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Discussion Starter · #1 ·
To the guys who know their stuff,

I have been looking through the forum and can't seem to find anyone with my setup for more info on jetting...
My bike is stock, as far as engine and exhaust goes.
I have the raptor 660 2001 standard exhaust system with the spark arrester removed.
I had the standard airbox and filter, (which ran fine) I have bought a K & N high flow and adapter and fitted it, I WANT TO RUN IT WITHOUT THE AIRBOX LID.
As soon as I have done it it runs like crap...pops, backfires and dies if you keep the throttle pinned.
If I apply the choke when I start pinning the throttle it gets better... if this helps diagnose...
It idles fine, I took it to a bike shop as I did not want to stuff around and wanted it ready for a weekends ride. (Stupid me)
Their fix was stuffing the airbox intake with foam and restricting the flow of air, it runs better like that but backfires when you back off the throttle (but why buy a high flow filter, I say, can't believe these guys ! )
They did reset the float levels and cleaned out the carby and reset the needle positions, but the lid of still pops and dies ....hopeless)
I need to rejet (this is what I asked them to do, bloody hopeless) as I would imagine from reading the posts in this site...
Please send me your suggestions on what I can do to the carb setup, what size jets etc I might be able to use.
I usually run it along the beach so not far from sea level.. Any help would b gr8...cheers
 

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So you're running with a no lid setup and stock exhaust correct?

If you're going to increarse airflow, you need to increase fuel flow. You said they "reset the needle positions", well the stock needles were probably fine on the 3rd clip. The bike needs to be rejetted, either by them, you, or someone else. You'll probalby want something like mikuni 145 left, 150 right mains, oem needles in stock 3rd clip position, and you'll probably want to turn your fuel screws out a bit to make it idle better.

It's also possible from what you're describing, if it's as bad as it sounds, that your bike's parking brake is not adjusted properly and the associated rev-limiter is kicking in causing essentially an almost complete loss of power.
 

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does it run ok (or better anyway) if you put the airbox lid back on it?

Take the foam out of the airbox and try 25 pilots at 2&1/2 turns out on each screw, 150/155 mikuni mains with needles on 3rd clip
 

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The wife's Z400 leaned out so badly with the airbox lid removed that it wouldn't even run over 1/4 throttle. It felt like the rev limiter was kicking in. You definitely need to step up the jetting, you were probably slightly lean after gutting the spark arrestor, and the no-lid k&n setup put you over the top. You need to start by finding out what jets are in it now and stepping up one jet size for starters. If you are at 140/145, you will want to go to 145/150. So swap your right jet to the left carb and go get a 150 (or what ever is one step up from what you had) for the right carb from the nearest dealer (preferably not the foam stuffing dealer). If this doesn't clean it up, repeat with the next larger size. I can't imagine you would need to go up more than two sizes for just opening up the airbox.
 

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Discussion Starter · #5 ·
So you're running with a no lid setup and stock exhaust correct? Correct...

If you're going to increarse airflow, you need to increase fuel flow. You said they "reset the needle positions", well the stock needles were probably fine on the 3rd clip.
The needle postions were set to to 4th clip, i have now set these back to the 3rd clip (from the top)
The bike needs to be rejetted, either by them, you, or someone else. You'll probalby want something like mikuni 145 left, 150 right mains, oem needles in stock 3rd clip position, and you'll probably want to turn your fuel screws out a bit to make it idle better. It idles fine
I'll give it a go, thanks, i will buy 150, 155 and 160 just incase

It's also possible from what you're describing, if it's as bad as it sounds, that your bike's parking brake is not adjusted properly and the associated rev-limiter is kicking in causing essentially an almost complete loss of power. No not the park brake, if you restrict air flow the bikes nearly runs fine...

does it run ok (or better anyway) if you put the airbox lid back on it? Yeah heaps better.... just backfires a bit on decelleration when you ride it

Take the foam out of the airbox and try 25 pilots at 2&1/2 turns out on each screw, 150/155 mikuni mains with needles on 3rd clip, I will give it a go, cheers

My bike was too rich, my choke was broken previously once i found the problem i found that choke cable was broken and just sitting threre and had to get that fixed which has also been thrown into the mix....Got the valve clearences done also.
I checked the float levels, did the clear tube test. All fine there....
When it came back from the shop they had 6 turns on one side (air mixture screw) and 2 on the other carby (bit out of spec i would say), I have now changed it to 3 turns with the pilot changed it has made a difference, does not bog down until bit over half throttle, bought the wrong main jets today so back to get the correct mains tomorrow....I found i had 140/145 mains in it
 

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Sounds like you're well on your way. Just in case you weren't aware, 140/145 mains are stock.
 

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Discussion Starter · #7 ·
Yep, trying to get the girl up and running, tracked down a mate who knows a lot more about jetting, got the new jets on order now...
Thanks yes, I tracked down a raptor manual to find out what the standard jet size was, just wanted to make sure I explained exactly what was in it....

I appreciate your help guys... :thumbsup:
I am going to stay clear of bikeshops as much as I can now... :mad:
What a let down.... :3question:
 

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Discussion Starter · #8 ·
Today I changed the jetting.
I ended up with needle of 4th clip and 160/165 and 27.5 pilots, three turns on the mixture screw, no backfiring, no hesitations.
Still not enough to run without the lid off the airbox, though I have cut all the restrictions out of the airbox lid, left the chamber in the middle, but cut all the rest out.
I still have to run with the lid on so.
Still dies at 80% throttle, with the lid off.

I must say now it flies now.... 1, 2, 3 off tap, front wheels off the ground every gear except 4th and 5th.
Now by touching the throttle in first a touch lifts the wheels off the ground, much better, but think I can go more....

Do you think I still need to go more in the jetting to run without the airbox lid ? Say 165/170
 

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The stock exhaust even without a spark arrestor insert doesn't flow enough that it should need that big of a main jet. Basically the bike now is jetted (mains, pilots and needles) the same way it should be with many aftermarket exhausts, so conventional wisdom would say the jetting is already as rich as it should ever be with that setup.

All of that said, you're the one with the bike and doing the tuning and I can't and shouldn't tell you how your bike is running. So if you're unable to get enough fuel on top end, throw in the bigger mains.
 

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Discussion Starter · #11 ·
Today I changed the jetting again.
I ended up with needle of 4th clip and 165/170 and 27.5 pilots, three turns on the mixture screw, no backfiring, no hesitations on idle, middle response is good too.
Went for a quick run down the street, now hestitates a little at top end.
I went with the airbox lid on and it runs better with it on...
Will try another run on the weekend.
Close enough to run without the lid off the airbox for now..(maybe)
One thing, can the fine tuning up top end of the throttle be done with the mixture screws or are the mixture screws only to adjust the idling.:unsure:...any responses would b gr8.. :grin_nod:
 

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I am wondering if you don't have a vacuum leak somewhere. Your jetting is so rich, especially for a relatively stock bike, that I am wondering if you might have a bad carb boot or some other source of intake leak. You really shouldn't be jetted that rich.

Mixture screws are for idle/low rpm only. Your top end/high rpm tuning will be main jets only.
 

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Discussion Starter · #13 ·
Cool, I hear you guys, seriously..
Before I added the [email protected] N it ran fine but a little rich due to my choke sticking...
Now the choke has been replaced...
As far as breathers go...

I have the breather for the gearbox it breathes fine, it used to connect to the airbox lid...and the breather for the carby loose is sitting near the airbox, that's the way it always has been... i take it they do not connect to anything being breather pipes ?
I have checked my choke, boots, and park brake... I have now had the carbies off about 20 times...
I hear them slip into place and check the boots each time to ensure they are home and are tight and in the correct place...

The only thing that tells me to go in this direction is no top end power...just dies as soon as i remove the airbox lid..If I put the lid on the airbox i can rev it to the rev limiter without any hesitation whatsoever....
It has always idled fine and ran fine at mid throttle... I can see much better responses from the bike at each jet change, (when the lid has been removed)... with each jet change i can stop blocking the air box by a few inches i have been covering it in stages to see where it dies and how much i have to block off before it starts running correctly......
I too cannot belive how much it has changed the bike...it baffles me !!
 

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Discussion Starter · #14 ·
I have now got it running with the lid off..
I had to go 170/175 in the main jets, mukuni jets...
It now revs fine all the way through to 7000...
I have fitted a trailtech vapour (hence thinking it is 7000), it does not seem to want to push past 7K any more and does not seem to reach the rev limiter either...
No black smoke, can't find any air leaks, all the intakes are tight...
The bike should rev higher if I am not mistaken...
Any suggestions ?
 
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