ISC and IAC valves, how come to have both?

[szabgab]

Dear all,

Unfortunately my bike is sitting idle (sorry for the pun), as I have lost the oil through piece inside the generator cover and I fear damaging the bearings on the crankshaft by not lubricating it enough. Till I wait for a replacement (did I already mention, that it is f..ing difficult to get anything for this bike in this country?), I try to tackle other things. One ailment is the high idle, I d not seem to be able to get rid off - the bike idles at 2100-2200, no matter what I do. I do not have a vacuum leak, or I could not find it anyway, but I tried to determine, what is the issue. Whilst troubleshooting, I have realised, there are to idle speed operators, an ISC in the throttle body and IAC down below, sucking air from the secondary air filter and supplying air through that. Now, the ISC has been cleaned, so was the IAC, but it did not do anything to my idle speed, and I was just wondering, why are there two separate systems? If you look on the web, ISC or IAC are both the same thing, or at least google thinks so, so I am baffled. Before this oil piece fiasco I did test the IAC by disconnecting it, to see, if my idle changes at all, it did not. I could try to disconnect the ISC, but I am not going to start the bike as yet, so this all a bit of a theoretical exercise.... Anyway, first thing first, does anybody know, why is there a two system operation, and which sensor or valve is actually responsible for idle speed?

Thanks!

Gab

[CROSSBOLT]

Gab, you have the question of the year, I fear! This sounds like the transition from carbs to EFI. I do not know....

[szabgab]

Since last night I've investigated a bit more.  You could be right,  as there is no secondary air circle with a separate air cleaner on the DT,  but it is there on the various iterations of Xcitings.  I picked my brain,  and have realised,  that the secondary air goes to the head through a REED valve,  so that might be the emission control,  so most likely the IAC is supplying the exhaust with fresh air on an on-off basis.  I could be completely wrong though

[gwdoiron]

The Xcitings have a reed valve on the exhaust port and a control valve which allows air to pass through the reed valve.  The ECU will open the control valve whenever there could be unspent fuel in the exhaust; the back pressure when the exhaust valve shuts pulls in fresh air through the reed valve, which allows the unspent fuel in the exhaust to burn; the stock muffler does a pretty good job of muffling those secondary explosions in the exhaust pipe, but if for some reason you put an aftermarket exhaust on, it will be VERY obvious when you ease off the throttle, since the pops will be loud.

You dont say if your bike is the fuel injected version or not.   The non-EFI version has an idle speed adjustment that you can get at under the seat by removing an access door.  You need to wait for the bike to warm up then adjust it to the idle speed listed in the service manual.  The EFI models shouldn't need any adjustment, as there is an ECU controlled motor in the carburetor which controls the idle air mixutre.

[szabgab]

The Xcitings have a reed valve on the exhaust port and a control valve which allows air to pass through the reed valve.  The ECU will open the control valve whenever there could be unspent fuel in the exhaust; the back pressure when the exhaust valve shuts pulls in fresh air through the reed valve, which allows the unspent fuel in the exhaust to burn; the stock muffler does a pretty good job of muffling those secondary explosions in the exhaust pipe, but if for some reason you put an aftermarket exhaust on, it will be VERY obvious when you ease off the throttle, since the pops will be loud.

You dont say if your bike is the fuel injected version or not.   The non-EFI version has an idle speed adjustment that you can get at under the seat by removing an access door.  You need to wait for the bike to warm up then adjust it to the idle speed listed in the service manual.  The EFI models shouldn't need any adjustment, as there is an ECU controlled motor in the carburetor which controls the idle air mixutre.

HI, thanks for the info. The bike is an injected one, although I don't think, a carburetted bike has got an ISC valve. I did remove the IAC, and connected it to the battery, closes and shuts, as it should, but the ISC does f. all, I did spray it with contact cleaner, but upon connecting it to it's connector, and powering up the bike (only ignition, obviously no start) it barely clicks and does nothing to the idle speed, connected or not, whilst engine running. As I don't have access to a known functioning valve, I can not test, if this one works, or not compared to an another one. Idle is steady at 2000-2200, that is way too high, but I guess I will have to live with it till I find a working valve, that does not cost an arm and a leg