Right Cylinder Not Firing When Engine Cold?

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dltowers

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I have a fuel/carburator problem with my 650:
My Yamaha is a 1981 XS 650 Special II that I bought brand new.
It is in storage about 99% of the year, and it only has 1,184 miles on it.
I am having a problem starting the bike when the engine is cold.
When it cranks, it is only running on 1 cylinder, the right side is not firing.
I can spray spray starter fuild in the right intake and the right side will start firing.
Once the engine is warm, it starts correctly, with no problem, it is just when I initially try to start the engine cold.
I had thought that maybe the low-speed jets were bad, so I had the carburators
rebuilt at a local Yamaha dealership, this helped, but it is still not correct.
Utilizing the choke level does not help?
I haved cleaned the fuel lines/petcock and they are working correctly.
I really hate to have to use starting fluid each time I start the engine cold, but it will not fire on right cylinder without it?
Any suggestions/tips?
dufflebag51@aol.com
 
You could try swapping over the plug leads to see if the non-firing follows. Resistor cap could be going bad. Also measure the resistance from one plug lead to the other plug lead.

What do the plugs look like? Plug swap to see if it follows.
 
Had the same exact problem with my 77. Turned out the little passage in the float bowl that feeds the choke circuit was plugged. See the carb guide in the tech section for pics and explanation.
 
I cleaned the carburators myself, then also had the local Yamaha shop clean them. They soaked and vated them for over 6 hours. When the engine is hot the bike will start right up, idles great, with no problems. But if the engine is cold, it will start but not run on right cylinder even with the chock out. If I can keep it reved up and running for 1 or 2 minutes with it running on only the left side, the right side will eventually start firing.
I usually have to squirt some starter fuild in the right side intake behind the side cover and the right side will fire right up. I guess with a 30 plus year old bike, and with under 1,200 miles (yes 1,200 miles is correct) on it, my problem is probably caused by the bike being stored and not riden maybe once or twice a year at the most. Here is a photo of the bike:
1981 Yamaha XS650 Special II.jpg
 
Same problem I had. Bike would start but run on left side only. After a minute the other cyl would kick in and it would run great. That passage is very small and difficult to open in my case.
 
Grinder said:
Had the same exact problem with my 77. Turned out the little passage in the float bowl that feeds the choke circuit was plugged. See the carb guide in the tech section for pics and explanation.
Click to expand...

So can I just remove the float bowl and have access to the passage without removing entire carburator assembly?
What link in Carb Guide Section has information, I could not find exact link?
 
Go to the orange tech section, carbs, guides(1st one) and download/open the first link there. When you get the bowl off make sure the gasket has the corresponding hole for that passage. There is a section there on the choke circuit. I ended up using compressed air, carb cleaner and wire to unplug mine.
 
Possibilty that it could be air inleakage on the right side. Check around the carb intake boots, and vacuum line to the petcock. Too much air making the mixtures so lean it wont fire when cold, but manages to fire when the engine heats up.
 
Yes, you can just drop the float bowl to inspect the choke feed jet. It does sound like it's clogged. Here's how to check it .....

ChokeJet2.jpg
 
Have one of your guitar playing buddies give you an old .010 guitar string. cut 6 in. piece as needed. Works great for getting into all those little holes,and checking to see if they're clear.
 

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