long story short
bought a big bore (Honda TB/DR atv) and had it installed by a reputable individual. CT70 piston, ATC 70 head, ported etc. Dragon cam. 22mm carb with 89 jet, and I'm runnin stock pipe. Older z50 block, so it has points and a condenser for ignition.

Problem is when I crack the throttle wide open, it bogs SEVEReLY, and has no power. I have been SMOKED, and I mean SMOKED by friends on stock XR50s. I"m also geared, one up in the front, and one down in the rear. When I pull the choke in about 3/4, and grab a handful o throttle, no bog. Does this mean I am running lean?? I, and a few friends played with the needle clip up and down, to no avail. What size jet is recommended for a big bore? This thing backfires like a banshee and shoots flames at night; someone suggested my point timing may be off. I just want to unleash the power of the big bore. Any one help??


Thanks

 

could be both fury
points are gapped at .013 then set
if you put the choke on and its fine then it is probably carburation
two ways to fix it ,restrict the air from the filter (if your running a unipod or something like that ) or fatten it up. back firing is usaully a lean problemo
one thing about the big bores it takes a lil bit o' time to dial them in
also as the weather changes you might write down the set up you have now because when winter comes along it will probably be the right set up for the
colder weather

 

ummmm


jet size? jet size???????????

what is everyone runnin in their big bore carb??

 

96 main in mine.

Take it back to Ron and tell him whats going on. He'll toss it back on the dyno and fix it right. Did you talk to him about this?

 

yeah. I did. I think we got stuff straightened out.

For everyone else: Putting a big bore kit into a non-CDI motor is a hassle. I don't even know why they bother selling kits for them

 

no thats not right it should make no difference
if its points or cdi
mine is points no probs at all

 

A 70 cylinder with a 22mm carb. sounds like over kill to me. And '98 z50's have points? I would try a smaller carb. cus you might be playing with that 22mm forever.

Hey Z50NATIONALS, do you or anyone else know if a head off an older ct70 will work on a xr50?

 

yep yep it will a 70 head will bolt right up and a ct is a good one with bigger valves, only bad thing is its not a roller bearing cam so use a big oil pump
and he said it was an older bottom end so it has points