On the hunt for a bike dyno place here.. I've already seen jets r us but they don't ship outside USA .. I've found a reputable source in the UK that has parts and will ship to me. Also just so happens my friend who has a cb1000 of 1993 has a full dynojet kit for his bike and wants to sell the jet kit! The part numbers match and even the stock main jet is a 108 same as the CBR, I guess makes sense since bhp is about the same. I'm gonna see if the jets in this kit help me out, if not then I'll order some from UK. I'm not after peak bhp, just a smooth engine. I live on island that's 37 x 25 km across lol so highways cruising etc is non existant here and the longest journey is 30 mins

 

I would think there are suppliers like Jets are Us that will ship to you. I would be surprised if the 750 jet kit is the same as the CBR. There are differences in the lengths of the needle jet tubes and pilots. Inside diameters also. I've rebuilt carbs on many different bikes and rarely are the jets and needles the same. The main jets themselves might be the same but I doubt it. Main jets are cheap, just buy some. Why would you want a set that has 108 jets anyway? I thought the whole point was to increase the jet size ��

 

Stock they are the same, so the jet kit should provide bigger ones, at least that's my assumption. This is a cheap and fast way to get jets I need so even if I only use them out of the whole kit its still a good buy

 

Maybe I missed it, but I'd still tape up the holes. I understand not wanting to get less HP, but jets may not fix this issue alone.

Are you running stock air needles? The taper on the needle needs to change for the air box you have as well. I tried 3 different needles on my Bandit before I found f the right one suited for my pod filters. The OEM one wasn't even close to being correct because the air box changed. There is also a different needle for people that drill holes in the air box too, because it drastically changed the speed at which air enters the venturi on the carb.

When you start modifying the intakes, you are changing a ton of variables... To figure this out, try eliminating the variable of 30 different holes in your air box first.



But, I'll second JetsrUs.com They have everything for every bike.

 

I suggested this very early on in the discussion.

 

Yeah stock needles, i know about tapering them, but they are the only stock ones i can find locally so didnt want to ruin them until i had a spare set.. Not like you lucky folks in USA where u can order these parts from almost anywhere and postage is next to nothing! :P

But i have found out some interesting things!!

after some good ole googling i found out that my airbox lid is drilled in the pattern that a dynojet stage 2 kit requests! There is most certainly not the rest of the kit in the carbs. so it must have been removed and sold separately or something (this also explains why there are epoxy glue marks where the airbox holes were previously covered).... The other thing that the stage 2 kit requests, is drilling out the carb slide holes. What does this achieve? i presume quicker throttle response, ie the slide opens as fast as the butterfly? tbh at low speed riding it has amazing throttle response which i do like.... Anyway i found what jets are required in a stage 2 kit, and i have managed to source them off a mate, and even some tapered needles.. So it looks like ill have a stage 2 "tuned" machine!

will report back with my findings... its always a crap shoot when u buy a bike with 20 previous owners, but doing this detective work is pretty satisfying lol, and ive learned a great deal about carbs which i think is a dying art!

 

Doing a bit of reading on carb slide drilling and found this on the fireblade forum....

quote::

The kit drill bit is listed as DD#44 so it _might_ be 4.4mm, or it might be a random number they use.
You don't want to drill them too big or you risk them lifting too quickly and getting the "flatslide" effect where the engine gets a lungfull of air but not enough fuel, causing it to stumble when you crack open the throttle.

end quote::

thats EXACTLY whats happening with mine.. Lets see if the big jets help the "lungful of air" as this guy put it.. i would rather run a little too rich than any lean so big jets it is!

 

I didn't say this before when you mentioned modifying your needles before...now that you mentioned it again I need to comment. Don't try to taper your needles! There is no way to do this. Not sure where you got that idea from. They sell needles with different tapers. That is the only way to do it properly.

 

I got the idea from other forums.. But I'm not gonna do that..

I'm in the carbs again.. It has strange jets!! They are pretty big! Have 107 rd on the top, no markings on the sides.. Any idea what they are??

 

Sometimes, Dynojet will make their own needle, or you can find a different needle from Keihin that has a different taper that fits your carb. You do not file a needle by yourself. You'd never get them to be the same. I bought my needles on eBay, but again, I had suggestions from other forum members on different needles to try.


If you're saying that Dynojet told the PO to drill the box in that fashion, they most likely supplied their own needle as well. I'd bet you have that needle in the carbs already too.


Drilling the slides let's the slide open quicker, which means the needles pulls quicker, and you get fuel quicker. People either do that or they'll chop the spring in the slide to achieve it opening quicker.


The flatslide effect is too much fuel too quickly. You open the throttle too quickly, the needle pulls up (since you control the slide with your wrist). On a CV carb, the vacuum slide controls the needle, not the throttle action.