Triumphrat

GeneralPig · 03-14-2008

Having read and re-read the MPG threads, as coz I don't get good mileage from my 98 TBird (early type), I'm considering buying a set of used Keihins and Ebaying the Mikunis.

I notice that the Mikunis have an oval section on the intake. The Keihins I've found may have a round section? is this correct? Will I need a different set of intake carb rubbers? The Keihins I've found don't have any rubbers with them-but I do have a perfectly good set on the Mikunis.

Also, late Tbirds had the airbox on the left, rather than across the frame. Will I need to resite the airbox and buy the newer type of airbox, or can the old type be fitted onto Keihins?

Any advice gratefully received.

IrlMike · 03-14-2008

I've just changed the Miks for Keihins on my 98 Tbird (today!) - success, no more slider/needle jet gremlins

The Keihin rubbers are all different to the Miks, and looking at them side by side I wouldn't try & adapt them. I was lucky, came with the carbs off ebay for 100 euros.

Stock airbox is ok & cables are fine with Keihins, a little rerouting but connect up perfectly.

One other plus - the Keihins have more clearance between engine & airbox, easier fit. They also look way better built than Miks. Recommend this mod.

GeneralPig · 03-14-2008

Thanks. I wuz scared I was getting myself into major work there.

Wombat · 03-14-2008

Quote:

Originally Posted by GeneralPig

Also, late Tbirds had the airbox on the left, rather than across the frame.

Mine is an '04 which is about as late as you can get and the airbox is no different to the early models.

Woody1911a1 · 03-14-2008

set of used 2002 kehin rubbers here , http://cgi.ebay.com/ebaymotors/Trium...4900QQtcZphoto

TonyD · 03-15-2008

I seem to remember it being said in bygone threads that the Mikuni carb rubbers were the restricted ones (with the dimples) resulting in lower bhp than with those for the Keihins (?)

IrlMike · 03-15-2008

The power of Mikuni & Keihin carbed TBs is quoted as same by Triumph. That said, TBS has identically jetted/needled Keihins & all engine/ airbox components the same except for exhaust with 'crossover' pipe to have quoted 14hp more. A 3 into 1 pipe does much the same job I think. I haven't tried a stock TB or Legend to see how much is down to carb make/rubbers or exhaust. But have tried stock TBS & sure my setup with 3-1 has same or little more power as i have K&N filter too. I have unrestricted Mikuni rubbers & dynojet kit spare if anyone wants (pm me), classified going up when get round to it!

Slinky · 03-15-2008

I am running keihin carbs with the Mikuni rubbers, it all fits together fine. I did switch to the Keihin-carb rubbers but then switched back again. I am also running the Mikuni #90 main jets in the Keihins, along with #40 pilot jets.

IrlMike · 03-15-2008

Slinky

Interesting, the Mikuni airbox rubbers have a separate duct for the carb 'vacuum' top, but makes no difference in practice for Keihins ? Didn't bother to try them as I had the 'right' rubbers, tho' I'd also seen a post here saying Keihins needed their own rubbers - now we know!

Are you saying also that a 90 Mik main jet does the same as a 98 Keihin, when fitted in a Keihin ?

Slinky · 03-16-2008

I am not sure what you mean by a separate duct, but yes, I am running Keihins with the original restricted boots from the old Mikunis. I do have a later airbox too, but I am not sure if that has any relevance. I was never happy with the later unrestricted boots, the bike seemed to lose a little midrange urge, that's why I reverted.

The 90 main jets are the right size for the restricted inlet ruibbers. If I were using unrestricted rubbers I would have gone with the 98's. All metric jet sizes are measured in percentage of a millimetre.