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bog off idle

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I have an 86 xr250r with a carb off of an xl250r (has accel. pump) I dont know the jet sizes, havent gotten that far yet. It seems to run well, start well and all that, but has a real bad bog when you whack open the throttle off idle. If you hold it open long enough it will die, but it only does it from throttle all the way closed and the rpm's down. If you open the throttle a little bit slower, it wont do it. I notice it mostly on jump landings and when sitting still reving the bike. I need a good idea of where to start, I'm hoping I can get this carb to work on this bike, as it is in good shape.

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i'd say ur slow jet is too small. bump it up a size, ctake carb apart and make sure it is all clean orifices and all.

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i'd say ur slow jet is too small. bump it up a size, ctake carb apart and make sure it is all clean orifices and all.

The slow jet is for idle only, and will have no effect.

WOT bog is either way too small of a main jet, but most likely the accelerator pump is too lean. Not knowing that carb it's hard to reccomend a specific option, but generally, putting in a small leak jet, a fresh accelerator pump diaphram, and adjusting the linkage, will cure the problem.

Since when did Honda put a pumper carb on ANY XR or XRL?

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hey krannie, if this guy is having a dead spot bog when he cracks off idle wouldnt that be more of a slow jet deal? im still new to this jetting/carb stuff i to am trying to get educated. thanks i have an 86 xr250 and it does the same dang thing as original posters. my jet sizes are 135/40. needle 4th position, screw is 1.5 turns. 50-60 degs. and 0-1000 sealevel

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hey krannie, if this guy is having a dead spot bog when he cracks off idle wouldnt that be more of a slow jet deal? im still new to this jetting/carb stuff i to am trying to get educated. thanks i have an 86 xr250 and it does the same dang thing as original posters. my jet sizes are 135/40. needle 4th position, screw is 1.5 turns. 50-60 degs. and 0-1000 sealevel

Pilot jet is for IDLE ONLY. It is not changing fuel once the vacuum goes up, like all the other jets. Granted, if you pilot is waaaay off, it will have an effect, but it won't idle either, so.....

If he 'cracks' the throttle vs 'WOT', then that is a different problem.

As soon as the throttle moves, the needle moves out of the needle jet, and that would be the first thing to address: raise or lower the needle all the way to see if change occurs.

To define a solution, we need to first define the problem:

- year make model bike AND CARB

- existing jets: main, needle, pilot, leak

- condition of carb: no varnishing? pliable apump diaphram? apump nozzle not clogged?

- when does the problem occur: throttle position related (jets)

- when does the problem occur: throttle opening speed related (apump)

- RPMs are irrelevant at this stage.

Answer most or all of those questions and we can solve anything.

And again, The XLR's and XRL's never had a apump carb, to my knowledge.

In fact, some of them have the dreaded CV carbs, which are useless.

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Pilot jet is for IDLE ONLY. It is not changing fuel once the vacuum goes up, like all the other jets. Granted, if you pilot is waaaay off, it will have an effect, but it won't idle either, so.....

If he 'cracks' the throttle vs 'WOT', then that is a different problem.

As soon as the throttle moves, the needle moves out of the needle jet, and that would be the first thing to address: raise or lower the needle all the way to see if change occurs.

To define a solution, we need to first define the problem:

- year make model bike AND CARB

- existing jets: main, needle, pilot, leak

- condition of carb: no varnishing? pliable apump diaphram? apump nozzle not clogged?

- when does the problem occur: throttle position related (jets)

- when does the problem occur: throttle opening speed related (apump)

- RPMs are irrelevant at this stage.

Answer most or all of those questions and we can solve anything.

1986 xr250r, keihin carb (guessing its stock)

135 main, 40 slow, needle#? but its on 2nd clip from top position

carb seems to be in good working condition, however sometimes the slide gets stuck.

offf of idle, bad flat spot, wiull die. if held too long. rolling on works good. smokes alil smells of gas. intakes all look real good.

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I have an 86 xr250r with a carb off of an xl250r (has accel. pump) I dont know the jet sizes, havent gotten that far yet. It seems to run well, start well and all that, but has a real bad bog when you whack open the throttle off idle. If you hold it open long enough it will die, but it only does it from throttle all the way closed and the rpm's down. If you open the throttle a little bit slower, it wont do it. I notice it mostly on jump landings and when sitting still reving the bike. I need a good idea of where to start, I'm hoping I can get this carb to work on this bike, as it is in good shape.

So why did you change carbs? Did it run well before?

You HAVE to dissassemble the carb and know exactly whats in it and what works. You have to test the accelerator pump.

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