High RPM Bog... Help me please also CR250 Ignition?

[300excrazy98]

Hey guys my 295r has a bad bog in the high rpms... I cant go full throttle, but it doesnt stall when i do it just bogs down... I was thinking the jets..

Its got

295 bored out
duncan mx porting
hot rods crank
cases are machined out for a 340
keilhn carb 39mm??
some sort of alum. exhaust flange
bills header
lrd silencer
boysen rad valve


I was thinking that it was getting to much gas.. bc when i took the plug out it wasnt that oilly but had some gas on it.. so i thought back to when i bought it from the guy, and he said he had a 340 on it, so i doubt he changed the jets out of the carb.

Which jets would i need to change? would they need to be bigger or smaller? any sizes?

Also on the jets does it say what size they are?

One more thing, CR250 Igntion set ups? They any good? What would i have to do to put one on my 250r? Big power differnce? what years work?


THank you all!

[deathman53]

cr setups are better than stock for mx use, they are too stall happy for trail use and you can't use lights w/ them. What color is your plug? I use a 172 main , dej needle on 3rd clip, and what ever the idle jet is on 2 250rs.

[RIZZO]

Yes the jets do have #'s on them......If your sparkplug is wet, then it's running too rich...you will need to lean it out..with a smaller main jet..try not to drop to many sizes at once thouhg.

[C-LEIGH RACING]

Can be a lot of things causing it, new bike & a new rider & not riding it hard enough.
If it was set up for a rider that raced it hard, the carb could have big jets inside & now your riding it slower than he was & its puddling fuel in the crankcase & when you get on it kinda hard its flooding out up top rpm.
With the cases cut out for the big bore, the engine has more case volume now & the charge flowing up through the ports is a bit lazy like & better for a bottom end type engine.
Neil