Hanging Idle

A

Apsley Max

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Apr 1, 2007
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Location
peterborough.on.ca
Hi folks.I recently got a 98 srx 700 with 12000km on it that I traded a Vmax4 less engine for,I thought I got a good deal.It was in need of a powervalve and cable so I replaced these and also cleaned carbs.Carbs are all set to specs on here for a 98.Everything went great until I fired it up.The idle seems to hang around 3000rpm's sometimes a bit higher after reving it up a bit,then I have to flip choke on and off to get it to come down.It seems if I set idle for @ 1800 it hangs worse than if I set idle down to @1600rpm.The carbs are great and fuel screws are at 1-1/8, freeplay on throttle is good.I did a search on here and found some interesting stuff.It looks like some others have had this same issue,but no real reasons why this is happening.Should I be looking at replacing crank seals? I've never ridin' this thing before and it may go away after some run time?Any help would be greatly appreciated.Thanks Steve C
 
Apsley Max said:
Hi folks.I recently got a 98 srx 700 with 12000km on it that I traded a Vmax4 less engine for,I thought I got a good deal.It was in need of a powervalve and cable so I replaced these and also cleaned carbs.Carbs are all set to specs on here for a 98.Everything went great until I fired it up.The idle seems to hang around 3000rpm's sometimes a bit higher after reving it up a bit,then I have to flip choke on and off to get it to come down.It seems if I set idle for @ 1800 it hangs worse than if I set idle down to @1600rpm.The carbs are great and fuel screws are at 1-1/8, freeplay on throttle is good.I did a search on here and found some interesting stuff.It looks like some others have had this same issue,but no real reasons why this is happening.Should I be looking at replacing crank seals? I've never ridin' this thing before and it may go away after some run time?Any help would be greatly appreciated.Thanks Steve C
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If they are actually at 1-1/8, then try 1-1/4 not 2. Go in 1/8 turn increments.
 
That would really suck having to take the carbs off 7 times to do 1/8 turn adjustments till he found out he likes them at 2.

Yamaha set these fuel screws lean from the factory for emissions. Throttle response on low end is much better with them turned out that far and no more idle hang.
 
tomseal6 said:
That would really suck having to take the carbs off 7 times to do 1/8 turn adjustments till he found out he likes them at 2.

Yamaha set these fuel screws lean from the factory for emissions. Throttle response on low end is much better with them turned out that far and no more idle hang.
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Really? They were that far off? On the vipers they were only lean by 1/8 turn. Are all SRX's happier at 2 turns or just some? I didn't think Yamaha could be that far off.
 
Spec is 1.5 on my sx-r 700 and it would barely run, after several tries I ended up at 1 7/8 and it runs great there.Those things sure are sensitive, theres not alot of adjustment between too lean and then too rich!
 
and get fuel screw adjusters,save you down time removing carbs 7 times.If opened to 2 .25 turns and still hangs..go to next pilot size up.I just picked up 45 pilots for the SRX because hanging idle problem from last season.
 
ryanryan said:
Really? They were that far off? On the vipers they were only lean by 1/8 turn. Are all SRX's happier at 2 turns or just some? I didn't think Yamaha could be that far off.
Click to expand...
vipers have bigger pilots than SRX's
 
Many Vipers have this problem too-- I tried turning fuel screws out 2, then 2-1/4 turns, then went up a size on pilots with no luck. Here's something Scott- Betheviper explained to me. It may or may not be the answer to your problem, but it was the only thing that worked for me.

-I wrote:
"And lastly, still have that stupid high idle hang, and don't understand a real good fix. Some are saying it's the HC's? Already tried 47.5 pilots and didn't help much. I'm gonna try them again and see what happens. Just don't want it to be gurgling. Either that or just turn the idle down. I don't get why my plugs don't look lean if it's running lean at idle?"

-Betheviper wrote:
"Put the 45pilots back in, its not that the sled is lean at idle, what is going on is that the pipe is making it idle high. Pipes have more than one rpm where the resonance works out to be efficent. It happens to be on this sled that the stock pipe is also efficent at around 2-2500 when the pipe is hot. so what happens is you ride fast or hard, keeping the pipe hot, then come to a stop and let off the gas. As the engine passes down through that rpm, it is so efficient there that it doesnt need alot of fuel to stay there. the reason flipping the choke makes the rpms drop is it is adding enough fuel to cool the pipe at the same time it is flooding the motor, making less power and allowing the engine to drop rpm.

The only fix is to idle the sled to 12-1500, usually works."
 
daman said:
Right but this is on a stock sled/pipe machine..i think BTV was talking after market mod sleds?
Click to expand...

...........

Millinocket Rocket said:
Many Vipers have this problem too-- I tried turning fuel screws out 2, then 2-1/4 turns, then went up a size on pilots with no luck. Here's something Scott- Betheviper explained to me. It may or may not be the answer to your problem, but it was the only thing that worked for me.

-I wrote:
"And lastly, still have that stupid high idle hang, and don't understand a real good fix. Some are saying it's the HC's? Already tried 47.5 pilots and didn't help much. I'm gonna try them again and see what happens. Just don't want it to be gurgling. Either that or just turn the idle down. I don't get why my plugs don't look lean if it's running lean at idle?"

-Betheviper wrote:
"Put the 45pilots back in, its not that the sled is lean at idle, what is going on is that the pipe is making it idle high. Pipes have more than one rpm where the resonance works out to be efficent. It happens to be on this sled that the stock pipe is also efficent at around 2-2500 when the pipe is hot. so what happens is you ride fast or hard, keeping the pipe hot, then come to a stop and let off the gas. As the engine passes down through that rpm, it is so efficient there that it doesnt need alot of fuel to stay there. the reason flipping the choke makes the rpms drop is it is adding enough fuel to cool the pipe at the same time it is flooding the motor, making less power and allowing the engine to drop rpm.

The only fix is to idle the sled to 12-1500, usually works."
Click to expand...
 
Plus you need to factor in the carb slides are getting sloppier.... fuel is getting worse...engines are getting looser...seals are starting to leak some... all this adds into the hi idle hang...
 
i've got pipes on mine and i cant get it to stop idle hang .it wants to idle at 2500 rpm. so thats what it does. if i try to lower idle it would puke after a while on idle. It dosnt bother me one bit to have it idle that high. the sled absolutly rips ***!
 
i got an idea for pulling the carbs off... my sled still doesn't run right but i had to adjust my air screw and took the carbs off and it took me probably 15 minutes to take off adjust and put on, from now on i just turn the carbs in there boots and i can reach the screw with a long screwdriver, im not sure how it is with newer sleds or the viper/srx, but my 88 exciter seems to work fine and same me about 14 minutes turning carbs sideways... dont have to even unhook anything
 
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