I recently bought a 1987 XVZ13DT and started to clean it up. The boost sensor wasn't working so replaced it with a newer used one, it did help with the backfire problem to some degree but the bike still backfires .
The symptoms are that if you slowly come onto the throttle it will reach 4000 rpm then crap out badly.If you crank the throttle on it backfires really badly and will not pickup RPM.
Backfires through number 2 carb and the exhaust. The slides do not move much and just dance about at a partial opening when the backfiring starts.
Timing is okay, carbs are synched (checked them). Ignition coils and wires are good according to the manual, pickup coils are are okay (a least all the resistances match my other Venture which runs great). TheTDI is a newer one. Battery is new and fully charged. I checked the fuel pump pressure which is good. Grounds are cleaned up good. It starts up and idles but has a slght miss on idle. Comperssion is 170 accross all four cylinders.The carb slide diaphrams are visually good on all 4 as are the slides. Plugs are new but black an sooty as are the exh pipes.
So my thoughts are dirty carbs and a lean out a higher RPM as I have done all I can to the igintion system in terms of newer parts. Seems it will not transition to the high speed loop of the carbs. Hoping for some wisdom in how to fix the problem.
The bike was an ebay buy and is a real looker chrome wise but chrome don't get you home. I have redone the fork seals and bushings, new steering head bearings and progressive springs with superbrace. Newer rotors and brake pads. Have an 83 XVZ12TDK as well which has been a great ride I would take anywhere and have.
Any wisdom to confirm my thoughts or any ideas are surely welcome. This is a great site and have noticed some really great people willing to help keep these classic bikes on the road.
Sincere best wishes to you all.