1 lbs.  I've heard the stock Flywheel is 2.6lbs plus 14oz for the steahly = around 3.5lbs.
A stealhy on the powerdynamo would be about 3lbs
So still not as good as an effect as the stocker with the fww.
The PD and stock Flywheel look pretty d**n similar. Reason why they won't work?  Is the PD wider, using up more of the room under the cover?

Does a 13 front rub with a normal size chain?
I would like to run 13/51. But I will do 14/51 if I have too,. WhTs the largest that can be run on back without mods? If I can't run a 13 up front, maybe I could do a 52 or three on the back.
I don't know that I'll go all crazy with ultra-low gearing. I'm just more interested in knowing the limits without modification, just so I know what's possible.

[alward25]

What is not being considered is what the Power D is doing better than the stock ignition, creating a magneto effect.  There is more mass behind the flywheel using the Power D.  It is like a flywheel weight without the weight.  Power D recently changed the flywheel design, It was a 38oz now it is 35oz.  More weight out on the crank can also cause the bearings to prematurely wear.  The stock flywheel weighs 41 oz. But there is almost no mass behind it so there is almost nothing to create the same effect.  Running a 13t front sprocket will also increase the chance of wearing on your cases.  Lose the weight, use a reed spacer if you want to mellow the engine.  The 500 will lug way down better than any other 2T, using the Power D of course.