[mtvanstaden]

So I am fixing up a 2004 CRF100F that had been sitting a long time. Gas tank was gummed up, when I removed petcock it was broken off inside tank/crumbled, air filter foam crumbled when touched, carburetor looked worse than anything I've ever seen. So, I replaced air filter, and got a new gas tank (wasn't worth fixing the old/getting new petcock etc) which I put fresh non-ethanol 93 with fuel stabilizer in. Got a brand new carburetor as well and did the jet adjustments recommended on this forum as they run lean at spec settings. I replaced pilot/slow stock 35 with a new 38, and main 98 with 108. Again, new gas tank, fresh fuel, brand new carb. Mixture screw on bottom 1.75 turns out per recommendations on this side as well. I left the left-side crank cover off as I had adjusted valves (how were they out of spec with likely less than 10hrs on this bike????) and I still need to change the front sprocket/chain. Bike kicked over super easily with full or half choke, but would not run without choke. I turned up the idle and gave it some gas while turning choke off, it sputtered some smoke out the tailpipe, then looked like the engine itself coughed up some dust looking crap that simply fell onto the outside of the engine and bike idled fine for a bit, then cut off. I can now get the bike to start easily in 1 or 2 kicks everytime whether full or half-choke, but as soon as choke off she sputters out. COuld the left crankcase cover being off cause anything? Do I need to adjust the mixture screw (hard to get to while on the bike/running as it's on the bottom from of carb w/o a lot of room)? Adjust idle? Or is this an air leak somewhere? I know that jets aren't clogged as the whole tank/gas/carb/jets are all brand new. Thanks for any help everyone!

Matt

[JimDirt]

Welcome to the site !!

Question ,why did you change the size of the jets ?? , and you did not mention anything about the spark plug , new ?? , old ?? , checked it ?? , cleaned ?? ... once you adjusted the valves ,did you turn the engine a few times and check them again , to make sure they are set correctly ?? , if a valve is hanging open it will cause all sorts of issues .... double check the timing , make sure it is correct , and did you test the fuel flow thru the line without it being hooked to the carb ?? ....... Also ,did you try removing the gas cap ,to see if it runs better with it off ??? , if it does , chances are the vent tube , or the vent system within the cap is clogged since everything else was gummed up , I would not expect the vent to be clear , check the hose itself ( blow thru it with it off the cap) , then put the hose on the cap and suck thru it then blow thru it , it should be clear both ways , then with the cap still off the tank ,turn it upside down and suck thru the hose , it should not suck while upside down .....

As far as I know the cover off should not make a difference , if the bike started , then it should run...... was there any rust inside the cover ?? , if so the flywheel might be rusted and getting a poor connection ...

[mtvanstaden]

Jets were changed per recommendations on this site and other forums, all of which said bikes run lean from factory and those were the settings that people were getting better results with. Brand new spark plug. Working great. Turned the engine over and rechecked the valves 3 times after getting them torqued down. Yes I checked fuel flow of new gas tank/petcock/filter setup onto my garage floor before connecting to carb. Air vent hose and gas cap are new as well. No rust inside the cover. Thanks.

matt