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Discussion Starter · #1 ·
I just spent about 3 weeks trying to sort out a modified 660 raptor. In a way, this raptor helped me figure out a lot of problems with the different carb setup options we have available.

So, before is start, let's just clear up a few things. I am not here to promote any specific product. I am going to try and stick to the facts of what my A/F ratio probe and dyno was telling me.

Even though I have used a modified 660 (stock compression, stage 1 cam, ported head, dual exhaust system) it also applies to stock 660's running open air boxes and aftermarket exhaust systems. If you are running with the lid on, this might not be applicable to you.

Ok, so let's get started.

A lot of people seem to ask which jet kit is better and then you get people who believe jet kits are overrated and you only need to change the main jets. I never had the opportunity to test all of this until now.

For now, let's forget about the main jets. Frankly, I don't believe the main jet design actually have a big affect on the performance. As long as it supplies the right amount of fuel the motor needs, then you’re fine. You can use either DJ or Mikuni main jets. I personally like to use DJ jets, because I got use to their sizes or numbering.

The biggest and most important piece of hardware is the needles. The needle will affect fuel delivery across the whole RPM and throttle range. I know some people say the needle has nothing to do at top RPM, but I found it does.

The right needle can make the difference between a bad, good and excellent running engine. The reason all this has come about is the fact that a lot of people out there believe the 660's are slow and can easily be beat. Well they are not wrong and it comes down to how riders have their 660's set up. Those carbs, and especially the needles hold the key to release a serious amount of power.

I made a post to explain on how to set up the float levels correctly and what other little mods to do to get more power out of these carbs. Doing those mods will get you half way, but here is the rest.

Stock needles.

As mentioned earlier, a lot of people believe that stock needles are fine and jet kits are overrated. After hours and hours on the dyno testing all possible settings on the stock needles, the only conclusion I can come up with is.... TROUGH THEM AWAY!!!!

The stock needles are actually very nice for low RPM power, but as soon as you get over 4500 RPM, those thick tips on the needles prevent enough fuel to come up through the emulation tube and it causes massive lean conditions. I was running massive main jets with these needles and even then, I could not get them even close to supplying the right amount of fuel for top end RPM. The tips of the needles are just too thick

GYT-R needles.

I never used them before now, and the only reason I used them was because the client provided them to me and said I need to fit them.

So, after testing all possible settings here is my conclusion on the GYT-R needles.... They are average, and I would not use them, ever again. These needles cost me weeks of sweat and tears to sort out this modified raptor.

With these needles, even in clip1 and the metal spacer removed, it was supplying way to much fuel at low RPM. (2000 to 4500 RPM) Even in the leanest possible setting, these needles produces a A/F ratio of between 11:1 to 12:1. That is very rich. Also, when you accelerate from low RPM with full throttle, those needles dump so much fuel into the motor, that my A/F ratio meter read off the scale and the engine started to splutter. The fuel actually kills the spark on the plug. From 4500 to top RPM these needles are fine, they work good, so for guys spending most of their riding at high RPM, these needles are not bad, but overall, they are not the best.

Lastly, Dynojet needles.

These are the only needles that I could get to supply the right A/F ratio. For cruising or normal riding, they supply the perfect A/F ratio of 13:1 across the RPM range. From 2000 to 9000 RPM, assuming you have the right main jets obviously.

So, when it comes to needles, don't waste your money on anything else except the DJ needles. The DJ needles will allow you to adjust for basically any type of mod, from stock to modified, so they are the best choice to purchase.

With the needles sorted out, it leaves me with the last problem I am working on to resolve.

Even if the needles are perfect for normal riding conditions, they all have one major drawback. It is actually not the needles fault, but the slide and the way it reacts.

When you start a dyno run at 2000 RPM, all open airbox raptors show a massive amount of fuel supply from 2000 to around 4500 RPM. It produces A/F ratio readings of around 10:1 and lower. Again after testing hundreds of different setups, it seems that the slide is reacting to quickly and opens up way to quickly and dumping a lot of fuel into the motor. With the airbox lid on and limiting airflow, you don’t have this problem, but them the airbox lid reduce top end power output.

So my mission is to sort out that rich low RPM acceleration condition. I also suspect that this is also the reason why the 660’s splutter when you pop a wheelie or crawl up steep hill in low RPM.

The following is not fact and only based on initial testing.

To limit the slide movement, it seems like running dual slide springs per carbs help with the rich low RPM condition. Yes dual springs, meaning I have installed both he DJ slide springs and the stock slide springs. You press them together, from the side, so to keep the total length the same as a single spring.

Initial testing seems to indicate that this leans out the very low RPM acceleration fuel delivery, but it might, note, might, limit top end power output slightly. I will need to test this further, but it might drop around 0.5 or 1 HP.

One last thing I want to try is to modify the slide vacuum holes. I will try and get some used slides and reduce the oval shaped hole at the bottom of the slide. In theory , with smaller holes in the slide it should react slower to throttle changes. I am hoping this will do the same job as the dual springs, but allow the slide to open fully and not limit top end RPM.

Anyway, that’s my findings, use it or don't. It might give some of you some ideas and also help most of you to set up your 660's better and whip some butt.
 

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Nice post Freez, you are a true tuner and not a bolt on fanatic. I am the same way with snowmobiles and two stroke, since all the power is in your carbs half the time. Never played around too much with the rappys carbs. But I did with a 400ex and had a very strong running 400.
 

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when you say in clip one on the needles are you talking from the top (flat side) of needle or the bottom(pointy side) of the needle? thanks i wa wondering when i installed mine i did it as one would be from the bottom pointy side and they go up from there
 

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another? I have i bought the dj kit and have a big gun exhaust slip on and a k&n what clip should i run it in and should i use the little washer spacer in it. Would you recommend using the two springs in it or not. the reason im asking all this is cause i jetted my raptor and now its running real rich and fuel dumps out the carbs when i wheely any help thanks
 

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Discussion Starter · #7 ·
If you are running with the airbox on, the DJ kit recommends clip 4 as far as i can remember. Clip 3 is also worth a try.

Meaning, 3rd clip from the flat end of the needle and below the clip, you need the white plastic spacer and the thin metal spacer.

If you are running without the airbox, use clip 2 or clip 1 with the DJ needle. Plastic spacer and thin metal spacer to be used below the clip.

See which clip position feels the best for slow rpm acceleration.

Also try crawling up a steep hill or rock to see if the bike stutters at very low RPM and small throttle openings. if so, go a clip higher if you can.

Main jets with a slip-on, should be around 148/150 to 146/148 with open airbox. The larger jets are more for coastal riding. You can also try 144/146 if you are at a high altitude...all DJ sizes.

If you still have low down acceleration stutter, try the dual spring setup to see if it helps.

Also, do the clear tube and float mods. You will find it under the sticky/technical posts.
 

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da_peas_2097 said:
thanks for the help
I tried your advice Freez and have installed the dual slide springs to get rid of my hesitation and it works, the stumble is gone completely, I do think the top end has got a little sluggish in response but it will still open up. I now have to go back and reset the floats, I was sure it was a float problem and have them too low. Great stuff Freez


2001 Raptor, 12-44 gearing, Yosh pipe, Dynojet kit, K&N and and many holes in airbox lid
 

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I recently had issues with a newly built 686. The shop I took my bike to hated to work on raptors b/c they could not get them to run properly. A new mechanic started at the shop recently and installed a DJ kit in my bike. I have also tried stock and GYTR needles but had nothing but issues. This bike truly rips throught the powerband. I have P/P, HC stage 2, yosh ex, L/A open air adapter and all I can tell you is that after riding this thing after it is properly tuned I dont want to sell it anymore. :nod: :deal:
 

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Discussion Starter · #11 ·
Great, glad this is helping you guys. Also, if you can, try the 2nd clip or 1st clip on the needle with a worked motor. Maybe that will help instead of the dual slide springs, but it might run a bit lean at small throttle openings if you use clip 1, so check the plug or have it checked out on a dyno.
 

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Does anyone know if the Dynojet needles are available seperately?
 

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mleaky said:
Does anyone know if the Dynojet needles are available seperately?
No they are not. Other wise dynojet would not sell a kit. Everyone would buy just there needles.
 

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This was an awesome post. I found it so interesting that the stock jet needle does not provide a flat fuel metering accross the rpm band. I suppose like you say that when you alter the air box the vaccum provided to the slide block is different so it's throwing your jetting off that way by the slide moving to much or to little.
I think the biggest point that comes to my mind is that the main jet size effects fuel flow, at anything above 1/4 throttle even at mid throttle points. That's something I never knew for a long time. It's not just the jet needle and the needle jet effecting fuel flow. So always tune the pilot, main then needle at least from what I've found for me works the best.
Freeze have you tried different needle jets?
I would think (IMO) that you would have better luck with using springs in the diaphrams rather then messing with the vaccum ports to the slide.
 

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Discussion Starter · #15 ·
Once the motor is modified, it becomes a very different ball game. Each quad will need it's own setup, and it might be different that another raptor.

I am not yet 100% sure what the answer will be to the low RPM richness. If I have time again, I will start playing with the slides to see what I can figure out. I did mention some things that help with the problem, so the stumble should go away, or most of it at least.

In the end, we might have to get new needles springs and even slide hole mods to get that right. The slides react to quickly to the low end power, so you need to slow them down or make them open less at the low RPM with full throttle. The dual springs work well for it, but at less than full throttle, those dual springs can make the bike run a bit on the lean side. Not that I would say it is a dangerous lean, but I would still like to get it perfect.

My problem here is that the carb spares are not cheap, so to go mess up a perfectly good set of slides is costly.

I have a guy who said I can get his old slides, so I will try and use them to get a fix for the open lid fuel supply problem.
 

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Very good post Freez!

I've never really been to interested in Dynojet kits, (mostly because of their numbering system), but after reading this post, I wouldn't mind trying the Dynojet setup, just out of curiosity if nothing else.

One small question. Did you use GYTR jets, (Mikuni), with the GYTR needles?
I'm guessing you did, but you didn't mention it.

I often thought my, (666cc, GYTR jet kit, LA Designs filter kit, Stage 2 cam), was getting to much fuel at low rpm. It did have the typical off idle stumble until I lowered the clip one notch from the middle. That eliminated the stumble. I've never had it on a dyno, but it runs good now.
 

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Discussion Starter · #17 ·
Yes, I did try the GYT-R needles and jets, but the main jets that come with the GYT-R kit were too small for the modified 660. In the end I used Dynojet jets with the GYT-R needles to get the top end tuned in, but the low end was a problem with the GYT-R needles and the open lid.
 

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Yea the GYTR kit doesn't come with very big jets. 165 IIRC?

I've always heard not to mixmatch the dynojet jets/needles and Mikuni jets/needles.
Maybe that was part of the problem?

Here's a dumb question for ya. Is there a way to tell the difference between the Dynojet needles and the GYTR needles?
I bought a set of carbs for parts a year or two ago and they had aftermarket needles in them. The seller had no idea what they were.
 

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Discussion Starter · #19 ·
Sorry, don’t know how to identify the GYT-R and Dynojet needles. I speak under correction here, but as far as I can remember, the dynojet needles don’t have any markings on them. The stock needles have a number at the top , just underneath the last clip position.
 

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I know this topic is really old..... But I just found it and it explains the issues I've been having with my jetting.

I have the dynojet kit. Could never get the settings right with the lid off..... But with everything setup as the instructions there is no missing out stuttering at all.

So if I double up the slide springs what needle setting should I start with? The 4th as it is now? Do I need to change the mains with doing this?

Sorry for posting in such an old topic..... Hoping someone is still around that can answer this one for me.

Thanks
 
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