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Discussion Starter #1
Hello, last year I bought a ‘98 Thunderbird with a locked up engine. It looks like I can easily swap in any carbureted 3 cylinder engine from other models around the same year. I’m looking for some verification on this because this would be the determining factor for me doing the swap or letting it go to find another one.
 

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As far as I know (admittedly that is not very far), any 900 3 cylinder will fit. Be nice to slip in the 6 speed 97 h.p. version, if it will work. Anyone know anymore please correct me if I am wrong. ...J.D.
 

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I agree with Wire Wheels a Trophy, Sprint or Trident should work just fine. But then if a Super III engine comes available it will fit also. That's the beauty of our Triumphs using a modular design, lots of the parts interchange with others. Or you could really go crazy and stuff in a 1200 four cylinder Trophy engine. 900 and 1200 Trophy use the same frame, even the same wiring harness. By the way, did you figure out why your engine is locked up? Pistons and liners can be replaced with the engine still in the frame.
 

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Discussion Starter #4
No I haven’t really even had time to look at it this past winter. The guy that I bought it from told me that it lost power while riding and just rode it home. I’m thinking that it probably lost oil pressure in #3. But that may be another option to just re-sleeve it.
 

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If he was able to ride it home, it can't be all that bad. I'd change it's oil and coolant and fire it up. Probably something simple. My Legend was a trade-in at a Kawasaki dealer. They sold it to me cheap. It was a pretty neglected, "sick puppy" when I got it. A good carburetor cleaning, some rejetting, a new airbox, coils and sparkplugs. She runs like a champ ! ...J.D.
 

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Discussion Starter #6
I put it on its center stand and put it in 5th gear and the engine wouldn’t rotate. Pinwall has a few triples available so I’m going to go with a replacement. I’ll remove the cylinders later to see the damage. If the bottom end isn’t damaged then I’ll rebuild the top end and keep it around so if I ever sell the motorcycle it will come with the original engine. The guy said that he rode it home. It sounded like he wasn’t too far away when it lost power and turned around.
 

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Discussion Starter #7
Were are some good places to buy performance parts for the Thunderbirds? On my Speedmaster I removed the factory air box and exhaust among other things and would eventually like to do that on this one. Are there performance igniters and coils out there?
 

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Green Cams from a Trophy engine are easy to get. A Trophy air box does a good job a breathing. Are you getting another engine? To check out the old engine, I'd take the spark plugs out and take off the right side crankcase cover off and turn the crank with a 15/16 wrench. If it turns easy then put the spark plugs back in and feel for the compression on each cylinder.
 

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Discussion Starter #9
As of now my plan is to replace the engine. I’m still going to remove the head and cylinders soon to see the damage. If the bottom end looks good then I’ll re-sleeve it. The engine block would still have to go to the machine shop to have them re-sleeve it right or are they replaceable like in a heavy duty Diesel engine?
 

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Discussion Starter #10
So greg96brg, the green cams are the factory cams or are they aftermarket? What gives the other models more power? I’m thinking that it was by cams, carbs and exhaust. I could bump my engine up to the sport model power but still have the 5speed transmission.
 

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Green Cams are the stock factory cams for Trophys. Red Cams are the stock factory cams for the Daytona Super III. Someone else will have to tell you if the red cams were in the 900 Daytonas, because I don't have experience with them. The factory put a dab of paint on the #1 end of the cam. Green, Red, I think the Thunderbirds a Tiger got a different color Blue?, Brown?
As with most engine parts they are placed in an engine where they think the rider will want the power band to be. Daytona being the higher end of the rpm scale, Trophy in the middle, and Thunderbirds and Tigers down lower. For going slow around town Daytonas and Trophys aren't happy, they are freeway flyers. Maybe someone else can chime in on how slow traffic friendly the Tigers and Thunderbirds are.
 

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Discussion Starter #13
I think that #3 connecting rod is broken. I removed the plugs, cam cover and right crank case cover. It only rotates a few degrees. #1 moves, couldn’t see #2 due to the frame and #3 piston doesn’t move. Next step is “off with its head”!
 

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I bought a broken engine Trophy 3 years ago. The piston and and rod on #2 were in a hundred pieces. What a mess. The rod was flopping around long enough to break part of the upper engine case. Ebay is my friend. I bought the parts needed to bring the engine back to life. Piston and liner, engine case, I don't remember if I changed out the crank. I bought all new crank and rod bearings. My brother is now enjoying that bike.
 

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Discussion Starter #15
So what do you think happened that to it? Lack of oil in the cylinder or something on the carb side.
 

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I'm open to educated guesses on that one. If it was a lack of oil, all the cylinders and pistons should have been effected. My guess is a big time air leak on #2. The air mixture it was so lean it burned a hole in the piston. But its hard to tell the piston was in 50 pieces or more. I found little pieces of ring material down in the engine sump. The rod was bent big time.
Years ago I was driving a Corvair van across the desert. The engine had 4 carbs. Turned out carb #1 was running lean and I burned a hole in piston #1. The hole was as big as a quarter. I limbed the Corvair back home and must have gone thru 7 quarts of oil while laying down a smoke screen. Highway Patrol wrote a citation. Getting it fixed and there would be no fine.
 

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Discussion Starter #17
Do all of the models with the triple engine have the same carb bodies?The jets will probably be different. If do replace my engine then I’d go with a 6 speed version.
 

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The earlier triples came with Mikuni carbs. Later ones came with Keihin carbs. I think they're are alot more out there with Mikunis. With respect to the cams, all the classic models had the brown cams. All sport touring models (Trident, Sprint Trophy Daytona) came with the green cams. The red cams were only on the Super III. I've owned an Adventurer and currently have a Sprint Sport. IMO, the green cams are by far the best cams for the street.
 

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In terms of the horsepower differences, from the classic models to the sport touring models it is only cams and exhaust. That's it. The sport touring models also have 2 discs up front. Rumor has it that the Super III had additional head work, but I've seen threads that say this isn't true.
 

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Discussion Starter #20
So I’ve decided to replace the engine. I got one out of a sprint. I’m going be starting my winter project a little bit early.
 
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