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General Category >> Rubber Side Down! >> Jetting question.
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Message started by arteacher on 06/22/12 at 07:44:08

Title: Jetting question.
Post by arteacher on 06/22/12 at 07:44:08

I have Raask exhaust and a K&N slab filter. I have 55 pilot and 150 main jets installed with a 3/4 white spacer mod. I have a Dial-a-Jet installed. The mixture screw is 2 3/4 turns out. I drive around at roughly 1000' altitude. The plug looks good.
The specific problem I am having is the idle drops down too low, sometimes to the point of stalling, when I let off the throttle quickly from about 2000- 2500 rpm or higher. I have replaced the spring and the diaphragm in the TEV, and cleaned the carb thoroughly twice.
This problem disappears when running with the choke out one notch- in fact the bike runs much smoother that way, except that it is too rich.
Would going up to a 57.5 pilot be the solution? I ask because I have never heard of anyone running a pilot that large.

Title: Re: Jetting question.
Post by verslagen1 on 06/22/12 at 08:05:57

2 3/4 out tells me you should up the pilot jet.
most bikes will run a little smoother a little rich.
Not many with your setup so an unusual size is expected.
worth a try anyway.

Title: Re: Jetting question.
Post by Routy on 06/22/12 at 08:12:20

I remember when mine ran smoother w/ 1 notch choke. But it did that from day one.
But how do you figure it runs much smoother when choked, but yet runs too rich ? That just doesn't add up.

Normally if its running lean (1 notch choke) in the low to midrange, the white spacer mod fixes it. But you already did that, so you have to suspect there is another issue. Seems this all started when you modded the carb to get rid of backfire. This is one reason why I warn against it.
I have read of a lot more carb problems after modding, than before.

Title: Re: Jetting question.
Post by bill67 on 06/22/12 at 08:28:32

I would go up one richer on high jet.

Title: Re: Jetting question.
Post by justin_o_guy2 on 06/22/12 at 08:36:55

For several years Ive had to use choke to start & idle, even on 80* days,,

Now, Ive cleaned the carb & got the slide in Clean & Dry. It runs better than ever,, If the pilot doesnt smooth things out for ya, give pulling the slide & cleaning inside the cab & outside the slide,. I dont think I got it right the first time,,

Title: Re: Jetting question.
Post by Serowbot on 06/22/12 at 09:08:19

I might guess that one of your idle passages is partial blocked...

You can try some "snake oil" cleaner if you like,... or clean the carb...
(running thin wire, compressed air and carb cleaner through the holes is the real way to do it)...

Title: Re: Jetting question.
Post by arteacher on 06/22/12 at 09:10:38

Where to get it?

Title: Re: Jetting question.
Post by justin_o_guy2 on 06/22/12 at 09:17:58

If, as Rowboat suggests, your pilot is partially clogged, Id go straight in with a tiny wire. YOu can get one thats way stiff, as tiny wires go, from a hobby shop. Expect to spend about a dollar.
You mite win with a squirt of brake cleaner ( the cheap er answer compared to) Berrymans, Expect to spend 3 to 5 bucks,depending on choice.

Let it get in your eyes & the cost of the can wont matter any more.

Title: Re: Jetting question.
Post by arteacher on 06/22/12 at 09:37:33

I have had the carb completely apart, and cleaned it twice- all the passages, jets etc etc. with wires and carb cleaner and compressed air. It is clean.

Title: Re: Jetting question.
Post by justin_o_guy2 on 06/22/12 at 09:45:03

Then make sure you can get the pilot out with the carb on the bike, get the carb clean & dry where the slide runs, slide clean & dry. Shoot the inside of the carb with the cleaner & paper towel it, no fingerprints, no leftover bits ot paper,,slide super clean, too. Slap it together & see how it acts. If ya need to swap pilots, its easy enough on the bike,

You may have cleared the pilot,, it doesnt have to be something youd feel.

Title: Re: Jetting question.
Post by arteacher on 06/22/12 at 09:48:21

57584259454350525A5443310 wrote:

It runs rich because I don't tune the idle screw with the choke out. I probably could try that, but what good would it do?
And I replaced the spring and diaphragm in the TEV with new parts. (that little diaphragm cost $70! )

Title: Re: Jetting question.
Post by arteacher on 06/22/12 at 09:54:33

Ordered a 57.5 and 60 pilots from Niche cycle in Florida.

Title: Re: Jetting question.
Post by LANCER on 06/22/12 at 17:39:34

707B7B727E71706A6B1F0 wrote:

K&N filter and a Raask and you only did a 3/4 white spacer mod ?
The K&N and Raask moves more air for you so you need more fuel to mix with it. The Dial-a-jet picks up in the mid range but you could still have a lean spot in the 1/4-1/2 range. I would go to at least 1/2 white spacer, if not a bit more to richen the low-mid range crossover. If you have a good distinct setting on your pilot jet then you could possible to to a #57.5 to try.
I have a stock S40 with a small cone filter and an Emgo reverse cone muffler from RYCA. I am currently running a #52.5 pilot with the screw at 2 3/4 turns out and a #52.5 main jet. It runs smooth and strong and have twice hit 105mph indicated on the speedo on a flat freeway run.
The Emgo is as flow through as a muffler gets, at least as much as a Raask. I've not tried a #55 pilot or #155 main jet yet but will this weekend and see what if any difference that makes.

Title: Re: Jetting question.
Post by arteacher on 07/12/12 at 10:07:59

I thought I would update this thread: I took a washer off the needle, so now there is only one washer. It did not fix the idle drop problem. I put in a 57.5 pilot. I don't think that fixed it either, but it started without choke and was easier to tune.
I will go for a ride today and "road" tune it and report back.

Title: Re: Jetting question.
Post by arteacher on 07/12/12 at 14:19:49

Report back: The idle dropping problem is no better. However, the bike runs a lot smoother, acceleration is stronger and more even, and it hardly ever pops between shifts, and didn't backfire at all. The idle seems more even as well.
BTW, I installed an oil temp gauge and the oil temp was 248 deg after a 45 min ride in city and country. Is that about where it should be with the ambient temp at 86?

Title: Re: Jetting question.
Post by renegade1 on 07/12/12 at 14:49:59

i have a 47.5 pilot and 155 main, stock jets for my 88 i was told but running lean. any suggestions. already took the carb out did a big clean to it. Washed the diaphrams and cut the tev spring. all in hopes i could get my throttle response quicker for my test. also moved the white spacer down a notch (my slide needle has three settings) and still no better response. what you think?

Title: Re: Jetting question.
Post by arteacher on 07/12/12 at 15:03:54

I have had nothing but grief after cutting that effing spring. The white spacer mod was a good idea, and your jetting should be good as it is, although you might try a 52.5 pilot to see how it works for you.

Title: Re: Jetting question.
Post by renegade1 on 07/12/12 at 15:06:00

maybe you'll know... my main has a larger hole then a new 155 do people mod the jets?

Title: Re: Jetting question.
Post by arteacher on 07/12/12 at 15:08:50

It's possible. Also it may have been cleaned too vigorously. And be aware, Dynajet has a different numbering system than Mikuni. You may have a Dynajet and be comparing it to a Mikuni.

Title: Re: Jetting question.
Post by renegade1 on 07/12/12 at 15:11:34

should i get 52.5 pilot w/ bleed holes?

Title: Re: Jetting question.
Post by arteacher on 07/12/12 at 15:17:00

If you have a stock exhaust and clean stock air filter, and a plug read is telling you you are too lean, then yes I would try a 52.5 pilot with a Mikuni 155 main. How many turns out is your mixture screw?

Title: Re: Jetting question.
Post by renegade1 on 07/12/12 at 15:39:24

im guessing right now its about two turns out i didnt really pay attention while i was riding, and should this help on the throttle response?

Title: Re: Jetting question.
Post by arteacher on 07/12/12 at 16:05:30

Sorry- should what help with throttle response?
This could get confusing. :-/ Let's start over. :-?
Let us know:
Stock filter? Stock muffler?
How much of the white spacer did you remove?
What jets do you have? Are they Mikuni jets?
To the nearest 1/4 turn, how many turns is the idle mixture screw turned out?
What does the spark plug look like after at least 1/2 hr run?
What specific performance issues are you having? (start with that.)

Title: Re: Jetting question.
Post by renegade1 on 07/12/12 at 20:36:19

Gettin a new pilot jet,
stock air filter and stock muffler (wanting to get a cone filter)
my needle has three slots to move the spacer, i put it on the lowest setting.
pilot 47.5, main 155
about two turns out
Have not checked the spark plug
performance issues are that i dont have great throttle response been trying to get it to 25 km/h but it bogs out about at 15 kilometers. mainly trying to get better throttle response

Title: Re: Jetting question.
Post by arteacher on 07/13/12 at 04:50:30

Bogs out at 25kph
That sounds more like a serious carb problem, rather than just jetting. Possibly a damaged slider diaphragm. If you aren't comfortable investigating, I suggest you take it to a trusted bike mechanic to have it looked at.

Title: Re: Jetting question.
Post by justin_o_guy2 on 07/13/12 at 06:06:42

Bogs out.. please be more specific..

engine power decreses or fails to increase?

does it slowly pick up from there or is that as fast as it runs?
What happens if you pull the choke a click?

Have you had the slide out? Were you super duper extra persnickety about it goin back in without so much as a fingerprint on it?