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Hinckley Classic Triples 885cc Classic Styled T3's: Legend, Thunderbird, Thunderbird Sport & Adventurer.

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Old 09-19-2011, 10:31 PM   #1 (permalink)
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Tuning Carb on 1995 Thundebird

I bought a 1995 Thunderbird w/ 11K miles from a dealer, got it home and it wouldn't stop backfiring. Took it back and they told me the injection coils were bad. So they fixed them for free. I moved, and couldn't find a mechanic within 65 miles who would even change my tires, and I was having issues with not having any power over 70 mph. So I got a Haynes and started going over the engine. I found pieces missing. The biggest issue I found was that the airbox and aux airbox were cracked, and there was no hose connecting them. I glued the cracks back together and replaced the hose, and the bike appeared to be running much better for about two weeks. Then I noticed some performance issues.

Sometimes when I start riding, there doesn't appear to be any horsepower (I've almost fallen off a couple times when the expected acceleration wasn't there and I lost my balance). This occurs all through the RPM range from 1k through 6K. However this usually only happens in the afternoon (I ride to a carpool about 7 miles from my house twice a day). However, the most pronounced time was when I rode 65 miles to work in the morning with no problem. It sat in the shade all day, then I rode home. Six miles from my house, the engine died, with all the symptoms of running out of gas (it had half a tank, however).

The only way to get it started was to apply 3/4 choke, and it fired right up. Took off the choke and rode home. It tried to die on me again, but I just feathered the throttle at high RPMs (I was doing 75 on the freeway) and it stayed alive. However, I noticed the drop in power once I got onto surface streets and was hitting light after light. The only other thing I have noticed is twice, when pulling out from a stop, I could swear I heard a "pop-psss" like a popped tire just as I'm pulling away. I can't find any holes or anything in the hoses, I've talked to engine fellas I know, and I'm at a loss. And, like I said, the local mechanics won't even look at my bike. I'm wondering if anyone has had a similar issue (I've got Mikuni carbs), and a solution that doesn't require jet adjustment or the like, since this is way above my skill level.

Thank for any sharing any info

Semper Fortis
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Old 09-19-2011, 10:36 PM   #2 (permalink)
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Old 09-19-2011, 10:51 PM   #3 (permalink)
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Maybe your gas tank vent is not working properly and creating a vacuum and not allowing fuel to flow. I am stating this based on the pop and hiss you heard. Try running the bike with the fuel cap loose and see what happens. Remember to eliminate all the small possibilities before moving on to larger ones.

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Old 09-19-2011, 10:58 PM   #4 (permalink)
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I can't imagine why any mechanic who is worth his pay would not work on these bikes.
They are pretty old school. Multi cylinder Carbureted bikes.

O most of the mechanics who work in dealerships these days are only trained to work on fuel injection. If they can't plug it into a computer they are too lazy to spend the time to diagnose the problem.

Can you find any independent motorcycle mechanics? Maybe one who has some Kawasaki experience? Several of the parts are interchangeable with some Kawasaki models so one of those guys should feel right at home.

Do some searching on the Mikuni Carbs. They have some parts that wear rather quickly but once those are replaced they work quite well.
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Old 09-20-2011, 12:21 AM   #5 (permalink)
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@BRG-BRD, I hadn't thought of that, but the dealer did mention when I got it that the tank cap was aftermarket (due to cali emmission laws, whatever) and it is a pain to seat correctly. I'll give that a whirl.

@ denny, the only one I found (when I needed my tires changed) failed to mention that my rear brake was at bare metal. I specifically asked him about its condition and he said it was fine. So I don't want that dude touching my engine (he had some bad reviews on yelp). I may go farther afield (more than 60 miles) and may be able to find someone, but I want to make sure it isn't something simple.

The next thing I was thinking after I replace the air filter (its rotten) is to run fresh plugs and see if its running lean or rich. Not exactly sure how to do that, but I understand its not too difficult. Then go from there.
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Old 09-20-2011, 01:42 AM   #6 (permalink)
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In order to change the air filter, you have to remove the carburetors. So you might as well clean them and check for worn parts while you have them off the engine.

There is lots of good info here about those carbs and what parts you need.

If you are not comfortable with doing it yourself, at least print out the info and a good mechanic would be comfortable doing the work with that info as advice. Replacing both airboxes and all of the rubber parts will run you close to $300 for those parts, including new clamps. You might not need all of that though.

It's most likely a combination of little things. I believe the Carbs are the best place to start.
Actually the entire fuel system. Make sure the tank is clean too. clean the petcock and tank first.
There is nothing worse than reconnecting clean carbs to a dirty tank. You'll just have to do it all over again if you don't clean the tank.

Check all the connections to the coils. Clean and lubricate (dielectric grease) those connections, make sure they are tight too.
Just a little squeeze with some pliars will make sure they are making good contact. And of course spark plugs.
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Last edited by denny; 09-20-2011 at 01:50 AM.
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Old 09-21-2011, 08:17 PM   #7 (permalink)
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Yep, got the air filter in today. Was hoping I would have time to get it done after work, but looks like it will have to wait until this weekend. Ran it with the tank cap loose and haven't noticed the problem, but I've only put about 30 miles on it. I'm also going to check the hoses, in my Haynes there's five (2 vent, 2 fuel and one vacuum) but maybe its just a generic set up. However, I only can see two under there, but its hard for me to see exactly whats going on with the tank on. And the previous owner didn't appear to run it very hard, but I'm normally at 5k RPM or higher. I believe he was running it in 5th gear on surface streets, which is only about 2.5-3K. And with only 11k miles, may be some gunk in there.

Mahalo for all the suggestions, let y'all know the status next week.
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Old 09-22-2011, 11:32 PM   #8 (permalink)
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So I pulled the carb and the air box and replaced the filter. That was probably the first problem, as you can see below (I think, still trying to figure out how to work these thread things).

Next I looked at the carb, and it appeared to be pretty clean, and the jets are clean and shiny as well. The only thing I saw that may be a problem was there appeared to be oil in one of the vent tubes. The second problem was there are actually no vent tubes, just two bases coming off the carb. Its my understanding that this can cause air to be pulled out of the carb during cross winds or high speeds.

After putting everything back together again, I took it out for a quick spin (about 12 miles) and it appeared to be running better (smoother accelaration, as well as less of a "pull" when I would let off the throttle all the way when at high RPMs). However traffic was too dense and slow to get up to normal highway speeds (80mph+) nor did I have time to really put miles on it before heading home. I'll try to get a long ride during the heat of the afternoon and see if there is a difference, as well as get up to speed for a considerable distance.
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Old 09-23-2011, 05:08 PM   #9 (permalink)
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Keep us posted. I think you're on the right track. If you have to remove the tank, it's surprisingly easy.
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Old 09-25-2011, 09:50 AM   #10 (permalink)
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Just thought I would chime in on the plugs.....my 96 bird came with ngk dpr9ea9....fouled all the time...switched to dpr8ea9.....all good.....and yes please keep us posted...a few people leave those who follow these posts hanging...we all can learn more from each other if we all follow up with a bottom line......"this was this was wrong...that was wrong"...cheers.....Tom
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