high rpm miss please help

[250r4life]

Hey Guys just got my new motor done for my 86 250r I am having some trouble getting it to run right when in starts to get into the power band mid-high rpm it cuts ou like a 4-poke with a rev limiter I can't figer it out timing? Fuel? here my set up,1.50mm o/s wiseco pro-lite,shaved head,88-87 long rod crank,cylinder spacer,86 style piston,boysen pro-series reeds,reed spacer,cr 500 carb,low mid runs awesome but what fun is that,what I am wondering is if their is a offset timing key available,i think long rod maybe throwing the timing off or maybe that big cr 500 carb is to much let me know what you all think thanks

[glowpowered]

Did you try a new spark plug

[bushwesl]

The long rod shouldn't be your problem because what you've explained is the correct setup for running a long rod and an '86 cylinder. You say "CR500" carb, but what carb is it actually? What jetting are you running? The main jet on the carb controls mid-top. Check that out first; you might be a little rich.

[250r4life]

Spark plug is brand new split fire plug,mainjet is 165 or 168 not sure exactly wich one,cause I can't look right now I keep my r about 20 miles from my place,carb is a stock 1985 cr 500r carb keihin flat slide I believe it's a 38 0r 39,also if it helps at all fuel wise i'm running 110/super unleaded 50/50 mix with amsoil dominator at 50:1

[atcsteve]

I'd say carb or reeds need to be checked!Also make sure the silencer isnt getting plugged.My buddys quad had the same problem and we tried everything.It was a plugged silencer.We took it off and it ran great.After a re-packing it was still good.Just some things to look into.Good luck! P.S. 50-50 is kinda lean for that motor!I always do 32:1 to be safe!!!

[250r4life]

Silencer has newer repack,also about the 50:1 thing thats what amsoil told me when I called them cause that didn't seem right to me either but they said no matter what the application 50:1 but I think 40:1 would be better,also what size main jet,pilot,and needle clip position should I be running with this setup?I run a 50/50 mix between 110 and superunleaded cause it's cheaper than running pure 110 @ 5.69$ a gallon wich I purchase right at a local gas station

[250r king]

wut is ur comp at bout 175 180 and if im not mistakin thats a flat slide wit adjustable choke for ur idle get a adjustable timing plate like 80 bucks shiped to ur house it does wonders go plus 4 on the timing wit that setup mix half pump half c-12 for a motor under 180 comp if its 180 or a bove go straight c-12 wit 32;1 wit caster 927 thats a fast bike

[bshee]

split fire plugs are junk, go get an ngk...and your too big on your main jet. drop it down 2 sizes. do a plug chop and see what your motor is telling you and go from there.

[250r4life]

As far as comp 175 on the nuts,also fuel wise I run the 110 from the local station right outta the pump,cause it's easy access,main jet will be getting lowered this weekend,but I have been working on 2 srokes for years now and whats happening really doesn't seem like a to rich issue it doesn't sputter and bog like it's to rich it straight up cuts out like you pushing the on off button wich seems to me like timing wich made sense to me with the mods that I have,as far as a adjustable plate where can I get one?I love my amsoil I use it in all my toys have not lost a motor yet on it even at 50:1 mix,but I may check in to this caster 927 though,ngk plug will also be going back in,just thought I would try something new

[bshee]

advancing your timing is going to be the problem, yea when it is running good that is a performance part. when your at full throttle the only thing that is tunable in the carb is the main jet size. the first thing that should have been asked is do a plug chop look at the base of the porcalin and that will tell you what to do!!!