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Compression coming out of the left carb


4overbanshee

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I want to start off that I searched but I couldn't find any topics directly related to my problem.

On my last trip to the dunes I lost the left cylinder. I was heading back to camp with my daughter and a buddys nephew, I stopped to wait for them to catch up then when I went to take off I had half the power I had before so I limped back to camp. I thought maybe the plugs were fouled so I replaced them, didn't help. The left pipe was blowing cold and the right was hot so I swapped plug wires and the issue stayed with the left cylinder.  At that point I parked it for the weekend.

 

 Let me back up a little. Over the weekend the bike got harder and harder to start (used to fire up after the first few kicks). I don't recall ridding hard before the bike lost 1/2 power, I was riding slower so my daughter and buddys nephew would be close.  Nothing that I can think of would have led to an issue other than maybe sand getting in and blocking fuel. Thats what I assumed.

 

 Fast FWD to now. I thought that I would give spraying some carb cleaner in the carb while running (won't idle, had to keep on the throttle).. I removed the filters and sprayed in..  The right pipe  was looking normal but the left looked really clean and only had the puffs from the carb cleaner.. The exhaust was cool on the left pipe.  I noticed that the left carb was blowing out air/exhaust as I revved the engine. Compression was coming out of the left carb when I revved the engine (not the right at all). I shut it down, but both pipes were hot.

I have my thoughts as to what it is, but I am looking for others input and advice before I start on the fix.

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Here's a Clymers Manual.

http://www.farmandsandtoys.com/partdetail.asp?partid=172

 

Just like said above, the reed cages are between the cylinders and the carb intake boots.

Before you go tearing into it, you can remove the left carb and let it hang over the frame.

Shine a flashlight in thru the intake boot and look at the reed pedals.

Chances are the left cylinder reed pedal(s) are broken.

If the reed cages are stock, then you can get a set of these and be on your way cheap.

http://www.ebay.com/itm/Boyesen-Power-Reeds-YAMAHA-YFZ350-BANSHEE-1987-2006-REED-/400570100168

 

Since you have a 4mil stroker and these are good for some pretty decent horsepower gains over the V-Force 3's, you might want to give these a shot.

They're not as cheap as just swapping out the reed pedals on stock cages, but you'll feel the difference over stock, guaranteed...

http://www.ebay.com/itm/BRAND-NEW-V-FORCE-4-REED-VALVE-SYSTEM-BANSHEE-87-06-/121159970663?pt=Motorcycles_Parts_Accessories&hash=item1c35b26f67&vxp=mtr

 

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Since you've worked on auto engines for some time......reed "valves" on a 2 stroke are the literal comparison to valves in a 4 stroke motor.  Different is.....they are a spring loaded flap......its intent is to let air/fuel pull the reed open using vacuum to suck the air/fuel charge in....and on a 2 stroke since there is exhaust back-pressure/reverb.....when the pressure comes back due to the exhaust.....the reeds are meant to snap shut and be held shut by the pressure. 

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