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Recomendation on next step jetting

S

sandskipper

Joined Aug 2003
517 Posts | 0+
Chandler, AZ, USA
Hello all :) Last week I decided to try my hand at dialing in the jetting of my '02 Fc550. I started by pulling the carburetor and doing a thorough cleaning and inspection of all the bits and pieces. I baselined my settings as such:

Dellorto PHM 40

Main Jet= 200
Needle Jet(atomizer)= DR272
Needle= K35
Needle Clip posn= #3
Pilot Jet(idle jet)= 33
Throttle Valve(slide)= 40
Starter Jet= 45
Mixture screw= 3 out
Idle screw= to my liking

Upon reassembly, everything went back in the same except I changed the MJ (main jet) to a 185 instead of the 200.

Took it out for a ride and the Berg ran no different than it had over the last three years of riding. Now I should mention that I have not had any problems in the past with starting, hesitation, or flat spots.... Im just searching for the "Jetting Nirvana" as Taffy has mentioned in numerous posts :twisted: ! I have read many a posts on this topic but have never tried my hand at it in the past until now. Can any of you fine people tell me what my next logical step is in this search for carburation bliss :lol: Should I continue to drop the MJ? Do I need to make any other adjustments before doing so? Any thoughts, comments, or suggestions would be gladly welcomed.

Regards,
 
have you ever thought about a keihin carb , and the changes it would make to your berg .

or does the cost of the change make it not an option .
 
The Dellorto can be a superb carburetor. You need to check your spark plug color, as these motors will happily run very rich, darkening the plug excessively. The plug should run a medium to slightly dark brown. As you lean the mixture, watch for negative feedback from your motor, hesitations and coughs, meaning you have leaned it out too much. I ran at about 2000' elevation with a 178 main, 38 pilot, and K35 in pos #2. Other folks have found other jet combinations that suited them. Various jetting set ups can and will change the character of your motor, how hard the power hits at certain RPMs, and so on, while still being within acceptable fuel air ratio range. Keep written record of what you have done, and try a few changes. Chances are, some you will like, others will have unsatisfactory results. Good luck, and have fun!
Buzzard
 
Just remember to keep the #200 MJ around for the dunes.....your gonna want to keep it fat out there.
 
Hi Keith,
Depending on a couple of variables You could quite likely remove the main jet and note little difference. Such is one of the primary stumbling blocks regarding the "as delivered" OE carburetor.

Simply remove the main jet. If you can pull top rpm drastic measures are in order be it via carburetor body modifications and / or a heavy investment in tuning Brass.

Best Regards,
Dale
 
whosahberg said:
have you ever thought about a keihin carb , and the changes it would make to your berg .

or does the cost of the change make it not an option .
Click to expand...

whosaberg,
Truth be told, I want to keep the bike in stock trim and experiment a bit with the Dellorto. I find it not worth the investment to start spending buckets of cash on this bike now as my hopes is to buy a newer Berg in the next year or two. I am currently using my bike now as a test platform for educational purposes as I do not have volumes of knowledge on the principles of motorcycle mechanics. I hope to edjumacate :lol: myself starting with what I have and move on and apply my learned skills to my next ride.

buzzard said:
The Dellorto can be a superb carburetor. You need to check your spark plug color, as these motors will happily run very rich, darkening the plug excessively. The plug should run a medium to slightly dark brown. As you lean the mixture, watch for negative feedback from your motor, hesitations and coughs, meaning you have leaned it out too much. I ran at about 2000' elevation with a 178 main, 38 pilot, and K35 in pos #2. Other folks have found other jet combinations that suited them. Various jetting set ups can and will change the character of your motor, how hard the power hits at certain RPMs, and so on, while still being within acceptable fuel air ratio range. Keep written record of what you have done, and try a few changes. Chances are, some you will like, others will have unsatisfactory results. Good luck, and have fun!
Buzzard
Click to expand...

Buzzard,
Thanks for the comments and suggestions :wink: I appreciate the jetting spec info you posted as well so that I can use them for testing, I will post later on my results when I get test them.

berger said:
Just remember to keep the #200 MJ around for the dunes.....your gonna want to keep it fat out there.
Click to expand...

Ken,
Why do you suggest I would need the 200MJ for the dunes :?: Are you thinking I will have an over heating problem by running a leaner condition? As of yet, I have not had a single overheating problem including the reduction in MJ down to a 185, the engine did not change it's behavior at all as far as I could tell. Thanks for the comments :thumb:

LeFrog said:
Hey Keith come pick me up next time you go riding!
Click to expand...

Nic,
I will more than likely be out at the Pobroceto riding area on Tuesday June 6th early morning. My fiances sister just picked up a Honda CRF230 today and she is interested in taking her first ride. Shari, my fiance, had a 35MPH superman crash over the handlebars last week when we went out to Sycamore and has been a little shaken up since then but I believe if I get her away from the sand washes for awhile, she may get her witts again. I will keep you updated but right now plans are for 6am Tues morning.

LINEAWEAVER said:
Hi Keith,
Depending on a couple of variables You could quite likely remove the main jet and note little difference. Such is one of the primary stumbling blocks regarding the "as delivered" OE carburetor.

Simply remove the main jet. If you can pull top rpm drastic measures are in order be it via carburetor body modifications and / or a heavy investment in tuning Brass.

Best Regards,
Dale
Click to expand...

Dale,
Thank you for the tip, I will give it a try. As I had posted previously to Whosaberg, I am just experimenting right now to see how much potential I have left in the old Dellorto... Right now the bike is more than I can handle safely in the higher RPM range so sapping more is not my primary objective. When it comes down to it, I am just doing the cause and effect testing to see if I can find a setting with less brutality and more linear delivery without adversely sacrificing the high end rush that the 550 can give. Of course dialing it in without a resulting hesitation, stutter, or any other undesired side affect will be my major goal.... an increase in fuel economy will also be a goal in my experiments. With the exception of doing the sand drags in Glamis, very rarely do I ever get the bike into 6th gear WOT. I am simply trying to fine tune the bikes carburation to suit the types of riding I enjoy which calls for a less brutal grunt off closed throttle.... better manageability for better words. Hope this explains things a bit better, I know its asking allot out of the Dellorto/Husaberg combination but well see what I end up with. No hurries :wink:

Always a pleasure Mates....

Regards,
 
Dale,
Thank you for the tip, I will give it a try. As I had posted previously to Whosaberg, I am just experimenting right now to see how much potential I have left in the old Dellorto... Right now the bike is more than I can handle safely in the higher RPM range so sapping more is not my primary objective. When it comes down to it, I am just doing the cause and effect testing to see if I can find a setting with less brutality and more linear delivery without adversely sacrificing the high end rush that the 550 can give. Of course dialing it in without a resulting hesitation, stutter, or any other undesired side affect will be my major goal.... an increase in fuel economy will also be a goal in my experiments. With the exception of doing the sand drags in Glamis, very rarely do I ever get the bike into 6th gear WOT. I am simply trying to fine tune the bikes carburation to suit the types of riding I enjoy which calls for a less brutal grunt off closed throttle.... better manageability for better words. Hope this explains things a bit better, I know its asking allot out of the Dellorto/Husaberg combination but well see what I end up with. No hurries
Click to expand...


Hi Keith,
Such being said changing the main jet will be the least of your concerns.
Remove the main jet and tune the carburetor through half throttle. Such insures the main jet is not a contributing factor regarding the circuits for which you wish to experiment.

Hope this helps.

Sincerely,
Dale
 
Dale,

Simple, understandable, and as always educational... Thanks for the pointer Dale. Always a pleasure having your input and feedback.

Regards,
 
LINEAWEAVER said:
Dale,
Thank you for the tip, I will give it a try. As I had posted previously to Whosaberg, I am just experimenting right now to see how much potential I have left in the old Dellorto... Right now the bike is more than I can handle safely in the higher RPM range so sapping more is not my primary objective. When it comes down to it, I am just doing the cause and effect testing to see if I can find a setting with less brutality and more linear delivery without adversely sacrificing the high end rush that the 550 can give. Of course dialing it in without a resulting hesitation, stutter, or any other undesired side affect will be my major goal.... an increase in fuel economy will also be a goal in my experiments. With the exception of doing the sand drags in Glamis, very rarely do I ever get the bike into 6th gear WOT. I am simply trying to fine tune the bikes carburation to suit the types of riding I enjoy which calls for a less brutal grunt off closed throttle.... better manageability for better words. Hope this explains things a bit better, I know its asking allot out of the Dellorto/Husaberg combination but well see what I end up with. No hurries
Click to expand...


Hi Keith,
Such being said changing the main jet will be the least of your concerns.
Remove the main jet and tune the carburetor through half throttle. Such insures the main jet is not a contributing factor regarding the circuits for which yo wish to experiment.

Hope this helps.

Sincerely,
Dale
Click to expand...

Dale:

Does removing the main jet while tuning the other circuits apply to all carbs or only just the Dellorto?
 
Thanks. That is very interesting. I suppose that by removing the main jet the resulting copious amount of fuel essentially disables the high speed circuit except in the case of some Dellorto carburetors as you stated.
 
husabutt said:
Thanks. That is very interesting. I suppose that by removing the main jet the resulting copious amount of fuel essentially disables the high speed circuit except in the case of some Dellorto carburetors as you stated.
Click to expand...

Quite contraire,
The Dellorto metering rod and emulsion tube have more of a tendency to influence WOT operation (ie main jet) during near WOT conditions as a result of improperly matched brass and body casting air bleeds.

Case In Point:
One may spend hours sorting through metering rods and emulsion tubes to perfect light throttle fuel delivery only to discover that the main jet now has little or no control near WOT. (ie too lean)

What to do:
Order up another $100.00 worth of tuning brass and spend two more weekends playing with the low speed settings. However, this time you
are likely to leave out the main jet.

Hope this clears things up a bit.

Sincerely,
Dale
 
:D Keith it seem's as though you must be close with your settings

otherwise you would have asked for help? I say leave her alone &

don't spend any money! Work on your body so you can hold on longer!

hope this helps

BOSS
 
I am simply trying to fine tune the bikes carburation to suit the types of riding I enjoy which calls for a less brutal grunt off closed throttle.... better manageability for better words
Click to expand...

Hi Keith,
Sorry, I overlooked the above portion of your reply.

To soften power delivery your best option is a camshaft with increased duration and overlap.

A keihin and / or crisper jetting will only sharpen the low speed power delivery.

Best Regards,
Dale
 
Something came to mind the other day Keith?

What about a intake restrictor? Does not cost much & will tame

the beast inside!
 
BOSS said:
Something came to mind the other day Keith?

What about a intake restrictor? Does not cost much & will tame

the beast inside!
Click to expand...

Hi Rick,
Unfortunately restricting the inlet most often sharpens throttle response and only limits peak power.

In nearly every case of restrictor testing for FUSA said restrictor boosted the bottom and limited the top. For DT, limiting peak power was the objective. The boost on the bottom was simply a by product.

Hope you are doing well.

Sincerely,
Dale
 
BOSS said:
:oops: Yes dale that is the case,but maybe try resricting the exhaust?
Keith
Click to expand...

Such works great on most two strokes and even came as an OE option on many small displacement models (ie PW 50 / 80, etc.)

Unfortunately regarding a four stroke such provides similar results to that of restricting the inlet except now the exhaust valves are being thermally punished. :(

Note:
As previously mentioned a camshaft with increased duration and overlap (mine or someone elses) will indeed soften initial power delivery, provide for a more linear delivery overall, reduce exhaust valve temperatures and improve the life of the entire valvetrain.

No free ride:
Fuel economy will decrease as will the "hard initial hit" which many enjoy.

Sincerely,
Dale
 

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