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2003 LC4 SXC 625 Questions

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I did a few searches but found nothing on the auto decompression cam failure that I believe I have and a fuel starvation issue at high RPMs.

The bike is new to me and shows only 3,350 miles, the decompresser made a pretty load snap at start up but the last time I tried to start it I heard a crunch followed by a back fire. It still turns over but doesn't make the same snap noise and it won't start. I was planning to remove the auto decompresser and just use the manual lever. The cost of a new cam is under $150 and I may replace it but not if it is prone to the same failure. Does anyone else have or had this issue and what did you do to resolve it?

My Mikuni CV carb seems to have a sticky float valve because at a continuous high speed (and high RPM) the fuel runs out and the bike starts to sputter and stalls. I cleaned it but it still runs out of fuel. I did notice a plastic reducer in the fuel inlet, has anyone removed this and did it solve the issue or do I have to replace the float valve?

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I have sticky float too on my Mikuni. I removed the carb and I am in the process of rebuild it however It lookslike the pin that hold the float is a press fit and I can not remove it :bonk:easily

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I did a few searches but found nothing on the auto decompression cam failure that I believe I have and a fuel starvation issue at high RPMs.

The bike is new to me and shows only 3,350 miles, the decompresser made a pretty load snap at start up but the last time I tried to start it I heard a crunch followed by a back fire. It still turns over but doesn't make the same snap noise and it won't start. I was planning to remove the auto decompresser and just use the manual lever. The cost of a new cam is under $150 and I may replace it but not if it is prone to the same failure. Does anyone else have or had this issue and what did you do to resolve it?

My Mikuni CV carb seems to have a sticky float valve because at a continuous high speed (and high RPM) the fuel runs out and the bike starts to sputter and stalls. I cleaned it but it still runs out of fuel. I did notice a plastic reducer in the fuel inlet, has anyone removed this and did it solve the issue or do I have to replace the float valve?

The plastic reducer you refer to is in actual fact an inline filter that you can lift out by hooking with a screwdriver...

Chances are your float needle + valve are not sealing because the needle is worn out or debris is caught in the seat... The floats themselves are pretty much trouble free once the float tang is set properly...

Now if you have been running with the extreme rich problem caused by a leaky float needle assembly it is not so good for the engine.... The cylinder will fill up with gas in some cases and will not start.... If you heard crunching that is not good, I would shine a flashlight down the spark plug hole and try to inspect the piston to see if it is still intact....

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The plastic reducer you refer to is in actual fact an inline filter that you can lift out by hooking with a screwdriver...

Chances are your float needle + valve are not sealing because the needle is worn out or debris is caught in the seat... The floats themselves are pretty much trouble free once the float tang is set properly...

Now if you have been running with the extreme rich problem caused by a leaky float needle assembly it is not so good for the engine.... The cylinder will fill up with gas in some cases and will not start.... If you heard crunching that is not good, I would shine a flashlight down the spark plug hole and try to inspect the piston to see if it is still intact....

Thanx for the reply, I am probably going to buy a 41 mm FCR for it soon so the carb is not a big concern, the lack of compression however is a major concern. I don't think what I heard was enough to believe the piston was damaged but I can believe the auto decompresser jammed and is holding the valve open because it isn't clicking any more when the motor is turned over. I will pull the valve cover off this weekend and see if something jumps out at me....

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I have sticky float too on my Mikuni. I removed the carb and I am in the process of rebuild it however It lookslike the pin that hold the float is a press fit and I can not remove it :bonk:easily
My pin wanted to fall out on it's own but I have rebuilt carbs that were stuck from dried gas residue. If you spray it with cleaner first it should free up. I had one that was oxidized real bad but I managed to drive the pin out with a small punch while resting the other side of the carb on my bench vice with the jaws open enough to let the pin pass through. Hope that helps...

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Just wanted to state for the record that the crunch noise I heard was probably the starter clutch and the auto decompressor was freaking out because the idle was too low. I took the valve cover off and everything looked and worked great so I turned up the idle and it is running pretty well for the CV carb. It still starves out fuel on the freeway at speed, I need to find a good 41 mm FCR soon...

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Update: The float valve housing was sticking out from the carburetor body causing the valve to close prematurely and lowering the fuel level in the bowl. I pulled it out and noticed the "O" ring had swollen so I replaced it and reassembled the carb and it seems to be working but I still want an FCR 41mm...

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