I don’t have the instruction booklet, but here is a link to MRR review of the engine with some instructions with views of the inside and related parts…this may help You some what…click on link:
From the FAQ’s For Walthers products, search on your item and if a manual is available, a PDF of the manual will be listed the Product Detail information.
I looked at a couple versions, that are in stock, and no PDF is listed. Hard to believe in this day and age.