wont rev past 8k

[Mick77]

I'm sure you guys are tired of hearing of my stupid mistakes and easy-fix problems by now, but here's one more
It seems that 1am is not the time to be monkeying around with things trying to get them together to ride the next day.  I had no choice, the water pump went out on the wife's car so i had to make haste with the reassembly.  (this was after cleaning the carbs, see sparkless thread)  I thought "this thing is always rich, no matter what I do.... wonder if making this snorkel hole bigger will give it more air?"  So yes, I cut it *a little* wider.  Only about 1/4 inch around it.  Now it won't rev over 8k unless you put your hand over the hole in the airbox.  I tried adjusting the mixture screws, but unless I'm mistaken, it made no difference. 
I have a K&N replacement filter (single) and a supertrapp exhaust (no discs ATM... another of my bright ideas) other than that, stock jets and no other mods.  My question is this: living in central TX, (dont know sea lvl) should I have to go with a bigger MJ with my setup?  I'm going to try putting the discs back on tonight and see if that makes any difference.  What do you guys think?

[Chris H]

Hi Mick,
You got it ruff with that bike! Take a look at the jetting thread thats a sticky, its got loads of help.

[Mick77]

Tell me about it  ... even the 82 honda cm 450 I franken-biked together from 3 different bikes didnt give me this much trouble.  Of course IT was a HONDA... just kidding guys    As far as the sticky jetting thread goes, I read as much of it as I can stand at one sitting, digest that, and come back.  I think that if putting the box back to norm (I kept the piece I cut out) and putting the baffles back on the supertrapp doesnt work, I'm gonna have to buy a jet kit.  Will keep studying the sticky, re-fit and report tomorrow. 

[Chris H]

I dont see why you will need a kit, i run a 442cc kit, K&N filter and a full 4/1 race pipe and jetted up fine. I had to up the mains to 110 at a cost of £6, upped the pilots to 35's, £10, and finally droppped the needle one goove and its bang on. I know a lot of the guys were running factory needles as they give good midrange so there maybe a plus to buying a kit, also if the carbs have been apart it maybe worth putting new o'rings in as these are known for causing allsorts of problems.

[tomacGTi]

Mick, you're lean everywhere. Here's where I would start for your setup:

-115 mains or 120 mains (the stock needle tip is big and needs a big jet)
-Shim the needle up one washer
-3 turns on the screws (you'll have to see how the idle is to fine-tune the screws)

Resynch and tell us how it goes. Look for Thief's posts because he is using OEM needles with his setup. Because of the taper and shape, the jets are much bigger than if you use a jet kit.

Use the one guide I had in one of the last posts adding and subtracting jet numbers to get close. Guessing what you've done, this should be in the ballpark but it is much easier with a jet kit but not impossible.

It is a bit more difficult to jet this bike because of the size of the carbs and the fact that they're very sensitive to airbox changes. That alone is causing alot of your problems.

[PitterB4]

^^^  What Randy said.  You're way lean with all that extra breathing and stock fuel delivery.  Shims and bigger mains should make a huge difference. 

[Mick77]

Well, after much mucking about, it's finally running and rideable.  I decided that the whole airbox thing wasn't working out, so I put it back together and fiddled with it til it ran about right for now.  Until I get my own synch tool, I just have to go by intuition and plugs.   That being said, before I go any further with it and buy the bigger jets and tear the carbs apart yet again to shim up the needle (which I have NO idea how to do, cant see any clips or anything obvious) is the whole "more air" thing going to do anything at all besides make it use more gas?  Don't get me wrong, I want to get all the power I can out of it without spending big bux, but Its my daily rider and has to have *decent* mpg.  If it's not going to make it more enjoyable to ride, then I may just leave it.

One other note:  So I can buy jets by themselves, right?  dont have to go and buy a whole kit?  If it's so lean, why all the soot and the SMELL? 

[tomacGTi]

Here's the deal with jetting, the more air you stuff into/out of the motor, the more fuel needs to go along for the ride. Once you stray from the stock parameters, there's a good chance your mileage may take a total dump. The more time you spend on the main, the more gas you'll suck. I know that nowadays 35-40 is good MPGs for me. There are literbikes that get better mileage. YRMV via your right hand and what you want out of the bike. Power and economy are not synonymous things with these bikes.

Jet kits just make everything easier: little to no having to dick around "guessing" since they'll come with a good starting point and several similar configurations that are proven to work. What you're paying for is the needle design and how it affects the midrange, the jets themselves are the easy part and generally $12 for 4 through just about anyplace.

The bike also may be running fat inadvertently because the o-rings might need to be replaced. If you're going to go through the trouble of the jet kit, contact Jay: gsxrracer for some o-rings just to make sure. If they've never been done, chances are they should be if you're going in there anyway.

These bikes came lean on the bottom and fat on the top courtesy of the EPA. In an effort to give it some grunt, the mains are big for what they are. If running stock with a slip on, your best bet for the time being is to just shim the needles up and open the screws to 2 1/2 turns. You're running a K&N which leans the bike more already. Airbox mods affect jetting more than exhaust.

Search for posts by BrianM to familliarize yourself with the carbs.

You can make your own synch tool, just search manometer on the boards. Should cost you no more than $10.

Tailpipe soot happens, probably because of the main. As long as it rides fine I wouldn't worry about it.

[Mick77]

The o-rings were replaced just 6 months ago, so I should be good there.  On the next rainy day I'll pull the carbs and look at the needles and see about shimming them up one notch.  I'm already at 2 turns out on the screws. 
I really appreciate the advice.  I'll do a little more research on the manometer, and shimming needles.....I'll do my homwork before I come back with any more questions    heh heh just kidding.   YOu know I'll be back with more

[PitterB4]

If I didn't already sell them to someone, I had a good selection of mains out in the garage.  LMK if you're interested and I'll check.  To make things easy on yourself, I'd just pull the carbs and start with Randy's set-up of like 115s, a shim and 3 turns.  With your airbox/filter/Supertrapp combo, that should be close or at least a lot better. 

On the shimming...  do a search.  "Notches" and "shimming" are different things depending on what needles you have.  If you have the stock US needles, you'll need to buy the Radio Shack washers for shims.  There are no "notches" in that case.  Jet kit needles and IIRC some of the stockers from other markets have notches where you can adjust them without shimming to get the same effect.  Like I said, do a search....