Re: slight backfire

[TC]

In addition to what Tyler has listed below ... the 90/100 (calif), pilot air jet is the "primary" air jet. It is the one at the top of the carb. Of course ... where there is a "primary" ... there must be a "secondary" ... sooooooo ... there is more than one pilot air jet blowing bubbles in the pilot/idle mixture ......   The "secondary" pilot air jet is a MK170 on all Vmax carbs and it is located behind the slide rubber. Anyone looking at the "long" instructions that come with a Dynojet stage 1 kit will notice that a set of four DJ150 jets come in the kit and they tell you not to use them if you can adjust your problem out with the needles. Unfortunately, if you bring your needles out enough to deal with this problem, (coughing and/or attempting to hold the engine at 1500-1800 RPM), you will be running too rich in mid-range .. and the plastic around your battery will melt .. and your plugs will foul and ... well .... you get the picture ......   The DJ150 jets are much smaller than the MK170s they replace ... the idea is to restrict the air, (which comes jointly from the primary and secondary pilot air jets ... except during deceleration when the secondarys are blocked off), that mixes with the fuel from the pilot fuel jet to produce the "pilot mixture".   Sooooooo ... if you want to do something about this problem .. .you can either make the pilot fuel jet bigger, (as someone has already suggested), or make one of the pilot air jets smaller, (If you do the air jet I would suggest the secondary pilot air jet). This assumes you have already blown the pilot circuit out to make sure the bypass or mixture screw holes aren't plugged/restricted .... You can also take the lid off the airbox and slowly open the throttle to see/hear which cylinder is actually popping back through the intake and give that one a little more on the mixture screw .... if you are already out past three turns-ville on the mixture screws then you need to richen the pilot mixture as described ...   If you don't have this problem at all after you warm up .... then this is perfectly normal and you should leave the enrichment lever operated slightly until the bike warms up ..... Any effect from having the enrichment lever operated, (choke), drops off as the throttle is opened ... so it isn't a big deal ... On the other hand ... if you warm up and try to hold the bike at 1500-1800 RPM and get an occasional pop or the tach wanders everywhere "except" 1500-1800 RPM then you need adjust you pilot mixture ........ (honest !! ... would I lie ??) ........ campbell   ----- Original Message ----- From: Tyler Pennock To: V-MAX TECH LIST Sent: Saturday, March 11, 2000 3:42 PM Subject: Re: slight backfire The air jet 1 in the air intake should be a # 90, some bikes export or Cal. have # 100, just a thought if you want to check?, example Can 87max stock, a.j.1=90, a.j.2=150. pilot jet=37.5, mains=152.5 Tyler Pennock,VMOA # 380 Eastern-Canada Director 1987vmax 1260 Ottawa,ON,Canada <[EMAIL PROTECTED]>