Throttle Body Cleaning & Why Chains have O-Rings

While riding from Stockholm to Kolbu my motorcycle was a bit hesitant with throttle response. It felt like it had quite some lag picking up from idle or low revs. I’ve done some maintenance on it that has resolved these issues and it was interesting to see the causes for this.

One huge culprit was the chain. I’d been looking at a replacement chain in January since my last one got worn down a bit faster than I wanted from over-tightening it during my Baltic trip last year. I realized afterwards that the steady ‘thump’ I felt in my footpegs at low speeds was the chain being over-exerted. It’s still tricky to correctly set the slack on the G650X since there’s a huge difference in tension between leaning on the sidepeg and having a rider and gear on the bike.

I’ve always been surprised by the huge prices chain and sprocket sets command, even on eBay. You could easily pay 200 euros for a full set. I thought I’d do a little experiment and got the cheapest reputable-brand chain I could find, a standard DID 520 chain with no O-rings for about 30 euros, about half of what one with O-rings goes for.

Above you can see the result of that after about 2500 km. The 2 days of rain and dusty roads to Norway really took its toll, where the chain went from acceptable slack to being extremely loose once per day! When I took it off to replace it with a better, new one, I could bend it a full 180 degrees where it’s supposed to be able to bend at most 10 degrees or so.

So that makes it pretty clear: a more expensive O-ring, X-ring or FB-ring chain is definitely worth the money since chains wear extremely fast without them, even more in wet and dirty conditions.

Another part of the bike I worked on, was the throttle body. This bike is fuel-injected and I’ve never really worked much on a system like that before. It was an interesting contrast compared to the 4 or 5 carburated engines I’ve worked on the past weeks.

A fuel injected throttle body is much simpler than a carburetor to clean and dissassemble, the complexity sits instead in the ECU that controls the mixture. Fuel is pumped into a pressurized fuel line to the injector, a valve that opens and squirts fuel electronically. The throttle body is where the fuel and air are mixed and it contains just an air valve and sensor that are controlled by the throttle, as well as an electronic ‘Idle Actuator’ which is a valve that automatically keeps the idle RPM steady by allowing small amounts of air to bypass the main throttle valve.

I had read about the idle Actuator needing cleaning on a post on AdvRider. Mine was not nearly as problematic as his, but it was definitely time to clean it.

I opened the air filter box as well and it was a bit dusty and had obviously been wet a bit inside, despite being cleaned only 4-5 months ago or so. The result was a lot of black grime in the actuator that came off easily.

All in all there was not so much to it:
You run through the usual, tedious procedure of removing all panels and the airbox. Then it’s easiest to unplug the Injector and Idle Actuator, and to unscrew the Throttle Position Sensor as well as remove the throttle cable. If you the unclip the injector you can unscrew and take out the throttle body easily. The only really tricky part is if you want to remove the injector for cleaning: the fuel line might still be pressurized, resulting in fuel splashing around if you unplug the injector. It’s best to have it sit a day and not run it before doing this.
Since there’s way less mechanical parts that could fail or be put together incorrectly compared to a carburetor, it’s relatively risk-free. You have to make sure to take care of the injector seals considering the pressure that comes onto them, mine got loose and was mounted incorrectly at first.