Short 4th gear dilemma

Short 4th gear
Wanting to put a short 4th gear into rally 200 femsa engine.
Have found on in my garage from a 1978 px125, also 150super cog. But here’s the rub- the teeth wont mesh as they appear to be alot smaller.
Is the recommended 4th gear from a late px125(pre EFL)?
Will my standard 200 run quicker top end with a short 4th and left hand Mickeck?
Could be a question for you Beerace!

Cheers Beerace, But i am rebuilding the engine and I thought I might try something a bit different for a change . Unfortunately you didnt actually answer my gear id problem!!
Thanks anyway

you need an early efl 4th gear or change the layshaft for a new efl one

Unless youre rebuilding the rally engine anyway I’d leave as it is. You use a shorter 4th gear to get the most out of a revvy cylinder kit, not necessary with a standard cylinder unless major porting done. Rev range will increase regardless using a mickeck, but go with it and just bolt pipe on, retard timing a degree or three (depending on what you read on this forum), and upjet by two sizes. A mickeck uses a good configuration of angles, many of todays pipes dont equal a mickeck. Loud tho’

Cheers vespadoctor, I thought as much[:rotate:]