Printable View
I just got ahold of an '89 Mighty Max with 54,000 original miles. Did a full tune up, with the exception of a fuel filter and a timing belt. The truck idles fine when i first start it but as soon as i tap the gas, it bogs down and acts like it's going to stall. I was wondering if anyone knew a solution to the problem other than raising the idle? I have considered a vacuum advance, but I want some tips before i start pulling things apart, as I'm new to these trucks.
Try a fuel filter.
Also, replace the carburetor diaphragms, they are cheap. Most likely the ones on your Mikuni are dry rotted and not working correctly. Its a quick job.
Take the air filter off and twist the throttle linkage - look for a squirt of fuel in the primary throat from the accelerator enrichment jet (might have to hold the choke butterfly open to get a better look). As the name suggests this gives the primary throat a booster shot of fuel when you first crack the throttle open. If it drips or just doesn't do anything the carby needs either a big clean out or a rebuild. Also try starting it with the air filter off and starving it of air by covering both primary and secondary throats with your hand. Sometimes a sudden jump in vacuum can purge junk out of the jets. The 2 main issues with the Mikuni griefing you are the automatic choke and the secondary vacuum actuator. Let us know how you go GoodApollo :)
^ oh the third issue occurs when some monkey takes a screwdriver to it and starts messing with adjusters and stop screws without knowing what they're doing. This can cause a level of frustration that will make you want to claw your own eyeballs out in frustration :slap: