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Main Area => General GS500 Discussion => Topic started by: Grizzi on May 20, 2004, 03:27:26 PM

Title: RPM problems
Post by: Grizzi on May 20, 2004, 03:27:26 PM
I have a big problem.

If i am parked and in neutral and i then crank the handlebar a bit , my rpm thends to go from the normal 1200 rpms in idle, to 4000 rmp and it doesn't drop. The only way i can get i to drop is to turn it off and then start it again.

I have checked the handlebar and it's not stuck, but something tells me that it might be the carps, can any1 confirme this and maybe tell me what to do cause it's really anoying.
Title: RPM problems
Post by: Ed_in_Az on May 20, 2004, 03:33:52 PM
Your throttle cable may be pinched or it may need to be lubricated.
Title: RPM problems
Post by: dgyver on May 20, 2004, 03:34:06 PM
If you are moving the handlebars and the rpms change, better check the throttle cable for being loose at the carbs or binding somewhere. Check the choke cable as well.
Title: RPM problems
Post by: Kerry on May 20, 2004, 03:57:39 PM
If the choke cable is "too tight" (usually because of how it's routed) you can tell by watching the choke lever.  When I mounted my handlebar risers I had to re-route both the choke and throttle cables.  Before I rerouted the choke cable I could watch the choke lever "turn itself on" as I turned the bar ... to the left, I think.

In the stock configuration both cables are routed from the handlebar grip to the front of the bike (below the headlight) and then around the fork tubes and back underneath the fuel tank.  I rerouted the cables so they don't go around the fork tubes anymore - they describe a curve in the air from the handlebar grip to directly under the fuel tank.

(Note: If the bike is totally stock and "nothing" has been done to it, you technically shouldn't need to re-route either cable.)

My bet is that your throttle cable is incorrectly adjusted.  It needs more slack!  Try the adjuster on the throttle grip end of the cable first.  if you run out of adjustment there, pull the fuel tank and goof around with the adjustment at the other end of the cable - where it attaches to the carburetor assembly.
Title: RPM problems
Post by: aslam on May 20, 2004, 04:14:35 PM
Of course this seem like symptoms of the infamous lean condition.  Maybe carbs check for air leaks on intake.  Also I had a similar problem like this that was fixed by adjusting valves.

ASLAM.
Title: RPM problems
Post by: dorian chapman on May 20, 2004, 04:15:09 PM
This is not related to your problem.  But I have a similar concern.  I've started to notice since it has started to get warmer here, that once the bike is warmed up and I've been out riding for 15 mins or so, If i crank the throttle at a stop sign or stop light, while in neutral (or just have the clutch in) The RPM's will shoot up to 4 or 5 etc. but they take a long time to drop back down to idle. Like much longer than when i was riding around in the winter months.  I jsut wanted to know if this is normal or not. It's a 2003 GS, with 2000 km's on it
Title: RPM problems
Post by: Grizzi on May 21, 2004, 01:18:20 AM
I dont think u guys really got what the problem was.

My problem is similar to dorin champmans

Qoute:

This is not related to your problem. But I have a similar concern. I've started to notice since it has started to get warmer here, that once the bike is warmed up and I've been out riding for 15 mins or so, If i crank the throttle at a stop sign or stop light, while in neutral (or just have the clutch in) The RPM's will shoot up to 4 or 5 etc. but they take a long time to drop back down to idle. Like much longer than when i was riding around in the winter months. I jsut wanted to know if this is normal or not. It's a 2003 GS, with 2000 km's on it
Title: RPM problems
Post by: Jasco on May 21, 2004, 04:04:58 AM
If you turn the handlebars back straight will the rpm's drop to normal?
Title: Re: RPM problems
Post by: MarkusN on May 21, 2004, 04:55:47 AM
Quote from: GrizziI dont think u guys really got what the problem was.

My problem is similar to dorin champmans
so by "crank the handlebar" you meant "twist the throttle"? Then it sounds like false air being sucked through the intake mainfolds. Check those for tightness.
Title: RPM problems
Post by: Grizzi on May 21, 2004, 12:33:26 PM
Yes i meant twist the throttle, if i do this with the clutch pulled or in neutral the rpm's will rise to 4000 and stay there.
Title: RPM problems
Post by: Briggs on May 21, 2004, 12:49:03 PM
I would say that you probably bent a rod or snapped your crank shaft. Thats what mine was doing when my rpms would raise up for no reason.







j/k
Title: RPM problems
Post by: BadBatzMaru on May 21, 2004, 12:57:06 PM
Quote from: BriggsI would say that you probably bent a rod or snapped your crank shaft. Thats what mine was doing when my rpms would raise up for no reason.







j/k
:mrgreen: mean :mrgreen:  hahahha...  :thumb:  :thumb:

vacuum leak maybe? or could be that your idle is set to high.. ie calibrated for cooler weather and not when the engine was fully warmed up... but since you say it idles ok then a blip on the throttle sends it to 4k and slow to come back its probably vacuum related. try the WD40 trick. Spray wd40 around suspect area, ie carb boots etc, and see if the RPMs rise.. if so, the you've got a vacuum leak
Title: RPM problems
Post by: dorian chapman on May 21, 2004, 01:01:08 PM
Mine RPM's don't stay at 4000, they just take longer to drop than I remeber.  Afterwards the bike will idle at 1.5  I did have it tuned up in January, so maybe they set it up for the colder weather ?!
Title: RPM problems
Post by: GRU on May 21, 2004, 01:04:36 PM
i had the same problem after i rejetted my carbs with biger jets....i fixed it when i tightend the air filter to the carbs and when i set the air/fuel mix screw to 3 turns out
Title: RPM problems
Post by: richard on May 21, 2004, 07:41:03 PM
Based on a lot of time troubleshootoing a similar problem,
sounds like it's probably one of two things:

1.  your throttle cable *might* be too tight.  If it's just tight enough, it can cause idle to hang, even though when you first start it it idles normal.  I had this prob after reinstalling my carbs once.  As Kerry said, check your adjuster screw on the throttle on the handlebars... easiest thing to check, actually.

2.  your bike is "lean" for some reason.  Common reaons include:  carbs need to be cleaned, leaky boots on carbs/intake/air box, incorrect valve adjustment.

My bike had this problem and it was fixed by adjusting the valves.  I'd recommend first checking the throttle cable tightness, but that's probably not what it is, just an easy thing to check.  If that's not it (likely), then pull your carbs and clean them.  it doesn't take too long, and everyone should take them apart sometime, just to see whats inside. ;-)  While you have the bike that far apart, check the valve clearances... another good thing to learn to do.

If those things don't fix it, I'll be pretty surprised... and we can try something different.

While you're at it, of course, keep a sharp eye open for cracks, loose seals, etc.
Title: Re: RPM problems
Post by: CRXDrew on May 12, 2006, 11:33:46 PM
I'm having the same problem as the orginal poster. (Yes I know this is a very old post)

Any other suggestions?

-I have checked my throttle, there is slack.
-I have also checked the boots for tears etc.
-I have also cleaned the carbs a few times.
-choke is not sticking

On stock jets. Could rejetting to 40 on the pilots help?
Title: Re: RPM problems
Post by: scratch on May 13, 2006, 08:33:26 AM
Do the revs increase when you turn the bars to the right?
Title: Re: RPM problems
Post by: CRXDrew on May 13, 2006, 09:55:13 AM
Quote from: scratch on May 13, 2006, 08:33:26 AM
Do the revs increase when you turn the bars to the right?

nope, plenty of slack in the throttle cable
Title: Re: RPM problems
Post by: scratch on May 14, 2006, 12:41:53 AM
Are the clamps around the carb boots and air boots tight enough?
Title: Re: RPM problems
Post by: corndog67 on May 14, 2006, 01:14:27 PM
Clean and lube your cables with a cable lube device that clamps on to the end of the cable.  Make sure the cables aren't pulling tight when you  move the bars from stop to stop.  If they are pulling tight and changing the rpms when you turn the bars, you might have to re-route them.  You don't want kinks, and you don't want them to open the slides at an inoportune time. 
Title: Re: RPM problems
Post by: CRXDrew on May 14, 2006, 03:17:25 PM
all boots tight and sealed. No rips and I tried the wd40 trick (one of the first things I tried with my experience with bad idles in Hondas)

Cables definitely have slack. (another common problem in Hondas that I see people do ALL the dang time)


I'm thinking its a lean problem. I have 40 pilots coming my way. I have replaced mains 142.5's and stock pilots. With the mixture screws about 5 turns out it is better but the top end is way to rich. with the pilots i should be alot better off. I'll report back with results.
Title: Re: RPM problems
Post by: scratch on May 14, 2006, 04:10:41 PM
Quote from: CRXDrew on May 14, 2006, 03:17:25 PM
I'm thinking its a lean problem.
It's definitely a lean problem, and we're narrowing it down.

Quote from: CRXDrew on May 14, 2006, 03:17:25 PM
I have 40 pilots coming my way.  I have replaced mains 142.5's and stock pilots.
I'm confused, you contradicted yourself here.  Please clarify.

One thing for sure is that 142.5 mains are way too rich for the stock pipe.

What you got right now is, too lean down low, and too rich on top.
Title: Re: RPM problems
Post by: CRXDrew on May 14, 2006, 04:18:35 PM
Yea, I found the mains easily in stock at a local shop but couldn't find the pilots anywhere.

I ordered the pilots and and put the new mains in with my K&N big airbox replacement filter. I also plan on welding up a new muffler. I can probably get something universal style (with an appropriate diameter) and weld it up all cool with extra mandrel bends I have sitting around from all the automotive exhaust work I do.

So to sum it up... it runs like a champ up top but idle is funky.

K&N box replacement
142.5
37.5 (stock)
1 washer
soon to have opened up exhaust