Tuning Help...99cbr600f4

[mcoble613]

I've tried to upgrade my bike a bit, I've done a micron header with a jardine race no-baffle can ( not a perfect match but without any restriction, it's good right?. Dynojet stage 1 jet kit (don't even say it; I know, I'm working on the FP 1.7 RK.) Also, 4 degree timing advance, BMC race filter, other non related upgrade. It runs a little rich it seems due to the jet kit ( judging from the exhaust, soot. Why, it's rich I don't know. I've tried 87,93,100,=&110 octane fuel and really cannot feel a difference. It should be breathing well... but it feels slower than before the header, jet kit and timing change which was done all at once basically (it feels sluggish almost bogging especially from say 3rd gear up and above 8k+ rpms. Any constructive criticism or advice is greatly appreciated. Maybe i'm just getting used to it, but i swear it's losing power with everything I do. I'm just getting started with tuning and need much help. Anyway thanks. :adore:

 

[Joe Vital]

are you certain it is rich?

did you get an assortment of jets in the DJ kit? if so install smaller ones. if not get smaller ones.

do you know what the stock sizes are? with a pipe and filter i would put a main jet that was two sizes larger. for example, if the stock jets were 150s, i would put 155s in.
i would guess that honda uses kiehin carbs, so the size scheme is something like this: http://www.keihin-us.com/am/_media/pdf/jetlist.pdf

read the factory pro website's instructions on how to jet a cv carb. don't despair, there are some smart guys on this bbs and they will be along shortly to chime in.

 

[Steve]

I put a Dynojet kit in my now long gone F4. It did appear to run rich to me too. I don't remember the sizes, but IIRC the 2 inner carbs used jets that would allow more fuel than the 2 outer carbs. I ended up using the stock jets from the inner carbs in the outer carbs and the aftermarket jets for the outer carbs in the inner carbs. I hope this makes sense, if not let me know and I'll try to explain it another way. I never dynoed it or anything but it seemed to work the best that way for me. The only other mods I made for power were a K&N and Jardine slip on though.

HTH

Edit (please read the part about the needles):
I just read Joe's post a little more intently and it may have jogged my memory. IIRC the stock jets for the outer carbs were 145 and the inners were 147.5. The kit had 150 for the outer and 152.5 for the inner. This would agree with Joe's putting in 2 sizes bigger, but I ended up using 1 size bigger, the 147.5's in the outer carbs and 150's in the inner. I also think I used the stock needles from the inner carbs in the outer carbs and the aftermarket needles for the outer carbs in the inner carbs.

 

[Steve]

Joe,

I don't know if you still have the jets, etc. I gave you intact, but if the needles in it all appear stock (non adjustable), or you remember them to be stock, or all aftermarket, please feel free to post up and correct my faulty memory.

Thanks

 

[mcoble613]

Steve

IIRC the stock jets for the outer carbs were 145 and the inners were 147.5.

This is correct. But the DynoJet kit has 2 dif size jet sets (one set for just intake filter and one for intake filter and pipe. Both of which appear to be smaller in diameter than the stock ones (side by side comparison.) The DJ # doesn't seem to correlate with the jet size as do most jets. So the stock jets are actually bigger (they look it anyway) but I had to drive a plug in the main air passage which changes everything, according to one of Factory Pro guys. I did read the factory pro's guide to tuning cv carbs. I think maybe changing the needle height may help. I don't know.

The reason I think it is rich is because it had a bit of black soot in the exhaust can which was freshly cleaned just for that purpose. Also, loss of power comes from runnning to rich correct. I'll check the plugs for symptoms today. I just got her tore down last night. She 's going on a diet.

Thanks guys keep'm coming.

Oh, and they're mizuni carbs.

 

[Joe Vital]

mikuni.

steve I hadn't thought to check those jets...it might be useful.

the outer diameter is not what is important. the hole through the jet is what meters the fuel. i absolutely despise DJ carb kit because their numbering system does not corelate to anything standardized. somewhere i have a chart making the comparison i will look around and post it if i locate. it

if you asked me i would take the DJ jet, tie them on a string and give them to your girlfriend as a necklace...then go to the local bike shop and ask if they have mikuni jets in the following sizes: 2 150s, and 2 152.5s. they are about 5$ or so each. combined with the stock jets you should be able to get the main circuit sorted out.
possible main cominations:
cyl 1 & 4 150 cyl 2 & 3 152.5
cyl 1 & 4 147.5 cly 2& 3 150


i am not sure what you mean when you say you put a plug into the main air passage. let me cogitate on this and i'll get back to you.

listen to steve, he has ridden and worked on a few cbr in his day. he know of which he speaks.

and keep us updated, some of us don't have a life outside of this sport and this stuff is our entertainment.

 

[mcoble613]

No, I am not sure it is running rich, that was just my first thought. About the jet size; I meant the ID is smaller, not the OD. I agree about the DJs, I didn't know till it was to late. What you mean by main circuit sorted out (unknown jargon?) Here are some links to pics of the spark plugs and the air plug I had to drive in with a hammer (per DJ instructions.) I know she's old (10yrs. 19k mi), but she's all I got till sometime after graduation next spring.




http://i135.photobucket.com/albums/q133/mcoble613/cbr600%20carbs/IMG_2558.jpg
http://i135.photobucket.com/albums/q133/mcoble613/cbr600%20carbs/IMG_2559.jpg
http://i135.photobucket.com/albums/q133/mcoble613/cbr600%20carbs/IMG_2561.jpg
http://i135.photobucket.com/albums/q133/mcoble613/cbr600%20carbs/IMG_2562.jpg
http://i135.photobucket.com/albums/q133/mcoble613/cbr600%20carbs/IMG_2564.jpg
http://i135.photobucket.com/albums/q133/mcoble613/cbr600%20carbs/IMG_2566.jpg

 

[Joe Vital]

main circuit: the path the main jets control. jargon.

the sparkplugs look ok to me. did they come out wet?

 

[mcoble613]

not wet, but it seemed to have some oily residue on the end of the threads but not on the electrode or insulator. I ran 2 tanks of 104 and 1 tank of 110 octane last weekend. The exhaust has that greyish "soot", which I just noticed. But no noticeable difference over 93.


What's the 'proper' way to set it up? A wideband A/F gauge and run it through rpms.

 

[Steve]

I just remembered I used a factory-pro jet kit. That's why the numbers matched. Your plugs look OK to me too, how long did you run them at high rpm and there much time spent idling before shutdown? Greyish soot is a lean condition, black soot is a rich condition. You want a light to medium brown. Also on the plugs. Did the air plug you're pointing to have a small hole in it? The factorypro kit had me drill the hole in one of those 3 brass pieces just a tiny bit bigger and I think that's the one. Sorry if my offhand coment about my long gone F4 offended you, I really liked that bike and kind of wish I had it back.

I don't know if you'd notice a difference in octane unless you boosted the compression. :dunno: IMHO, the "proper" way to set it up would be on a dyno and "run it through rpms", but that's not always feasable.

 

[mcoble613]

I'm in no way offended, no worries. I love her old, fat ass. On 93, it was black soot, before running those 3 tanks in it, now it's greyish white. Only time it idles is when warming up for the track. Plugs were new a month ago. Has three track days on it, so 20 or so, 20 min sessions at redline. No street. Yeah, that thing I'm pointing at is a brass plug that I drove in the hole with a hammer. FP rep told me it was an air passage (also suggested I drill it out and buy a new FP kit.)