Up to the 60's is fine for main jets. #60 = .0400. It seems most of the time I'm drilling I'm using the ones in the 50's or so.

#97 = .0059. That's SMALL!

 

well, for now, it is just going to be used for trail riding and riding at a friends farm. no real racing(well at least not on a track), nothing but riding with friends and family. it is the only quad that has a clutch and i want to use it to teach my son to ride before getting on his yz80 that i just restored. this quad is my first and i originally bought it to beat around on. now i have 5 quads and this is the only one that is not running in tip top shape. i just got the polaris rebuilt and like i stated before, boredom got to me. the lift was empty, it was raining and i was off work. once i do go back to work, it will be non stop work for a few months. also on the rough riding, i broke by back last year and had to have surgery. well, the surgery didn't fix the fractures, so i do have to take it sorta easy( yeah, with 5 quads, 3 dirt bikes and 3 harleys=fat chance). well, i am leaning toward a webcam or the 250 as justrandy suggested. now on that note, is there any mods that will be needed to run the 250 cam? i haven't looked at their specs yet to compare. i am going to check the rod out better tomorrow. i am thinking of just going ahead and having a new rod installed. it shows a little wear from the wrist pin and since it is about a half hour from the cases being split, i might as well right? also, why do you suggest such a big overbore? will it gain that much more?

 

Because of the long stroke (like a harley), you'll gain a lot of cc by running a larger bore. So, unless you're expecting to have to change pistons a lot (like a 2-stroke), then its probably a good idea to get the biggest you can or maybe one size down. Also, used jugs are easy to find on ebay should you ever run out of overbores.

It costs about $250 for a bore job with piston and everything. It costs about $350 for a big bore kit. $100 difference. A stock 230 is 229cc. .060 or .080 is around 246cc. The big bore kits are 255 and 265cc. I guess its all up to how much you want, but if I were doing it I would go as big as possible, yet leaving one more overbore for later. So, that's either the .243cc for $250 or the 255cc for $350.

The 250s cam is exactly the same as the 230 cam, only the duration and lift is different. For that matter, the LT4WD cam is exactly the same too, just less duration and lift. All 3 will work in any one of the quads with no modifications.

The specs for webcams is at .050 lift while megacycle is at .040 lift. So, you can't compare unless you call one and get the specs in the competitors numbers. OR untill I find where I have all the specs and post them here for you. I'll see if I can find them.

 

Btw, while looking for the cam specs, I found this.... For whatever its worth:

"This is a comparison based on measured orifice size:

Dynojets numbers are simply the hole diameter. A 140DJ main has a 1.40mm (0.055") diameter hole in it at the threaded end. A mikuni 140 Mikuni has a 140 cc's of fuel flow per minute. I don't know where Keihin got their scale from.

Width------Keihin # -- DynoJets # -- Mikuni #
0.0350---- 92.5--------- 92----------- 86.3
0.0360---- 95----------- 94----------- 88.1
0.0370---- 97.5--------- 96----------- 90.0
0.0380---- 100---------- 98----------- 91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105.0
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120.0
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135.0
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150.0
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 157.5
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165.0
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180.0
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5



Keep this in mind---> From a Dynojet tech rep:

We are often asked for a "cross reference" sheet that compares our main jets to Mikuni or Keihin. The fact is you cannot directly interchange the jets for a given size. Many things affect fuel flow through a jet of the same orifice size. The entry and exit tapers of our main jets differ from those of other companies. Due to this, the fuel flow changes as a function of velocity through the carburetor venture. This means that two jets of equal orifice size will have a different fuel flow curve relative to intake air speed. At a certain speed the two may flow equally, but a change in velocity changes the flow characteristics. The Dynojet main jet hole size is measured in millimeters. For example, a DJ142 has a 1.42mm hole.

Michael Cory
Research & Development
Phone: 800-992-4993 EXT. xxx
Michael@Dynojet



Dynojet does have the main air jet plugged on some of their kits, supporting the idea of a unique flow characteristics for their jets. So, while I think the chart is fine to use as a general reference, I do believe there is no such thing as a direct comparison between DJ jets and others. Practical testing might show varience from the chart."

 

Webcam stage 1:

Intake:

seat-to-seat duration: 270
.050 duration: 244
centerline: 107
max lift: .340

Exhaust:

seat-to-seat duration: 270
.050 duration: 244
centerline: 108
max lift: .340

cam lobe-center angle: 107.5
Valve overlap: 29

Valve opening/closing based on .050:
IVO: 15
IVC: 49
EVO: 50
EVC: 14

Valve opening/closing based on seat-to-seat:
IVO: 28
IVC: 62
EVO: 63
EVC: 27

Ramp rate as calculated by dyno2003: 2.65


Webcam stage 2:

Intake:

seat-to-seat duration: 278
.050 duration: 250
centerline: 103
max lift: .368

Exhaust:

seat-to-seat duration: 278
.050 duration: 250
centerline: 107
max lift: .360

cam lobe-center angle: 105
Valve overlap: 40

Valve opening/closing based on .050:
IVO: 22
IVC: 48
EVO: 52
EVC: 18

Valve opening/closing based on seat-to-seat:
IVO: 36
IVC: 62
EVO: 66
EVC: 32

Ramp rate as calculated by dyno2003: 2.67


Megacycle stage 1:

Intake:

seat-to-seat duration: 244
.050 duration: 229
centerline: 108.5
max lift: .400

Exhaust:

seat-to-seat duration: 244
.050 duration: 228
centerline: 104.5
max lift: .400

cam lobe-center angle: 106.5
Valve overlap: 15.5

Valve opening/closing based on .050:
IVO: 6
IVC: 43
EVO: 38.5
EVC: 9.5

Valve opening/closing based on seat-to-seat:
IVO: 13.5
IVC: 50.5
EVO: 46.5
EVC: 17.5

Ramp rate as calculated by dyno2003: 4.46


Stock 230S cam as measured by me:

Intake:

seat-to-seat duration: 337
.050 duration: 229
centerline: 122.5
max lift: .336

Exhaust:

seat-to-seat duration: 313
.050 duration: 227
centerline: 134.5
max lift: .311

cam lobe-center angle: 128.5
Valve overlap: 15

Valve opening/closing based on .050:
IVO: 14
IVC: 35
EVO: 46
EVC: 1

Valve opening/closing based on seat-to-seat:
IVO: 46
IVC: 111
EVO: 111
EVC: 22

Ramp rate as calculated by dyno2003: 1.73


Stock 250S cam as measured by me:

Intake:

seat-to-seat duration: 300
.050 duration: 245
centerline: 125
max lift: .339

Exhaust:

seat-to-seat duration: 338
.050 duration: 230
centerline: 133
max lift: .345

cam lobe-center angle: 129
Valve overlap: 19

Valve opening/closing based on .050:
IVO: 7
IVC: 58
EVO: 38
EVC: 12

Valve opening/closing based on seat-to-seat:
IVO: 25
IVC: 95
EVO: 122
EVC: 36

Ramp rate as calculated by dyno2003: 1.82


Stock LT4WD cam as measured by me:

Intake:

seat-to-seat duration: 330
.050 duration: 213
centerline: 125
max lift: .321

Exhaust:

seat-to-seat duration: 315
.050 duration: 218
centerline: 132.5
max lift: .284

cam lobe-center angle: 128.8
Valve overlap: 6

Valve opening/closing based on .050:
IVO: 4
IVC: 29
EVO: 36
EVC: 2

Valve opening/closing based on seat-to-seat:
IVO: 40
IVC: 110
EVO: 110
EVC: 25

Ramp rate as calculated by dyno2003: 1.68

 

Would DJ Jets work in the stock carb? Better Idea than drilling them out?

 

Maybe this will help: When I ran the 230 cam, I could do a donut in 2nd or 3rd gear (whichever) at, say, 3000 rpm max. When I put the 250 cam in I could pull about 2800 rpm max. Hardly a difference in low-end torque, but the top end is WAY better on the 250 cam.

 

I don't know. Never saw a DJ jet before. I always drill them so I can gradually move in the direction of "running good" a little at a time without having to have a complete $300 set of jets. Once you get close you might get a few jets and try to dial it in perfectly, but I think air temp/humidity/pressure will screw it up the next day anyway, so you can never have it perfect.

 

any websites for the bigbore kits? i want to check it out. i am really leaning toward the big bore for the extra hundred.

 

Dial-a-Jet Well, right now, I just want to get it running good and starting. What he wants to do with it then is up to him.