jet suggestions?

mmarm300 · Full Member Joined: Aug 10, 2009 Posts: 28

78 xs650 with straight pipes and pod filters...any suggestions for a good combination?

jayel · Posted: August 19, 2009, 9:06 pm Post subject: Re: jet suggestions?

every setup is different try this to figure out whether you're rich or lean

www.4secondsflat.com/p...chart.html

then there is this:...........

At The End Of The Day A Carb Does Nothing More Than Meter The Fuel... The Motor Doesn't Care What The Carb Looks Like Or What Jets Are In There.....So Long As It's Getting The Right Fuel Air Mix For The Conditions...

Here's A Few Symptoms/Fixes

When Trying To Tune A Bike You Need To Know What Circuit Is Covering The Area Where You Feel You Have A Problem.
Changing The Main Jet Will Have No Effect On The Idle And Up To 1/2-3/4 Throttle
Whereas A Part Throttle Problem That Requires An Increase In Pilot Jet Size Will Give A Little Extra Fuel Over The Whole Range

If You Have Had The Carb Off Then Check The Float Level ....You Will Need To Refer To Your Factory Manual....

Idle - 1/8 ... Pilot Circuit

Signs Of Too Lean

If The Bikes Surges Back And Forward At A Steady Throttle At Around 3000+ Rpm
Excessive Popping Or Backfiring At Closed Throttle Deceleration..
The Bike Runs Better When Hot But Still Not Right
If You Blip The Throttle From Idle And As It Drops Back Down To Idle It Tends To Hang Up A Few Revs Too High And Then Come Down To A Lower Rpm...

Wind Out Pilot Screw By Half A Turn At A Time And See If It Improves.... If You Get Past 3 1/2 Turns Then Go Up To Next Size Pilot Jet

Other Things That Will Give A Lean Condition Are Intake Leaks..... If In Doubt Then Replace Intake Seals And Lube Them With A Silicon/Rubber Grease As They Are Assembled...

Sign Of Too Rich

Sooty Plugs..... Too Large A Pilot Circuit Will Soot Your Plugs Up Way More Than A Rich Main Circuit
The Bike Runs Better When Cold But Still Not Right...
If The Bike Doesn't Require Choke To Start And Idle From Cold Then You Are Too Rich
If The Throttle Is Blipped From Idle And The Revs Drop Below Normal Idle And Then Come Back Up To Normal Idle....This Will Be Worse When The Motor Is Hot.

To Correct... Wind Pilot Screw In 1/2 Turn At A Time ... If It Gets Less To Only 1 Turn Out Then Reduce The Pilot Jet By One Size

1/4 - 3/4 throttle

This Is A Hard One To Pick........
Try Running In 2nd Or 3rd Gear And Crack The Throttle...

If It Pulls Clean ... Leave It....It Takes A Lot Of Experience To Pick The Difference Between A Rich Or Lean Condition Here...

A Lean Condition Will Tend To Surge Or Feel Flat.... A Rich Will Tend To Feel A Bit Soggy...

Try And Take Notes On The Weather ... If It Is Better When The Motor Is Cold Or When You're At Sea Level Or The Ambient Temp Is Lower Then You Are Probably Rich

If It Is Better When The Motor Is Hot Or You're At A Higher Altitude Or The Ambient Is Higher ...Then You're Probably Lean

Wide Open Throttle .. WOT

A Main Jet Guide To Rich Or Lean ...

A Few Points ... Your Lower Speed Circuits Tend To Work More Off Vacuum Than Airflow..... Whereas The Main Jet Or WOT Tends To Work Off Airflow.

WOT Throttle Runs Are Best Done At The Drag Strip And You Want The Jet That Gives The Best Mph Thru The Traps...... I Prefer To Start Rich And Come Back Down While The Mph Keeps Increasing Until The Mph Drops ... Then Go Back Up A Size...But You Can Start Lean And Go Up One Size At A Time Until The Mph Drops And Then Come Back One Size..

If It Runs Better At Night .... You Are Probably Rich ... If It Runs Better In The Afternoon, You Are Probably Lean..

If You Don't Have Access To A Drag Strip Then A Dyno Is Good For WOT Runs But Not Very Good For Part Throttle Runs Unless You Have A Good Operator..

Without Access To A Drag Strip Or Dyno, Here's A Few Tips..

As Stated If It Runs Better When It's Cold You Are Probably Rich.....
If It Runs Better When It's Hot Then You Are Probably Lean....

Another Way Is To Take It Past 5000 In A High Gear At WOT
Then Close It To About 7/8 Throttle
If The Engine Accelerates A Touch Then You Are Lean....
If The Engine Hesitates, Then You Are Probably Rich...
It Should Just Slow Slightly...

If The Engine Pops At The Change Rpm At Full Throttle Thru The Gears It Is Usually Lean.

Another Guide For Rich/Lean ...

If You Remove The Air Cleaner And The Bike Improves Then It Is Probably Rich

If You Tape Up Half Your Air Cleaner Element And It Improves Then You Are Probably Lean

Turn The Fuel Tap Off And Keep Riding...

If It Improves As The Fuel Level Drops, Then It's Rich

If It Gets Worse As The Fuel Level Drops Then It's Lean

If It Runs Better In That Range When The Air/Motor Is Cold It's Rich

If It Runs Better In That Range When The Air/Motor Is Hot It's Lean

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

deleted

woodman · Full Member Joined: Oct 12, 2008 Posts: 256

Try marking the throttle in 4 places with white out from idle to wide open and see where your problem is. Hard to get them right with straight pipes though

jayel · Posted: August 20, 2009, 10:29 am Post subject: Re: jet suggestions?

there you go woodman dissin' someone for his choice of pipes.... Laughing

can't we all just get along?

mmarm300 · Full Member Joined: Aug 10, 2009 Posts: 28

Im aware of how to find the problem, and i am aware that straight pipes defeat the purpose due to back pressure issues, i was just wondering if anyone had success with using different combos similar to the combination im running. Thank you for your suggestions.

jayel · Posted: August 20, 2009, 1:04 pm Post subject: Re: jet suggestions?

well with pods and Str. pipes you're going to be moving more air, won't effect the main jet circuit so much but the slow jet will probably need bumped a size or two there is really no way to give a one size fits all anwser without out testing, ie: what do the plugs look like, how does it run at different rpm ranges, throttle settings ect.

twinsarehot · Posted: August 20, 2009, 6:01 pm Post subject: Re: jet suggestions?

I got 135's for sale! Bought an extra set....same price as mikesxs.

What Happened to 650rider.com?

Yamaha xs650