Boyesen QS 2, 3, or not at all

[mrgem]

Been reading a number of old posts on the WR450 "Bog." There seems to be some difference of opinion on the best way to prevent it -- but those using the 2 types of Boyesen accelerator pump covers (Quick Shot 2 and 3) seem to like them and generally agree that they cure the bogging that occurs when the throttle is opened quickly. I've not put much time on my 2003, but during a test ride in a driving snowstorm today, the bike bogged badly when the throttle was snapped open. 

 

I'm not convinced the Boyesen covers are the ultimate solution, but I like the idea of an adjustable leak jet -- like the one on the QS 3. 

 

Any testimonials as to how useful that feature might be -- or would you suggest I forget about the QS and look for some other cure (tying the pump lever to the spring, etc)? The Boyesen covers are pricey - but smoother throttle response is something you don't want to compromise on.

 

TIA

[yz133rider]

I bought the quickshot 3 and never used it, if your interested in it id sell you it for a good bit off retail. Let me know.

[mrgem]

I bought the quickshot 3 and never used it, if your interested in it id sell you it for a good bit off retail. Let me know.

 

I'll PM you...

[FORMA MOTO]

The QS does not solve the problem!

 

It can't.

 

The problem is in the linkage, not the diaphragm cover.

 

Billlllllions of posts on the subject.

 

https://www.thumpertalk.com/topic/1070702-yz450f-bog/

Edited February 23, 2014 by TheKoolAidMadeMeSick

[mrgem]

The QS does not solve the problem!

 

It can't.

 

The problem is in the linkage, not the diaphragm cover.

 

Billlllllions of posts on the subject.

 

https://www.thumpertalk.com/topic/1070702-yz450f-bog/

Interesting. Yes, saw many posts that swore the pump lever to spring connection was the fix. Also saw many that said the O-ring fix was the ultimate. Others said replacement of the cover worked for them. 

[beezer]

I bet your bike bogged because of the temperature.  Opening up the fuel screw would help.

 

When we ride in the winter I always do that or if it's real cold I run a bigger pilot jet.

 

I always run an adjustable leak jet and fuel screw on all my WR's.

[mrgem]

I bet your bike bogged because of the temperature.  Opening up the fuel screw would help.

 

When we ride in the winter I always do that or if it's real cold I run a bigger pilot jet.

 

I always run an adjustable leak jet and fuel screw on all my WR's.

LOL No doubt the air temp could have had an impact. As I said in my original post, it was snowing hard and about 30 degrees. 

 

I definitely think that fattening the pilot circuit might help with initial throttle roll on response. Just paid my dealer a bunch of money to rebuild and re-jet and adjust to compensate for the fact that I have ditched my FMF Titanium and gone back to the stock exhaust and he told me he fiddled with the PC and the jet alot before getting it to reasonably behave.

 

But this thing just fell flat on its face whenever I would go from the pilot or midrange circuit to WOT abruptly. I mean, it just died for a half second and then lit up. That kind of throttle control can get you in trouble...

 

I have one of those externally-adjustable fuel screws that I'll be adding next time the carb comes off- and that should help, as we typically ride from about 7500 to 13,000 feet in a single day.

 

I know volumes have been written here about misbehaving fuel systems and I respect everyone's views. You guys have forgotten more about WRs in the last 10 minutes than I know now. This bike is new to me and I'm looking at the whole body of knowledge and experience from you guys before I come up with the ultimate solution.

 

Thanks!

Edited February 23, 2014 by mrgem

[William1]

1) You cannot go from idle to WOT without a bog unless you have a very high idle speed.

2) A properly set up AP works wonders. See the sticky. Very little money needs to spent, unless you want to.

[mrgem]

1) You cannot go from idle to WOT without a bog unless you have a very high idle speed.

2) A properly set up AP works wonders. See the sticky. Very little money needs to spent, unless you want to.

William. First, thanks for weighing in on this. As I said, you guys are a font of knowledge on these bikes. I've got a ton of stuff to learn.

 

I read through your sticky article several times. I also read a couple of dozen other posts on this site and others on the subject. You and Kool Aid, who is also very knowlegable, are in agreement about the AP being the root cause. 

 

That said, does it seem to you that the Boyesen covers are a waste? The idea of an externally adjustable leak jet seems like it might be worthwhile -- even if the cover otherwise had no real benefit. But I really don't want to invest in one if there are no real advantages.

 

Thanks again for the feedback.

[William1]

Well.... if a major change to the AP was needed due to a design flaw, you'd think the major manufactures would demand it. Honda sort of did with a push Vs pull actuation mechanisim in the AP and they have exclusive use of it.

 

An adjustable leak jet, while handy, is not something many riders ever actually change. Thy find a setting and it stays there forever.

 

Few big bore (400cc and above) even need a leak jet at all rather they need every drop an AP can deliver.

 

I suggest first, confirm the AP timing is set EXACTLY per the book. If you have a leak jet, try a smaller on, like a 40. Do the oring mod or safety wire (make sure the linkage does not bind) or better still, install a stiffer AP link spring.

 

The covers will not make it worse. They do cost money. I have one (it was a freebie) on my WR250F. I last adjusted it in 2011, I think. All my other bikes are just properly adjusted.

[beezer]

 

 

An adjustable leak jet, while handy, is not something many riders ever actually change. Thy find a setting and it stays there forever.

 

 

          I agree.  But finding that sweet spot can be a giant suck particularly on the 450.  Taking off the float bowl 11 times is no fun.  It took me 5 minutes in the backyard with a screwdriver to get it right.

 

          Both my 250 and 450 are where I set them initially.  The fuel screw I change all the time.  The R & D flex screw is the one to get.

[mrgem]

 

Well.... if a major change to the AP was needed due to a design flaw, you'd think the major manufactures would demand it. Honda sort of did with a push Vs pull actuation mechanisim in the AP and they have exclusive use of it.

 

An adjustable leak jet, while handy, is not something many riders ever actually change. Thy find a setting and it stays there forever.

 

Few big bore (400cc and above) even need a leak jet at all rather they need every drop an AP can deliver.

 

I suggest first, confirm the AP timing is set EXACTLY per the book. If you have a leak jet, try a smaller on, like a 40. Do the oring mod or safety wire (make sure the linkage does not bind) or better still, install a stiffer AP link spring.

 

The covers will not make it worse. They do cost money. I have one (it was a freebie) on my WR250F. I last adjusted it in 2011, I think. All my other bikes are just properly adjusted.

 

Thanks for the insights. I am humbled every time I get a response here. Seems this is largely a best-guess, then trial and error process. 

 

My situation is somewhat unique in that it is not uncommon for me to go through a 2-4k change in elevation (and its attendant change in air temp) during a single day of riding. I'll start riding in 70 degree weather at 9k and find myself in snow and 35 degrees an hour later.

 

Funny thing is, I also own a DR-z400 that has an FCR39 on it. It needed some work when I first bought the bike, so I took it to Eddie Cisneros. He set it up for the altitude riding I do and I haven't had to touch it since. That bike has been over Mosquito Pass -- more than 13k -- and ridden around Denver (less than 6k). Never misses a beat. I really was spoiled by that experience.

 

So...It sounds like I ought to do the safewire on the AP linkage and a stronger spring first. 

 

Thanks again for the great advice. 

[William1]

As Beezer says, leak jet (and th AP for that matter) once set, is 99% of the time a forget, unless it needs repair. Fuel screws need adjust several times a year if not more often if the air density changes a lot where you ride.

 

The best fix is the stiffer spring for the AP. The cheapo fix is the safety wire (but you have to test to ensure no binding). You do not do both.

 

 

If the AP timing screw has been fiddled with and you are not positive where the OEM settign was, take the time to so through the steps to get it EXACTLY correct. Then if you change it in the future, keep excellent notes.

[grayracer513]

The Boyesen cover is only intended to correct one particular problem, that of refilling the accelerator pump well quickly to support a quick second or successive use of the AP.  In some situations where the OEM AP check valves aren't working well, they can be useful, but for the most part, they don't resolve any throttle response problems at all.  

 

The safety wire mod is a straight-up caveman approach to the problem.  The O-ring mod is a cheap way to temporarily do what the linkage spring replacement does permanently.  Time the pump according to the manual, get the carb tuned right, and go from there.