Before I begin typing I just want to remind you that I am far from any type of speed demon. Once I hit 80 mph, I start getting quezzy and immediately back off the throttle. Recently I noticed that I my engine has a hard time getting to 100 mph and holding this speed. For instance I believe that right around the redline in 4th gear I can come close to or maybe even hit 100 mph. But once I hit 5th gear to keep going I immediantly lose speed and feels like there is a wall right at 100 mph. When in 5th gear with the thottle wide open it doesn't feel like its making power. I also noticed too there is an immense amount of wind resistance too that I was feeling on my shoes so maybe that is a factor but my main concern is jetting. I believe the reason why I have a hard time surpassing 100 is due to my main jet size. Right now, all my modifications are listed in my signature. I am running Dynojet needles set at the stage 2 position or 4th groove from the top. My pilot jets are stock 38s, at 2-3/4 out. My main jetsare Keihin (not Dynojet) 117.5s. The stage 1 main jets in a kitare equivelent to Keihin jet numbers 100s and 105s. The stage 2 jets are equivelent to Keihin numbers 127.5s and 132.5s. So basically my main jet sizes are about a stage 1.5? Driving around town the bike feels great and has lots of power. Sometimes to me when your in the higher gears it feels like the engine takes tolong to reach the redline. Also note that I am running the stock gearing (15, 44). So basically I am asking other Hurricane owners to give some imput to the mods and jetting they have done and to see how hard it is for you all to hit and stay at 100?

EDIT: Also note that my elevation ranges from about 1500 ft to about 2300 ft. and stock mainjet size is keihin 110s.


Width------Kehein # -- DynoJets # -- Mikuni #
[font="times new roman"]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---

 

my bike is all stock and has no problem hitting close to 120 but once i let off the throttle it decelerates pretty fast.
are your throttle calbes adjusted correctly?

 

my 88 cane had no problem what so ever breacking 100mph. It did have a yosi slipon n a ignition advancer installed tho.

 

Maybe take the bike out and go somewhere where you gan get to that "point" safely. Get right to the 5th gear 100 mph point that you don't enjoy and if you can reach you left hand up and turn on the choke about halfway and see if it gets better. If it DOES, then that's an easy (but really crude) indication that you could stand to go richer..

My gut reaction ( but it's quite possible I"m an idiot!!!) is that you could move up to AT LEAST DJ 118s or Keihin 125s and notice an improvement. If you do that, you might want to move your needle clips a notch or two towards the top, to keep your midrange from getting too rich.

All in all, if you don't notice a PRETTY big jump in the power right around 7K rpm, then you're probably too lean. It should feel like the world's coming to an end when you hit 7 or 8K.

Also, remember that 1990 Keihins are 34mm TBs and 1987-1989 are 32. So, the stock jet size in 1990 may be 110/38, 1987-89 it's 105/35. That's what helped them get that extra 10HP in 1990.

But, that means you could stand to probably go EVEN FARTHER if you've got the stock 1990 engine with 34mm keihins..

IF your main jet is too rich, your Wide open 1st and 2nd gear will stumble and bog a little bit at 6-7K and then run ok to the redline. If too lean, it will run fine but be kind of gutless and boring up top. Which sounds kind of like your problem, no?


My bike is a frankenstein of everything as far as that goes. I have a 1990 engine, 1987 carbs with a Stage 2 kit, EXCEPT I'm using stock needles, and I have DJ 114 main jets. I"m at 5000 feet. And I feel like i could probably do DJ 116s and feel better. SO, good luck with that helping out, huh?

 

While I am no expert at all, I can tell you mine hit 110 with little effort and had more to go. I think 130 is pretty attainable for my '88. It does decelerate pretty fast once off the throttle as previously stated.

 

Gogar, I just remembered about the choke trick you mentioned to me earlier. I wasn't moving at speeds that high but i did a few redline passes with the choke at about half way and I really couldn't notice any major differences. Next time though I should try it at some higher speeds. You have told me in the past to richen my main jet but I honestly haven't had the time to rip the bowls off and change jets. I just cant believe any exhaust change would require this much jetting change. Again your help has been greatly appreciated!!

 

I guess all I'm saying is; If you have $10 and some free time go grab some bigger jets and give it a try. If it's too rich, you'll definitely know. It will bog right in the midrange and It might have a little misty white smoke and it will stink like gas. But it's not going to hurt anything if you do it for a day.

If you're using the (DJ equivalent 112) at 1500 feet, and
I'm using DJ 114s at 5500 feet, and
I feel like Icould go up a size with no problem,

Then that's all I really got to go from, saying you could DEFINITELY go up a few sizes, like DJ 120 maybe.

Good luck, man!

 

Only mods I have on mine are a D&D pipe and sprockets (14 front, not sure about back). No problem getting up to 100mph and that's about as fast as I took her but she can definately pull further quickly, even in 6th. Like others have said, great deceleration when I let off the throttle at that speed. However, I'm about to upgrade the main jets to Keihein 120s (will pick them up later today) and will report the difference here once they're installed.

Just wondering (sorry, no threadjack intended) what I should look for before I purchase them to make sure they're the right size and will fit. I was told they're made for carb models KJK30. Is that the carb model on 87-89 CBR600's?

 

Go ahead and pull the old ones out and take them with you when you go to get the new ones. But any shop should know if you tell them your make/model.

The basic shape is the same as the "DJ style" jet on this page:

http://www.dynojet.com/jetkits/jetassortment.aspx

 

Thanks. I agree, best way would be to have them with me but I'm going to pick them up right after work (before the shop closes) and have no time to pull them out before. I know they're round and 8mm long so it shouldn't be too hard to spot a difference (if any), just needed a quick confirmation. I'm doing this in a rush coz it's raining today and probably tomorrow too, so it's perfect timing for a swap