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Author Topic: 75 Z340 serious bog issue  (Read 179 times)


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75 Z340 serious bog issue
« on: May 19, 2017, 11:12:02 PM »
I bought this sled that supposedly was raced a number of years ago by the owners and it starts very easy without choke. Running rich and smoking heavy. Cannot even drive the sled. PTO side is noticeably cooler pipe and head temp. Suspected richer on this side than the PTO side. Checked to verify the following were doing their jobs.
Fuel needles...holding air tight at 10 psi now. PTO side originally was leaking at the gaskets but new gaskets and Ultimate gray sealer resolved this.
Enricher plugs were replaced and sufficient slack to assure seal off (verified with Vernier to assure this)
Fuel pumps opened and visually checked and tested. No leaking to the crankcase via pulser lines. All valves perfect and diaphrams not torn or deformed. Ran sled with each pump pulser line off to assure 1 pump can supply fuel to carbs. No issues. Tank clunk check on one was stuck so fixed that.
All internal jets and needles are stock part numbers except high speed jets are 380 instead of factory 400. Should be ok right???
I have had to replace these mid range jets and needles on a 91 EXT special a few years ago as they were actually worn out and the jet ID was larger than new. Same symptoms of running rich. So I dropped the jet needle to the 5 position to see what would happen and the engine did lean out some so it would respond to throttle at least to about half throttle now and then bog out after that. I will replace the needles and jets and see what happens. The thing that is a question about this is that how can a sled with low miles (260 on the gage) assuming the speedo always was working, have worn out jets. Has anyone else had this experience that can comment on this?
78 el Tigre 5000
75 el Tigre 440
75 340 Z
74 el Tigre 295
74 TX 440
79 TX 340


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    • SnoPro
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    Re: 75 Z340 serious bog issue
    « Reply #1 on: May 20, 2017, 06:46:02 AM »
    Does it have spark/good spark on pto side?


    • SnoPro
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    Re: 75 Z340 serious bog issue
    « Reply #2 on: May 20, 2017, 07:05:36 PM »
    What was the outside air temp when you were testing this sled. The z free airs like it cold out. Never did get my Z440 running correctly in the warm weather, but get it less than 20 degrees and it would come to life.