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Discussion Starter · #1 · (Edited)
After 2 years of tuning and jetting and trying to get the jetting right on my very low mileage 1997 CBR900RRV I am here to share the results of my 2 year experience and hard lessons learned. My CBR has only 7,000 miles and is still practically new. The only thing done to the bike (besdides tuning/jetting) was a micron slip on exhaust can.

Over the last 2 years I have removed the carbs at least 20 times and have had at one time or another every possible combination of main jet, pilot jet and number of M3 washers under the stock needles. First I want to say these bikes come VERY lean from Honda...VERY lean. Add a slip on exhaust or K&N air filter, or both, and you are dangerously lean with the 115 main jet on the outer carbs and 118 main jet on the inner carbs (stock).

At one point I installed the K&N but the change to air flow dynamics and air velocity, evidenced by a net decrease in power, forced me back to the stock airfilter.
So again, the only non-stock item is the Micron slip-on exhaust can, and jets of course.

Final result after 2 years of trying to get it right is this: stock unmodified airbox, stock airfilter, stock needles....with a total of 3 M3 washers under the stock needles (stock had 2 washers); a #42 pilot jet, fuel screw at 1.5 turns open, and 4 #135 main jets! Yes, #135 main jets in all 4 carbs!

My 919 now pulls the front wheel off of the ground at 1/2 throttle in 1st gear every time. The bike pulls very hard to the redline and all "flat" spots are gone throughout the rpm range. The power delivery is smooth and the bike just runs beautifully from idle to 11,500 rpm. I hope someone here benefits from my hard lessons learned, and the 20+ times I have jetted, rejetted, shimmed needles, and changed pilot jets and been through just about all possible combinations of pilot, main, needles and fuel screw settings. It is this exact combination above that has resulted in the most power for me and my stock 1997 CBR900RRV (919) with the micron slip on exhaust can as the only non-stock upgrade.
 

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Discussion Starter · #3 ·
Really useful, thanks for sharing your experiences.

I had a CBR600F with a K&N and Micron fitted, it never ran right. They do run better stock.
I am glad to be able to share the result of 2 years of work. In spirit, I agree with your statement that they run better stock, but technically, I disagree that my CBR919 runs better stock. It took me 2 years to get it right, but it now pulls the front wheel off the ground at 1/2 throttle. Even new off of the showroon floor a 919 RRV couldn't do that! They come sooooo lean its harmful to the pistons & rings, but emits less pollution. Generally speaking, I am of the opinion CBR 919RRV owners, and perhaps others, just need to get rid of the stock exhaust can, raise their stock needles by adding 1 M3 washer, and increase the main jets several sizes, which, in the case of my stock 919 RRV, was a 5 size increase from #118 to #135.... I could have just left the #40 pilot because I just ended up turning my fuel screws in because the #42 made idle to 1/8th throttle a little bit rich....so leaving the #40 pilot and setting the fuel screws to 2-2.5 turns open achieves roughly the same thing. Regards!
 

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Sorry to sound somewhat stupid but where did you source your replacement parts. I checked the Honda fiches and they don't list the #42 pilot jet or the 135MM main jet. I have a 96 with a Leo Vince slipon that has a slight bog a low to part throttle.

Thanks.

Nick
 

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Sorry to sound somewhat stupid but where did you source your replacement parts. I checked the Honda fiches and they don't list the #42 pilot jet or the 135MM main jet. I have a 96 with a Leo Vince slipon that has a slight bog a low to part throttle.

Thanks.

Nick
From what I remember is you just change the last number in the part number to the size you want and the dealer can order it for you.

I did that back in the day and had a collection of 4 up and 4 down of each main and pilot from the stock sizes.
 

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Thanks for the idea Ian, but I tried that with a couple of different oem sources I had and I came up with no part found. I took one of the original part numbers 99101-maz-1150 (115 main jet) and changed it to 99101-maz-1350 and no part number found. Did the same think with the 118 main jet. Not sure what to try now.

Nick
 

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Thanks for the idea Ian, but I tried that with a couple of different oem sources I had and I came up with no part found. I took one of the original part numbers 99101-maz-1150 (115 main jet) and changed it to 99101-maz-1350 and no part number found. Did the same think with the 118 main jet. Not sure what to try now.

Nick
Nick, when you say OEM source, do you mean a dealer or a website? I’ve never done it through a website.

It is possible that they have been discontinued, it’s probably been a decade or 2 since I’ve done it 😂

I know the Factory Pro Air Box Plus jet kit has a selection from like 130 to 145 or close to that in the jet kit. It’s pricey though, and hard to find.
 

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Discussion Starter · #9 ·
Sorry to sound somewhat stupid but where did you source your replacement parts. I checked the Honda fiches and they don't list the #42 pilot jet or the 135MM main jet. I have a 96 with a Leo Vince slipon that has a slight bog a low to part throttle.

Thanks.

Nick
Get on Amazon and search "Keihin jets". I bought 4 variety sets of mains & pilots, each set was about 12$. Regards
 
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