gpx 433 question.....

kartman

kartman

Member
Joined
May 2, 2003
Messages
53
Age
53
Location
fife lake, mi
I bought another 75 433 gpx this week and have a motor question....This one has a hole burnt thru in the center of the mag side piston. I assume it would be a timing issue. I am going to pull it all down and check the variables. I will be sending this all to Delaughter for a complete go thru along with his pipes. Would this be the result of a out of phase crank? Could it be from to many rpms with the stock cdi? It did have some sort of mod pipes on it before i purchased. Any insight would be great...Thanks in advance all.
 

pre-ignition,detonation , wrong plug heat range, bad fuel , timing, could be a few things
 
timing was .072 btdc, fuel quality is an unknown,plugs were b8 ngk. I think stock gpx is equivelant to a b9 and with gyt pipes it crosses over to a b95 or b10 ngk. This had some sort of mod pipes on it and jetting is unknown. I would assume just from the plugs being to hot is reason enough to burn it down let alone the other problems. I am in the process of rebuilding the top end today and will be putting it all back together today . I have two sets of pipes to work with on this project.....a set of aaen mod pipes and a set of gyt pipes. What differance real world between the 2 sets? I will be using mikuni 38's or 40's with them. Any help will be great. thanks
 
.72 isn't too bad. .65 is pretty good depending on RPM. Since you are using Dave's pipes it must be for racing so just ask him on carbs and jetting. He is probably going to say at least 44's. No way of knowing on the pipes without dyno time.
 
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