Questioning todays findings

[alke46]

I set the carb air screws to get the best idle setting then did a compression check which showed better numbers than I had suspected.

I put in new plugs and did a 5 mile ride at 1/4 throttle to get the idle circuit readings. Pulled all four plugs and they showed no signs of any coloring. Just looked like they did when I put them in new.
Is this OK or should I have ridden it for more than 5 miles?

I have read the method for plug chops as outlined on BassCliff's site. Am I correct to understand that because my plugs showed no coloration that everything is OK in the idle circuit? Thanks

 

[seuadr]

i hate to ask it but if #3 was not responding to air ajutment at idle.. when you cleaned the carbs did you pay attention to the #3 idle circuit? sounds like it could be plugged.

 

[Big T]

When did you last adjust your valves?

 

[alke46]

i hate to ask it but if #3 was not responding to air ajutment at idle.. when you cleaned the carbs did you pay attention to the #3 idle circuit? sounds like it could be plugged.

It responded to air and carb cleaner being sprayed through it. I also made sure all small holes were clear and open that I could see.

 

[alke46]

When did you last adjust your valves?

Valves were adjusted at the time the carb cleaning was going on.

 

[seuadr]

did you check (and preferably) replace the orings between the boots and head when you had the carbs off? what kind of condition are the boots in? still pliable and rubber? i had a cylinder that didn't wanna respond to syncing and it turned out to be a crack in the orin so it was running exceptionally lean.

 

[alke46]

yes, new o-rings between the boots and head. boots seemed to be OK considering the age of the machine.

 

[Guest]

I set the carb air screws to get the best idle setting then did a compression check which showed better numbers than I had suspected.

Setting your air screws won't effect your compression readings. You should have the throttle wide open when doing a compression check (or have the carbs off).

Your plugs should be tan, not white. You are running too lean for some reason. Make sure you have no intake leaks and your airbox is sealed.

 

[Guest]

Look at the threads on the spark plug. If the heat range is under 1.5 threads your good. Might take a week or so to show color on the plug.
The heat range shows how hot the cumbustion is.
Is everything stock or did you do some mods.

 

[alke46]

Look at the threads on the spark plug. If the heat range is under 1.5 threads your good. Might take a week or so to show color on the plug.
The heat range shows how hot the cumbustion is.
Is everything stock or did you do some mods.

I will check the threads tonight.
The PO had an aftermarket exhaust (4 into 2) installed, supposedly by a m/c shop and he claimed they told him the new exhaust would NOT require any rejetting.
I am not sure how much of the PO's statements about the bike are believeable.
Thanks for your input. I will check those threads asap.

 

[hampshirehog]

A rich mixture will very often show up immediately on new plugs - even after a couple of minutes on tickover. A lean mixture or a correct mixture sometimes takes a wee bit longer to declare - a 'few' miles on new plugs.

The PO + the m/c shop might be right about the exhaust - there are plenty of types ou there that don't require any fiddling with the carbs.

Don't forget that to tune a carb in you need to look at the plugs on tickover, 1/4 throttle, 1/2-3/4 throttle and WOT - (pilot circuit, slide cutaway, needle and main).

 

[alke46]

A rich mixture will very often show up immediately on new plugs - even after a couple of minutes on tickover. A lean mixture or a correct mixture sometimes takes a wee bit longer to declare - a 'few' miles on new plugs.

The PO + the m/c shop might be right about the exhaust - there are plenty of types ou there that don't require any fiddling with the carbs.

Don't forget that to tune a carb in you need to look at the plugs on tickover, 1/4 throttle, 1/2-3/4 throttle and WOT - (pilot circuit, slide cutaway, needle and main).

Thanks hampshirehog. Very informative. This is the reason I joined the GSResources forum.

I will do the 1/2-3/4 throttle and WOT just as soon as this damned North wind quits blowing and the temperature gets above 40*F.

 

[duaneage]

A replacement 4-2 exhaust should be OK from a tuning standpoint, unless it is extensively modified, like no baffles. When you change things on the airbox side by going to pods, well then your going to be re-jetting for sure. Especially with CV carbs.

Is the bike hesitating or showing signs of fuel starvation, like sputtering at high RPM or lacking power?

 

[alke46]

A replacement 4-2 exhaust should be OK from a tuning standpoint, unless it is extensively modified, like no baffles. When you change things on the airbox side by going to pods, well then your going to be re-jetting for sure. Especially with CV carbs.

Is the bike hesitating or showing signs of fuel starvation, like sputtering at high RPM or lacking power?

No the bike is running pretty much like it should be running. The performance seems good, I am just trying to fine tune things since the carb dipping.
It acts like it is going to be pretty close without having to do anything inside the carbs

 

[alke46]

Look at the threads on the spark plug. If the heat range is under 1.5 threads your good. Might take a week or so to show color on the plug.
The heat range shows how hot the cumbustion is.
Is everything stock or did you do some mods.

chef1366, I am not sure exactly what you are talking about here. I have the plugs out now but am not seeing anything on the threads.
sorry, but I am just not familiar with what I am supposed to be seeing.

 

[Guest]

[SIZE=+1]Follow steps in order....[/SIZE]First[SIZE=+1], dial in:[/SIZE]

• [SIZE=+1]1. Top end (full throttle / 7.5k to redline -
  [/SIZE]Best Main Jet must be selected before starting step 2 (needle height)!
  • • [SIZE=+1]Select Best Main Jet [/SIZE]
  • To get the best, most even top end power (full throttle/after 7500 rpm), select the main jet that produces the hardest pull at high rpm.
    • If the bike pulls harder at high rpm when cold and less hard when fully warmed up, the main jet is too large. Install a smaller main jet and retest until you find the main jet that pulls the hardest at high rpm when fully warmed up. This must be done first - before moving on to the other tuning ranges.

• • • If the bike doesn't pull well at high rpm when cold and gets only slightly better when fully warmed up, the main jet is too small.
      • In order to properly tune the midrange and low rpm carburetion, THE MAIN JET MUST FIRST BE PROPERLY SELECTED after 10 to 15 minutes of hard use!
        
        

        • Do not pay too much attention to the low-end richness when you are changing main jets - you still need to be using the main jets that produce the best power at high rpm. You will deal with the low-end / cruise later - after step 2.
• [SIZE=+1]2. Midrange (full throttle /5k-7k)[/SIZE]
  Step 1 (Best Main Jet) must be selected before starting step 2!
  • • [SIZE=+1]Select best needle clip position[/SIZE]
  • To get the best power at full throttle / 5k-7k rpm, adjust the needle height, after you have already selected the best main jet.
    • If the engine pulls better or is smoother at full throttle/5k-7k in a full throttle roll-on starting at <3k when cool but soft and/or rough when at full operating temperature, it is too rich in the midrange and the needle should be lowered.
    • If the engine pulls better when fully warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k.
    • If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set.
      
      

      • Do not pay too much attention to the low-end richness when you are changing needle clip positions - you still need to be using the clip position that produces the best full throttle / 5k-7k power in conjunction with the main jets (Step 1) that produce the best power at high rpm. You will deal with the low-end / cruise next.

• [SIZE=+1]3. Low end (full throttle / 2k-3k)[/SIZE]
  Step 1 (Best Main Jet) and Step 2 (needle height) must be selected before starting step 3!
  • • [SIZE=+1]Float height (AKA fuel level & how to..)[/SIZE]
  • To get best low-end power, set float height (fuel level) so that the engine will accept full throttle, without missing or stumbling, in 2nd gear from 2.5k to 3k rpm at minimum.
    • Float heights, unless otherwise specified in the installation guide, are measured from the "gasket surface" of the carb body to the highest part of the top of the float - with the float tang touching but not compressing the float valve spring.
    • If the engine has a "wet" rhythmic, soggy area at full throttle / 3k-4k rpm, that gets worse as the engine heats up, lower the fuel level by resetting the float height 1mm greater (if the original was 13mm - go to 14mm). This will lower the fuel level, making full throttle / 2k-3k rpm leaner.
    • If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level.
    • Example: change float height from 15mm to 14mm to richen up that area.

• • • REMEMBER, since the main jet WILL affect low speed operation, the MAIN JET has to be within 1 or 2 sizes of correct before final float setting.
      • Warning: If the engine is left with the fuel level too high,, the engine may foul plugs on the street and will be "soft" and boggy at part throttle operation. Adjust Floats to raise/ lower the Fuel Level.
        • Base settings are usually given if a particular application has a history of fuel level criticalness. The Fuel level height in the float bowl affects full throttle/low rpm and, also, richness or leanness at cruise/low rpm.
      • Reference: a bike that runs cleanly at small throttle openings when cold, but starts to show signs of richness as it heats up to full operating temperature, will usually be leaned out enough to be correct if the fuel level is LOWERED 1mm. Check out and RESET all: Suzuki (all), Yamaha (all) and Kawasaki (if low speed problems occur). Needless to say, FUEL LEVEL IS EXTREMELY IMPORTANT!!!
    • If there are low-end richness problems, even after lowering the fuel level much more than 1.5mm from our initial settings, check for needle wear and needle jet (part of the emulsion tube). See Worn Needle and Worn Needle Jet diagram. It is VERY common for the brass needle jets (in the top of the "emulsion tube") in 36mm, 38mm and 40mm Mikuni CV carbs to wear out in as little as 5,000 miles. Check them for "oblong" wear - the needle jet orifice starts out round! Factory Pro produces stock replacement needle jets / emulsion tubes for 36mm and 38mm Mikuni carbs. Click here
• [SIZE=+1]4. Idle and low rpm cruise[/SIZE]
  • • [SIZE=+1]Fuel Screw setting (AKA mixture screws)[/SIZE]
      • There is usually a machined brass or aluminum cap over the fuel screws on all but newer Honda. It's about the diameter of a pencil. Cap removal details. Newer Honda carbs have no caps, but use a special "D" shaped driver, usually supplied in the carb recal kit. We do have them available separately, too. 800 869-0497 to order -
    • Set for smoothest idle and 2nd gear, 4k rpm, steady state cruise operation. Set mixture screws at recommended settings, as a starting point. For smoothest idle, 2nd gear 4000 rpm steady state cruise , and 1/8 throttle high rpm operation. (pj tuning information)
    • Pilot fuel mixture screw settings, float level (but, you've "fixed" the fuel level in Step 3 - which you have already done!) AND pilot jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation.
      • If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
      • Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
        • NOTE: A rich problem gets worse as the engine heats up.
          • If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
        • NOTE: A lean problem gets better as the engine heats up.
          • If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!

 

[alke46]

Thanks chef1366, that is quite detailed information. Definitely should help getting the fine tuning done. I appreciate the help.
Larry