Hi something ? Then M_501###_D_5  hidden last 3 numbers looks like a Alpine model for reference square barrel looked on chart and 50 el bandido 350 and not that so could it be a go cart i have a go cart European 110 but has more 0 in it.You gentleman have more knowledge than me Thank you

I'd like to help but am having trouble understanding the question

Hi looking at a Bultaco engine similar to this ( Image ) the first letter is ? don't know then M-50129#-D-5 hidden last number with hash tag any help in recognition Thank you

I think it's an Astro (model 90) and you've either misread the first number or someone has altered the number.

How about you cover up your secret last number and take a close-up photo and post it up?

Hi engine is not mine so that's why covered number just trying to find out what it is curiosity as can not see on model chart or production Thanks

Hi update no first letter just M then numbers in Photo above just assumed letter was cut off in picture but NO.I really hate guessing but could it be a Go Kart 250 model 55 as on production list numbers start 501 018 i dont know  .Thanks 

Hi, Old man - 

Kart - model 5 (not 55) originally available in 100/ 125/ 175/ 200cc   capacities, I believe.........??

It’s definitely not a bandido engine.   It looks like it’s a model 5 kart engine.  The D means it’s a 250cc and the 5 at the end indicates 5 speed.  They made this engine over a long period of time so that’s why it has the mid 70’s barrel and head.  They may have started production of that engine in the mid sixties and continued it sporadically over the years.  I’d guess given the higher than 1000 serial number that it’s a later model produced in and around 73-74

steve