To Bog or Not To Bog? Is QuickShot The Answer?

If you have a liquid cooled Honda CRF you either suffer from the "bog" or you know someone who does. While the bog, off idle hesitation, seems to be more pervasive on the CRF250X and CRF250R the big bore thumpers aren't immune. California editions of the CRF250X and CRF450X seem to suffer more than the standard models.

So, what actually causes the off-idle hesitation in the first place? There's a lot of theories and I'm not exactly sure which theory is correct. It's possible the cause is a combination of several of the popular theories. If you're interested in reading through some of these theories do a search for "bog" or "quickshot" in our CRF's Only message board and you'll find lots of reading. Theories aside, the bottom line is when the accelerator pump doesn't deliver the correct amount of fuel quickly enough off idle you'll experience the bog.

Obviously, this problem is pervasive enough to have caught Boyesen's attention and interest. They have developed what they believe is the answer to this problem with their QuickShot Accelerator Pump Cover. Essentially Boyesen's cover replaces the stock cover. As you can see the covers are very similar at first glance. However, a closer look reveals the Boyesen's cover has two holes at the top versus one hole just above center. Each as a similar hole at center. One of the more common theories on what the Boyesen QuickShot does has to do with the two holes at the top. This theory suggests that air gets trapped during normal operation. The stocker doesn't have the ability to purge this trapped air. The QuickShot, with the dual exit holes, purges the trapped air and hence delivers a steady stream of fuel right off idle. Forget all the theories. All any of us care about is whether or not it works.

Installation

Installing the cover could not be easier or quicker. Once you get to the carb that is! The cover itself is held in place by three phillips head screws. So, removing the stock cover with the QuickShot is quick and easy. The hard part is getting to the carb. Boyesen suggests completely removing the carb. To speed installation, I removed the sub-frame, shock, and the carb from the intake manifold. This allowed me enough space to access the pump cover.

Safety Tips

When you are working on your bike, especially when involving the tank or carb, make sure you are in a well ventilated area where there is the absence of any source of spark or flame. In this case, make sure the petcock is off, remove the fuel line and drain into an appropriate container, and then drain the carb. When removing the cover additional fuel will leak out. Be prepared with an appropriate container to catch this fuel.

Before removing the cover, I placed a shop towel below the carb to catch any screws, spring, D-ring, O-ring, or the diaphragm that might fall. Once the cover is removed make sure you set aside the D-ring, O-ring, diaphragm, and spring. Place the small D-ring in the QuickShot cover with the flat side facing the cover. This puts the round side facing the float bowl. Place the O-ring in its place in the carb. There will likely be some fuel still on the carb and this will help hold the O-ring in place.

Stock Pump Cover

Install the diaphragm in the carb with the machined pin facing the QuickShot cover. Place the spring in the center of the cover and install the cover. DO NOT OVER TIGHTEN THE SCREWS. The carb material is very soft and you could easily strip the threads if you over tighten them.

QuickShot Pump Cover

Not so quick, we're not done yet. It's important to check the timing screw for proper adjustment. Mine was spot on but I've heard that others are set from the factory incorrectly. In some cases, others have changed there's in an attempt to chase away the bog. It's best to remove the throttle pulley cover and check this with the supplied tool.

Stock Versus QuickShot Pump Cover

Once the cover is installed and timing screw set correctly, put the fuel line back on and test for fuel leaks. If there are no leaks, proceed to finish installation by putting the carb back on the intake manifold, install the shock, sub-frame, and seat. Now the fun part, testing!

Testing

I had no problem starting the CRF450R. Three quick blips of the throttle with the choke on and the motor came to life as usual. Once it was properly warmed up, I realized I had neglected to adjust my fuel screw richer by 1/4 to 1/2 turn. Mine definitely needed this adjustment. I went the full 1/2 out and that smoothed out the idle and increased response off throttle.

Geared up now I took it out for the first time. Even though my '05 CRF450R didn't suffer from the bog, I immediately noticed greater response and increased power off idle. The CRF450R is not lacking in power. It's a wheelie machine that eats rear tires for breakfast. Even still the Boyesen Accelerator Pump Cover added to that power and decrease hesitation while increasing the "grin factor". I have to admit that I wasn't expecting this much increase in performance and responsiveness from this cover. I actually felt my bike was about as good as it gets. I was pleasantly surprise to find that was not the case.

Conclusion

I wish we had a CRF in our stable that was suffering from the bog to test how well this eliminates that condition. Lacking that installing this on a well jetted CRF450R, I was still very impressed with the responsiveness and the added power down low. I came into this review thinking there wasn't much room for improvement. The Boyesen QuickShot proved me wrong.

Review by: CRF's Only Staff, May 2005
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