QuestionQUESTION: Hello,
My bike has ~5K miles on it. In the manual it says to "manipulate the air screw to obtain the maximum and stable engine speed. The standard air screw setting is 1 1/4 turns open from full close position".
I have mine adjusted well beyond the 1 1/4 turns. It is MANY more turns. If I don't do this the bike seems to run great but then after about 10 minutes bogs down, loses power and dies. I think the bike is not being able to reach full power or speed due to the fact I have the air screw adusted so far out. Currently I can drive it no problem but I think it is lacking performance with the current setting I have. Does it seem right the air screw adjusment would need to be so many more turns than the manual says ? Would it have an affect on the bike running fine for 10 minutes than bogging down and losing power ? How many miles can I get out of the front and back brakes and then what do I need to change. Thanks for all your help !!!
ANSWER: Adam.... go back to the basics before you adjust/condemn the idle screw settings. That is just about the last thing to adjust on a tune-up. If the bike doesn't idle correctly with the 1 1/4+- turns out, then there are possible issues in several areas. Start at the beginning:
*Adjust the valves and check the compression. If compression is low in one or both cylinders, all the "adjusting" in the world won't fix it.
*Remove the spark advancer from the end of the camshaft (behind the points plate) and check it for proper advance/retard function. Then, clean the points, set the maximum gap at .014" and then move the point plate around until the points just OPEN at the F mark alignment on the flywheel. Use some light grease on the points cam and/or put a drop of oil on the felt pad that lubricates the point cam.
*Remove the float bowls and check to see that the idle jet and main jets are clean and clear. With the bowls off, jets out and air filters removed, spray some carb cleaner into the two air bleed openings in the carburetor inlet (or just take the carbs off and clean them properly). The float level setting is 21.0mm. measured from the floats to the carb gasket surface, just as the needle has closed the float seat, but not compressed the spring loaded tip of the needle.
*Finally, check the carburetor slides to see if they are in backwards! The slides are L&R side specific and are correctly installed with the cutaways facing towards the air filters. It is likely that the slides are in backwards, which causes a very rich running condition that fouls the spark plugs. The air screws being turned so far out is trying to compensate for excessive fuel and/or lack of air flow to the air stream. Excessive fuel symptoms can occur from high float levels, blocked air bleed passages, plugged up emulsion tube holes on the main jet holders or the slides installed backwards.
If you drive and stop mostly with the rear brakes, they will wear out in a few thousand miles. If you have been properly schooled in motorcycle riding from an MSF course, then you know to use both front and rear brakes, which will spread the wear out more evenly between the two systems. The front brake does MOST of the stopping of the motorcycle, so should be the ones that wear down before the rears. If the brake adjustments are pretty much used up, the wheels have to come off and new brake shoes installed.
Merry Christmas...
Bill Silver
---------- FOLLOW-UP ----------
QUESTION: Hello Bill,
To check the carbureator slides to see if the L&R are mixed up do I have to completely remove the carburetor ? I am not sure exactly what they look like and have been searching for pictures on the internet. I have removed the float bowls in the past to clean them and the jet. Can I check the carburetor slides in this area ?
AnswerAdam, you just have to pop up the seat, loosen the back of the fuel tank mount to get enough room to remove the carburetor tops where the cables go into them both.
http://www.cmsnl.com/honda-cb175-super-sport-175-k6-us_model422/partslist/E20.ht #8/10
If you just remove one side cover and the air filter, you can peek into the carburetor throat and see if the carb throat is closed down tightly or if you see a cutaway at the bottom.
http://cgi.ebay.com/ebaymotors/Honda-CB175-K0-CL175-K0-Valve-RH-Throttle-Carbure cutaway side is where the 2.5 marking is located. You should see it on the air cleaner side.
Only cleaning the float bowls and jets often misses the other critical air and fuel passages.
Bill Silver
