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My simba (Project bike) an RD07 suffers from high idle speed when Hot.. It revs at about 2000 rpm mark when I stop at lights, etc.. The idle sometimes drop slowly to below 1000 and sometimes it won't.
When stationary and on gear, by letting the Clutch out while breaking, that tend to bring the idle down to normal and stays that way. Switching off and on again also brings idle down to normal.
I am not sure if diaphragms could be the factor here, air leak or else ??.. (The carbs are fairly new came off a 2002 bike that did about 7k but were not used for quite a while.. I put them in while I did some work on the bike).
Everything else seems fine.. I had them balanced during last MOT and mixture is fine..

Any thoughts on the matter before I dismantle unnecessary?

Thanks ..
 

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standard reply is

chokes
scotoiler connertion off so drawing air?

air leaks

sticking cables or linkage

mine was doen to the right carb linkage a bit stiff cleaned with carb cleaner and the ACF50 every where.. to sort

cheers

Ray
 

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Of an 2002 bike? I think those carbs (RD07A) have throttle position sensors that the RD07 do not have.
Anything in that area that's not connected the right way?

By the description it sounds like the carbs are running a bit lean, that could be caused by an air leakage.

One way of testing that is to use a spray can of starting gas

and spray around the carbs. If you have an air leak, the revs rises as the starting gas enters the combustion chambers.

//Kjell
 

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Is it hunting? What about the filter?
 

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Discussion Starter #7
Of an 2002 bike? I think those carbs (RD07A) have throttle position sensors that the RD07 do not have.
Anything in that area that's not connected the right way?

By the description it sounds like the carbs are running a bit lean, that could be caused by an air leakage.

One way of testing that is to use a spray can of starting gas

and spray around the carbs. If you have an air leak, the revs rises as the starting gas enters the combustion chambers.

//Kjell
Sorry, RD07A and all connection are fine. Bike runs really well and tick over is spot on.. until its worm and then revs up..

I am going to look for air leak, I was told WD40 is as good..
 

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Discussion Starter #8
No hunting, Filter is new.. I suspect an air leak or sticking Diaphrahms ..Will have ago at it this weekend weather permit..Thanks to all :thumbup:
 

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WD40?

I would be surprised if that also works.
WD40 is mostly oil, is it not?

Starting gas is made out of Ether and when the ether reaches the combustion chambers while the engine is running, it makes the idle speed rise for a short moment.
This is an old trick used for many years to locate any air leakage in the manifold/carburator area.

Just spray around the carbs and manifolds while the engine is running and see if the idle changes.

//Kjell
 

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WD40?

I would be surprised if that also works.
WD40 is mostly oil, is it not?


//Kjell

read it somewhere on another forum, not tried it so cant confirm if it works..

depends what the propellant is..

you ever done the old flame thrower trick with a lighter and a can of hair spray :toothy1: :nike:
 

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Hi African Simba, I wonder if you've identified the root cause of this and fixed it? My AT has exactly the same problem. Any advice is greatly appreciated...
 

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I've been having the same problem with my RD07A. I recently bought it and as it was lying up for a while I changed filters and stripped and cleaned the carbs set the pilot screws. Everything looked good but it's still the same althought the hunting problem is improved. I'm really hoping I just need to balance the carbs now, gauges are on order.
 

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I've been having the same problem with my RD07A. I recently bought it and as it was lying up for a while I changed filters and stripped and cleaned the carbs set the pilot screws. Everything looked good but it's still the same althought the hunting problem is improved. I'm really hoping I just need to balance the carbs now, gauges are on order.
I've done that. The "high rpm idling when warm" problem kinda improved, but came back after a few weeks of riding.
 

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I've done that. The "high rpm idling when warm" problem kinda improved, but came back after a few weeks of riding.
Bollox! Does it run OK other than the uneven idling then? Or are you having any other hunting/uneven acceleration?

I find sometimes it pulls fine through the revs but then other times there's a flat spot between 4-5K and then it pulls fine after that. It's not major, I don't get stumbling or backfires or anything like that, it really just feels like air leak (which I've check for) or carb imbalance.
 

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Bollox! Does it run OK other than the uneven idling then? Or are you having any other hunting/uneven acceleration?

I find sometimes it pulls fine through the revs but then other times there's a flat spot between 4-5K and then it pulls fine after that. It's not major, I don't get stumbling or backfires or anything like that, it really just feels like air leak (which I've check for) or carb imbalance.
It runs quite well other than this idling problem. There isn't any obvious hunting. I've also tune the air/fuel mixture, but it doesn't seem to help. I have not check for air leakage yet. Does air leak happen around the carb seal or the tubing connections?
 

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It runs quite well other than this idling problem. There isn't any obvious hunting. I've also tune the air/fuel mixture, but it doesn't seem to help. I have not check for air leakage yet. Does air leak happen around the carb seal or the tubing connections?
I guess it could be either, I looked for perished or split hoses and then checked for cracks in the carb intake rubbers and also made 100% sure that they were seated properly when refitting. Everything is in good condition. I might try spraying carb cleaner in or something and see if there are leaks that i missed. :sad1:
 

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Have you checked the choke?

My RD04 basically lives off road and I suffered from an ever increasing idle... After much head-scratching, I discovered that the choke "tube" (for want of a better word) was sticking (a known problem and an easy fix).

It has been mentioned many times on here before and indeed earlier in this post...

Unclip the top from the plastic tube that splits the cable and get in there with copious amounts of WD40 to rinse it out (sliding the cables up and down to free it off). I then packed mine with grease and reassembled it - works like a charm and no idle issue anymore. It is also worth cleaning and greasing the points where the choke cables enter the carbs at the same time...

Might not be the case with yours but worth a try...

Cheers

Slidey
 

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Have you checked the choke?

My RD04 basically lives off road and I suffered from an ever increasing idle... After much head-scratching, I discovered that the choke "tube" (for want of a better word) was sticking (a known problem and an easy fix).

It has been mentioned many times on here before and indeed earlier in this post...

Unclip the top from the plastic tube that splits the cable and get in there with copious amounts of WD40 to rinse it out (sliding the cables up and down to free it off). I then packed mine with grease and reassembled it - works like a charm and no idle issue anymore. It is also worth cleaning and greasing the points where the choke cables enter the carbs at the same time...

Might not be the case with yours but worth a try...

Cheers

Slidey
Thanks for the suggestion man but I'm afraid I was aware of that problem from reading around on this site and did as you say during the strip down. Cleaned out the choke on both carbs and lubed them up. The choke works fine; choke on and revs rise and then choke off the bike dies when cold.
 

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Sure sounds like a carb rubber not sealed. To find that leak i have used
isopropyl alcohol (very flamable...caution) in a spray bottle with a fine mist...which seems to be the key
for finding the small leaks. The mist is important for it to combust.

These rubbers commonly pop off from overtightening or get turned inside out and visually they may look
ok. Best just to take the airbox off again and re-seat them. The torque on the clamps is very light...barely anything at all.
 

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Just a possible update. A strange thing happened on Saturday evening when I was out and about, the bike ran almost perfectly, more responsive, no flat spot and pulled harder through the revs but then yesterday it was back to the old ways. The only difference I can see is that it was alot cooler than it has been lately on saturday evening so now I'm thinking it's running a bit rich due to worn needles. I did notice some polishing on the needles when i stripped them but didn't really think it would affect the bike that much, i suppose that's normal with a bike with over 30k miles.

So now I have ordered new needles, I'll also be replacing the choke cable guides with metal ones from rugged roads and then check for leaks and balance the carbs and hopefully I'll be laughing!

I'll let you know how it turns out ;)
 
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