1986 250R rear sprocket tooth count (quick question)

[Dave8338]

As the title mentions. What was the standard tooth count for the rear sprocket? There is a 39 tooth on it and wasn't sure if it was original (looks to be) or if someone at some point changed it out. This is on my little project trike so stock anything, really doesn't apply. Also, anybody know off the top of their head, what the largest tooth count available is? Looking for clearance on the front of the swinger. My little idler set up is getting tiring to change out, twice a year.

I'm upping the front on the 185/200S engine to a 13-tooth so I'm looking for a few numbers to run the math on.


Thanks


Dave

[manbearpig]

13/39 stock gearing

[3wheelrider]

39 is stock (85-86 250R) for the rear. Not sure why you would consider a bigger one the rear though really?
As for the 13 on the front of a 185/200- You wont be able to run a case saver. You will lose alot of power you need. I woulnt put anything more than 12 on the front no matter whats on the rear. Change the rear sprocket size (to smaller) instead -if you want more speed. (Helps with rear clearance from chain to ground too)

[Dave8338]

THANKS guys ! 13/39 is the starting point.

As for the front sprocket and case saver. Yep, know I'll have to ditch that though I'll make a new set up.

As for the "loss of power", that is EXACTLY why I need to know the stock setup. I'll keep the ratio the same. A little math involved but really quite simple. As long as I keep it in the window of what I have now (love the pull of the 11/39 setup I have) I'll lose nothing. Just need to gain clearance over the front pivot of the swinger so I can run a chain slider and ditch the idler gear that runs under load. Wears them out in a few months ~

[3wheelrider]

I assumed you had the typical 41tooth or bigger on the rear. Didnt know about the custom swinger either. I can see your reasoning now.

[Dave8338]

Not a problem. It is a bit of a odd ball, to say the least.

So currently, my sprocket ratio is 3.55:1 using the 11 front and stock 39 250R rear.
If I go to a 12 front and a 41 rear, I'll be at 3.42:1 /Not bad but I think I'm going to need all the height I can get. With a 13 front and a 42 rear (the largest I can find without fitting a custom setup, the ratio will be at 3.23:1 In effect, actually increasing my potential ground speed though this thing is plenty fast enough as it is. Also I'm running some Douglas rears with Hole shots so the rotating mass is less than either a stock 200S or a stock 200x.

Not too concerned in the power category.

[3wheelrider]

You lost me from the beginning-lol. I thought you had a 250R & a 185S. And were sprocket sizes on both machines.lol

[Dave8338]

Well... I ordered the 42T for the rear. I'm going to wait until I get it on the the bike and then do a remeasure. If the 13T front isn't needed, it can stay on the shelf. I have a 12T from the original 185S engine that I can use to get a measurement, if needed.

Thanks again guys.


Dave

[Dave8338]

UPDATE:

Got the 42T rear sprocket yesterday and went out to measure things up. Looks like I will be splitting hairs with the 12T / 42T combo when the suspension is unloaded. With me on the machine (230 lbs) there "appears" to be enough clearance over the front pivot to be able to run a modded slider. Now to order up a slider and see what all will have to be changed.

Final ratio will be 3.50:1 or only a .05 difference from what I have on it now.