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Discussion Starter · #1 ·
Just picked up an 02 on the cheap. Bike not running when I picked it up, did a thorough carb clean and adjusted valves. Fired it up and front cylinder was dead. Found I wasn't getting spark, so replaced the coil and new plug and am now getting spark. Cylinder still not firing. Checked compression, getting around 180 psi with throttle open, compared to a little over 200 on the rear. Re-checked timing and it seems to match with the markings specified in the manual. But I'm not entirely sure if the front cams are where they need to be relative to the rear since the rear is firing properly or if 180 psi is actually too low to fire. Seems like the vacuum is low pulling through the front carb. Not really sure where to go from here, any ideas?
 

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180 is plenty of compression. Try a squirt of carb cleaner or a dribble of gas to see if it's not getting fuel into the front cylinder.
 

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Discussion Starter · #3 ·
180 is plenty of compression. Try a squirt of carb cleaner or a dribble of gas to see if it's not getting fuel into the front cylinder.
Sprayed brake cleaner into both to get it started. Worked for the rear cylinder but not the front. Checked the float bowl, it did have fuel.
 

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Discussion Starter · #5 ·
Air, fuel, compression, spark, and timing. You have to be missing at least one.
Air, fuel, compression, spark, and timing. You have to be missing at least one.
I feel like it must be timing, getting a strong blue spark when I turn the engine over. Here's some photos of the timing. First is the front cylinder with the timing mark on F, lobes are facing up and out . Second photo is the rear cylinder with the engine in the same position. When looking at the photo of the rear cylinder, the exhaust lobes are at 8 o clock and the intake valves are at 6 o clock. Is this the correct position based on where the front timing is?
58413

Front Cylinder with the timing mark on F
58414

Rear cylinder with the crankcase still on the F mark.
 

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I'll let someone more experienced than I answer specifically. I do know that you do not set the rear cylinder timing at the same place as the front. You are supposed to set the front and then rotate the crank 360 degrees and then set the rear cylinder. I also know that if you don't rotate the engine like this, it will still run, but it will sound funny compared to other SVs.
 

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Discussion Starter · #7 ·
So it looks like timing is correct. I rotated the engine 360 degrees to line up the F mark again, and my rear cylinder looks like it is correct (1R mark on IN is flush/parallel with head surface, 2 mark is top center and 3 mark on EX is 16 pins from 2 mark on IN cam, nearly perpendicular to head surface). Since my rear is firing properly and the front seems to be timed correctly relative to the rear, I'm not exactly sure what else could be the issue. 180 psi compression, fuel is flowing into the floats of rebuilt carbs with brand new stock jets (and have tried spraying brake cleaner into carb to get combustion), and right now the air box is totally removed (allowing as much air as possible to fire up). I don't see any visible cracking in the intake boot, so I can't imagine there being a major air leak before vacuum gets to the carb that would reduce intake vacuum enough to not pull fuel through the jets. I'm not sure how important exhaust manifold seal is on these bikes to help create vacuum, but I don't see any major red flags of an air leak from the exhaust manifold. Unless anyone can think of anything else, I guess the last step would be to pull the head, check the valve surfaces, and maybe just go ahead and re-ring the piston?
 

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I would just dump a half teaspoon of gas down the front cylinder first. I've seen too many people assume the jets are flowing and go way too far chasing after unusual mechanical issues. 98% of the time it's a carb issue.

For a mechanical issue to cause a dead cylinder, it would be so obvious. You wouldn't have good compression. You probably wouldn't have any compression. You have great compression.
 

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You could run an experiment if you're so inclined. Be sure both bowls are full of fuel. Pinch off the fuel line from the tank and let the engine run on one lung until it dies from lack of fuel. Then drain the bowls. If the front bowl is still full of fuel, the front cylinder isn't getting it.
 

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Discussion Starter · #10 ·
Thanks for the advice. Tomorrow I'll try bypassing the jets entirely, holding throttle wide open to keep butterfly open while feeding fuel or carb cleaner into the intake to see if it fires.
 

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Discussion Starter · #12 ·
So the plug cap can actually cause timing errors? I swapped the entire ignition coil, which came with a new lead and cap. It was just a cheap aftermarket one. I am getting very strong spark (visibly blue spark from the plug when grounded to the engine), but had to swap the wires from their original position on the coil to get spark. If I don't get combustion bypassing the carb, I'll try swapping out caps to see what I get. Thanks for the advice!
 

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It's just another component to eliminate. Also with the Air filter out you can spray some volatile aerosol into the front carb to see how it fires like Carb/Brake cleaner or even WD40. If it seems to run OK then it's most likely back to fuel delivery.
 

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It's just another component to eliminate. Also with the Air filter out you can spray some volatile aerosol into the front carb to see how it fires like Carb/Brake cleaner or even WD40. If it seems to run OK then it's most likely back to fuel delivery.
OP said he tried that and was unsuccessful but I'm not convinced. See @GeoSmith's Saturday post for his carb saga. He even had another set to test with.
 

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Good call and reminder. To the OP. Use the forum search option for,"Choke Plunger" problems. If it's stuck on it will flood the cylinder and can prevent it running correctly. I serviced mine as part of my fuel system service and the front screw was corroded in. I had to use lots of rust release fluid/heat and vise grips with the carbs off the get it to move and then replaced it after cleaning and making sure the mechanism worked correctly.
 
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Hey guys, I'm working with the OP on this bike and had some stuff come up causing a delay in the fix. Anyways, we got the valve covers back on and tried spraying wd-40 and brake cleaner directly into the intake of the carb. Still no firing, but seem to be getting decent vacuum through the carbs (feeling it suck with my hand covering the carb intake). At this point I feel like the issue has to be carb related like you guys stated before lol. My main reason for thinking this is because the slide on the front carb doesn't move at all when trying to fire up the bike, while the rear bounces up and down a bit. The slide moves freely and it feels like there is pressure, but I'm assuming one or more of the internal ports on the carb that creates vacuum/lift of the diaphragm is clogged or something? Does this seem like it could be the primary issue? I inspected the diaphragm when I rebuilt the carbs, and it looked fine (no cracks, discoloration, or thin spots). I also replaced all of the gaskets that came with a rebuild kit. Is there a specific hole/port in the carb body that I should double check/clean to make sure the vacuum is working correctly through the carb to create lift of the diaphragm? I feel like the carb dip that I did may have actually gunked something up rather than clear it out when it comes to the intake ports around the carb body intake.
 

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I heard carb dip is a no no with our carbs. Mucks up rubber stuff. I've read time often in the forums how important it is to clean and re-clean every carburetor port when rebuilding. The blow with air. Then clean again. After rebuilding my carbs three times, I can attest to that.
 

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a possible vacumn leak is the rubber part of the choke where it screws to the carb....if theres a vacumn leak the choke wont pull fuel...there's a connected vacumn passage from the choke up to the diaphram cap.so the choke and the diaphram operate on the sAME VACUMN.........is there a small oring under the cap?.
 

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my 02s front cylinder wont fire until the motor warms up. some kind of choke problem.
Same here. I can make the front cylinder fire sooner with throttle. But if I start the cold engine on choke and let idle, the front will not fire until the temp comes up some.
 
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