K-- Boys- Here's the deal ! Runs perfect without the Air cleaner Rear Housing and Filter. Put the Filter and Rear Housing on and it Misses Mid range on up ! Too Rich -Right ? Plug looks black ! Next- New Plug- Exchanged Carb off my other Z that runs perfect ! Exact same Mid to full throttle seems like the choke is on !- Plug Black Next- Hoist up on the Bench- Checked the Points gap-- Perfect .014, Next- Checked Valve Gap- Perfect .003 Any Ideas ?? Before I set this on Fire ?
Seems fairly obvious where the problem is...the airbox assembly. Only a question of whether it's the foam element or rear housing. How's it run with the housing assembled, sans foam?
I changed Air boxes and Filters- As soon as I put on the rear Cap with out the filter the same symptom mid-range to WO stumbles. As soon as I remove the rear Cap it'll go wide open- No Problems.
I have the EXACT same problem with my K5 (74) Z50, if I use a “sock” filter it runs great but with the factor air box and filter it bogs down. I hope your find the answers because I have been fighting this issue for months now with no luck. Iv posted about this before and will add my links so you can read the replies I received.
I'm going to take a different approach and start with the basics-1st is a compression test- New Gauge set will be here today. If that test ok- I'm trying a 3rd Carb from My Grandsons Z50 (72) That worked fine on His Tired Old Engine-His is torn down for a full Restore anyhow. New Plug Check Points again Check Valves again I'll check back in later today Thanks
Rich Stumbling with Air Cleaner on ! Compression Test---150 lbs---Eng warm Throttle full open------- I'm good with that --- Specs call for 170 lbs- must have been at Sea Lever and No Barometer -- That will make a difference to the numbers- 10 to 15 % Put the 3rd- Older Carb on with the Air Filter and Housing - Adjusted to Specs- Perfect-- No Stumble at all through full open Throttle. Took it for a test ride and Wow -- Really Runs Nice. Carb # 3 has a 55 main Jet I need to look into Carb # 2 and Carb # 1 the Aftermarket Carb to confirm Jet size- Maybe Someone upped the Main Jets= Pulling too much fuel.
Rich Stumbling with Air Cleaner on ! Conclusion and Observations. Carb #2 the Orig Carb has a 55 Jet but No O-Ring for sealing- Also a Minor Clog- Float level looked ok- I suspect it was permitting Fuel up past the non-existent O-Ring - Therefor too Rich Carb# 1 the Aftermarket Carb --Main Jet has No number on it- as best I can measure the Hole -looks to be .060 -using different strands of copper wire to measure. Well that's it for now--Until the next unfamiliar challenge arises. Learning as I go !
