Keihin OEM vs Factory Pro jet sizes

[kkim]

yes, provided each washer's thickness is about 1/2 of a clip position. why not just move the clip?

[dubojr1]

Thought it might be easier that way in the event they are removed later. No biggie, I can move the clips. Do I leave the screws at 3 or start over at some other point?

[kkim]

you can start at 3, but I'm pretty sure you'll be going leaner on the mixture screws once you richen the needle position.

[dubojr1]

Thanks kkim. All goes well I'll be making this adjustment tomorrow afternoon.

[kkim]

Let us know how it turns out. I'm sure Bob would be very interested in your results, too.

[dubojr1]

Ok. Results from this mornings commute. Bike seemed ok at first. Started with no choke, idled fine, seem to accelerate up to speed maybe a little on the rich side (boggy feel). The bike seems to be louder now too as if the air filter/carbs are making more noise. (Remember that I have no airbox) The first 10 miles went ok. Halfway to work the stumble returned. At times it felt as if maybe too much fuel was present but others as if the fuel was running out. Idle hangs a little over 2k occasionaly as if the choke was still on. Blipping seems fine at times while others it falls below idle and struggles to return. Even one time of idling lower than 1k and almost to a stall. Low enough to make headlight dim.

Bob: do you by chance have an aftermarket fuel filter.

kkim: should I bypass mine for now to make sure that it is not an issue. Oddly when the stumble happens, as Lee at FP suggested, you can pull the choke and the stumble seems to go away. Makes me think the filter has nothing to do with it. Your thoughts on where to continue? Still move to 4th clip and re-adjust screws?

[g21-30]

Since kkim is working with you on this, I have been watching from the sidelines (remaining silent ). My 2 cents thought is you should consider removing the filter (replace with straight tubing) because the fuel supply is gravity fed and it has been proven that particular filter (in some instances) restricts the flow of fuel! I'm willing to bet that has been your problem all along. Why not give it a try? .........back to the sidelines...........

[dubojr1]

Originally Posted by g21-30

Since kkim is working with you on this, I have been watching from the sidelines (remaining silent ). My 2 cents thought is you should consider removing the filter (replace with straight tubing) because the fuel supply is gravity fed and it has been proven that particular filter (in some instances) restricts the flow of fuel! I'm willing to bet that has been your problem all along. Why not give it a try? .........back to the sidelines...........

Thanks Sam. I guess it couldn't hurt to try. I think I have a brass connector I could swap that filter with to bypass it for now. My thoughts have been that when the stumble happens you can throttle up and it will go away. Seems to me that if the filter was restricting fuel flow then when the you throttle up there would be nothing there. Again I'm sure it won't hurt anything to remove it.

[headshrink]

I do not have an aftermarket fuel filter. The thing is, this started when I installed the FP kit.... just for S&G, I wonder what would happen with DJ needles (not that I'm going to go buy some, just a thought)...

[kkim]

Originally Posted by dubojr1

Thanks Sam. I guess it couldn't hurt to try. I think I have a brass connector I could swap that filter with to bypass it for now. My thoughts have been that when the stumble happens you can throttle up and it will go away. Seems to me that if the filter was restricting fuel flow then when the you throttle up there would be nothing there. Again I'm sure it won't hurt anything to remove it.

yes, bypass the filter to eliminate it as the problem source... and unless you've removed it, there is still the small stock filter in the fuel line at the base where it enters the carbs.

lol... go buy a length of fuel line from the parts store and keep it handy for fuel problems.

Bob.. for S&G, you could always pop the stock needles back in with like 3 washers under each needle to see what happens.

[dubojr1]

Originally Posted by kkim

yes, bypass the filter to eliminate it as the problem source... and unless you've removed it, there is still the small stock filter in the fuel line at the base where it enters the carbs.

Ok. Agenda for this afternoon...

1. Bypass AM fuel filter
2. Move needle clips to 4th position

I'll try to report back tonight after a test ride.

[kkim]

Originally Posted by dubojr1

Ok. Agenda for this afternoon...

1. Bypass AM fuel filter
2. Move needle clips to 4th position

I'll try to report back tonight after a test ride.

one thing at a time and test between changes. if you do 2 things and then test, you'll never know which was the problem, if the bike is "fixed" after testing.

[headshrink]

Originally Posted by kkim

Bob.. for S&G, you could always pop the stock needles back in with like 3 washers under each needle to see what happens.

This is true....

[dubojr1]

Originally Posted by kkim

one thing at a time and test between changes. if you do 2 things and then test, you'll never know which was the problem, if the bike is "fixed" after testing.

I meant to put that in there. My mind was thinking it but it didn't type it.

1. Remove AM filter- Test Ride
2. Move needle clips to 4th (if needed) - Test Ride
3. Report results

[dubojr1]

Ok... Report

1. Removed AM filter and replaced with new hose from tank to carb = No change
2. Moved to 4th clip position = seems to be better. I want to evaluate for a couple days before saying it's fixed.

Also ended up going back to 2.5 turns to fix the low end issues. Idles better now and not so boggy feeling pulling off from 1st.

Prior to changing the needle position, I also pulled a plug for future reference.

[kkim]

plug looks pretty good. I assume you didn't do a WOT and chop method to read it, but merely pulled it after riding it?

If so, I can see where the mixture during higher running is about perfect (if not a tad rich) and it appears like the idle or pilot circuit is rich.

[dubojr1]

Yeah I just pulled it after test riding with the AM filter removed. Should I do the WOT/chop method for better results?

[dubojr1]

Should I go back to the smaller pilot?

[kkim]

Originally Posted by dubojr1

Yeah I just pulled it after test riding with the AM filter removed. Should I do the WOT/chop method for better results?

if/when you need to redetermine your main jet size, you might want to, but for now, stick with what you have and see if we can get things a bit better w/ what you have in there.

btw, what do you have in there?

pilot jet- keep what you have now and see if we can come up w/ a solution using the 40 pilot. as you can see from the other thread we just posted in, getting the off idle responses is a combination of the needle taper and pilot circuit. When cruising at light throttle settings in 6th, these same circuits come into play, so the answer is somewhere between the needle clip settings and the pilot jet selection/mixture screw settings.

[dubojr1]

Originally Posted by kkim

btw, what do you have in there?

fp #112

[kkim]

from the looks of your plug, 112 is damn close. you might want to experiment w/ some 110s later on, but it's always better to jet a bit richer on a street bike to allow for temp, altitude and other changes that may affect the fuel/air ratio.

you never want to jet so that your jetting can't accommodate changes that will cause you go too lean. always stay a tad richer of that fine line of optimum.

[dubojr1]

I'm pretty confident saying the stumble is better if not completely gone. With strong winds blowing today is was hard to really study it. I will say that I seemed to have lost some mid and low still seems boggy. Grabbing the clutch to stop from highway speed results in almost engine stall. Kkim, would agree that I should turn the mixture screws in a half turn or so or is it time to change that pilot jet back to the smaller one?

[kkim]

stay with the pilot jets you have in there now... play with the mixture screws until you get what you're after. once you find that magic sweet spot , then go back and count the number of turns the mixture screws are set. that will determine if you need to move to a larger or smaller jet than what you presently have. no sense introducing another variable when what you have in there now can be used to point you in the right direction.

you may well need a different sized pilot jet, but you can use what you have in there now to help troubleshoot which way you need to go.

I recommend you turn the mixture screws in 1/2 turn at a time until the stumble comes back, then back it off 1/4-1/2 turn.

on the dirt bikes, for me this mixture screw setting it critical cause it can make the difference of the engine dying/stalling when you lug it in muddy/rooty sections or stay running cleanly to pull me out of a bad situation. I have installed adjustable mixture screws on them and can compensate for temp and altitude changes with a 1/4 turn of the mixture screws w/o using any tools.

[dubojr1]

Thanks kkim. I'll turn them in 1/2 turn for the commute in the morning. May actually go out for ice cream tonight and test ride. Excuse for ice cream or excuse to test ride?

[dubojr1]

Ok. 1/2 turn in. Should be at 2 turns out now.

Power delivery seems to be smoother as you ease into the throttle. Idle is more stable and maybe even smoother and regained some engine braking.

However, with minimal throttle (1/8 or so) during light acceleration (slowly working up from 3k to 5k) and slow shifting, bike sometimes bogs and then recovers. High speed cruise may be a tad worse but once again with strong winds today, hard to confirm stumble. Also felt a possible flat spot around 10-11k during a couple WOT expressway runs. Almost as if the bike is increasing RPM's but not building power.

Kkim, suggestions now?

[kkim]

try turning in the mixture screws another 1/2 turn and see if the symptoms get better or worse... or if you think you can live w/ it like this w/o doing damage to your engine, ride it as is so you can get a better feel of what the changes you've done really feels like after you've lived with it for a few rides.

needless to say, this is what fine tuning jetting is about and can get pretty involved and labor intensive to reach a final setting. keep in mind, now that you're so in tune with what the bike feels like at different settings, you may never be 100% happy with the results and might have to live with compromises or go nuts working on jetting.

get to a place where you are relatively happy with the results, then live with that for awhile before making changes.

btw, you do a have a clean air filter while you're fine tuning the jetting, right?

[dubojr1]

Air filter is good yep. Actually I may take your advice prior to making any more changes. The ride in this morning was pleasant and without studying every cylinder firing and just enjoying the ride, everything seemed fine. I'll give it a week or so to evaluate it more but my 650R rear wheel conversion starting this weekend so it may be down anyway. Guess I'll be riding the big boy (1000RR) for a bit.

[kkim]

Originally Posted by dubojr1

Guess I'll be riding the big boy (1000RR) for a bit.

glad you clarified that (1000RR). thought you might have a boy toy on the side we didn't know about.

[headshrink]

I don't know if this will disqualify me from this thread, but I just ordered an AP quiet core from a Ninjette member, and plan to remove the air box too. Oddly enough, when I contacted FP about the additional main jets I would need to purchase to convert to a stage 3 kit, they (Marc) seemed confused. He said he had never done one w/o an air box. Now I am confused, because they sell filters for the 250 to directly to the carbs... in fact they sell a jet kit WITH the filters. He is quick to return emails, but sometimes the responses are quick and cryptic too. Seems nice though.

Anyways, I looked at the jetting db, and it looks like most with "stage 3" setups end up using 110-112 main jets. So, I presume these are the extras I should buy? Should I get one size bigger too, just for testing and in case I need it?

[kkim]

no, for now just get the 110 and 112s. those will get you close and you won't kill your bike if you need to go up or down a step from those 2 sizes in the future.

be aware, you will lose low end when you remove the airbox.

[headshrink]

Originally Posted by kkim

no, for now just get the 110 and 112s. those will get you close and you won't kill your bike if you need to go up or down a step from those 2 sizes in the future.

be aware, you will lose low end when you remove the airbox.

Good point (canceled K&N from amazon). Damn... I totally forgot about that point!
I really want to get low and mid as strong as possible. So, other than leaving the airbox on, am I on the right track with the AP and re-re-rejet?

[kkim]

I thought you had your jetting pretty good except for the surge?

[headshrink]

Originally Posted by kkim

I thought you had your jetting pretty good except for the surge?

Yes, I think so... but I have the AreaP in the mail now , so I expect to have to redo jetting.....again.

[kkim]

lol... which is why I always recommend planning out your intake and exhaust mods, installing the hardware, then rejetting.

[headshrink]

Originally Posted by kkim

lol... which is why I always recommend planning out your intake and exhaust mods, installing the hardware, then re-jetting.

*sigh* you are so right about that. But, I did break my own rule too. I wasn't going to get an aftermarket pipe.... but the more I worked on my bike, the more it called my name. Then the "hypothetical" questions I was asking in research encouraged an offer I could not refuse.

On one hand I am relieved to keep the airbox (and limit extra db), but on the other hand, I was REALLY looking forward to being able to remove my carbs SOOOOOOO easily w/o the box.

[headshrink]

Originally Posted by kkim

for now just get the 110 and 112s.

Just double checking before I place my order.... The fisch lists 98, 100, 102, & 108. Of course I have the 100 from the jet kit, but it sounds like a big jump to go up to 110 from 100. I know you are probably right, just want reassurance first... second guessing everything today.

[kkim]

wait... so you're NOT going to remove the airbox? if not, run the 100s w/ the AP pipe.

if you're removing the airbox and going with a separate, bolt on filter, use the 110/112s.

check the jetting database for what others have done to date.

[headshrink]

Thanks.

Well, knowing me and how things have been done thus far.... I'll do it one way, then get curious, and try it the other way, wondering why I didn't do it that way the first time. Not sure which way will be first yet

[headshrink]

Ordered the jets, in case I need them. I hate the nagging "what if" doubt of not knowing if a bigger jet would be better. So even if the 100 is the right one for this setup, at least I can confirm that.... for only a few dollars.

On a related topic:
In another thread, about 6mo. ago, we talked about upgrading the CDI to the BRT unit. You (Kelly), and another member (I think it was Sam) brought to my attention the 88-94 CDI upgrade. There is a member of the forum who is currently selling his BRT for roughly what I would pay on ebay for a 88-94 CDI (maybe a hair less). Do you recommend this? Could you please describe the benefit I would feel from it (high, low, mid power increase)? Also, would this type of mod have ANY effect on the intake/exhaust mods?
I have read all the threads I could find on the BRT, but am still trying to get the info to stick to the right places in my brain... don't yet have that "cognitive schema" in cement

[kkim]

I don't own a BRT, so I can't/won't comment on what it does.

perhaps post up a separate thread and ask those that have the unit to comment?