In the mid '80s after crashing his Funnybike, a pal built a turbo-nitrus Kawi combo little dragster that ran 7.90's - when it didn't break.
I'm seeing more of the bike powered dragsters at West Coast tracks that have long been the domain of the NHRA Jr. Dragster programs, NHRA's stepping stone to becoming professional level drivers. I spoke with one group that had both in their pit, they said the older kid outgrew the horsepower of the Jr, and this was an easy way to go fast. He ran brackets, while the younger boy still competed in the sanction Jr. program. Guys can get pretty creative with a bike motor build rather cheaply, I've even seen a few on the bottle.
Not to say there haven't been some pretty bad a$$ Briggs & Stratton 5hp engine based Jrs out there though.
In '95 we took a Funnycar to Australia to run their National Championship series, along with the owner's sons no-expense spared all billet motor methanol burning Jr. Dragster. The promotors had to give that thing extra pit space as it was constantly surrounded by herds of amazed dads, both racers and fans, and during exhibition runs the starting line was packed. The kid ran 83mph in the 1/8th mile - with a lawn mower engine. Oh dear, how quick did you say your CB 750 is?
I'd love to see some pics of those Baby Funnycars.