Carb Mixture Screw Settings On A 790cc Bonnie With Tor's Anyone?

...and this is why we have electronic fuel injection!

Had a lovely 2004 790cc T100, which ran beautifully. Fitted Dunstall TOGA exhausts, still good. Fitted 115 main jets to compensate for potential leaness. (Apparently in the early years some dealers would swap out the stock 110s for 115s). After fitting a bell mouth and free flow filter I started messing with needles and shims. Never ran as well again!

 

All good points, and yep....I don’t much above 80 at all.

 

Ah....the bogging occurs for sure in 4th and 5th....starting and idling are fine. A curious thing though is since last week, the popping of the exhausts has just stopped. im going to go through the jerks guide very carefully....and it’s off with the carbs again.

 

The farther you deviate from stock, the more the bike becomes your own creation. The more you deviate from the factory creation, the more you have to assume the role of engineer. ...J.D.

 

Too right on all counts. ☹️

 

Ain’t that the truth.

 

Take it from an old man who has been doing this since he was about 12yrs. old. You can tweek yourself in to a corner. At times I come up with ideas, but then think "if I DO that, then I really should change that, and that and... Do I want.to go there?."..You need to know your limitations. It is like me with music. I play the radio. I do not have the dna to make the music. ...J.D.

 

Those are wise words indeed. I come late to the party having always let things be and given my bike to be serviced at garages. Now retired I have the time to look over the bike closely and thus picked up first the pilot screw bodge and then upon recommendation fitted the 115s. I’m beginning to regret it. Upon close inspection today I also find the seal between air box and LH hose (the catalogue calls it a ‘runner’) to the carb is not tight all the way around. Not helped of course by recent twice removal of carbs. A visit to a dyno test centre beckons.

 

The standard silencers on the Bonneville are awful, too heavy and too restrictive, when I replaced mine the bike felt like it had just lost a ball and chain. I didn't notice any difference from replacing the main jets, but that I think was just me being over cautious and wanting to make changes in small increments, I have larger jets that I plan to experiment with and install over the winter. Changing to a K&N filter also did not make any noticable difference, but getting rid of the snorkle and fitting a bellmouth made a very noticable difference, not necessarily to increased performance but to smoother running and especially noticable on cold start up.

All the changes I have made to my Bonneville were made bit by bit, first silencers, followed by filter, AIS removal, then jets & carb setup, finally snorkle & bellmouth. I'm happy with the way my bike rides and performs, but I'm sure in the hands of someone who knew what they were doing it could be greatly improved.

 

Exactly. One thing at a time unless you have an exhaust gas analyser. My 865 ran markedly better after opening inlet and exhaust and most combinations have been tried and documented so there is really not much guesswork involved. However, creating air leaks etc., isn’t going to help!

 

Well you can’t really avoid unscrewing the float bowls and seeing what is in there. The thing to remember is that nothing will work as it should if the carbs are not clean. Garage queens get progressively more furred up with fuel residue. I spent £90 on an ultrasonic bath and £10 on cleaning additive that got crap out I didn’t know was in there...... they also came out shiny on the outside in all the nooks and crannies. TTP supplied the right jets for my silencers and inlet mods and all I had to do was tweak the air screw a quarter turn to minimise popping on the overrun.

 

The point of doing one thing at a time is a good one. That being said, one thing usually leads to another. My 790 came to me already set up with a pair of Stayintune pipes. I assume it has had some jet work. The airbox is stock. I have just left that one alone because it runs great. One of the previous owners did a good job. On my other 2 Triumphs I have delved deep in to tuning. Pipes, jets, changes on needle heights, chopped airboxes, etc. Depends on how far you want to take it.
...J.D.

 

Ah, I understand changing the filter, jets and carb set up, even removing the snorkel and bell mouth. But, the AIS removal...I’ll have to google it. How easy was it?

 

Just watched Delboys video on AIS removal....looks easy.

 

It's all what you consider enjoyment. I turned the idle screws out 1/4 turn from stock and greatly reduced the popping on overrun and it helped low throttle surging. Cold start up is still a bit touch and go, and I may get the vacuum gauge out to troubleshoot. Or maybe replace ignition coils. I guess I am a tinkerer at heart.

 

Gearhead to the bone myself. Spent my whole life with mechanical things. Never was much good at anything else . ...J.D.