So Im building a hpi baja out of spare parts I’ve accumulated. I have a CPI bigbore pipe from back in the day im going to use.
What is a good cleaner to use to clean all the gunk buildup inside the pipe?
some sort of carbon disolver and some small brushes mick,
be careful though cos ya don't wanna us anything that will affect the chrome on the outside,
those cpi bigbores only really gum up at the end where the hammer head type bit is,
you could try raw petrol/gas, seal the ends and put some gas in, then leave alone for a while, slosh it around then empty and see what comes out,
but as above, the only real place to worry about is the hammer head bit,
time and patience with wire brushes and small pics and remove as much build up as ya can

,
one of the fellas on the old baja forum from years ago actually cut the end plates off (the bits with cpi embossed in em), then made em bolt on,
didnt look that good tbh so just clean it best ya can,
his was an old well used pipe and was really gummed up in the end of it,
edit; obviously be very careful if yer using anything flammable to clean it with as well,
just added this bit cos there may be the odd person that reads this ( a newby or something like that) that wont think about the flammable thing and end up getting toasty hands etc,