Modded 300ex jetting help!!!!!!!

[riley1374]

Need help jetting my bike. 300ex 11:1, stock carb, port & polish, big cam, HD valve springs, fmf Q series full exhaust. Below is what i have tried so far:

1) 155 main/ 38 Pilot 2 1/2 out on screw, needle clip 2nd from bottom-RESULTS
Backfired on deceleration 1/8 Throttle but rev'd ok

2) 140 main/ 42 pilot 1 1/2 out on screw, needle 2nd from bottom-Results
Wouldnt rev at all, it would idle but nothing above that

3) 155 main/a 42 pilot 1 1/2 out on screw, needle 2nd from bottom- Results same as above.

4) 155 main/ 38 pilot 3 out on screw, needle 3rd from bottom. Results- Rev'd great glowing header and high idle(couldnt get idle to come down at all)

5) 140 main/ 38 pilot 3 out on screw, needle 3rd from bottom,
Results- Rev'd great thru entire range but glowing header and backfire on decelaration on mid to low rpms.

Please help!!!!!!!!!!!!!!

[hardkoratvmxr]

try a 142 main 38 pilot 3 out on screw, needle 3rd from bottom

[riley1374]

ttt

[2muchquad]

a 155 is way too big,im running a 158 or so with a 385 kit.:rolleyes:

[riley1374]

I tried the 42 pilot 1 turn out on mixture screw with needle clip in second position from bottom, 140 main and its running much better. Still pops on deceleration a little bit, but i think if i turn the screw out another 1/2 turn i think i may have it. Any other suggestions are greatly appreciated.

[kc8pnd]

riley1374, I am in the same boat as you, just wondering if you found the right jetting? I am about to place an order for some jets. 130, 132, 135, 138, 140 Keihin main jets. 40, 42 pilots. my dynojet kit let me down, 128 is as big as it goes and it runs like crap, cuts out big time at the top and has no where near the power it should.

[2muchquad]

if you have a stock bore 300 with just a exhaust system,i think even a 128main in the dyno jet kit would be too big.try a 122 from the kit.your probably way rich thats why it loads up at full throttle;)

[kc8pnd]

Stock bore, 11:1, K&N, Power 4 Core FMF with vents in air box lid. I put the 124 in it and it felt like I was riding a moped.

[Sjorge450R]

Originally posted by kc8pnd
riley1374, I am in the same boat as you, just wondering if you found the right jetting? I am about to place an order for some jets. 130, 132, 135, 138, 140 Keihin main jets. 40, 42 pilots. my dynojet kit let me down, 128 is as big as it goes and it runs like crap, cuts out big time at the top and has no where near the power it should.


do you know that they dynojets are measured different???? I have a 128 Dynojet (equivilent to like a 132ish kehin) and my quad runs great.

[kc8pnd]

hmm I thought they were like 2 sizes bigger. I will try the 128 again and mess with the mixture screw some more.

[Sjorge450R]

Originally posted by kc8pnd
hmm I thought they were like 2 sizes bigger. I will try the 128 again and mess with the mixture screw some more.


what kind of set up are you running?

[kc8pnd]

No lid, 11:1 weisco, K&N.

Just spent got done messing with it some more. I forgot to put the dynojet adapter in :| I know I am an idiot. Put the needle on the 3rd clip and it runs a lot better, still kind of falls on its face when you just mash it when its in neutral. But! I think that can be fixed with a little more time on that mixture screw. I did notice the head pipe no longer glows!

[Sjorge450R]

Originally posted by kc8pnd
No lid, 11:1 weisco, K&N.

Just spent got done messing with it some more. I forgot to put the dynojet adapter in :| I know I am an idiot. Put the needle on the 3rd clip and it runs a lot better, still kind of falls on its face when you just mash it when its in neutral. But! I think that can be fixed with a little more time on that mixture screw. I did notice the head pipe no longer glows!

do you have a aim screen name? Hit me up : Sjorge3442

[bwamos]

Originally posted by kc8pnd
No lid, 11:1 weisco, K&N.

Just spent got done messing with it some more. I forgot to put the dynojet adapter in :| I know I am an idiot. Put the needle on the 3rd clip and it runs a lot better, still kind of falls on its face when you just mash it when its in neutral. But! I think that can be fixed with a little more time on that mixture screw. I did notice the head pipe no longer glows!

Thought that might be what you did when I read the upper posts.

We all make silly mistakes.

The 11:1 is going to jet a little different than stock. You're going to have a higher intake velocity, due to a lower airspace at the start of the stroke, less air for elasticity. You will probably need to go a size or two larger than what the DJ kit reccomends.

However you're runngin stock exhaust is sounds like. That throws a wrench into the deal.. lol. Not sure where it would jet. Might look into an exhaust of some sort (just no cobras).

Does it bog down or sputter and act sluggish at full throttle?
Bog down = too lean
Sputtering and sluggish = too rich

[kc8pnd]

err I failed to add that, fmf core 4 header also

I do have some larger mains coming, 130 to 140 all the sizes in between also. along with 2 bigger pilots.

[kc8pnd]

Ok, my frustration is about to get the best of me. I have tried every jet (125 - 140 main) with screw settings from 2.5 turns all the way up to 5 turns out on the mixture screw and 2nd and 3rd notch on the needle. Right now it run ok on 3 turns out on the screw and a 135 main 38 pilot. But when I blip the gas over and over its fine on the first3 or 4 blips then starts bogging out after. I am about to see if my ak47 can fix it...

Any tips? Sounds like this http://caksquad.com/Downloader/

I have cleaned the carb 3 times now, checked main jet pilot and mixture screw holes, all clean.

11:1 Wiseco
FMF Power Core 4
Lid off
K&N with outerwear

[rooster300ex]

yea when i read it i thought it the main is way way way to big.