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ok....im a little PO'd right now...i had the same issue as CrazyCanuck a little while ago with my 1982 Yamaha xj650j.(see previous posts) Now i tried to start it up today, 3 days after the carbs were cleaned and it ran like a champ...and it would not run, whatever i did. When I first started it, it lit up in seconds without being choked even. A few seconds later, it would not stay on no matter what I did. Eventually I got it to idle for like 10 mins nicely without it being choked at all, but even at that it died the second i gave it gas. the throttle wouild respond after a HUGE lag sometimes, and sometimes it wouldnt respond at all, but instead would just idle lower...down around 500. when it idled normally for about 10 mins, it was at 1100-1200 rpm. now all i changed since i had it running well was that i added a lead substitute from Mag1. I also pressure washed it, but was EXTREMELY careful to not go within a foot of the carbs and plugs. im sorry for such a long post, but i am too puzzled.
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how to make hash

Here are a couple of questions : If I understood your post, it ran good for a while after you cleaned the carbs ? Does it still leak gas from the carbs and exhaust like it did before ? Did you install inline gas filter? Are the spark plugs wet or dry during your second attempt at starting the bike? Why did you add a lead additive ? The old Yam is designed to run on unleaded gas, it should be very happy on 89 octane. I have to think your problem is gas related. On an old bike, it's hard to do a systems check without hands on, but here is what I would check:

Check to make sure the gas cap is venting ok...run the bike with the filler cap ajar

Check for rust in the tank...run your finger around the inside of the tank just inside the filler cap, if your finger is brown, you have rust particles, and need a flush and filter

Check to make sure the petcock runs free..put it on prime and see if gas runs freely

While the petcock is on prime, with all hoses hooked up, open the drain plugs on the carbs and see if gas is running freely from the drain plugs on all carbs

Check all carb boots and intake seals to make sure you are only drawing air thru the carbs and nowhere else

Make sure your air filters are installed and sealed...the bike will not rum properly on unfiltered air... with no filters, it draws too much air for a proper mixture.

Check all vacuum hoses on the carbs and petcock, they both need vacuum to operate correctly....any vacuum leaks will cause a problem like you describe...there should be multiple hoses

It could be possible be that your lead additive didn't mix properly and gelled somewhere in your fuel delivery system and clogged something

If all the above check out ok, it's possible you have set the carbs floats improperly and they are not letting gas thru to the jets. XS

the bike was running great after i cleaned the carbs i rode it around and it responded nicely. it says on the side panel of the bike that it rund on 91 octane leaded gas. i can only assume that it is the lead additive, though. something muct be wrong with Mag1's mixture. im going to drain the tank and flush the carbs with good gas. then ill retry to start it. i need to find time for that unfortunately...as for the gas cap and such it should be ok since it ran so nicely the other day...I'm going to drain and flush ad get back to you guys
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Nutrition Forum

Yes, I know about the warning on the side panel, both of my old Yams say to use leaded gas, but trust me, Yamaha looked way ahead when they designed the motors back in the 70s and 80s, and provided for unleaded gas. I have been running 89 and sometimes 87 in my 81 XS650H for over ten years and 8,000 miles, and it runs as clean and fresh as the day it was new. The only motors that I know of that require a lead additive are the old high compression motors which run 10:1 compression ratios or greater. The old Yam is more like 8.5:1.

thanks,
im going to put 91 octane in it for a while to help it out a little(it has 41,000 miles on it) and im draining it Fri. morning before i go out
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Ordinary life insurance Forum