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Author Topic: Machine faltering carbs?  (Read 1849 times)

Offline jamo

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Machine faltering carbs?
« on: September 28, 2018, 05:52:50 AM »
Hi All
I am at my wits end. My 1983 R65LS. Was running rough like running to higher gear at to lower speed no matter what gear it was in.
I had all the parts to overhaul the carbs. So set about the work. I had the carbs balanced and timing set by a professional he also fitted new pushed tubes and rubbers at the same time.  Twistgrip and all cables have been changed.
The machine runs lovely at tickover and at full throttle. But at a constant speed at 30/40 mph,the thing if faltering  it make riding in traffic and bends a little interesting. Without pulling carbs to pieces again any ideas where I go next?

Offline Barry

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Re: Machine faltering carbs?
« Reply #1 on: September 28, 2018, 06:49:24 AM »
At a steady 30/40 mph the carbs are still running substantially on the idle circuit so although you don't want to get into them again the idle passages and jets are where I'd look assuming valve clearances and plugs/ignition timing have been checked.

Depends who it was of course but having the carbs balanced by a professional is not an absolute guarantee of it been done correctly.
« Last Edit: September 28, 2018, 06:51:58 AM by bhodgson »
Barry Cheshire, England 79 R45

Offline Bob_Roller

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Re: Machine faltering carbs?
« Reply #2 on: September 28, 2018, 01:55:50 PM »
Are there rubber caps or some other means of closing off the ports on the carbs where the manometer, gauge hoses connect ??
'81 R65
'82 R65 LS
'84 R65 LS
'87 Moto Guzzi V65 Lario
'02 R1150R
Riding all year long since 1993 .
I'll give up my R65, when they pry my cold dead hands from the handlebars !!!!!

Offline mrclubike

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Re: Machine faltering carbs?
« Reply #3 on: September 28, 2018, 09:10:37 PM »
Yes they are threaded so you can run a screw into them
1982 R65 running tubeless Snowflakes
2004 R1150R

Offline Barry

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Re: Machine faltering carbs?
« Reply #4 on: September 29, 2018, 02:41:51 PM »
I once left those screws out after balancing.

It didn't run too badly but I could tell something was not quite right at low speeds.  If the the screws are missing they are:

M3.5 x 0.6  part number 13 11 1 259 869.
Washers are 13 11 1 259 870.
« Last Edit: September 29, 2018, 02:42:57 PM by bhodgson »
Barry Cheshire, England 79 R45

Offline tunnelrider

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Re: Machine faltering carbs?
« Reply #5 on: September 29, 2018, 03:13:15 PM »
Quote
assuming valve clearances and plugs/ignition timing have been checked.

2nd that - I had an annoying stumbling around those speeds before, bought a timing light to check and turned out the timing was out. 
'85 Black R65 / '74 GT185 / '83 Pantah 500 / '01 DRZ400 dirt only

Offline jamo

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Re: Machine faltering carbs?
« Reply #6 on: October 01, 2018, 03:02:01 AM »
I am now buying a timing light and vacuum gauges.
Also an over site on my part did not check the jets supplied to me were the same as I removed. So it is off with the carbs again.

Offline Barry

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Re: Machine faltering carbs?
« Reply #7 on: October 01, 2018, 06:35:44 AM »
Have you considered making a vacuum balancer. Just a length of plastic tube, some ATF or other thin liquid and a means of mounting it.





Barry Cheshire, England 79 R45

Offline jamo

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Machine faltering carbs?
« Reply #8 on: September 28, 2018, 05:51:22 AM »
Hi All
I am at my wits end. My 983 R65LS. Was running rough like running to higher gear at to lower speed no matter what gear it was in.
I had all the parts to overhaul the carbs. So set about the work. I had the carbs balanced and timing set by a professional he also fitted new pushed tubes and rubbers at the same time.  Twistgrip and all cables have been changed.
The machine runs lovely at tickover and at full throttle. But at a constant speed at 30/40 mph,the thing if faltering  it make riding in traffic and bends a little interesting. Without pulling carbs to pieces again any ideas where I go next?

Offline Matt Chapter

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Re: Machine faltering carbs?
« Reply #9 on: October 02, 2018, 09:41:56 AM »
Sounds like carbs, so it's probably electrical.  ;D

Honestly I would go for a full tune up if you haven't already.  Perhaps there's a sticking choke mechanism, or there's a tear in the carb diaphragms?
'04 R1150 RT ~41000 miles
'86 R65 / '84 motor ~72000 miles. SS lines, Spiegler rotor, Progressive monoshock, Keihan silencers, a piece of Pichler fairing.
'76 CB400F ~26000 miles. non-runner!

Offline jamo

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Re: Machine faltering carbs?
« Reply #10 on: October 02, 2018, 10:18:57 AM »
All new jets and diaphs in the carbs. Only thing done to carb bodies was an ultrasonic clean. I do not know about the drillings