38 miks on a gpx 433

[thunderjet440]

Tossed the keihin"s and ordered a set of 38's ,they come with 360 main jet and a 40 pilot jet,is this set up rich enough to start testing? i usually run the sled from 0 to 30 degree's or so.sled has stock pipes,.40 over and combustion chamber machined and 180 psi.any tips would be helpful.haven't messed with a mik on sled before.thanks

 

[gpxsrxracer]

Tossed the keihin"s and ordered a set of 38's ,they come with 360 main jet and a 40 pilot jet,is this set up rich enough to start testing? i usually run the sled from 0 to 30 degree's or so.sled has stock pipes,.40 over and combustion chamber machined and 180 psi.any tips would be helpful.haven't messed with a mik on sled before.thanks

Rob, depending on what # slide your useing you will most likely need to run alot smaller pilot jet, otherwise it will be too rich at idle and off idle. I spent a couple hour with a set of 40 roundies on one of my stock gpx's and I ended up with something lime a 25 pilot and it still seemed rich. You might want to try a 35 or a 30 pilot first.

 

[thunderjet440]

Derek,how well do the 40's run on your sled? a few guys told me to try those but 38's are the legal replacement for stock/superstock.Lousy thing is i had the pumper carbs working great last year but it may have sucked some dirt in the carbs and wrecked the needle seat.i may try another carb body this weekend,probably a good idea to have a digitron when i try the 38's

 

[gpxsrxracer]

Well, they arent tuned in perfect yet, but they will work. I am also going to try a set of 38's on it. I think for a shorter race the 38's would be ideal. The 1-2 more h.p. if that isnt worth the loss in torque running the bigger carbs. I have an idea for useing the pumper carbs and I will post back eventually about this. I might have solved the pump diaphram problem but I have to try it out first. As far as the 38's go, I thing your right about that rule of running 38's as replacement for the pumpers. Kinda sucks as the pumpers are 40mm in size so one would think you could run a carb of equal size but rules are rules unfortunately.