Modified GS1100 Katana needs jetting help.

[Anonymous]

O.k,

Ive got mikuni RS flatslide 38's, Ported head, dialed in web cams, wiseco 1134 kit, good 4 into 1, dyna s, dyna coils......
Put it on the dyno and its got O.K bottom end, BIG flat spot in mid, & Marginal top end, only 108horses .

Was expecting more like 125-130.

No wonder my arogant showoff friend on his GSX-R1000 "majorly" blew me off in a drag we had.

So, obviously needs a bigger main than the 135 thats in it.....How much bigger???
Shifting needle clip didnt change flat spot in mids at all (4400-5400), What should I do here???????
Im at sea level so im hoping someone out there can help me.

The nearest decent dyno is 6 hr's away so I cant afford to be too far off when I take it back there.

Please help me show the new dogs a few tricks.
HELP!!!

 

[Anonymous]

all carb adjustments should be started by selecting the right main jet first..
only then the rest of the adjustments can follow because they all are influenced by the size of the main jet..
(select main jet by trial and error )

also the stock float levels of Mikuni RS's are often way off..

anyway.. here's a useful link:


http://members.tripod.com/anders_brink/mc/tech_carburators.html[/url]

 

[Motorcyclemodeller]

Put in a larger main jet one size at a time. Take the bike for a ride and crack it full open at about 4500 RPM. Keep increasing the jets and repeat, when you crack it and it bogs or hesitates or drowns the motor; go back to the last jet size that works and you are all set, then you can play with the needles, pilot and starter jets. Also make sure you prime your accellerator pump and check to see if gas is squirting out of all four jets before comenncing.

Hope this helps,

8) Andre 8)

 

[Katana]

This site is the Australian Katana site it'll link up to the other state sites in Oz, are a heap of Katana links there as well . Hope it helps!

http://groups.msn.com/KatanaOwnersClubofVictoria/_homepage.msnw?


cheers katana

 

[Dink]

Yeah great we go and create a national site and you send him to the Victorian site 8O . so for the Katana Australia site go tohttp://groups.msn.com/KATANAAUSTRALIA
Dink :wink: :lol: :lol:

 

[streetfighters]

All carb adjustments should be started by first making sure the engine is operating at correct efficiency! Is the cam timing and rocker arm clearance right, ignition timing and spark ( good coils ) right on, decent exhaust system with optimum flow. Good to great cyl. compression. It ain't just the carbs folks.

 

[Anonymous]

I wrote a long winded progress report but when I went to post it I kept getting INVALID something come up.
The problems are deeper than jetting....
All the thing streetfighters mentioned were O.K.

 

[Robert Corrie]

Carbs

Carbs

What are the small hoses that come off of the bottom of the float bowls suposed to go to? The instuctions dont tell anything about them. I'm putting 38's on one of my 1150's and this is one thing that has me confused.

 

[Dink]

Robert they are drain or overflow hoses, run them down towards and preferably under your swingarm and you are away.
Dink

 

[Anonymous]

would like to coment on jetting procedure main jet only affects from around 6000rpm upwards below this first is pilot jet then needle for mid range best way to jet main new plugs so you can read colour plug spanner in pocket wind the bike up about 7000-8000rpm hold there 15 -20 secs clutch and kill motor roll to stop remove at least 2 plugs look at colour white lean increase jet size tan or light brown perfect black to rich decrease jet size it is important to kill the motor at revs idle and the plugs soot in a few secs
ozman just a thought

 

[robinjo]

would like to coment on jetting procedure main jet only affects from around 6000rpm upwards below this first is pilot jet then needle for mid range best way to jet main new plugs so you can read colour plug spanner in pocket wind the bike up about 7000-8000rpm hold there 15 -20 secs clutch and kill motor roll to stop remove at least 2 plugs look at colour white lean increase jet size tan or light brown perfect black to rich decrease jet size it is important to kill the motor at revs idle and the plugs soot in a few secs
ozman just a thought

The method that I heard about was to wam up your bike, change the plugs for new ones, then accelerate flat out atleast up to 3rd preferably 4th and kill the engine and let it coast to a stop, then check for plug color.

That should get the mains right.

 

[Anonymous]

robinjo you are correct when i said wind the bike up i mean get on bike and ride if you get it up to rev req try and hold for brief period gives better colour when checking you are looking at the white porcilin in centre of plug
ozman

 

[skip]

Re: Carbs

Re: Carbs

What are the small hoses that come off of the bottom of the float bowls suposed to go to? The instuctions dont tell anything about them. I'm putting 38's on one of my 1150's and this is one thing that has me confused.

those are over flow tubes ,put them through any frame opening like you would your battery vent tube. you went them to flow onto the ground ,not your bike

 

[Anonymous]

As was stated before, the main jet size has to be determined first. Below is some text from the Mikuni site on a technique known as 'roll-off'.

ROLL-OFF:

The Roll-Off technique is the quickest and is almost as accurate as the Roll-On method. First, one gets the engine warm on the way to a safe roadway. If there is room, use fourth gear as this allows more time to assess the result.

Now, get the engine rpm high enough that it is on the cam and in its power band. This may need to be as high as 4000 rpm with some cam choices. Apply full throttle. Let the engine accelerate for a couple of seconds until it has settled in and is pulling hard. Quickly roll the throttle off to about the 7/8ths position. When you do this, the mixture richens slightly for a second or so.
If the engine gains power as you roll the throttle off, then the main jet is too small and you need to fit a larger one.
If the engine staggers slightly or has a hard hesitation, then the main jet is too large and you need to fit a smaller one.

I hope this helps.

 

[skip]

Re: Modified GS1100 Katana needs jetting help.

O.k,

Ive got mikuni RS flatslide 38's, Ported head, dialed in web cams, wiseco 1134 kit, good 4 into 1, dyna s, dyna coils......
Put it on the dyno and its got O.K bottom end, BIG flat spot in mid, & Marginal top end, only 108horses .

Was expecting more like 125-130.

No wonder my arogant showoff friend on his GSX-R1000 "majorly" blew me off in a drag we had.

So, obviously needs a bigger main than the 135 thats in it.....How much bigger???
Shifting needle clip didnt change flat spot in mids at all (4400-5400), What should I do here???????
Im at sea level so im hoping someone out there can help me.

The nearest decent dyno is 6 hr's away so I cant afford to be too far off when I take it back there.

Please help me show the new dogs a few tricks.
HELP!!!

I dont know if you need larger mains..........my bike is 1230 cc I have a midly ported head, cam motion g-4 cams and the bike runs low 10 sec 1/4 at 136 mph in stock trim(no slick ,wheelie bar or extended swingarm) on 135 main jets in my 38 flatslides. the motor pulls really hard to 10500 then drops off but no flat spots. i have done the rider/bike weight(760lbs) 1/4 trap speed mile math and the motor should be about 150 rear wheel hp. the trouble may be in the cam timing or combo of your head porting and cams. If you go larger with your mains jets and it works let me know

 

[Anonymous]

roll off method will get you near jet size is ineffective when fine tuning say within 1 or 2 jet sizes
ozman