Triumphrat

jellybelly · 07-25-2007

The time has come to add some more free flowing pipes to the wife's 790cc & my 865cc 2005 Bonnies. They will both be getting the same treatment - uni filter, AI removed, snorkel removed, EMGO 17" reverse cones, petrol is 95 octane at the pump here in NZ. The Jenks bolts setting guide suggests 135 main jet, 1 shim, 42 pilot jet, standard needle & 3 turns for a 790cc engine. And 125 mains , 1 shim, 40 pilot jet, standard Thruxton needle for 865cc engine under these conditions. As both bikes are used daily I'm keen to get the jetting close straight away (and the wife wouldn't be happy if I get it wrong). Dyno runs will follow for fine tuning. Does this sound about right?
I am also keen to carefully drill out the air holw on the 865cc - has anyone done this with an electric hand drill and decent 3mm bit. Any suggestions would be much appreciated.

Sheepdog · 07-25-2007

I have a similar setup on my '03 T100 (790cc). With BellaCorse Teardrops (EMGO original Bonneville-style...), AI and snorkle removed, UniFilter, and Norman Hyde Bellmouth I use #125 mains, #42 pilots, Thruxton needles, and about 2.5 turns on the idle mixture screws. I reside at 900 ft of altitude. This works well, though it is just a tad on the rich side (I prefer to run just a little rich to prevent heat issues down here in the sunny South). Still, the bike starts well, doesn't pop on decel, pulls hard, and revs cleanly all the way to the limiter.

BlueJ · 07-25-2007

On my 865cc '07, I have exactly that set-up (except with TORs). Just finished it over the weekend - it was really quite easy. With the exception of drilling the slide hole, you *could* do it with the carbs on the bike but I'd suggest pulling them anyway - not very hard at all (at least, the first time pull them all the way - then you'll know where you're looking the 2nd time). I drilled the slide holes with a hand (power) drill, 7/64" bit, the metal is quite soft and drills easily. I used a couple tips to clean out all the aluminum dust before reassembly.

I put in 125 mains, one shim. The shim - wow - my wife has TORs and 115s (stock air) on her Bonnie, and it's been sluggish to warm up from the get-go - the shim on mine seems to have been a great help there. I'm thinking I'm still a tad lean, overall (especially low rpms), however, (currently at 3.5 turns out), so I'm thinking about 42 pilots and a re-adjust of the mixture screws. Need to re-read the Tuning Guide before I go there. Dyno runs are $100 for the whole shooting match around here, with advance notice required.

I would strongly recommend having tne NB carb screw kit on hand - I stripped the head one of the 8 screws on my carb, pulled the screw off with vise grips (easy), and am glad to have the hex head screws in place of them. Have fun, and good luck!!

cdk80gs · 07-25-2007

For drilling the slides I used a cordless drill, the metal is really soft and it took a second or so to drill, not sure the drill size as I just used the one supplied in the Dynojet kit.
Chris

Geoff · 07-25-2007

the 865's do not require the 42 pilot, in most cases. its too rich, if you have a shim on a thrux needle
G

BlueJ · 07-25-2007

That's what I would have thought, but I'm getting what I suspect is a bit of the 'lean surging' at steady cruise, and I'm already out 3.5 turns (how many turns are there before the screws fall out?)... wonder if I need to to to 130 mains with just TORs and free-flow filter/no snorkle??

badrufus · 07-25-2007

Drilling the slides is not difficult. I did it on a drill press, but you could easily do it with a hand drill. As noted, the metal is thin and soft, so the main thing you need to do is be aware of how quickly you will drill through. Make sure you are holding the slide firmly, as the drill bit will grab in the soft metal and try to spin the slide if you're not holding on. Be careful if you try to chamfer the edges of the holes (I wouldn't bother) as the metal is very thin and you can easily go through and enlarge the hole further.