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Discussion Starter · #21 ·
I cleaned both plugs last night, regapped and checked them for fire. The rear cylinder has weaker fire than the front cylinder. I swapped plugs to see if it was the plug, but the same problem. I also too the carb off, raised main needle one notch, checked and reset the float level and checked for debris. Everything was clean as a whistle. Next is swapping coils and doing a compression check. I am removing the vacuum diaphragm for the breather and replacing the vacuum lines, just to be safe. I sure hope there isn't degradation in the cylinder. I don't feel like doing a rebuild in the peak bike weather! LOL. Anyways, will post updates. Thanks for all your input folks!
 

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Motomedic is incorrect, your front cylinder is certainly lean. The rear cylinder looks rich. I'd bet that you have a vacuum leak somewhere that is allowing fresh air into the front cylinder which is causing the rear cylinder to get all the fuel. You need to look at the carb boot and intake manifold and see if there is something wrong. My guess is it's your boot. It can be a pain in the butt to get on and off and that's why a lot of people make mistakes when installing them
  • Unfortunately, You are receiving conflicting (and incorrect) information about the air to fuel ratio each of your cylinders is receiving from a SINGLE carb design.
  • Each cylinder draws the amount of fuel it needs based on throttle plate opening. This is basic 'suck, press, bang and blow' 4 stroke internal combustion engine operating theory.
  • Carburetors, as most of us are aware, DO NOT inject fuel into the airstream based on predetermined pressure and timing.
  • If there is a vacuum leak after the throttle plate then the total flow demand for THAT cylinder will be lower and less fuel will be drawn through the main jet which will create a lean condition FOR THAT CYLINDER ONLY
  • IT WILL NOT TRANSLATE TO MORE FUEL BEING SENT TO THE REAR CYLINDER. THE REAR CYLINDER WILL CREATE ITS OWN DEMAND BASED ON TOTAL VACUUM FOR THAT CYLINDER.
  • The front cylinder is not lean. The 'white strap' JonnyV is referring to is the ground electrode or anode. It's grayish color is normal and the location of the graying means that the timing is slightly retarded.
  • The reason the tip isn't carbon covered is because the center electrode end and the opposite ground electrode are the HOTTEST parts in the cylinder. The fact that there is carbon on the ground electrode means that excess raw fuel came into contact with a hot plug OR that the electrode is indexed into the incoming A/F mixture.
  • A lean A/F mix on a carbureted bike would not leave the brownish coloring as seen on the ceramic/insulator (front plug). Nor would a lean mixture leave ANY BLACK DEPOSITS on the plug body and threads.
  • The rear cylinder can not be any leaner or richer than the front as a result of fuel supply because they share the same carburetor.
  • By JonnyV's 'logic' you could essentially block off one of the cylinders entirely and still use the same amount of fuel simply because there are two (2) cylinders.
  • And if that was the case every multi-cylinder bike on the planet would have one carb or one fuel injector and we would all be using less fuel.
  • BUT THEY DON'T.
  • Your rear cylinder has a compression and/or ignition problem. It is obviously getting fuel but the fuel isn't being burned properly. The plug insulator is coated in carbon and this reduces the ability of the spark plug to conduct across the gap and eventually will become fouled to ground. It should be replaced.
  • The wet look of the plug could be either non-vaporized fuel or oil. ONLY you can determine that.
  • If it is fuel then compression or ignition could be the problem
  • If it is oil then rings (also a low compression contributor) or valve stem seals and more likely than not it would be the intake seals.
  • As far as the low end rich condition I mentioned in my earlier post: The low end INCLUDES the idle/pilot and enrichment circuits. The black on the bottom of the plug threads is common and doesn't indicate a need for change. It is there because ALL cold engines use more fuel to get the necessary atomized fuel to run until they reach operating temperature. If you stayed by your machine and reduced the enrichment while increasing the throttle every time you started it cold, there would be less of a ring. Or if you just started it with the throttle and kept it a higher rev to warm up there would be less of a ring.
  • The front spark plug indicates, IMPO, a good A/F ratio coming from the carb into the front cylinder.
  • It is reasonable to conclude then that the rear cylinder is receiving the same A/F mixture.
I hope this clears up any confusion you may have had as a result of the analysis of the symptoms you have described with the photos you submitted.
And as always, if ANYONE doesn't agree with my opinions, you are welcome to share yours openly here in the forum OR privately in the conversation tab under your icon.
If you would like to argue your point out in the open forum and direct it to a certain person, then you can expect to receive the same treatment.
This is an open public forum but we still attempt to maintain a level of civil professionalism and courtesy. At least that is my understanding
 

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I cleaned both plugs last night, regapped and checked them for fire. The rear cylinder has weaker fire than the front cylinder. I swapped plugs to see if it was the plug, but the same problem. I also too the carb off, raised main needle one notch, checked and reset the float level and checked for debris. Everything was clean as a whistle. Next is swapping coils and doing a compression check. I am removing the vacuum diaphragm for the breather and replacing the vacuum lines, just to be safe. I sure hope there isn't degradation in the cylinder. I don't feel like doing a rebuild in the peak bike weather! LOL. Anyways, will post updates. Thanks for all your input folks!
If it has weaker spark.. you more than likely found the issue... The cylinder is probably fine...relax until you find out otherwise lol

Sent from my SM-A115U1 using Tapatalk
 

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Discussion Starter · #24 ·
I'm going to track down a compression tester and get a new set of plugs to start馃憤馃嵒
 
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If you know you have weak spark, get that squared away before you move on to the next thing. If you do 3 or 4 things at once and the problem is fixed you won't know what fixed it. Then if it happens again you're in the same predicament.
 

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Discussion Starter · #26 ·
If you know you have weak spark, get that squared away before you move on to the next thing. If you do 3 or 4 things at once and the problem is fixed you won't know what fixed it. Then if it happens again you're in the same predicament.
Exactly. Compression test first. Bought new plugs as well. Cleaned and checked carb, made sure floats were set right, raised the main jet needle by one notch. Replacing vacuum lines too. Will update soon.
 

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And these things have non-adjustable rockers. They have to be shimmed. They tighten up over time so if you are showing an odd compression or leak down reading you may want to look at the valve shims. It's a pain in the butt to do, I just did my 800 a couple weeks ago, but it's pretty important. I had to order a box of assorted shims and only used 3 of them.
 

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Discussion Starter · #28 ·
Motor vehicle Gauge Measuring instrument Gas Automotive tire

Gauge Measuring instrument Gas Motor vehicle Auto part

$75 for compression tester was well worth the investment. Compression is good. Phew!
 

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Discussion Starter · #29 ·
Can someone tell me where this hose is supposed to connect to? It comes from a 90掳 nipple on the rear cylinder.
 

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Discussion Starter · #31 ·
I figured out what the hose is. Searched through the forum and it is just a crank case breather tube. I'll plumb it in the route suggested by other members 馃憤. Up near the rad cap. Some have put a PCV valve in it, to prevent from back feed, etc. Hoping to fire her up tomorrow after work, once I finish putting her together, and cross fingers that all I may need to get is a pair of coils and wires.
 

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Discussion Starter · #32 ·
Put her together tonight and went for a ride in mixed traffic settings. World of difference. Quick throttle response and much more power through the torque curve. I'm going to take her for a long ride tomorrow, with a buddy of mine, so will see when I get her on the highway. Thanks for all the input, folks. Glad I joined this forum馃嵒
 

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Discussion Starter · #33 ·
So I took her on the highway, on my way to meet my buddy for a road tour and got up to 110 km/hr and no issue. Did our tour, which stayed between 80&90km/hr and no issues. Got on the highway to go home and it starts losing power and misfiring over 100 km/hr. Gonna pull the plugs again, but I think my next step is new coils and another set of plugs.
 
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