*Parts Compatibility - TBS 1998

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Biiim

Biiim

Well-Known Member
I’ve got a 1998 thunderbird sport 900. I’m replacing a few things and rebuilding the engine but the main thing is replacing the crank shaft. A tooth broke off that’s why the bike is mine now.
TBird and TBS - what’s the difference? Are the engines the same? Say I find a crank shaft for a 98 tbird- are the engines interchangeable- more importantly the crank shaft! Thanks so much
 
Qship said:
Pretty sure they have the same engines just aesthetic differences to the bodywork. Do you know the cause of the tooth breaking off? Some years had problems with the sprag clutches. Not sure if yours is one.
May have better luck posting in the Thunderbird 3cyl 900, (885) Legends & Adventurers
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I don’t know the cause of the cranks shaft gear tooth break. Once I get inside I’ll have a better idea. Still wrestling a stripped socket hex screw rn
 
There is a high likelyhood ricocheting parts caused more damage than you might think. Unless you are in no hurry to ride your bike and sourcing engine parts isn't a problem I would imagine my swap motors and rebuild idea might gain some added traction.
 
atomsplitter said:
There is a high likelyhood ricocheting parts caused more damage than you might think. Unless you are in no hurry to ride your bike and sourcing engine parts isn't a problem I would imagine my swap motors and rebuild idea might gain some added traction.
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Where would you recommend finding a new engine? eBay?
 
That or motorcycle salvage yards. There were some Triumph 3 banger engines on eBay (like the one I posted). Since it's not an injected engine no ECU, just an igniter. If it were my project this would be how I'd approach it since I could get the bike up and running faster with a different motor that had been tested to work. Once that was in the bike and I could ride it around I would then go about rebuilding the original motor with some performance mods. Once that engine was properly sorted, go about swapping the motors out and sell the used motor (probably on eBay). You could provide video evidence of it working before you pulled it out of the bike. Just how I'd do it. Then again I'm retired.
 
Biiim said:
Say I find a crank shaft for a 98 tbird- are the engines interchangeable- more importantly the crank shaft!
Click to expand...
TBS and Legend engines are the same. Thunderbird and Adventurer are the same internally but have a "chrome" motif whereas the other two are black. Some also have Mikuni carbs and the rubber connectors are different. Stick with your Keihins. Thunderbird and TBS are 6 speed transmissions; Legend and Adventurer are 5 speed. (Early T-birds may have been 5-speed, I'm not certain.) TBS shift drum is unique.

All the cranks are interchangeable.
 
sikatri said:
I think you’ll learn more by the rebuilding experience.
You can always get a spare engine as well.
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I’m absolutely going to rebuild the engine but slowly so it’s more fun. Just got laid off because the company I worked for his broke. Might run off to ny to work at my old shop.
 
JCooper said:
TBS and Legend engines are the same. Thunderbird and Adventurer are the same internally but have a "chrome" motif whereas the other two are black. Some also have Mikuni carbs and the rubber connectors are different. Stick with your Keihins. Thunderbird and TBS are 6 speed transmissions; Legend and Adventurer are 5 speed. (Early T-birds may have been 5-speed, I'm not certain.) TBS shift drum is unique.

All the cranks are interchangeable.
Click to expand...
Thank you this is incredibly helpful !
 
atomsplitter said:
That or motorcycle salvage yards. There were some Triumph 3 banger engines on eBay (like the one I posted). Since it's not an injected engine no ECU, just an igniter. If it were my project this would be how I'd approach it since I could get the bike up and running faster with a different motor that had been tested to work. Once that was in the bike and I could ride it around I would then go about rebuilding the original motor with some performance mods. Once that engine was properly sorted, go about swapping the motors out and sell the used motor (probably on eBay). You could provide video evidence of it working before you pulled it out of the bike. Just how I'd do it. Then again I'm retired.
Click to expand...
I looked at that one on eBay and if I don’t get work in nyc I’ll most likely buy that. I don’t have wheels to commute down here and need that to get a new job thank you !
 
JCooper said:
TBS and Legend engines are the same. Thunderbird and Adventurer are the same internally but have a "chrome" motif whereas the other two are black. Some also have Mikuni carbs and the rubber connectors are different. Stick with your Keihins. Thunderbird and TBS are 6 speed transmissions; Legend and Adventurer are 5 speed. (Early T-birds may have been 5-speed, I'm not certain.) TBS shift drum is unique.

All the cranks are interchangeable.
Click to expand...
Couple things;
Only Thunderbird AFTER 1998(?) are 6 speed, all previous Thunderbird/Legend/Adv. are 5 speed with a blanking sleeve in place of the 6th gear, otherwise transmissions are quite identical, even, (as I recall), in both 3 and 4 cyl models up to 1998. TBS are 1998-on, so 6 speed. Remember, they were attempting to cheaply and simply, make as many variations of models as possible- "modularity".
1998 saw running changes, so check part numbers!
You can check part numbers on "Pandora" or "Hermy's" Triumph website. A hot weather roadside breakdown last season on my 1996 Thunderbird led to a search for igniter, (ECU), - (turned out to be pick-up coil), and igniters are $$$$$$$$!!!! (from memory about $400+) and they are DIFFERENT between years and Thunderbird vs TBS. ignition curve, timing, etc is likely different. Also, (from memory) they changed ignition suppliers around 1998. This, along with possibly cams, intake boots, exhaust differences, etc, accounts for the 15HP or so difference between Thunderbird/Legend/Adv. and TBS
 
dearborn said:
Couple things;
Only Thunderbird AFTER 1998(?) are 6 speed, all previous Thunderbird/Legend/Adv. are 5 speed with a blanking sleeve in place of the 6th gear, otherwise transmissions are quite identical, even, (as I recall), in both 3 and 4 cyl models up to 1998. TBS are 1998-on, so 6 speed. Remember, they were attempting to cheaply and simply, make as many variations of models as possible- "modularity".
1998 saw running changes, so check part numbers!
You can check part numbers on "Pandora" or "Hermy's" Triumph website. A hot weather roadside breakdown last season on my 1996 Thunderbird led to a search for igniter, (ECU), - (turned out to be pick-up coil), and igniters are $$$$$$$$!!!! (from memory about $400+) and they are DIFFERENT between years and Thunderbird vs TBS. ignition curve, timing, etc is likely different. Also, (from memory) they changed ignition suppliers around 1998. This, along with possibly cams, intake boots, exhaust differences, etc, accounts for the 15HP or so difference between Thunderbird/Legend/Adv. and TBS
Click to expand...
Why two threads? My response is in the other one.
 
No difference in crankshaft. Cams and pistons are main difference. So yourself a big favor and find the triumph pistons for the 750 or from a Super III. They have a higher compression ratio. Cheap and easy oem factory bolt on. I’d also consider a different cam. I think many run a green or blue cam for more power and hp. I have a set of red cams and pistons from a Daytona Super III I will install someday.

Ignitors are available! Ignitech Ignitors can be had for every model of CDI for these bikes. Derek at Motolab (Iowa USA) or Ignitech directly via Cech Rep. I bought mine for $200-250 US in 2019. There are others but do not waste your money.
 

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