Unstable rpm when drivin downhill

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May 4, 2006 | 09:30 AM

hd1952

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Stage II

Joined: May 2006

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Unstable rpm when drivin downhill

I have a custom buildt bike with an 88 evo and a 103 cui engine with rev tec top. s&s g carburator. When i drive downhill or on flat road and try to keep a low rpm on the engine it jumps like it`s running on kangoro petrol. I don`t have this problem when i turn the gas handle to cruising speed.

Does anybody have any suggestions?

Kindly

Mr. Hansen
From Norway

http://img67.imageshack.us/img67/5364/9967478728wk.jpg

May 6, 2006 | 12:06 AM

pococj

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Joined: Dec 2004

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From: Texas! Ya mean there's someplace else?

RE: Unstable rpm when drivin downhill

What gear(s) are you in and what speed(s) are you going when this happens?

May 6, 2006 | 03:11 PM

hd1952

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Stage II

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RE: Unstable rpm when drivin downhill

The gearbox is Sputhe 5 gear. It happens when i drive in low rpm on 3-4 or 5 gear and try to keep a low speed about 20-40 km/h.

May 6, 2006 | 09:38 PM

pococj

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Joined: Dec 2004

Posts: 11,068

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From: Texas! Ya mean there's someplace else?

RE: Unstable rpm when drivin downhill

I think you're running too low an engine rpm for the speed you're going. Drop a gear at that low a speed, and see if that cures it. Hard on the main bearings, too.

Jun 15, 2006 | 07:06 AM

BIGHUS

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RE: Unstable rpm when drivin downhill

Id have to agree with poco, sounds like your lugging the tranny! Does it have a tach? Optimal RPM for any gear is between 2800-3300 RPM. 40 km/hr is only 25 mph, you shouldnt be out of 2nd gear at that speed! Dont lug your tranny dude, bad bad things will happen!