Throttle bog at low RPM

[The Snowman]

I'm having a little issue with my CBR. Short of getting a new bike (as I KNOW some will suggest, since we're all smart-asses here)

I get a low-rpm bog between 2K and 3K. I thought it might be something in the fuel system, so I ran a full 16oz. can of Seafoam through one tankfull of gas with no change.

I've also cleaned my air filters (I have a Factory Air Box Plus jet kit installed, which requires the modification of the air box to accommodate their dual foam filters. They're cleaned just like you would a dirty-bike's filters.) Same thing, no results.

Looking for other things to try, short of tearing the carbs apart. I'm going to check the plugs next for fouling.

Any other suggestions? (no, I'm not getting a new bike anytime soon)

[bigred875]

never heard of the seafoam stuff...i've always used the chevron/techron stuff...

bad gas? Are you filling up at the same station? what octane do you use?

[highsider]

Is it very specifically in that RPM range, or does it vary some?

If its that specific, I'd be looking for something in the ignition system rather than the fuel system.....

[The Snowman]

Is it very specifically in that RPM range, or does it vary some?

If its that specific, I'd be looking for something in the ignition system rather than the fuel system.....

It's around that point and goes away after about 3K. It sounds like the bike is being fuel-starved. (like the older bikes that were running out on the main gas tank and needed to manually bne switched to reserve [like mine]).

For Red: Sea Foam Info

I tried Techron originally and it didn't work.

I tend to use 87 octane gas and usually from the same location. (yes, it's a Cumby's I usually go to) It's run great since I bought it last June. Think I should try higher octane gas with more detergent? (like Shell?)

[Paul_E_D]

Take the carbs off and clean out the pilot jets with dental floss and carb cleaner.

This is the FIRST thing to try. Other troubleshooting is a waste of time til this is done IMO.

[Degsy]

Take the carbs off and clean out the pilot jets with dental floss and carb cleaner.

This is the FIRST thing to try. Other troubleshooting is a waste of time til this is done IMO.

Fer shizzle. Pilot jets Chuck. Paul is spot-on.

[bigred875]

It's around that point and goes away after about 3K. It sounds like the bike is being fuel-starved. (like the older bikes that were running out on the main gas tank and needed to manually bne switched to reserve [like mine]).

For Red: Sea Foam Info

I tried Techron originally and it didn't work.

I tend to use 87 octane gas and usually from the same location. (yes, it's a Cumby's I usually go to) It's run great since I bought it last June. Think I should try higher octane gas with more detergent? (like Shell?)

i would try a different "brand name" station....they could have gotten a bad batch...

maybe a higher octance....the ethonal is doing funny things to some vehicles....my friend with an f150 has to put in 89 now because 87 makes it knock and ping like crazy.

[The Snowman]

then I'll be paying someone to do it for me.

I'll take wheels off, but to f**k with something as critical as the carbs is WAY beyond what I can do.

[LuvDog]

ditto the clean the jets comments.

[Paul_E_D]

This is dead easy with nothing the fuck up. On a streetbike it can be a wrestling match just to get the carbs off though... especially a Honda!

[The Snowman]

This is dead easy with nothing the fuck up. On a streetbike it can be a wrestling match just to get the carbs off though... especially a Honda!

I was close this past weekend. I had the tank and top half of the air box off. Close, but no cigar. I'd still like to get a look at my plugs to see if there's any fouling before I commit to doing any carb work.

[Paul_E_D]

They're not fouled. You've been riding the bike for years, why would they suddenly foul? No reason. Plus, fouled plugs wouldn't run well at higher rpms either.

If you got that far, just go for it. Unhook the cables and pull the rak out. Take the bowls off the bottom, and remove the brass jet that has a slot for a flatblade screwdriver. Clean as above, replace and reassemble the mess.

[The Snowman]

They're not fouled. You've been riding the bike for years, why would they suddenly foul? No reason. Plus, fouled plugs wouldn't run well at higher rpms either.

True. I put them in back in December and have put about 4K on it since.

If you got that far, just go for it. Unhook the cables and pull the rak out. Take the bowls off the bottom, and remove the brass jet that has a slot for a flatblade screwdriver. Clean as above, replace and reassemble the mess.

It's called fear of completely fucking the thing up. Last time I messed with a carburetor, it was on a single-carb quad and I ended up having to bring it to a dealership to fix what I had screwed up. I'd rather pay someone I trust to look at it.

[Wishbone]

get a new...damn you beat me to it

jk chuck

if you want once again i will offer my help to work on your bike, and what the hell you might learn something

[TLRMan]

They're not fouled. You've been riding the bike for years, why would they suddenly foul? No reason. Plus, fouled plugs wouldn't run well at higher rpms either.

If you got that far, just go for it. Unhook the cables and pull the rak out. Take the bowls off the bottom, and remove the brass jet that has a slot for a flatblade screwdriver. Clean as above, replace and reassemble the mess.

Some main jets have slots too.....

[The Snowman]

I had Degsy tear into the carbs. He cleaned all the mains jets, the pilot jets, the float bowls, and the floats.

The problem still exists, IMO. Degs said he thought he didn't see a problem, but it's definitely different from what it was a few weeks ago.

So, what next? The ignition system? The plugs aren't fouled. Spark leak? Wires? Coils?

OY!!!

[Josephd14]

I'm gonna say it's electrical, If it was fuel or air problem it would bog all the way through, and worse at High RPM's then low.. I guess you should start at the ignition.. Pull out the walled nad start replacing parts, I'm sure there are way to test it and maybe eliminate some choices, maybe someone else can chime in that knows more then I do about the ignition system on a bike..

[JeffL]

Check your output voltage from the stator and rectifier? I know my old pig used to be really picky on how it ran with a low battery, and especially when the rectifier melted itself.

[TLRMan]

Just for shits and grins, raise the needles up a notch.

If it runs well WFO then I wouldn't think it would be ignition, because that's when you need the voltage at the coils to light a leaner mix.

In any case, if someone just came to me and said it bogged right around those rpms, I would suspect lean, and go after the needle/needle jet.

Since you said you never had a problem, and then all of a sudden it starts, and if the carbs check out OK..(did he check fuel level in the bowls?), I would look at other things...If You just recently replaced the airfilter with a different brand, would put up a flag. I would next do a leak down/check valve lash, just to make sure conditions are correct in the cylinders, and while I was at it, I would double check cam alignment, and the cam chain tensioner. Just some food for thought.

[beet]

Mark Chucks like Oddball on the dirty dozen, he just rides um he don't fix um man!

[The Snowman]

Mark Chucks like Oddball on the dirty dozen, he just rides um he don't fix um man!

Yeah, if I touched it, I'd have to buy a new one.

[The Snowman]

BTW, it looks like it's starting to work itself out. After I cleaned and reoiled the foam air filters (the bike has a Factory Air Box Plus kit), and asked Degsy to run through the jets (np, he didn't check the fuel level in the float bowls), and ran the tank out of Sea Foam and/or any bad gas that might've contaminated the system, it seems to be working itself out.

Hopefully, this might be the end of this particular situation. Time will tell.

[Stoneman]

Check your output voltage from the stator ...

That's the second thing I thought of. It sounds exactly like a bad stator. It will at times run great. Other times it'll exhibit exactly what you're describing...

My first thought was carbs (cleaning)...

[The Snowman]

That's the second thing I thought of. It sounds exactly like a bad stator. It will at times run great. Other times it'll exhibit exactly what you're describing...

My first thought was carbs (cleaning)...

I'll keep this in mind if it starts acting up again. This model 900RR was notorious for having stator issues.

[TLRMan]

I'll keep this in mind if it starts acting up again. This model 900RR was notorious for having stator issues.

That's another thing to put on my list.....