need help with gearing on banshee w/ gs engine!

[Anonymous]

For you guys that read my other post, I put an 82 gs550 motor into a yamaha banshee atv quad. anyways, the banshee uses a 520 chain, and the gs used a 530 chain, so i just kept the rear shee sprocket and front gs sprocket, and ran a 530 chain - it works fine.

But now it almost done, and i dont have any power past 3rd gear, so i need to regear!

so what should I take my sprockets too? lower in front and bigger in back right?

(by the way, when i do this, i will probably convert to a 530 rear sprocket!)

thanks alot in advance guys!
Ray

[Anonymous]

If you want to match the stock gearing of the 550, you'll need to figure rollout of the stock bike, and alter gearing of the quad to match that number, which has shorter tires.

Rollout = (tire size * 3.14159) / (large gear/small gear)

Assume the small sproket is 14, and the large is 40 for both currently(I have no idea really)
GS550 tire is 25 inches tall, the quad is 15 inches tall.
GS550 rollout: 78.5 / 2.85 = 27.54
current rollout: 47.1 / 2.85 = 16.52

To adjust, you'd either go up on the small gear(23), or down on the large gear (24), or a combo of both. That's a pretty extreme gearing change, but again, my number are made up, yours will be different.

[AOD]

go bigger in the back, maybe 1 or 2 smaller in the front. usually lowering the front sprocket can cause some problems...so that's why i suggest going rear. i think the 550's have a 15 up front...which is huge. you probably could run a 13 safe, maybe a 12.

get that ratio up high and that ATV will haul.

[Anonymous]

awesome tips guys! thanks alot!

keep them coming!

[Anonymous]

ok guys, im stuck again - what gears should i use? should i try to match a stock banshee's gear ratio, or should i try to match a stock gs550 ratio? currently my gears are 15 front, and 44 in the back, no power in 4,5,6th.

i was thinking about going 60 in the rear, and leaving the front, then changing the front if need be

do u think that will be too much? or affect ground clearance too much?
the rear sprocket for a banshee hub (normally 520 chain) converted to a 520 chain is about $55, front is about $21, so id rather play with the front after the initial regearing.......

Help
Thanks in advance

[AOD]

i think the rear might be too small. 44/15 is a 2.933 gear ratio...that's really low. my boat of a car has a 2.73 in it.

what is the stock ratio for the banshee? stock for GS550?

~Adam

[Anonymous]

What do you mean by no power? Does it not want to pull in those higher gears, or does wind out to early?
Usually, you want to match the gearing characteristics of the engine, so for you, try to match the rollout of the stock bike (the GS550). If you post what the stock gearing for the GS550 is, along with the tire height of both the GS and the quad, I'm sure one of us can do the math for you. My earlier example was outta my head, I just posted it as a 'for instance'.

[Anonymous]

problem is that i have no idea about stock gs gearing or tire size, i have only the engine with 15 tooth front sprocket!

banshee has 20" rear tires, and 14/41 gears

i have no power, meaning i start the bike, pull the cluthc and shift between forst, second and third gear fine, but once i shift into 4th, it has 'no more go', and when i punch the gas, it just doesnt pull at all, i can shift into 5, or 6th too, but no increase in power, and it usually stays at a steady 6000 rpms.....

[Anonymous]

Ok, I think I found it. If the motor is out of an 'L', it was 15/49. If it's out of an M, it's 15/50.
L Tire: 130/90-16 = 78inch circumference / 3.26 = 23.93
M Tire: 3.75 X 18 = 110/90-18 = 84inch circumference / 3.33 = 25.23

Currently: banshee has 20" rear tires, and 14/41 gears
62.8 / 2.93 = 21.43

14/36 gears will put you in between the stock gearing of the GS550 with a rollout number of
62.8 / 2.57 = 24.43 inches of rollout.

I'm sitting here staring at this knowing something's not right. If all the numbers are correct, with the gearing you have in there now, that thing should be screaming, acceleration wise, in all gears. You just won't have much top speed. (Think of riding a 10 speed). You have to take into account the huge difference in drag two skinny (comparitively) tires compared to four fat ones have however. The whole argument of matching the gearing (rollout) of the stock bike might have to thrown out the window due to this. I have to admit I'm at a loss as to which way to go. Are you certain the engine is in a good state of tune? Good compression, adjusted valves, clean and synced carbs, etc?
Anyone else have any ideas?

[Anonymous]

Jeckler, Thanks alot for hooking me up! I owe you a big one!

You are right about the gearing, it makes sense, but still theres something wrong

I think I will order the 55 tooth rear and see what happens! hopefully it will work out a little better

Yes, the engine seems fine - I cleaned out all the carbs myself, and compression is between 8-90 on all cylinders

maybe I didnt synch them? im not sure how to do that, but it turned all the main screw (the ones on top) out the exact same # of turns......

[lhanscom]

Isn't compression supposed to be over 100 somewhere?