The dynojet kit it designed for a piped raptor with the airbox lid on.

When you go to a ported head, overbore, cam, no lid, etc. Is it better to put the stock needles and springs back in. Change the pilot and main jets instead?

Right now, I have the dynojet kit in with mikuni main jets. DJ jets only go up to 150 for this kit.

 

no you will keep all that and jet up on the main jets and some adjustments to the other settings as well, more go fast parts means more gas needs to flow..

 

There are different stage kits you can buy with DJ. I have the stage 2, and I cant remember what they go up to, but you can get kits with over 175 main jets in it for heavy modded quads.

 

My Bike is rich in the mid range and lean at the top. When you up the mains, it also richens the mid. My needles are on the second clip position from the leanest.

I think I am pulling out that dyno jet kit and going back to stock with big mains and #25 pilots. This quad has not seemed to run right since I put it in when it was two months old.

Anyone else have problems with the Dynojet crap on a Rap?

 

Big Gun?

Thats funny, I fight the same problem and have a big gun also. At about 5000ft I found that the DJ needles (2nd clip), MK jets (165,160), and MK springs work very well. But higher up I need the MK needles (3rd clip). this makes it easy to adjust for altitude because now I just change the needles.

The throttle response suffers just a little when Using the MK springs but it actually makes the Raptor easer to ride in woops and rough conditions.

With a 686 I would think you would need some bigger jets (185/190 or 190/195). So buy some of those sizes at the dealer and play around. Don't worry....contrary to most advice the needles and jets don't have to match (they just need to flow the correct amount of fuel for your motor). Another point is that the jet size doesn't effect the low/mid fuel curve that much. The needle size, needle shape, needle position, slide cut out, and metering rods are much biger factors.....but no one offers replacments for these items, so you are stuck only being able to change the needle position.

Also on a thumper the length of the two header pipes before the merge in relation with each other will change the amount of back presure at different RPM's. The genneral rule is that at low RPM's the pipe needs to provide good back pressure to produce torque and at the high RPM's it needs little or no back pressure to produce HP.

I think the Big Gun Curve just dosn't match the DJ needle Curve. But it would take a lot of research to prove it....Bill

 

You know....I started with a Wright Bros, then switched to Big Gun full. That is when I started having problems now that I think back.

I run up at 7000 ft quite a bit. This thing sputters up there in the mids. But it's fine wide open. It is a pain!

A big problem is engine sputtering over rough terrain as well, even at low altitudes.

I think I need to go back to stock needles and spings. Big mains like you suggest.

Thanks!!

 

I run Dyno Jet needles and mikuni mains 187.5-190. The 686 runs strong bottom too top.

 

GaryC,

What exhaust system do you run?

 

I run an FMF powerbomb headpipe mated too a white bros E series with no end cap....yeah it's straight thru. I still run the diffuser disks because they still work (same principal end cap or not). Not exactly a stealthy quiet setup though.
Gary

 

Holey buckets! I can hear your quad thumping from here!

I guess you don't need a siren on your quad patrol bike. [img]i/expressions/face-icon-small-happy.gif[/img]