Jump to content
Sign in to follow this  

Jetting help needed badly...

Recommended Posts

Hi everyone!

I have some jetting problem, and hope that fellow TT member could help me. I have a list of my current setting of my bike below,

Model = S with FCR39 convert w/o CE

MJ = 160

PJ = 38

PAS = 5/8 out

Fuel screw = 2.5 out

Needle = JD blue 4th from top

Airbox = 3x3

Exhaust= E model stock

Altitude = 0-2000

Temp = 24 DegC to 38 DegC

Now the problem...while cruising at around 55mile... i can feel the bike pulling backwards now and then... the feeling is like slightly closing the throttle and the bike slows down giving you that engine braking then it go back to normal again. Its something like jerking but in a smoother way. So what can be the problem?

Second is, the bike pops alot when engine braking with a fully closed throttle.

Lastly, the fuel consumsion increases tremedously. Previous on my stock CV with dyno jets and stock exhuast, i am getting around 105mile before reserve. But now i am barely get 80mile before reserve. (Both in the same riding condition) Is this normal after all the modification? Will i get close to what i had previously if the jetting are set properly?

I hope you guys understands what i am describing, cos i hope to solve this problem before going on a long ride next month. 😢

Thank you

Share this post


Link to post
Share on other sites

the surge is a lean condition.close the pas down slightly and retest fuel screw settings.should calm the popping down as well.

as far as the fuel consumption goes,that doesnt suprise me.no one ever claimed the FCR to be a fuel economy set up.

you can optimize the settings and fuel comsumption should decrease.

what elevation?pipe?

Share this post


Link to post
Share on other sites
the surge is a lean condition.close the pas down slightly and retest fuel screw settings.should calm the popping down as well.

as far as the fuel consumption goes,that doesnt suprise me.no one ever claimed the FCR to be a fuel economy set up.

you can optimize the settings and fuel comsumption should decrease.

what elevation?pipe?

Hi burned,

"Surge" the word...so does that mean the rest of the settings are alright? As for fuel consumption, guess i will have to get a big tank.

My elevation is 0 - 2000ft and temp is 24degC to 38degC.

Thanks for you info.

Share this post


Link to post
Share on other sites

All your settings look right and are on the rich side. Yet you describe classic "lean surge"?? Go ahead and make the adjustment suggested and evaluate the results. If no improvement, strip the carb and look for some restriction in the jets, float level, etc. Oh yea, is the carb plugged into the carb boot all the way? How is idle and all that. Has the condition always been there with the FCR or did it run OK before? How long has the FCR been on the bike?

A properly set up FCR will give good fuel economy depending on how you ride it.

What gearing are you running?

You can also try different needle positions. Is 5 or 3 better than 4? (count from th top)

Share this post


Link to post
Share on other sites
the rest of the setting look fine.how does the bike run other wise?

Accelerating is fine...top speed is fine too... no hesitation... only the surge and popping thats bothering me. I will try your recommendation and see whats the out come...

thanks again

Share this post


Link to post
Share on other sites
All your settings look right and are on the rich side. Yet you describe classic "lean surge"?? Go ahead and make the adjustment suggested and evaluate the results. If no improvement, strip the carb and look for some restriction in the jets, float level, etc. Oh yea, is the carb plugged into the carb boot all the way? How is idle and all that. Has the condition always been there with the FCR or did it run OK before? How long has the FCR been on the bike?

A properly set up FCR will give good fuel economy depending on how you ride it.

What gearing are you running?

You can also try different needle positions. Is 5 or 3 better than 4? (count from th top)

Hi noble,

Idle is fine... carb boot checked and fine... gearing is stock... I will make necessary adjustment recommended. Do you think raising the needle by 1 position will help as well?

Hope to come back with positive results...

Thanks

Share this post


Link to post
Share on other sites

Moving the needle is mosty a test to verify rich or lean. You are at 4. Move to 5 (from the top) is richer. Assuming your bike is lean, as the symtoms suggest, 5 will make it run better. If it gets worse at 5 then, we know your bike is not lean and we need to go the other way. Generally it does not take lot of change to cure mid-range lean surge. Try burned suggestion and see what happens. If a little better but still there try clip 5. In general I think people are using 3 or 4 so it is odd that you are having lean surge.

Report your throttle position when the surge is worst. Use tape and make some referrence marks. 1/8, 1/4, 3/8, 1/2 etc.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...