My guess is the cork crankcase stuffers are expanding and rubbing against the casings,it'll ride like you're back brakes sticking on.
I think this is a known problem and sadly requires an engine strip .
I've a 16 80 that does it occasionaly at the minute I'm getting away with it as it's only used for playing.
I heard leaving the fuel on causes the cork stuffers to expand when it fills the crankcase so make sure it's always switched off when left.
Must be plenty know about this.
Thanks everyone for all of the very useful and informative replies - much appreciated. I have tried new plugs, back-to-standard jetting and tested the carb for correct functionality. I think I am going to get in there and check out these cork stuffers. Riding with the back-brake on is how I should have described it in the beginning because that's exactly how it feels, AND, because of the really annoying fuel tap on these (and this one in particular as it must be a Friday afternoon one with the tap tight against the coolant / head pipe) the fuel is always left on....
Hi. Our boy's Beta 80 (2014 b/w) starts and runs sweet from cold, but as it warms up, it's as though it's retarding. It feels tight like it's going to seize, has no power off the bottom, and sounds a bit rough. It revs out though. Fast 'blipping' of the throttle in neutral fails ("bwoooor"). Slightly slower blipping is fine, but it's like it can't wait to get back to tick over (i.e. no run-on of the revs). Leave it overnight, and the next day it's fine for 5 minutes, then same again. We have tried re-positioning the CDI to get it away from the direct heat of the cylinder / exhaust. No change. We have tried a brand new CDI. No change (no change in fact out £180!!). All manner of experiments have been made with regard to carburetor jets / needle / mixture screw, and fuel / air supply is all fine. We don't want to give up on it, because it is clearly capable of running ok, like when it's cold, but there are times when I want to dig a deep hole and bury it. Is there something that should be (but isn't) telling the CDI to alter the timing when hot? We have a 2018 s/w Beta 80 and apart from occasional touchy carb settings this generally runs well and as expected. Any help / guidance gratefully received. Thanks.
Beta 80 retarded when warm
in Beta
Posted
Thanks everyone for all of the very useful and informative replies - much appreciated. I have tried new plugs, back-to-standard jetting and tested the carb for correct functionality. I think I am going to get in there and check out these cork stuffers. Riding with the back-brake on is how I should have described it in the beginning because that's exactly how it feels, AND, because of the really annoying fuel tap on these (and this one in particular as it must be a Friday afternoon one with the tap tight against the coolant / head pipe) the fuel is always left on....