Throttle response - sudden twist kills it

[bug138]

Howdy folks -

I'm working on getting my 94 K75 rolling after a few years sitting. Over the past 12 months, off-and-on, I've replaced the fuel tank and battery. Today I replaced the throttle cable, which was in rough shape.

I got the bike started up, and it seems pretty smooth once most of the white smoke cleared out.

One problem though - even once it's warmed up, a quick twist of the throttle kills it. Smoother twists roll up fine.

Ideas?

Also, looking for tips on what sort of tune-up type stuff I should look at doing for a bike that's been sitting a while.

[wmax351]

Could be a couple things. First, sync you idle air bleed screws.

Next, check to make sure the paint on the throttle bodies is in tact. DON'T Adjust them. If there isn't paint, you will likely need them done with a flowbench.

Third, adjust your idle mixture. It can be done by ear with a screw under the tank, in the MAF sensor. There is a good writeup on IBMWR.org.

Also, check for vacuum leaks. Check the PCV hose that runs from the plenum to the airbox.

[Rick G]

Check for air leaks at where the throttle bodies attach by using a propane torch (BBQ Lighter not lit but with gas comming out, it gets sucked through the splits and causes variations in idle speed) and a leak at the crankcase ventilation hose which is rear of the plenum chamber to the crankcase. A Z shaped hose 5/8 dia and 3" long.
The other is the Fuel Pressure Regulator may be malfunctional and not giving a rich mixture when you open the throttle.
This thread will help its 3 pages but worth the read http://k100rt.aforumfree.com/t2007-k100-rt-engine-bogs-when-you-wrench-the-throttle It is the same problem even to sitting for a year or so.

[bug138]

Thanks for the tips, guys!

The PCV hose is in shreds, so that is definitely going to get replaced.

The throttle body calibration paint is in place, so that's a plus.

I'll take a look at the MAF sensor in the airbox to see if idle needs calibration. I was just in there when I replaced the throttle cable so I know my way around.

The pressure regulator is right there too, so I might replace that for good luck, if the price is right.

Having replaced the throttle cable, the adjuster is set all the way loose. Do I need to take a look at taking some of the slack out of the cable? I still want it to return to zero when I untwist!

Some posts recommend sending the injectors to Mr. Injector for ultrasonic cleaning. This probably needs doing regardless.

[wmax351]

AFAIK, the FPR rarely goes bad, and if it does, the bike runs like crap.

You can check it: it is 36 PSI with no vacuum on the Manifold line (pull it off of the throttle bodies, and check the pressure). Suck on the manifold line, and the pressure should drop.

[frankenduck]

If you haven't really gotten out and ridden it then the plugs can get kind of fouled.  At least that's what I've found when I run them in place while tinkering with them for too long.

Go out and ride the snot out it for a while and see if that helps.  Has worked for me in the past.... it's fun too!

[wmax351]

If you haven't really gotten out and ridden it then the plugs can get kind of fouled.  At least that's what I've found when I run them in place while tinkering with them for too long.

Go out and ride the snot out it for a while and see if that helps.  Has worked for me in the past.... it's fun too!

Ahhh, the classic "Italian Tuneup"