M900 jetting advice

[sur4die]

so what drove me to futzing with my carbs in the first place has decided to rear its ugly face again, though not nearly as bad.

previously i had power delivery problems when cruising at higher speeds (higher loads) and higher engine speeds.  scenarios like 80MPH in clean air (not drafting).  if in this scenario i will periodically experience a brief loss of power either upon gentle throttle application or simply cruising.  it used to feel like hitting a brick wall, now it's more of a hiccup.

i had thought that this was needle clip position related, and hence probably how i managed to break my fuel pump vacuum hose with the starter cable by removing my battery box to get at the slides.

does anyone have other ideas about what this could possibly be?

[Speeddog]

Perhaps your fuel pump is getting a bit marginal on delivery.

Is it the original?

[sur4die]

Perhaps your fuel pump is getting a bit marginal on delivery.

Is it the original?

you know, that was my FIRST impression also.  so i ordered the rebuild kit and installed.  no dice.

so i thought maybe my tank is flaking rust into the system.  so i ordered one of those tank sealer systems, flushed all the lines, the pump, and completely broke down the carbs, dipped them, and put it all back together.  no dice.

somewhere along that journey i ripped open the fuel pump vacuum line and the last thing i did was fix that hose and i'm kinda back where i started...  although not nearly as bad.   hey, at least it's rideable

[sur4die]

so after a day or so the bike began to have issues holding an idle.  it would run on one cylinder and intermittently.  the plugs looked a little too sooty so i decided that it was running too rich and changed out the main jet to the 145 that came in the factorypro kit. 

so far the 145 is really making a big difference!  there is definitely more power and everything seems to be behaving, for now.  i only went for a short ride to lowes for holesaws, i'm building a reef tank, but throttle response was much crisper. 

i'm going to have to get it out on the highway this week to see if this jet change solves my high speed cruising issues.

[Hedgehog]

Just a random comment here, on jetting.  I got the Factory kit, and eventually wound up with good plug color with 130 mains, 70 starter, 40 pilot, 60/1.4 pilot air, y-2 needle jet, factory springs, 3 1/2 turns on idle screws, and needle is 2 from top.  This is on my 94 900SS.

[sur4die]

Just a random comment here, on jetting.  I got the Factory kit, and eventually wound up with good plug color with 130 mains, 70 starter, 40 pilot, 60/1.4 pilot air, y-2 needle jet, factory springs, 3 1/2 turns on idle screws, and needle is 2 from top.  This is on my 94 900SS.

for whatever reason the 900ss likes smaller jets than the m900.  take a look at the example installs about half way down.
http://factorypro.com/Prod_Pages/prodd09.html
then look at the m900 page sample.
http://factorypro.com/Prod_Pages/prodd12.html

and the instructions that come with the kit give 2 more examples for the m900 and both recommended the 155 with an open airbox and high flow exhaust.

i guess my setup doesn't flow all that great after all.  i have always known that straight pipes and pod filters weren't the best performers, no scavenging, but i guess i just didn't want to believe it.

[sur4die]

took it in to work this morning...

it started easily enough, but idled a little rough, intermittently dropping a cylinder.  it was doing this before, but it would do this after it warmed up.  now i'm intermittently dropping the one cylinder only when it is still a little colder.

so my best guess is that my idle was a little rich, and now is a little lean.  i'm going to ride home and check plugs before i make any adjustments though.

oh, it is also definately running a little bit warmer than it has been.  i'm also going to try and duplicate this observation on the return trip.

[printman]

for whatever reason the 900ss likes smaller jets than the m900.  take a look at the example installs about half way down.
http://factorypro.com/Prod_Pages/prodd09.html
then look at the m900 page sample.
http://factorypro.com/Prod_Pages/prodd12.html

and the instructions that come with the kit give 2 more examples for the m900 and both recommended the 155 with an open airbox and high flow exhaust.

i guess my setup doesn't flow all that great after all.  i have always known that straight pipes and pod filters weren't the best performers, no scavenging, but i guess i just didn't want to believe it.

I would agree with this     142.5 main 4th clip from top (richer) and a 40 pilot

[sur4die]

I would agree with this     142.5 main 4th clip from top (richer) and a 40 pilot

what's your setup (intake and exhaust) on this jetting Printman?

[printman]

open air box and stock exhaust

Would really die off at 9000, cause of the long intakes


FCR's have it running strong on top 

[sur4die]

i really wish i had a tach...

[meano_lover]

this just helped me alot. thanks y'all.

[sur4die]

this just helped me alot. thanks y'all.

i'm glad it helped someone...  i couldn't quite get mine dialed in and i needed new tires mounted anyway, so i am having my local shop dyno tune it while it's in for the tires.

i'll definitely post the settings that come back on it though.

[meano_lover]

i'm in the middle of doing mine right now. i hope it all goes well...