XR100 woes

[rmyzit]

Hi all, I bought an XR100 '90 model for grandson having out grown his PW80. So the problem is I can't get the engine to idle consistantly, sometimes not all and will at times rev on after shutting the throttle off. Apart from this issue the bike goes well when I'm riding it but, fraustrating for a nine year old using a manual clutch for the first time!
My first thoughts were air screw adjustment, air leaks in the manifold and slide not returning to the bottom. I have replaced the manifold 'O' rings and checked the slide does go all the way home and adjusting the air screw all having not effect at all. Any ideas?
Thanks, Wade

[Bumper]

get a needle jet set.most times the needle spins
it wears out the tube
but try to ajust it first
lift the clip 1 notch up on the needle this should help
then ajust the air screw to suit

[smed]

Bumper is onto it, almost certain to be a worn needle & jet,common problem on little Hondas,makes them run exactly as you describe,put another sparkplug in while your at it,the old one is probably fouled from a rich mixture

[Tim754]

The boys have it,I fixed that identical problem on XR100 temporarily by replacing needle. (permanent fix by replacing carby with cheap eBay China copy ,but don't tell anyone please...)

[TT5 Matt]

yeah from xr80's to the 200's they all wore needle/needle jets out.lowering the needle wont fix it as the needle jet is already worn to the point that its not sealing off  when your on less then 1/8th throttle hence running on and poor idle,also check the floats for wear where the needle out of the needle and seat ass touches the tang on the float as they wear in that area as well.little motors like like over fueling where on a big 500 its not as obvious and you don't notice it as much

[huskibul]

       Has anybody ever fitted a mikuni to these small honda's ? would it be worthwhile or an advantage to do so ? cheers

[smed]

Yeah, I have the pitbike mikunis on a couple of my XR75's,they are the bolt on type like the originals,the mount holes on the inlet manifold have to be filed a bit,the throttle cable goes straight on,the only problem is you need to remove the choke arm as it fouls on the frame which then makes using the choke a bit fiddly,I'm running pod filters & a fury type manifold on one bike so not sure how they go with the original air cleaner set up,They worked fine out of the box jetting wise until I put on internal rotor cdi's,they then needed richening up on the needle & they run good as gold,they are a larger carb,so in theory should work well with a modded engine,both my bikes have megaphones & one runs a big bore kit  

[huskibul]

     Sounds like the go smed ! i have a xl100 with the same symptoms as above and have checked for leaks etc  and i have a small flanged mikuni somewhere looks like the time for the ol' switcheroo ! cheers   

[rmyzit]

Yep that helped heaps thats guys  I have ordered another complete carby, cheaper than individual needle and jets
Wade