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#1 m mccray

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Posted 20 December 2017 - 08:55 PM

If you are not going to use a sidecar rig for going off road,Would it be feasable to change the rear drive gear ratio to gain some top end speed? Bike is operated in california on mostly flat roads? Any advice would be greatly appreciated.

#2 Russ Noe

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Posted 21 December 2017 - 12:03 PM

I would expect the answer depends on what bike and year you have. This question was forefront in the late 1990s with Ural rigs.
Higher gearing led to crankshaft failures of the 650 engines. 750cc engines are more forgiving.

If you are asking about newer Urals with fuel injected engines, I would ask IMWA about the gearing.
These bikes are systems, and changing gearing can have unexpected effects elsewhere.
~RN

#3 m mccray

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Posted 21 December 2017 - 12:39 PM

RN the bike is 1974? 650 Dneper

#4 Russ Noe

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Posted 22 December 2017 - 11:18 AM

Hey Dnepr Experts:
Please assist m mccoy here.
My limited Dnepr knowledge is not useful for this gearing subject.
~RN

#5 3 bike mike

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Posted 22 December 2017 - 11:26 AM

many different gears available , look on ebay.de

#6 Garbage Bear

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Posted 22 December 2017 - 11:29 AM

... and my limited English lessons don't allows me to understand the asking problems. What is a ' rig'? Can anyone explain more what is the request ? :-):-):-)
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#7 3 bike mike

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Posted 22 December 2017 - 11:35 AM

A rig is motorcycle and sidecar. The question is ,,, if the bike is only going to be used on good tarmac roads can the final drive gear be changed for a different ratio to increase top speed.  Hope that helps

#8 Garbage Bear

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Posted 22 December 2017 - 11:59 AM

Tarmac roads. Ok. I experienced a lot. So. If the bike wil be used with sidecar is necessary to have sidecar rear drive ratio. I experienced also solo gear drive ratio combined with an easy Izh sidecar. Only driver and no additional weight added can be satisfied. But no big hills to claim.
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#9 Vance Blosser

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Posted 22 December 2017 - 03:01 PM

Part of the issue faced is air resistance of the sidecar which increases geometrically with higher speed. Although you would think you would gain more top end in practice the engine is now running too slow to develop the power needed to overcome the sidecar drag so any gains are  minimized. This will vary by model, level of tune, etc. and in some cases a gain may be obtained, but in most the overall performance will suffer. I tried both ratios in my first 650 and got little to no gain in top speed, just a lower rpm when cruising. Your mileage may vary.

#10 Peter Williams

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Posted 22 December 2017 - 10:02 PM

At one point in time there were 4.11 and 4.22 FD ratios available. They were very expensive and I haven't seen a set for sale in over 15 years. I wouldn't use a 3.89 FD ratio on an outfit unless you lived in the Netherlands and didn't travel to any place with hills. A MT-10-36 puts out a massive 36hp and won't be happy going up any incline with a 3.89 FD, especially if carrying any load.




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