I have a 1990 Viffer with some "mods" (i.e. fourth gen header and exhaust and poorly thought out carb kit)... The short of it is that the bike suffers from sluggish power and sloppy idle regardless of carb sync accuracy (also get quite a bit of popping and crackling during ROT). I plan to move back towards stock needles and jets on the carbs but the slides have been drilled. Finding NOS slides is almost impossible and I don't necessarily want to gamble on a takeoff set of $200 carbs having usable slides. 1. Is there any trick to filling and re-drilling those slides? 2. Could going back to stock needles and jets be enough? 3. How much effect do those larger holes have on carb performance? 4. Theoretically, would the adjustment in the stock carbs be able to compensate for the "anti-collector box" 4th gen exhaust system? Thanks for taking the time to read this and please forgive my noob-ish-ness.
No problem using JBWeld* to fill slide holes if you want to. If the bike won't run right with adjustable jetkit needles, it's much less likely to benefit from stock needles. It's always possible that your slide diaphrams are not seated correctly in their grooves, and even one slide not operating right will reduce your power drastically. Have you read and understood the carb tuning instructions included with the jetkit ?? You may need some experimentation before it runs proppaly with the exhaust mods. It's essential to get the main jets correct first, based upon high speed runs. *Not a compensated endorser.
So JB the holes and drill in a slightly different location?? What is the stock hole diameter? On the needle issue, I'd bet on improper settings. I think I just started in the center groove just as a starting off point. I plan on painful "tear-down/build-up/test-ride" experimentation. My concern is that I'm dealing with multiple variables (duh) whose "sweet spots" are all related yet unknown. I bet watching those carbs do their job under a thermal imager would answer a lot of my questions. I'm just having a hard time visualizing the effect of these adjustments. Do you know of any good articles on the function of these components and effect of adjustments with them?
Study the installation and tuning instructions included with K&N/Dynojet AND FactoryPro kits. Both have the essential tuning ideas and proper sequence of adjustments you need to know. Needles can't be adjusted correctly until AFTER the best main jets have been determined FIRST ! google "tuning CV carbs"
