Triumphrat

Berniebikes · 01-14-2009, 04:15 PM

can anyone tell me if the 885cc carbs for a thunderbird are the same as used on the other t3 engines like a Trophy or Trident 900? Are the TB carbs the same keihin or mikuni CV carbs?

IrlMike · 01-14-2009, 08:00 PM

I think the trophy, trident sprint T3s used the same type/size Mikunis as pre '99 Tbird & Adventurer. The Legend only has Keihin, same as later Tbird & Sport.

The jets & likely needles were of course different.

BigAl8295 · 01-14-2009, 08:31 PM

Quote:

Originally Posted by Berniebikes

can anyone tell me if the 885cc carbs for a thunderbird are the same as used on the other t3 engines like a Trophy or Trident 900? Are the TB carbs the same keihin or mikuni CV carbs?

What are you trying to do?

Berniebikes · 01-14-2009, 08:46 PM

I'm looking at a carb set from a 2001 885cc T-bird with very low miles and thinking of picking the set up to replace my Mikunis on a 97 Trident, which has a whole lot more miles.

denny · 01-14-2009, 09:10 PM

There is also a hole in the slides that is likely different from one model to another.
The TBird Parts book shows Carb Piston 2.5 mm hole.
for the Kehins. I don't have a Parts book for the Trident.

I also think they never put the Kehins on a Trident, but not sure.

So the size of that hole might be important with the different state of engine tune.

JimmyJ should be able to explain what that hole does.

jimmyj900 · 01-15-2009, 12:58 AM

That's the vacuum port for the slide and it determines how quickly the slide vacuum forms.

Too big a port and the slide opens too soon and you get a rich mixture at low rpm. Too small and it doesn't open soon enough so there's a lean mixture at low revs.

The stock cam in the Classics models has a short duration and therefore a fairly high velocity intake impulse through the venturi, so the 2.5mm port is calibrated for that that particular cam configuration.

The Trophy/Sprint type cam has a much longer duration and a lower velocity intake pulse so it needs the slide to rise proportionally faster than the it does on the Classics bikes.

If you mix the Classics carbs with the Trophy/Sprint cams (or vise versa) you'll have serious mixture problems that will be a nightmare to try and sort out if you don't know about the port diameter difference. [Experience.]

Jim

GeoffE · 01-15-2009, 05:54 AM

Hi,

Strange - I have been looking into this over the last couple of days. Fyi, I have a set of Keihin carbs from a Legend, and thinking about uprating them for my Sprint. The Keihin carbs where fitted to the last Trident, Sprint and Trophy (900cc) models.

There appear to be 4 differencies: The Vacuum Piston has indeed a 3.0mm hole; The Vacuum Piston Spring; Main Jets; Pilots.

Is anybody here able to confirm the jet sizes Keihin used for the 98ps T300 models?

Geoff

Berniebikes · 01-15-2009, 09:01 AM

Jimmy J, thanks. Geoff is right, they put keihins on the later model Tridents. Mine was a fairly late vin number from 1997, so they must have done it in 98. I expected I would have to rejet the carbs. Should I expect the hole in the slide is too big for my application? Anyone go an idea of the hole size in the 98 Tridents with Keihins?
I read somewhere that one of the things you have to do for the Dynajet conversion is drill out the slides (which makes it irreversible). Would Dynajets be a possiblility. Thanks in advance.

Bernie

jimmyj900 · 01-15-2009, 10:57 PM

Quote:

Originally Posted by Berniebikes

I expected I would have to rejet the carbs. Should I expect the hole in the slide is too big for my application? Anyone go an idea of the hole size in the 98 Tridents with Keihins?
I read somewhere that one of the things you have to do for the Dynajet conversion is drill out the slides (which makes it irreversible). Would Dynajets be a possiblility. Thanks in advance.

It only takes a drop of epoxy and a drill bit to reduce the slide port size. Experience again... I've messed with the ports 'just a bit' in my tuning experiments.

Anyhow, the port size is directly related to the camshaft intake duration on these bikes. The Classics cam gets the 2.5mm port and the longer cam gets the 3mm port, so that's pretty straightforward.

Jim

denny · 01-16-2009, 12:32 AM

Quote:

Originally Posted by jimmyj900

The Classics cam gets the 2.5mm port and the longer cam gets the 3mm port, so that's pretty straightforward.

Jim

There's another one of those tidbits I will file away in my notes!

I am also wondering what the stock jets are for the Trident and other 98 ps T3's with Kehins. I am also glad to know that they did in fact fit Kehin's to those bikes. That should make my upcoming jetting challenge a little easier.

well maybe.....