- Mon Jul 15, 2019 10:06 pm
#84115
Since I got the bike, a 1998 500, it was nearly impossible to 'rev up' without horrible spitting back through the carb, The bike had been fitted with a new carb, a 'Mikcarb', when I got it. I stripped it and blew it through to make sure it was clean, no difference.
I set the ignition timing spot on, and a bit advanced, and a bit retarded, no difference, so I re-set it back to 'spot on', I also checked the advance/retard mechanism, all good.
I squirted carb cleaner around the carb rubber mounting and inlet manifold while it was ticking over, no difference, if there was an air leak, the engine would have revved up. I checked the tappets, all ok.
So, back to the carb, as a shorter less restricted exhaust, and a cone type air filter is fitted, I have up jetted as per our hosts jetting guide, all to no avail.
I stripped it down again, this time, I got the magnifying glass out and examined the casting for defects, all appeared good until I looked at the drilling that the pilot jet feeds into, it was not round, it had a minute 'flat spot', this hole must have been cast. I got a ' micro' drill, I can't remember the size, but it just slid into the lower part of the hole, I twiddled it around with my fingers until it exited through nicely, removing the 'flat spot'.
I re-fit the carb..... drum roll..... CURED, it revs up lovely now, I was getting a bit worried, I must admit.
I set the ignition timing spot on, and a bit advanced, and a bit retarded, no difference, so I re-set it back to 'spot on', I also checked the advance/retard mechanism, all good.
I squirted carb cleaner around the carb rubber mounting and inlet manifold while it was ticking over, no difference, if there was an air leak, the engine would have revved up. I checked the tappets, all ok.
So, back to the carb, as a shorter less restricted exhaust, and a cone type air filter is fitted, I have up jetted as per our hosts jetting guide, all to no avail.
I stripped it down again, this time, I got the magnifying glass out and examined the casting for defects, all appeared good until I looked at the drilling that the pilot jet feeds into, it was not round, it had a minute 'flat spot', this hole must have been cast. I got a ' micro' drill, I can't remember the size, but it just slid into the lower part of the hole, I twiddled it around with my fingers until it exited through nicely, removing the 'flat spot'.
I re-fit the carb..... drum roll..... CURED, it revs up lovely now, I was getting a bit worried, I must admit.