Fast Idle Woes Continue

[Tor]

Hi all. Did the required dismantling, cleaning and lubing of the CSM after it stuck, but it soon turned out this hasn't done the job. The idle only comes down to normal ~1200 rpm after more than half an hour of running and immediately snaps back to 16-1700 after even a short stop, so my question is: Can anything be done to the sealed part of the unit to make it work properly, or do I have to spend big $$$ on a new one? 

 

The only thing I can think of is to take it out and test it in hot/boiling water, dunk it in penetrating liquid, and that's about it. Meanwhile I'm going to arrest the lever it pushes on. Which will give me regular idle from cold.

 

I did find that almost no coolant escaped when removing the hoses. There was coolant in the body and lower hose, but not the upper. Engine was cold at the time. An issue?

[Snowbird]

Maybe an airlock stopping the coolant getting to csm, I'm guessing as I know sod about 9ers.

This post was last modified: 19-07-2023, 11:23 PM by Snowbird.

[Catteeclan]

You could run the bike with the tank up enough to feel the pipes warning, checking circulation.

Another thing to check would be the thermostat, if it's stuck open or opening early it'll effect the idle operation.

Could still be a dodgy CSM.  

[Tor]

I'm pretty sure the CSM is failed, as the engine comes to temperature as it should - 10-15 minutes of running, no overheating. I'm just holding out for some way to make the unit work again.

[Catteeclan]

I'm pretty sure the CSM is failed, as the engine comes to temperature as it should - 10-15 minutes of running, no overheating. I'm just holding out for some way to make the unit work again.

:good:

[fixitsan]

You could run the bike with the tank up enough to feel the pipes warning, checking circulation.

 

 

+1 :good:

 

The water pipes to and from the CSM are small bore, the pipes can degrade internally, but also the spigots they connect to have a small bore too and might be blocked ?

[Tor]

Yeah, it seems worthwhile to make sure there's proper circulation.

[leehenty]

Are you sure the pipe are on correctly at the radiator end, its



possible to reverse the overflow and the one to the CSM on the nipples just under the pressure cap

[Tor]

Thanks Lee. Can you share some insight as to which one is which?

[leehenty]

Top spigot goes to overflow/ expansion tank, lower spigot should go to CSM

[Tor]

Thanks much! I've felt that it's always taken a little while to come down to normal idle, so with a bit of luck the hoses will have been swapped. But the way it is now, I'm probably looking at a soon-to-be defunct unit anyways.

[Boosh]

I've not had this problem on my 20,000 mile, 2002 but, I did notice that the tickover got a little slower when the engine was getting plenty hot - beyond where the gauge routinely sits.

 

I decided to remove the spring that holds the throttle arrangement against the CSM operating plunger (this was many years ago, so excuse the vagueness, but I can photo the spring I'm talking about - it's safely stored in the garage).

 

My bike, without this spring, starts fine, but the engine needs some controlling on the throttle for a short while, to stop it stalling.  But, I'm a fair-weather rider, so colder days may be much more, er, demanding, to prevent a stall!  But this is only as I remember cold-starting bikes before fuel injection became common.

 

Also, setting my bike apart from most others, I have my tickover set to 1300 to 1400 revs (Yamaha say 1200 to 1300, I think), because I find it reduces the engine braking a little, making for smoother town progress.  Well, for me, anyway.

 

What I'm thinking is, can you remove the CSM, by-passing (joining together) the coolant pipes, so you can still use/enjoy the bike whist tinkering/fettling the CSM?  I've never done this, I should add.

 

Is it not the case that the fast idle is as keen to lift the tickover as it is, so as to get extra exhaust gas through the catalysts; to get them up to operating temperature quickly, so reducing emissions?  I have an idea the cats work best at around 600C, and they are a long way from the engine, so getting them hot from a cold start isn't going to be quick without the engine putting some extra gas (fast tickover) through them.

 

If you've replaced your exhausts with aftermarket, then the cats aren't there anyway, so the feature, to the extent it works in normal use, is partly redundant anyway, I suspect.

 

Happy to be corrected of course!  I'm an infrequent user of this bike, so not a regular visitor to this site!  I've recently rejoined with a new ID, as my sign-on details and email address had all been lost/changed from my original joining in 2006.

This post was last modified: 25-07-2023, 11:45 AM by Boosh.

[leehenty]

You could, with a bit of ingenuity, make the fast idle manual like a choke. The CSM only moves a slide that gives extra air into the engine

[Tor]

And we have a win! The rad-to-CSM hose had clogged itself up with sedimentation where it bends inside the extra shroud, having stood garaged for long periods of its life. Cleared it out, hose is good inside. Now I get 1200 rpm idle as the needle starts moving off the pin. Hoorah

[dapleb]

Great find!

[Studley Ramrod]

:badgerrock:

[Johnners]

I've got a slightly different problem. CSM works fine from cold to normal temps, but if the engine gets hot, such as in queuing traffic, the idle speed rises again. It has also puked a bit of coolant when very hot. Any thoughts? I'm wondering if the pressure cap spring is a bit tired.

[fixitsan]

I've got a slightly different problem. CSM works fine from cold to normal temps, but if the engine gets hot, such as in queuing traffic, the idle speed rises again. It has also puked a bit of coolant when very hot. Any thoughts? I'm wondering if the pressure cap spring is a bit tired.

Is the fan thermostat functioning ?

On most bikes the fan comes on before you get into the red zone, but mine originally came on only when it was very hot.

 

If you're not sure, just let it idle and wait to see if it comes on before the temperature gauge reads maximum

[Johnners]

Yep, fan works OK, idle speed goes back up to around 1700 once temp needle approaches halfway. Below that, everything works as it should (1700 on cold start and drops to 1100 once warmed up). Bit confused.

[Trevini]

Could be mixture running too lean… that could be caused by co level set too low, faulty temp sensor forcing ecu to lean off the mixture and probably a few other things as well. 

 

Regarding the co settings, it has been known for one or both cylinders to “reset” to 0 or a minus number when trying to start if the battery is very low. I’d look at that first and then go for the engine and ambient temp sensors.