CRF 100 bogs

[sideseal]

Need some help with an issue I'm having.  I recently bought a stock '08 CRF 100 for my son.  Did a tune-up on it, new plug, air filter, oil change, valve adjust, etc...  I removed the carb and did a good cleaning on it and confirmed all jets and passages were clear.  The original pilot screw had a slight bend in the tip so I replaced it with a new one.

 

The original pilot screw was set about 2 turns in and the previous owner had the idle set pretty high.  After adjusting the idle, the bike runs great.  Starts on kick 1 or 2, idles fine, no hesitation going through the gears.  The only issue is if I blip the throttle from idle to full  the bike bogs and stalls.  If I give it just a bit of throttle, it revs right up no problem.

 

I pulled the carb again, checked nothing was clogged, and the float level appears to be spot on.  After experimenting a bit, I found the bike will not do the throttle blip bog stall if I set the choke in the mid position.  Now if I'm understanding it correctly that would lead me to believe that I'm a bit lean on the idle circuit.  

 

So, I warmed the bike up good and tweaked the pilot screw for best idle.  It's now at about 2 3/4 turns. Bike starts right up and idles great.   The bog is still there but not as pronounced as before.  I'm in Texas at about 600' elevation and temps have been in the 90's.  I'm thinking of putting a #38 slow jet in there (it has a 35s in right now) and see if that helps. Or, am I being too OCD and need to leave well enough alone? 

 

Thanks.

Edited June 21, 2014 by sideseal

[honda4100]

_{Try dropping the needle clip to lift the needle up a notch or two, a 38 pilot will help a lot also}

[sideseal]

Yeah I thought about that but the needle clip on a 08 is not adjustable

[keenxxx]

If the bike has air box or oe pipe mods it will need re- jetting. JD makes good kits.

[peaceofwork]

put a small washer or two on that needle to lift it up or check to see if the 04/05 needle is adjustable

[FORMA MOTO]

You are never going to remove that bog.

You can't ride the bike that way, so it does not matter

[13lemons]

So I am experiencing the same issue, I found the original pilot jet was a 35S which has smaller holes on the upper part "8 holes". I installed a regular 35 and found the bike idles much better but also has the bog on a full throttle twist, the bog is not an issue while in motion, only in neutral revving the engine. I cleaned the 35S and re installed it to find a poor idle (warm up for 2-5 mins before idles) but no bog at all. I do not have the answer to this riddle and I have not seen anyone else say "I did this and it was gone". An ongoing mystery...

02 CR 250R, 04 CRF 70, 78 TT 500, 06 Custom Chopper, Giovanni 110cc quad

[William1]

Pilot jet, fuel screw are for idle only. The AP is for sudden throttle openings.

 

A bog when not riding is not a problem. It only matters when actually being ridden. A properly adjusted fuel screw, set with a hot engine for a smooth, strong idle. Do not use the pilot jet idle circuit to do something it is not designed to do, you'll just make one nin-sissue another, insurmountable one.

Pilot jets do not repond well to cleaning. Buy a noew, stock OEM pilot and retest. Ensure the fuel screw is serviceable and all parts intact.

 

An actual bog is dealt with by the AP. You must ensure you get a strong squirt and the adjustment is correct per your service manual.

[Falcon 1]

Yeah I thought about that but the needle clip on a 08 is not adjustable

 

That's correct, but you can shim it with small washers which will improve the bog. I recently bought a brand new 100F for my wife, and I shimmed the needle which resolved the problem. The bike no longer bogs after shimming the needle. It took me a couple of times to get the washer stack to the proper height.

 

Let us know if you get it figured out.

 

Cheers

[peaceofwork]

I never had an 08 crf100 , its been a long time since my old ladys 05 100 but I'm pretty sure their is not an accelerator pump on these bikes.?

I do know that on the 150'/230 bikes 03-05 needl's had multiple clip positions and we hunted them down for the newer bikes so I say check the older 100 bikes and see  or again find them little washers to stack on the needle.

[13lemons]

02 CR 250R, 04 CRF 70, 04 CRF 100 78 TT 500E, 06 Custom Chopper, Giovanni 110cc quad

Edited September 8, 2014 by 13lemons

[FCR Expert]

I never had an 08 crf100 , its been a long time since my old ladys 05 100 but I'm pretty sure their is not an accelerator pump on these bikes.?

I do know that on the 150'/230 bikes 03-05 needl's had multiple clip positions and we hunted them down for the newer bikes so I say check the older 100 bikes and see or again find them little washers to stack on the needle.

This is correct, there is no accelerator pump on the CRF100's carb so that tuning option is definitely not on the table for this particular bike.

I would try going one bigger on the pilot. If that doesn't do it, try shimming the needle as described above.

Both of these adjustments are completely reversible and are harmless to experiment with.

Let us know what you find. I'm curious to hear how this one pans out :-)

Edited September 8, 2014 by techgreg

[William1]

My bad, I thought the 100 also had a FCR. Adjusting/changing the pilot/fuel screw for the bog is not a correct step. Falcon prodives the correct mindset.

[FCR Expert]

I think you're probably gonna end up right on this one... Shimming the needle.

[peaceofwork]

willam1 don't give it a second thought you are right on the money about thousands of other carb things - I'm usually  guessing at best but I remember stacking washers on the needle of the 05 100 we had and then hunting down an older style multi clip position needle for the 230 an newer ones only had the one clip position