I have a mm 700 2000. piped and ported. It has a flat spot on its response. engauges well at 4000. builds ok up to 5000, then faulters. at 6000 it kicks in hard and runs hard. I have been round and round with this. The carbs are clean. I have done numerous plug test, and the plugs look good at full, and mid range. I put a new silver spring on the secondary clutch, and it is running a a3 hartmann helix. clutches are at 70 deg rotation. I wondered if the clutching might be the problem. Down shifting too soon, I don't know. anyway, now the question. A friend of mine said I might try a mid grade gas. the high octane gas may not be working for my machine. I ride high at 10000-12000 ft. he said the gas may burn to cold or something for this altitude. I have not tried a mid grade, but I was wondering if anyone had any information, thoughts that might be relavant. thank you Merry Christmas. 
higher the altitude, the less octane required. give it a whirl and monitor plug color. also, do a 1/4 throttle plug chop and check the plugs. try a green spring at 80, but not at the same time. (dont make two changes at once or you wont know the outcome) remember it will take a few miles to dilute the existing fuel even if drain the tank prior.
tried it
ok rode this weekend. the good news is the machine did not burn down. I did 2 plug tests,seemed ok its a little hard to tell. these being new plugs. white tip on electrode about 1/3 of the way down. oil on threads, but hard to tell rim color. I believe this to be ok. It was also an unusually warm day. 40 deg+. the problem is that it did nothing about my bog problem. If snowdad4 or anyone knows about what snow4dad said about octane I am curious. "higher the altitude the lower the octane". why is this, and how low should I go? I realize this will require re-jetting probably. thanks
ok rode this weekend. the good news is the machine did not burn down. I did 2 plug tests,seemed ok its a little hard to tell. these being new plugs. white tip on electrode about 1/3 of the way down. oil on threads, but hard to tell rim color. I believe this to be ok. It was also an unusually warm day. 40 deg+. the problem is that it did nothing about my bog problem. If snowdad4 or anyone knows about what snow4dad said about octane I am curious. "higher the altitude the lower the octane". why is this, and how low should I go? I realize this will require re-jetting probably. thanks
ford428cj
New member
maxco said:
I run 89 in my 700MM I run from 5,000-8,000Ft. As for your Bog , Is it right off idle?? If so, you need to richen up your Idle mixture screw! JMHO
motor tech
New member
you may need to adjust the needles.
off idle
no the machine runs fine, until 5,500. idle is fine, engagement is fine. as for the needles, maybe, but would a plug test not show these needing adjustment?
the plugs show good at mid range.
no the machine runs fine, until 5,500. idle is fine, engagement is fine. as for the needles, maybe, but would a plug test not show these needing adjustment?
the plugs show good at mid range.
I would check clutch alignment, center to center on clutches and belt deflection. Also take the rollers out of your primary and see if the bushings are ok. Make sure the fixed and sliding sheaves move freely and that the bushing isn't too worn allowing the sliding sheave to cock to one side. If you still have all layers of your head gasket, 87 octane is all you need. I went 7000 miles with out an issue, then I removed two layers and now I run 92 octane. A free and well-worth it mod.
one final thought. Are you running a multi angle helix? COuld be shifting through the first angle too fast, hanging on the next angle until track speed comes up.
one final thought. Are you running a multi angle helix? COuld be shifting through the first angle too fast, hanging on the next angle until track speed comes up.
