[dirt2street]

I was having trouble with my daughters 04 CRF100 falling flat when the throttle was opened greater than 1/8-1/4. It idled fine but would not accelerate just act as if it was fuel starved or flooded (drop in RPM and looses all power). So i rebuilt the carb completely including gaskets (I assumed it was the pilot jet but figured it was time). Its still the same issue. Also, through my adjustments i was at a spot where the carb didn't seem to have any effect on the idle. Not sure what adjustment had that effect? Any ideas on that? Anyways back to the main issue....I attempted the WD 40 test looking for a vacuum leak and with the odd idle it is truly hard to tell the difference between a leak and the carb issue. Any thoughts? I am truly frustrated attempting to trouble shoot this. Perhaps it is something truly simple i am missing. Thanks in advance

[RCWSO]

I have the same bike and the same issues. I also have rebuilt the carb and set it all to stock settings and stock jets. I am at 1800 feet above sea level and about 50 degrees outside right now. Starts on the first kick or two. Idles great. I can snap the throttle to full and it responds fine. 1/4 to 3/4 throttle is bogging terribly if I hold it at any of those positions. It pops, hesitates and simply bogs. The spark plug is black. I cleaned it and ran the bike to have the same black spark plug after.

I am also looking for any help. Very frustrated for my son and his new bike.

Thanks.

[RCWSO]

I believe I have fixed my problem. Here is what I did and found.

I literally took the carb apart about 15-20 times. I changed the main jet, pilot jet, rebuilt the whole carb, changed needle positions and non of them in any combination helped my problem of 1/4-3/4 throttle with a loss of power. I emptied the fuel tank, cleaned it and the valve. Did the WD40 air leak test. Checked the grounding wires. Checked the float levels.

What I found after cleaning the carb one last time was a part that I did not clean very well the other times. I don't know what it is called but it is the threaded tube that the main jet screws into. that tube threads out of the carb housing where the needle comes in. That piece has many little holes in it which I did clean before. Although, this last time I noticed the threads on the piece were not very clean on the inside of the carb or the brass piece itself. There was corrosion on them. I cleaned them very well and screwed that piece back in. This time it went in about 1/8 of an inch further than previous times. I put the carb back together and the bike runs great now. No loss of power at 1/4 throttle. Full throttle response. I ran the bike for about 20 minutes today with no issues. I will take it out this week or next to give it a better run. I believe I found the problem. That piece not threading in all the way in the carb made the main jet stick further into the bowl causing a very rich condition. As if I had put a larger main jet in with the longer size and without the larger hole.

Anyway, long answer but I learned that when cleaning the carb out I should have been more diligent the first time. I didn't even notice the dirty threads the many other times.

I hate to suggest it, but maybe take it apart and scrub everything one more time. Let it soak, scrub, reset everything to stock settings and give a try. I was ready to purchase another carb and gave it one more chance. It was amazing how much more gunk I got off the carb the last time.

I hope that this was the final time for a while. As mentioned, I ran it for a while today with no problem. Idles great and starts on the first kick or two every time.

Wish I would have been more diligent the first time.

Good luck and let me know what you find.