Leaderboard

The best way to check for bad valves is to find TDC at compression stroke and then wiggle the rocker arm. If there is play, the valve is good. If not, a new seat must be cut and new valve installed. I've tried dozens of times to install a new valve in an old seat, but 100% of the time I've had to continually replace that valve. It seems there is no way around cutting a new seat.

Good points! Concerning carbs, I keep some guitar wire around for cleaning jets and small holes. Chemicals don't do much. Regulators are common problems on these machines and if it runs better with the lights on, that's the problem. I bought the biggest baddest regulator Rick's Electronics sells because I fried 2 OEM ones. Rev limiters can sometimes be improved by using an older CDI, but the problem with rpms is the weak valve springs. One of the first models of these machines (250 model) had ovate springs which are super-stiff. Zuki only used them one year and I forgot which year since that was 5 years ago for me. If there are changes in the spark due to heat, then it means a coil somewhere has lost enamel due to age. That is common on the 80's models 230 quadsports that start fine when cold but are impossible when hot. Alternatively, cold starting problems could mean worn intake valve.

Wow a lot of carb/reving issues might as well put my two cents in! I have had a few bikes do this. And to all the "carb specilist" as I feel I am lol to my surprise I have found that even though we clean, rejet, rebuild!!! There is or may be a blockage that still exists within an area you cannnot access! I've been through this over and over and when I finally tried a new carb bang the bike fired right up and worked beautyful go figure. I have cut one carberator open just to see and found that these things have a lot more going on inside then we may think. Fuel peckocks and filters are also a major factor in this type of situation and are a major contributor to some of these fuel delivery problems but most likely time for a new carb. Yes it sucks but most likely will clear up a lot of issues by replacing the carb. Also I recommend monitoring the spark. I was pointed in the direction thanks to this site of a device that you can put in between the spark plug and coil wire to monitor you spark intensity and to see if any changes happen after the bike heats up. This will save you a lot of time in diagnosing weather its electrical or a fuel delivery issue. And it's a cheap tool to buy. Lastly, take a look at all rev limiters these things suck! Over design and complicate things with the thought of safety (a good thing) but also are the culprit of a lot of backfiring and sputtering problems. Good luck.