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high compression stock bore jetting driving me mad

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this for a fcr39 slant with E cams MRD Z PRO with quiet insert, stock 400cc with single layer base gasket (paper kind) wossner 13:5:1 compression piston. originally it was rich ith dxp needle & 178 main jet , now I've tried both EMN & NCYR (rmz450) needles on different clip positions with every main jet from 160 down to 145 & every size between but its still got way more power o WOT if i leave the airbox door off. it runs smooth through the rev range & pulls well but it just pulls so much more with the airbox open at full wide open throttle, am I missing something else or do I need to go down smaller still on the main jet still, 

could the high compression have same affect as a big bore by pulling through more fuel hence needing a smaller main jet or is there someting else i need to be looking at??

its got 45 pilot jet, 60 starter jet & the 2 air jets are a 200 & a 60 with the coast enricher removed & a pipe connecting the ports (not blanked off)

I've been setting the fuel screw every time i change jets & sometime it can go more than 3 turns out without getting rough It just revs higher & with some jets it has a slight hang on the idle ( around 500-750 rpm more then drops back down)

I'm tearing my hair out ere I've had the carb off & on a stupiid amount of times in the last few weeks & I'm gettin to end of my tether, can anyone help plesae  :banghead:

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How old is the FCR ? Have you thoroughly cleaned the carb ? Have you checked the slide plate for wear ?

I would try a 155 main and go leaner on the needle , leave the 155 in and experiment with The Needle .

You could also try ( test ) it with a mildly vented air box door .

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How old is the FCR ? Have you thoroughly cleaned the carb ? Have you checked the slide plate for wear ?

I would try a 155 main and go leaner on the needle , leave the 155 in and experiment with The Needle .

You could also try ( test ) it with a mildly vented air box door .

its from a 2006 KLX that had done 2000 miles, it looks all good but I haven't completey stripped & cleaned it since i've had it on (6 months & 2000 more miles so far) my bike allways ran great with it untill the weather got warmer then it started to cough sometimes under load when i wound it full open from low revs. it runs almost perfect now as it is but its just got more power when i take airbox door off.

I've tried needle in different positions with every jet between & including 145 to 165 but it doesn't seem to vary much

would the higher compression have a similar effect to a big bore, ie needing smaller main jet?

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might just be the nature of the beast .. if its running well personally i would consider the job done .. you can do all kinds of things to them to get more power, same with a car, but having things in place to make it work well in the real world like a closed airbox is more important ... to most people .. another point is the noise level .. a loud intake can make a vehicle sound like it has more power when in reality it doesnt, or very little more ..

.. finally, i would guess that having a non-stock compression, which i have no idea about in a drz, but changing compression would generally call for the proper cam to take full advantage of it ..

Edited by cowpie

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might just be the nature of the beast .. if its running well personally i would consider the job done .. you can do all kinds of things to them to get more power, same with a car, but having things in place to make it work well in the real world like a closed airbox is more important ... to most people .. another point is the noise level .. a loud intake can make a vehicle sound like it has more power when in reality it doesnt, or very little more ..

.. finally, i would guess that having a non-stock compression, which i have no idea about in a drz, but changing compression would generally call for the proper cam to take full advantage of it ..

I dont wanna run it without air box door i just found out its quite a lot more powerfull wihout it while i was trying to get jetting set up right & would like to find right jetting to get same power with it on but I'm gettin down to small main jet sizes now for a 400cc goin off everything i've read so wanna know if i'm overlooking something before i go down smaller still.

its got E cams in there

Edited by carlspeaky

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Have you done the 3x3 mod?

ye ye did all that way back when i got the bike &  its actually more like 3.5 x 3.5 now coz i trimmed it up a bit & i also tried it with no air filter but with the door on to see if maybe a K&N might work better to see if that helped any but it didn't. (i wasn't expecting it too tbh but I'm clutching at straws now lol )

I've ordered  142 & a 140 main to try next & see how it is then but I'm gettin a bit worried about makin it too lean  :confused:

Edited by carlspeaky

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I dont wanna run it without air box door i just found out its quite a lot more powerfull wihout it while i was trying to get jetting set up right & would like to find right jetting to get same power with it on but I'm gettin down to small main jet sizes now for a 400cc goin off everything i've read so wanna know if i'm overlooking something before i go down smaller still.

its got E cams in there

 

 

You super sure it's running better with the air box door removed ...often the increased induction noise with the door removed gives one the illusion that it's going better...

I wouldn't believe it needs anything less than a 152 main jet...OBDXP needle on clip 5 won't be rich with the size of your enlarged 3x3  mod...

If your getting some hesitation on quick throttle applications it's because of the cork in the Mrd.... Inserts in race pipes in combination with an fcr carb is a known possible issue

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No it's defo not induction noise making it seem like that, I literally can't keep front wheel down in 1St gear when I wind it full open with airbox door off and it only comes up a bit with only power with it on

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What was the leanest jetting (needle and clip..MJ) you were you running when it made a big difference with the door removed.?

Edited by Craig-o

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It's been pretty much the same with every variation I've tried but leanest to date is 145 MJ with EMN needle on 1St clip (top one) I have noticed it doesn't pop on decel as much with the 145 MJ which is opposite to what I'd expect

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Haven't tried it without insert, I'll try that and see if it makes any difference, I've got 142 & 140 main jets to try and if that doesn't change anything I'm gonna try a different fcr carb I've got to see how that works
I'm at sea level

Edited by carlspeaky

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I would try a 155 or 160 mj. 45pj.emn needle on the 4th clip . Fuel screw 2.5 turns out

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Already tried all that mickey that's why I posted to begin with coz although everything's good set up like that (& various other combinations of jet & clip position) it still makes a lot power without the airbox door on, I don't know if people are getting what I'm asking here coz there are no problems with how it runs it just makes a lot more power if I run it without the airbox door

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Maybe clean or replace your air filter. I don't know how you can try all those different settings that work for the rest of us and still can't dial in good settings for your bike.

Have you tried jetting without the quiet insert?

Edited by sdhydro

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Air filter is clean I even tried it without a filter but with door on and that made no difference either. I Just took the quiet insert out today and there's not much difference. I'm on with trying a 140 main jet now. I've just got put carb back on and go try it and if that is same I'm gonna try and different fcr carb I've got

Edited by carlspeaky

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right I've just got back from a long ride with a 140 main jet in there now & its now not much different with door on as with it off although it does still have a bit more power without it still but its the closest its been so far, 

this makes no sense to me & I'm getting paranoid I'm way to lean & gonna cause some damage. 

is it only mine or does anyone else seem to have more upper mid & high revs power without the airbox door?? 

and what the hell could it be causing mine to be like this??

Edited by carlspeaky

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