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Discussion Starter #1
Hey guys!

I've acquired the carbs of a 2002 Raptor 660 to fit on my 1990 Yamaha XT600E.
If you're unfamiliar with this bike, it has the same engine as the Grizzly600.

I've tested several jets and right now I'm close to sorting it out. (I hope)
I've got 145L-145R #25 pilots and needles on the 2nd groove(from the top of the needles) and I think I'm still on the rich side as the bike hesitates a bit at constant speed and upon dropping the clips to the 3rd groove on the needle it gets worse..

Not really sure how many turns on the fuel screws as I got 1Vito's and 1 stock but I've dialed it in to where is idles good enough and very rarely pops on decel... (the stock carb with stock bike used to pop alot more lol)..
Don't remember if I have the Vito's or the stock needles..


My question is, Why the need for different main jets from the left carb to the right carb?


The main difference I can imagine for this is because the raptor engine and the XT's are that the raptor has 5 valves and the XT has 4valves (2exhaust and 2 intake).
Is this correct?


Last night I ordered online some new jets in increments of 2.5 from 127.5 to 140 and hopefully I can get this sorted out nicely..


Any help is highly appreciated!
Thanks!

Vando :)
 

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Hey guys!

I've acquired the carbs of a 2002 Raptor 660 to fit on my 1990 Yamaha XT600E.
If you're unfamiliar with this bike, it has the same engine as the Grizzly600.

I've tested several jets and right now I'm close to sorting it out. (I hope)
I've got 145L-145R #25 pilots and needles on the 2nd groove(from the top of the needles) and I think I'm still on the rich side as the bike hesitates a bit at constant speed and upon dropping the clips to the 3rd groove on the needle it gets worse..

Not really sure how many turns on the fuel screws as I got 1Vito's and 1 stock but I've dialed it in to where is idles good enough and very rarely pops on decel... (the stock carb with stock bike used to pop alot more lol)..
Don't remember if I have the Vito's or the stock needles..


My question is, Why the need for different main jets from the left carb to the right carb?


The main difference I can imagine for this is because the raptor engine and the XT's are that the raptor has 5 valves and the XT has 4valves (2exhaust and 2 intake).
Is this correct?


Last night I ordered online some new jets in increments of 2.5 from 127.5 to 140 and hopefully I can get this sorted out nicely..


Any help is highly appreciated!
Thanks!

Vando :)
Staggering the main jets on the 660 is due to the intake manifold and how it distributes the fuel to the combustion chamber. The middle intake valve is split about 30-70 on a stock cylinder head. The Left carb will feed 1.3 intake valves and the right carb feeds 1.7 intake valves. In your set up you would run equal mains on each carb.
good luck.
 

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Master of the Electron
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As blue said, it's due to the Rappy's 5 valve (3 intake) head and the distribution between the two intake ports and the valves. Assuming your head is ported symmetrically with 2 intake valves, equal main jets would be ideal.
 

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Discussion Starter #4
Ohhh, now that explains things a bit..
I totally forgot about the shape of the intakes..
Should've guessed it as I've seen a lot of those intake spacers on ebay saying it'll increase 4HP (so they say) on the raptor.


One more question, when one decreases the main jet a few sizes, when should you change the needle clips? after increments of 5?

right now I got 145's and if I go to 140's should I lower the clips one notch?

Thanks for the explanation blueranger! :)


Just to say that...
Earlier today I set the needle clips on the top notch to "compensate" by the decreasing the flow for the over-rich mains just to check how it behaved and it behaved slightly better at midrange but not as fast at WOT as on the 2nd groove..

And about half hour ago I went to try the bike as the air today is much cooler right now than normal by 5 or 6ºcelcius (clips still in top groove) and it behaved even slightly better all through the rpms..

Am I on the right track here?

Thanks again!
Vando :)
 

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Discussion Starter #5
Hi Quadmaniac!

Yup both intakes are ported the same!
Can't believe I was actually trying 160 and 165 mains 4th groove before.. my plugs got completely sooty dark and I could only rev the bike to wot in 1st gear but damn the bike would wheelie so easy lol

I've got a few mods on the bike tho..

K&N RU4710 with the stock boots (carb to filter) linked to some 45º hightemp PVC pipes so it could fit nicely in the fiberglass "airbox" that only protects from mud and debris coming from the rear tire..

One more thing.. what's the difference in matter of turns in/out from the stock fuel screw to the Vito's fuel screw?
 

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Master of the Electron
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Sounds like you're heading in the right direction - and having colder air as a test tool is nice - now you know what happens when you lean everything up a bit.

Unless the Vito's screw has EXACTLY the same taper on the end, then there's going to be little correlelation between the two screws... I'd suggest getting matching screws.
 

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Discussion Starter #7
Hi!

Yeah, I'm thinking of getting a rebuild kit for both carbs that has all those little parts..
And since I've already changed both of needle springs(from the throttle bodies) and the float seat o-rings as they were leaking fuel out of the drain holes and is starting to leak again from time to time..

I was gonna get the Vito's fuel screws but they want almost 20 bucks for each PLUS 15bucks for shipping to Portugal..
And one can get for the same price the whole kit of ebay WITH shipping! wtf :eek:

Everything else is nice and clean inside..

The only thing I didn't touch was the air cut-off valve because I don't have the parts to replace if anything is bad in there so I've left it for last..

Wish I'd have a Dyno in this freaking island to really test everything...:burnout:


I'll post a few pics later so you guys can check how everything looks now

Thanks again!
Vando :)
 

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Master of the Electron
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The Vitos kit is worth having - you'll have an assortment of Mikuni jets for future mods, 25 pilots and the extended screws... it's a good deal.

Other than removing the air cut-off diaphragm when cleaning (carb cleaner can damage the rubber), I don't do anything to it either, except spraying out the passages when the diaphragm is out.

I have never quite figured out what the air cut-off system's purpose is, although I expect it's emissions related - anybody know for sure what it does?

Happy riding!
 

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Discussion Starter #9
I already have one.. but I broke a tip of one of the fuel screws.
actually, I was turning it out and the tip stayed fully stuck in.. :rolleyes:

I don't think I'll be doing anymore mods in a long while lol..
I already have a Devil bigbore headers and fitted the exhaust of a 2008 WR450 (I removed the inside plate that has 2 offset small diameter tubes but kept the nozzle because of the popo)..


I actually made a list long ago of performance mods I'd like to do someday..

So the next thing up would be, but only if my engine goes Kaput, is stage 2 camshaft, Wiseco 12:1 high comp piston, titanium valves and springs, raptor 660 barnett clutch basket and plates with new springs..

but that takes alot of time and money lol

here are some pictures of the bike:
http://img706.imageshack.us/g/dsc02980gp.jpg/
 

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Discussion Starter #10
Hey guys!

Can anyone show me a picture of one of the fuel needles with all the little spacers in the right order please?

or tell me which the order of the shims...

I've received a repair kit for the carbs.
There is no more gas leaking!

Bike starts fine!
I'm down to 135 mainjets, #25 pilots, needles in 5th notch (rich) and 2.5turns out on each stock fuel screws.
Had it on 2nd groove: bike hesitated on high rpms and spark plug was white lean!

Now it's on the 5th groove and it has become darkish chocolate.. still a bit rich.
Bike stutters/hesitates from no throttle to about half throttle and if I let go of the throttle at WOT and then accelerate again..



I really need a picture of at least one of the needles with the shims on or in order...


Will take the carbs out right now..

I'm going to put both needles on 4th groove and check it but doubt the stutter will go away...

I'll check back in about an hour...

What can be causing this? over-rich low end? or lean low end?


Vando :rolleyes:
 

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Correct me if I'm wrong, but in your first post you said you thought you were rich so you lowered the clip on the needle? By doing this you would be making it richer yet. Moving the clip down you richen it.
 

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Discussion Starter #12
Hi!

I've went down on the mainjets from 145 to 135 on both sides of the carb!

Right now I'm getting changed and do the clip change I was gonna do yesterday...


BTW, Do you have a picture of one of the needles with the shims?
Or do you know the order of the shims?

I could really use the info...
Vando :rolleyes:
 

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Discussion Starter #13
Well..

Pros:
Changed the needle clips to 4th groove and it had a good effect as now there is much less hesitation/stutter...

Cons: WOT first and second gear...not as good as before.
It was better before with the needle clip on 5th groove.


Any ideas???

Vando :eek:
 

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Well..

Pros:
Changed the needle clips to 4th groove and it had a good effect as now there is much less hesitation/stutter...

Cons: WOT first and second gear...not as good as before.
It was better before with the needle clip on 5th groove.


Any ideas???

Vando :eek:
You have two problems to sort out. 1. The needle, which is the charge you feel at mid throttle response to WOT. and 2. the main jet which is WOT. If you get the bike to respond well at mid throttle and it charges fast when you whack the throttle the needle is fine. Then you will focus on the main jets for bog or popping at WOT. Both will work in concert so don't make dramatic changes, take baby steps.
As for the picture of the needle and the shims. I've built many carbs and they all assemble differently. I can't recall if there are shims under the clip on the stock carb and really it doesn't matter unless the clip isn't big enough to support the needle on top of the hole it's dropped into. Otherwise each shim would represent a clip position so adding shims is like dropping the clip on the needle which will provide more fuel delivery in the mid range.
 

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Discussion Starter #15
Well, I'm in a standstill right now..

I've sorted it out to two "goodish" combos:

1- Vito's needles 3rd clip, #22.5 pilots, 2.5 turns out on the fuel screws, 132.5 mainjets.

2- Vito's needles 2nd clip, #22.5 pilots, 2.5 turns out on the fuel screws, 135 mainjets.

Results:

1- Bike pulls good from low to wot but if you let go off the throttle and give it wot again it has slight "hesitation".
Also, sparkplug gets dark with black soot but half of the inner part of the sparkplug is perfect color.

2- Bike pulls good from low to midthrottle but not as good up to wot and misses slightly at wot but there is no hesitation whatsoever if at wot-let go off throttle and wot again.
Also, sparkplug looks clean (lean) with no brownish anywhere...
Bike doesn't sputter at constant throttle unless at a too high revs... (I'll try bigger jets tomorrow, maybe 137.5 or 140?


I got jets from 127.5 up to 145 in 2.5 increments...



I bet the problem is the needle taper.
What needles have a slightly less aggressive taper than the vito's??



I tried the needles from the carb rebuild kit..
They seem to be very similar to the stock needles in terms of tapper.

I went down to 5th groove and it was still too lean, 135's, 2.5turns, #22.5pilots. The bike felt slower in acceleration. Wouldn't top out and sparkplug was white.


Any ideas?
Vando
 

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keep #1, change pilot jets to 25's. Hesitation when coming on throttle should stop. Sounds like you are using DJ main jets (from the numbers you're using). Is this correct?
 

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Discussion Starter #17
Hi..

Thanks, I'll try that I got the #25's from the vito's jet kit :)

Nope, they are actual mikuni jets...
I bought them from an UK website http://www.oro2u.com/ because the shipping expenses are way lower than getting them from the US.

I believe it's them who make the jets tho but they look very well made!

They just didn't have the #132.5 so I bought them from here: http://cgi.ebay.com/ebaymotors/_W0QQcmdZViewItemQQ_trksidZp3984Q2em1439Q2el2649QQitemZ270749612800QQsspagenameZSTRKQ3aMEWNXQ3aIT


The bike feels a bit rich with the combo I'm trying right now..
same as #2 but replaced the thinner shims in the needles for a slightly thicker ones and put on 137.5mains..

It feels like a slow acceleration....

I'ma try the #25pilots with the thin shims on the needles and report back tomorrow :)


Good night!
Vando :)
 

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Master of the Electron
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Sorry, came into this and didn't read back to beginning - assumed it was for a 660... Now I remember that you're experimenting and the Mikuni numbers make more sense.

You might be able to get rid of the hesitation just by turning the fuel screws out (CCW) another 1/4 to 1/2 turn or so. They are just a valve that reduces flow thru the pilot jet, and you can go all the way to 3.5 turns before the jet has max flow... so since you're only at 2.5 now, you can turn them out to increase flow thru your 22.5's and, perhaps, get to where you need to be without replacing the pilot jets.
 

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Hi!

BTW, Do you have a picture of one of the needles with the shims?
Or do you know the order of the shims?

I could really use the info...
Vando :rolleyes:
not a pic though i do have one but its on my phone....

stock is in this order:

top of needle
thin washer
clip
plastic spacer
thick washer
tip of needle

by swapping thin and thick washers you can change the needle height by approximately half a clip position change
 
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