M750 '00 Carbed Jet Kit Idling

[J-Cee]

Installed Factory Pro jet kit. Started with a 145 main jet. Ran pretty awesome! I felt my bike wasn't pulling hard on the top end (idled great) so I put the next size down main jet (either a 142.5 or 140). It pulls better at the top end but now the idle is rough. I also noticed the pilot jet originally was a 45! I put in the 42.5 that came in the kit. Should I switch it back to the 45? Or did I not put something back together right? Tried adjusting air/fuel screw but did nothing.

[ChrisK]

If it was idling fine, then you changed the pilot jet, and now it idles rough I would try going back to the previous size and see what happens.

Also, there are two mixture screws, one per carb. I believe recommended turns out is usually around 4, but then you dial in your particular setup from there.

Also, there is a carb sync screw and a idle speed screw that you need to be wary of when dialing them in.

[J-Cee]

Yes, I synced them. I did reduce the size of the pilot jet to 42.5 from 45 but it idled great with the 145 main jet. I adjusted both air/fuel screws. I backed them out to over 5 turns with no change to the studdering idle.

[ChrisK]

I might be confused about what you're saying... but what I'm saying is, try and change the pilot jet back to 45. If it smooths out the idle, great. If not, you have to go back to the other main jet.

[J-Cee]

Gotcha. That was my plan.

[brad black]

if it idled great with the 42.5 pilot, then you made a main jet change only and now it idles badly with the 42.5 pilot i'd assume you did something wrong during the main jet change that is unrelated to the pilot jet.

[J-Cee]

That's also what I was thinking. I put the other pilot jet in and it runs good now. Also discovered that my petcock was bad. Is there a reliable vacuum operated one?

[ducpainter]

That's also what I was thinking. I put the other pilot jet in and it runs good now. Also discovered that my petcock was bad. Is there a reliable vacuum operated one?

Not really.

Get a manual one.

[J-Cee]

I went back to the 42.5 pilot. Idles better but still not great. The temp around here dropped a good bit last week (mid-upper 60's). I bought this bike when it was 90 degrees out so I don't know how it should run in colder weather. Seems to stumble at first then gets better when warmed up. Pulled the plugs and they look good. Again here's the specs:
K&N Pod filters
Factory pro jet kit
Main jet 140
Needle on 2nd notch
New needle jets
42.5 pilot jet
Fuel screw at 2.75 turns out

[ChrisK]

Pod filters suck in quite a bit of air, maybe go a little bit richer on the mixture screws by turning them counter-clockwise.

[koko64]

I would set the needle at the position recommended for open airbox or pods if the kit mentions it (just a thought).

If your main issue is running at idle rather than low speed operation then try the idle screws turned out 1/2 a turn. Go for the idle screw setting that gives the strongest/fastest most even sounding idle. Try 1/2 turn increments to find the sweet spot.. Some go each way with the turns to make the idle falter and then set in the middle plus a tweek. If you need more than 4 turns out for a good idle, then consider going up in the slow jet. If you need less than 1 turn then maybe go down a size on the slow jet.

If the problem is low speed tooling around, then you need to play with slow jets and maybe needle postion. The correct slow jet and IMS setting will show itself only when the bike is well warmed up. If its sweet straight up when cold its too rich and performance will degrade as it warms up.

[J-Cee]

Thanks! I was gonna move the needle to pos #3. I am going to try the fuel screw too.