Jump to content
Sign in to follow this  

Lean vs. Rich bog

Recommended Posts

Hi, is there a simple way to tell if you have a lean vs. rich bog? I'm still trying to dial in the FCR35mm on my KLX.

My WR250F has zero bog, (after working on it long and hard) and a strong blasting squirt of around .8 seconds. The KLX with it's FCR 35mm (very different carb, but still a pumper) has a very wimpy spray/squirt that lasts almost 5 seconds. They might pump out the same amount of gas, but do so quite differently.

I'm just wondering if I'm rich due to the loooooooooooong spray. It's pretty wimpy though, so I'm guessing no. There's no leak jet on these carbs, so it makes tuning the squirt difficult. On the pump arm there is no screw to adjust - just a couple of tabs that you bend. Bending full open or full closed doesn't seem to be making a huge difference.

I've tried everything I can think of with the 35mm and can't seem to de-bog the bike. Bummed. :applause:

Thanks for any help.

bp

Share this post


Link to post
Share on other sites

I've checked for rich or lean in similar situations in 2 ways. If the bike will run decent with the choke on give it a try. You about have to have a choke with a mid position for that to work though. The other thing that has been helpfull is to turn the fuel screw one way quite a bit and test the response. By getiing less bog one way you know which way to go.

Share this post


Link to post
Share on other sites

The carb doesn't have a choke, so that's out. I can check the fuel screw test next time. Burned, I haven't had a chance to "take it out" for a real ride - just around the block and fooling around, so I'm not sure. If it gets better with warmer temps on the engine, what would that indicate?

Thanks!

Bill

Share this post


Link to post
Share on other sites

Rich is a bog, lean is more of a hesitation.. If it gets better when it's warm then it's lean because a warm engine requires less fuel.. Look at the spark plug too, if it's white or bright white then it's lean.. If it's dark like brown to black it's rich.. Perfect would be somewhere in between like a tan or very light brown color plug.. :applause:

Share this post


Link to post
Share on other sites

Just to add to what Burned said, if it gets worse as the engine gets hot it is rich, if it gets better as the engine gets hot it is lean. Now I only owe you a couple Burned :applause:

Share this post


Link to post
Share on other sites
Just to add to what Burned said, if it gets worse as the engine gets hot it is rich, if it gets better as the engine gets hot it is lean. Now I only owe you a couple Burned :cry:

:applause::bonk::cry::cry:

Share this post


Link to post
Share on other sites

I suspect that this is an AP issue or possibly a pilot issue. The bike runs great after getting past the 1/8-1/4 throttle phase. The bog is only when whacking open the throttle. If I snap it to 1/2 it will probably go. If I whack it wide open it's like hitting the kill switch. :applause: If I snap the throttle with the revs above 1/8-1/4, it goes fine.

The reason I thought it might be rich is because of the loooooong AP squirt time. (around 5 sec., but a very small spray.)

I'm not sure what good checking the plug would do. The MJ and needle seem to be OK. Running the bike under normal conditions, the bike runs OK. if I check the plug then, wouldn't it reflect how the engine is running in the upper rpm's?

I just HAVE to get rid of the bog issue, cause I will seriously hurt myself unless I get it sorted out.

Thanks! :bonk:

Share this post


Link to post
Share on other sites

Burned, that's what I thought, but there is no way to get it shorter. No leak jet and the very crude adjustment on the AP cam/arm thing is not affecting the "length" of the squirt. The AP diaphram is OK. I tried a boyesen quickshot and it was similar, although I think it might have made it a bit longer.

So, no leak jet. Bogus external control of pump timing, Unclogged AP circuit with a very long and very thin spray.

Any new ideas? How can I make the spray stronger and shorter?

Thanks as always!

Bill

Share this post


Link to post
Share on other sites

yep,you use a 3/32" radio control air plane wheel collar on the pump shaft.you can limit the travel this way by adjusting the gap between the collar and pump body.

this is how we did it long before the fcr2 came about.

squeezing or spreading the fork on the linkage just controls when the squirt starts.

Share this post


Link to post
Share on other sites

Burned, thanks. Can you elaborate a bit more or can you direct me to a link that would describe this more in detail? I'm no carb expert and I'm not quite sure what you are suggesting and how to accomplish it.

As to the squirt length, I've been thinking about it. There's a finite amount of gas in the AP, right? So an unobstructed pathway to the squirt nozzle would yeild a short strong spray. An obstructed pathway would yeild a longer spray with less volume. Both squirts sending the same amount of gas into the venturi. (Just like a garden hose under pressure with a partially opened nozzle and a fully opened nozzle.)The thing is, when I shoot carb cleaner thru the passageway, I get a strong spray now. It was initially clogged, but now it seems to be clear. That make me think that the AP is not working right. It's not putting enough "pressure" to send the gas out in a strong squirt.

Would this mod you're talking about accomplish that? Thanks again. I know I really appreciate your expertise and I think everyone else does as well.

Cheers,

bp

Share this post


Link to post
Share on other sites

Mmaxed & Burned - THANKS! Now that made sense. I can try that. Hopefully that will take care of it. Question though, the mod says that if you drain your carb, the AP won't pump unless you move the collar and prime it again. Is that right? Seems like a PITA.

bp

Share this post


Link to post
Share on other sites

Yeah with the mod the pump can't move the diaphram through the full stroke so it may not prime. Once it's primed it doesn't seem to be a big deal.

Share this post


Link to post
Share on other sites

Also, there may be diaphragms available that have a longer rivet on the end. I know there are for the newer FCR's. I wonder if the newer ones fit the older FCR.

This has the same effect as the Taffy mod (by limiting pump travel), but may be a bit more sano. The drawback is that they are a fixed length, and you'd have to purchase a bunch of different ones, whereas with the Taffy mod it is infinitely adjustable.

Share this post


Link to post
Share on other sites
Mmaxed & Burned - THANKS! Now that made sense. I can try that. Hopefully that will take care of it. Question though, the mod says that if you drain your carb, the AP won't pump unless you move the collar and prime it again. Is that right? Seems like a PITA.

bp

its not a issue unless you try to limit it below 1 second.

Share this post


Link to post
Share on other sites
its not a issue unless you try to limit it below 1 second.

Cool! Because although Barton's diaphram solution would be slick, it would also be an expensive experiment. The diaphrams are around $25 apiece. :applause:

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×