Correct Jetting for CBR f2 with full exhaust?

Pater · 01-10-2004, 12:28 AM

I've got a 94 F2 that's had a full two brothers exhaust put on it. The fellow I bought it from said it was jetted and had a K&N filter. The thing is still pretty sluggish off the line, even with a 45 tooth sprocket. I've since cleaned the filter, which was filthy, and plan on adjusting the jets.

Anyone have the specs for jetting this bike with a full system? It would sure make things easier.

thx,

Jay · 01-10-2004, 12:51 AM

Factory actually uses smaller mains in their kits, but thats because they dont(didnt) have a kit for an exhaust and a K&N.

When I did mine, I use #140's on the outside two carbs, and #138's on the inside two. Reason being is that the inside two tend to run rich, so by using a slightly smaller main their, it helped to balance it out.

This is all info I was given ions ago, so some is a little vague. Do a carb synch first, and try to gradually increase the air mixture screws also.
The air mixtures are a little more trial and error without proper equipment.

Some multimeters will have a CO adapter that you can use to test the exhaust. I think you want a .2 reading, but no more, it would be too much.
Again, I am a little foggy on all this, so I know someone will tear me a new one correcting me.

You can always take a temp. reading from the base of each header pipe about 1" from the head. Any variations will indicate which cylinder is running lean or richer than the other.

Hope that helps a little.

CBRBob · 01-10-2004, 9:19 PM

Put a stock air filter in it. Dynojet will tell you to do that as it is basically impossible to tune a F2 correctly. If I remember correctly, even after dyno tuning the bike had a part throttle stumble so we raised the needles 1 line. The way to check if you REALLY have a jet kit in there is that there are shrouds crazy glued in place around where the needles drop into the emulsion tubes. They tend to loosen up(cant drop in thank god) but then the bike runs weird. If those shrounds arent there, its not jetted.

Pater · 01-11-2004, 11:49 AM

Bob, turns out it does have the aftermarket jets. However, whoever put them in did not epoxy the hole in the shroud. Got on dynojet's site and found the correct hole to plug.

The instructions say to put the clip two rings down from the top, which they are. Did you move yours up one more from that or did you have yours on the 3rd ring (right in the middle)?

Thx.

CBRBob · 01-11-2004, 8:00 PM

After it being dynoed for max power it had a slight 'rolling on the throttle' stumble in the midrange, right where you ride on the street 90% of the time. I knew the dyno op. real well so he gave me some shims to try. I used 1 under each, then 2. It got better but not quite perfect. I moved the clip down 1 ring(raising the needle) and it went away. He showed me the graph that he had and the bike was down like 1 hp from 10-13....I'll take it. If you dont have that stumble anymore, leave it be!