Mz-65 issue?

[Kitt]

Hello everyone! I made a post asking what I should purchase or do for my build and there were many helpful suggestions. Thank you all who took the time to read that. But anyway, I purchased an Mz 65. When I first started it up, it ran fine but it started “backfiring” at the top end. As soon as it started doing that, there was no stopping it, even when brought down to a lower speed, it would backfire when accelerated. Only when I stopped the bike completely, and started it again would it sound like the rpms were climbing normally until it reached the top end where it would have the same issue again. I figured that the stock carb was really restricting so I figured I’d order some parts. I ordered a high compression head and a race carb. I installed them today and unfortunately I seem to have the exact same issue. I really can’t figure it out so any feedback would be really helpful, thanks!!

 

[mark20]

Hello everyone! I made a post asking what I should purchase or do for my build and there were many helpful suggestions. Thank you all who took the time to read that. But anyway, I purchased an Mz 65. When I first started it up, it ran fine but it started “backfiring” at the top end. As soon as it started doing that, there was no stopping it, even when brought down to a lower speed, it would backfire when accelerated. Only when I stopped the bike completely, and started it again would it sound like the rpms were climbing normally until it reached the top end where it would have the same issue again. I figured that the stock carb was really restricting so I figured I’d order some parts. I ordered a high compression head and a race carb. I installed them today and unfortunately I seem to have the exact same issue. I really can’t figure it out so any feedback would be really helpful, thanks!!

your running too lean, thats going to cause the main backfiring issue, the stock carb is fine for 99% of all applications, and theirs really no need to put on a "racing" carb (most of the time they cause more issues then they fix)

try cleaning the carb BEFORE you rejet, as it could be clogged from break in (and stuff) and check for any air-leaks as this could cause a lean mixture.

if its still lean, buy a jet verity pack (about 10$)
https://www.ebay.com/itm/5mm-Carbur...epid=0&hash=item1c84f1bb14:g:vJoAAOSwXSJXOYJe

stock size is 70, id up jet to 75 on the stock carb, and maybe 65 for the "racing one"