Triumphrat

05-07-2006, 04:27 AM

Hi to all you RATS. This is my first posting as a new member and having perused the forum over the last few days I have a couple of questions.
I bought a 790 Bonnie in March 2001 and have been very happy with doing 15k miles since then. Recently I've had a couple of test runs on the Thruxton but in the end have opted for a new 865cc T100 as the Bonnie is the only bike my wife will ride pillion on, so I've sold the 790 to a friend.

The questions.

1. I fitted the Triumph 'open pipes' onto the 790cc Bonnie & they came with larger main jets, replacing the 110's with 115's. This gave much better performance above 5k revs.
I was told by my dealer that the 865 T100 doesn't need bigger jets when fitting the 'open pipes'. However, the workshop manual says that 110 jets are fitted(I've not yet looked inside the carbs) so I am puzzled :???: why this is. My instinct is to fit 120's. The 790 bonnie has a NAGB needle & a 52 starter jet whilst the 865 T100 has a NBZT needle & a 55 starter jet, all other details the same.

2. Examining the workshop manual & comparing detailed specifications of the T100 & Thruxton engines, they are IDENTICAL. Compression Ratio( the sales literature says the Thruxton has 10:1 CR but the book says 9.2:1),size & jetting & needles of carbs,valve head size,lift,duration & timing are all the same so the cams will be the same. The bikes weigh the same so where does the Thruxton get it's extra power from?

I would appreciate your views & opinions on both these questions.

T100 impressions so far.
I've fitted the Triumph 'open' pipes but have left the jetting as standard.
The new T100 feels a lot more stable than the old 790 particularly when pushing on in fast bends. The 790 started to weave a bit but became stable when relaxing grip on the bars. The T100( am still running it in so haven't gone above 70mph yet) tracks better & holds it's line in corners more easily. This may only be due to the fact the bike is new & everything is tight and that it runs on Metzeler tyres , not Bridgestones.
The big difference I notice is it romps up hills without losing much if any speed & without opening up the throttle. Several times I've found myself looking for that 6th gear so the 18T sprocket is a possibility.
Can't wait to do the 200 miles till 1st service & go for a proper run.
:chug:

Panthermark · 05-07-2006, 09:50 AM

Nourton,
This is something I've been wondering about for the last few months. I have TOR's and 120's, and I think I'm running rich. I may go back to my 115'. (UNI Filter, Polaris Bellmouth, no restrictor plate).

The early 2001 Bonnies came with 105's. They were later converted to 110's. When you purchased the "performance package" with your bike, you received TOR's and 115's.

When the Thrux was introduced in 2004 with the 865cc engine, it had different needles. You could also purchase TOR's for the Thrux which does not come with bigger jets....interesting.

There are not separate TOR's for the 790 Bonnie and the (starting in 2005) 865 T-100 Bonnie. However, when you buy TOR's they all still come with 115's anyway.

I bet everyone was so used to jetting up with the 790's on the original needles, it was assumed that the 865's would be jetted up in a similar fashion.

As far as HP differences between the T-100 and the Thrux, my guess is the exhaust pipes.

Oh, and your 2006 T-100 already has an 18T sprocket on it.

LaughingBob · 05-07-2006, 02:42 PM

I have Triumph TOR's on my 865 T100 and have the original 110's fitted. The bike run's perfectly well and when I pulled the plugs they were a good colour. Hope this helps.

EnglishBaz · 05-08-2006, 12:43 PM

I have had TOR's fitted twice on my bikes - both of them 05 T100s

My dealer fitted the new jets both times since they came with the pipes as a package and as part of the initial cost ie £300 pipes fitted and new jets installed

I'm thinking about the 19 tooth sprocket because I find myself looking for the magic 6th gear sometimes.

Apparently they are made about 5 miles away from my house so my dealer recommended I approach them direct so as to get them cheaper - You interested?

05-17-2006, 04:48 AM

Thanks for the replies.

Now having done a few more miles on my T100, I've decided to stick with the standard (18t) sprocket for the time being as it allows the bike to pull nicely 2 up loaded with luggage.

1st service later this week after which I'll fit the free flow air filter, bigger main jets(120's), 1 shim on the needles & remove the snorkel.
These mods follows Jenk's tuning advice but I won't be able to comment properly until the bike's done about 2k miles.

Nourton.